STRESS AND NOISE-INDUCED HEARING LOSS
.AMONG INDUSTRIAL WORKERS b y
CAROL ANNE NADER, B.A.
A THESIS
IN
SPEECH PATHOLOGY AND AUDIOLOGY
Submitted to the Graduate Faculty of Texas Tech University in
Partial Fulfillment of the Requirements for the Desree of o
MASTER OF SCIENCE
IN
SPEECH PATHOLOGY AND AUDIOLOGY
Approved
Accepted
May, 198 0

^6: tx.
ACKNOWLEDGMENTS
I wish to express my deepest appreciation to the members of my committee, Dr. W. K. Ickes, Dr. Michael
Smith, and Mrs. Becky Yarbrough, for their support and great help in this thesis.
1 1

TABLE OF CONTENTS
ACKNOWLEDGMENTS ii
LIST OF TABLES v
CHAPTER
I. INTRODUCTION 1
Review of Related Literature 4
Definition of Noise-Induced
Hearing Loss 5
^ Biological Effects of a Noise-
Induced Hearing Loss 7
Physiological Reactions to Noise . . . . 8
Physiological Stress Produced by
Noise 10
Stress-Prone Personality Types 11
Tests for Pattern A Assessment 14
Measurements of Vasoconstriction . . . . 16
Purpose and Scope of Thesis 17
II. METHODS AND PROCEDURE 18
Subjects 18
Equipment 19
Audiometer 19
Graphic Recorder 20
Procedure 21
Medical Case History 21 iii

Average High Frequency Hearing
Loss 22
Noise Exposure History 22
Noise Exposure Quotient 25
Personality Typing 24
Methods of Obtaining Data 25
Plethysmographic Recordings 2 5
Obtaining Data from the
Plethysmographic Recorder 25
Analysis of Data 26
III. RESULTS AND DISCUSSION 29 w Correlations 29
Significant Correlations 30
Insignificant Correlations 30
Bortner's Subjects Compared to
Subjects of this Study 31
Comparison of NEQ Scores for
Type A and Type B Subjects 35
Discussion 54
IV. SUMMARY AND CONCLUSIONS 3 7
P u r p o s e 37
P r o c e d u r e 3 7
R e s u l t s 40
Conclusions 41
B I B L I O G R A P H Y 44
A P P E N D I X 4 8
IV

LIST OF TABLES
TABLE
1. CORRELATION MATRIX 2 9
2. CRITICAL RATIO 32
3. MEANS OF THE PERSONALITY TYPES 32

CHAPTER I
INTRODUCTION
With the beginning of the Industrial Revolution some 100 years ago, and with its concomitant expansion of industry and mass production methods, the stage was set for noise-induced hearing loss to become a social problem.
Today, industrial hearing loss is of concern to the federal government, to industry, to business owners, and to the armed forces. Employers are now legally obligated to prevent workers from acquiring a noise-induced hearing loss either by reducing noise to acceptable harmless levels or by providing adequate hearing protection (Northern, 1976).
There is no doubt that hazardous noise conditions produce destruction of auditory sensory cells in the cochlea, and that sufficient destruction of these cells will produce hearing loss (Katz, 1978).
Clear evidence supports the following statements about the effects on people of exposure to noise of sufficient intensity and duration: 1) exposure to noise can result in a temporary hearing loss and repeated exposure can lead to a permanent hearing loss; 2) noise can

interfere with the performance of complicated tasks and can especially disturb performance when speech communication or response to auditory signals is demanded; and,
3) noise can inversely influence mood and disturb relaxation (Hines, 1966; Welch and Welch, 1970; Bohne, 1976;
May, 1978).
Since noise is one of the most common pollutants
/^ in industry, it becomei imperative that supervisors and safety directors whose duties include protection of employee health and safety, familiarize themselves with the basic principles of noise control and conservation of hearing (International Wrought Copper Council, 1968).
Federal regulation of occupational noise exposure started with regulations issued in May of 1969 under the authority of the Walsh-Healey Public Contracts Act (Katz, 1978).
This Act stated that any industry doing more than $10,000 annual government business must comply with noise reduction and control standards which limited the maximum noise level to which workers were allowed to be exposed to 90 dBA during an eight-hour day. In April, 1971, the Occupational
Safety and Health Act (OSHA) set up a damage risk criteria limiting the levels of intensity of sound in noisy areas to which a worker could be exposed for certain periods of time. This act covered all industries where noise levels exceeded 90 dBA. In 1973, OSHA recommended the institution

of audiometric testing programs in industrial settings when the noise exposure of an employee was one-half or more of the limiting value. The objective of this testing program was to detect changes in hearing before they become great enough to be handicapping (Olishifski and
Harford, 1975).
OSHA's 1974 limitations on the noise levels to which employees are allowed to be exposed during working hours are listed in the following chart. These are the permissible levels allowed before a worker runs the risk of acquiring a noise-induced hearing loss (Olishifski and Harford, 1975).
Noise Level (dB) Permissible Time
90 dBA 8 hours
9 2 dBA 6 hours
95 dBA 4 hours
97 dBA 3 hours
100 dBA 2 hours
102 dBA Ih hours
105 dBA 1 hour
In reviewing the published data available on noise induced hearing loss and data from research studies, the
OSHA committee found that a significant factor in evaluating a noise-induced hearing loss involved variations in

individual susceptibility to hearing damage from the noise
(Olishifski and Harford, 1975). Many researchers have explored the area of individual susceptibility to noise
(Summerfield, Glorig, and Wheeler, 1958; Bryan, 19:^3;
Welch and Welch, 1970; Lipscomb, 1974) and how an individual's personality and stress-proneness can be a determining factor in a noise-induced hearing loss (Cohen, 1969;
Kryter, 1970; Harris, 1979). Ickes, Espili, and Glorig
(1979) suggested that certain stress-prone personalities may acquire more noise-induced hearing loss than those personalities who are less prone to stress. Their research has demonstrated that people respond to loud noxious noise with vasoconstriction. The vasoconstriction ostensibly contributes to noise-induced hearing loss by producing a state of anoxia within the stria vascularis within the inner ear. As a result of this research, further research concerning noise-induced hearing loss and stress-prone personality types were proposed.
Review of Related Literature
The following discussion will be concerned with 1) a definition of noise-induced hearing loss, 2) biological effects of a noise-induced hearing loss, 3) physiological reactions to noise, 4) psychological stress produced by noise, 5) stress-prone personality types, and 6) measurements of vasoconstriction.

Definition of Noise-Induced
Hearing Loss
The term noise-induced hearing loss is used to describe the cumulative permanent loss of hearing of the sensori-neural type that develops over months or years of hazardous noise exposure. The hearing loss usually affects both ears equally in extent and degree (Olishifski and
Harford, 1975). The amount of hearing loss incurred from noise exposure is proportional to the intensity of the stimulus and the length of the exposure time (Newby, 1972).
^ ^ Hearing losses from intense noise exposure seem to present themselves in two forms: 1) those associated with brief exposure to high-intensity sounds, with partial or complete recovery within a short period of time which are classified as temporary threshold shifts (TTS), and 2) those hearing losses which are permanent, resulting from high-intensity sounds which are classified as permanent threshold shifts (PTS). ^Temporary and permanent threshold shifts depend on the level of the noise, the effective duration of the noise, the frequency spectrum of the noise, the rest periods away from the noise, and the years of repeated exposure to the noise j(Eldrige and Miller, 1968). '
Glorig (1958) indicates that there is a relationship between temporary hearing loss and permanent hearing loss. He suggests that many proposed tests for noise

susceptibility are based on the assumption that the magnitude of temporary threshold shift produced by short exposures to various types of sound can be used to predict individual sensitivity to noise-induced hearing loss. "The research dealing with temporary threshold shift would indicate that 1) exposure to typical industrial noise produces the largest temporary loss at 4000 and 6000 Hz;
2) the amount of temporary loss at the most susceptible frequencies varies with the amount and frequency of permanent loss: the more the permanent loss at any frequency, the less the temporary loss at that frequency; and 5) the major portion of the temporary loss is produced during the first one or two hours of exposure to the noise. Katz
(1978) states that noise-induced permanent threshold shifts are those hearing changes which persist throughout the life of the affected person. Once a threshold shift is permanent, there is no possibility for recovery. Usually, hearing loss produced by the effect of noise is a result of an accumulation of noise exposures repeated on a daily basis for a period of years.,
A distinction needs to be made between "acoustic trauma" and noise-induced hearing loss. Acoustic trauma is the sudden loss of hearing from noise, such as in the case of a blast or explosion which may rupture the tympanic

membrane and destroy some of the hair cells of the Organ of Corti in the cochlea. On the other hand, noise-induced hearing loss is the gradual diminution of hearing perception associated with noise exposure, which also occurs in the Organ of Corti, but which produces a gradually increasing hearing loss (Newby, 1972).
Biological Effects of a. Noise-
Induced Hearing Loss
-^ The primary lesion caused by high-intensitv noise is the destruction of the hair cells of the Organ of Corti in the cochlea. This hair cell degeneration is the cause of biological changes in the sensory cells, which, when prolonged or aggravated, lead to cell death and permanent hearing loss (Johnsson and Hawkins, 1976). Permanent elevation of hearing thresholds after exposure to noise means changes in the hair cell pattern of the Organ of
Corti. Noise can fatigue the nuclei of the auditory pathways, reduce activity of afferent neurons and exhaust the synaptic transmitter at the junctions between the hair cells and nerve endings (Gulick, 1971). After destruction of the hair cells, the nerve fibers may undergo atrophy ^^and degeneration (Guild, 1952).
\ Noise exposure usually causes reduction in sensitiviry for the higher frequencies first, presumably becaus the basal end of the basilar membrane is stimulated by

8 waves of all frequencies and receives more damage than the apical parts of the cochlea which are more concerned with stimulation from low frequency waves. The most susceptible areas of the basilar membrane which are usually first injured from noise exposure are those regions corresponding to the frequencies of 3000-6000 Hz. It is very common to see audiograms showing the greatest amount of impairment in this area. So much so that a 4000 Hz "dip" or
"notch" is taken to be an indication of damage caused by noise exposure and is classified as a symptom of noiseinduced hearing loss (Bohne, 1976). However, although the point of greatest impairment may be localized around 4000
Hz, loss due to noise exposure will spread and extend to frequencies above and below this point if the person with noise-sensitive ears continues exposure to noise over a period of years (Newby, 1972). Once those cells are destroyed, no known mechanism can regenerate them.
Repeated exposures to high-intensity sound will result in cumulative damage to the sensory cells of the inner ear, and will worsen the loss of hearing (Lipscomb, 1974).
Physiological Reactions to Noise
Kryter (1970) describes the effects of noise on the nonauditory system. These include arousal of the autonomic nervous system, which includes the glands.

heart, blood vessels, etc.; the reticular nervous system, which is involved in arousal of the higher brain centers, such as pain and pleasure; and the cortical and subcortical brain centers which include cognition, task performance, thinking, etc.
Welch and Welch (1970) report that loud noise causes a number of reactions in the human body, which the recipient cannot control. Some of these are the constriction of the blood vessels, the paling of the skin, pupil dilation, and muscle tension. Three stages of the effects of noise on the nonauditory system include: .1) the rapid tensing of the muscles at the onset of the noise, 2) the change in heart rate, respiratory breathing, secretions, blood vessel diameter, etc., and 3) the varied effect of hormonal activity. May (1978) describes the effect of the noise on the cardiovascular system as producing a peripheral vasoconstriction, which causes a constriction of the small blood vessels in the limbs, particularly in the skin, which reduces the blood volume and blood flow in these
V parts of the body. A critical aspect of this restriction is that at high intensity levels of noise, it affects the blood supply to the inner ear. She also states that the vasoconstrictive effect of noise may also be affected by the personality of the subject (May, 1978). Hawkins
(1971) states that peripheral vasoconstriction in

10 response to noise supports the findings that endolymphatic oxygen tension is reduced during and after noise exposure, supporting the fact of temporary threshold shift.
Psychological Stress Produced by Noise
The physiological disturbance produced by noise is made known at the conscious level as the feeling of annoyance or stress. Generally, the annoyance increases with the increase in loudness or intensity of the sound.
Fornwalt (1965) states that noise has a deleterious effect on human performance. These effects due to noise can alter sensorimotor performance, discrimination, decisionmaking vigilance, and mental work.
Man's psychological state is a complex of many processes including sensations, thoughts, attitudes, perceptions, feelings,- and actions .'^ Noise or unwanted sourids may have adverse effects when interacting with these processes, and could result in loss in work performance, annoyance, and irritability. There are two main theories which attempt to explain psychological noise disruption.
First, noise causes brief lapses in attention to the relevant stimulus information (Poulton, 1977); and second, noise may cause conditions of cortical over-arousal with resultant loss in behavioral control (Broadbent, 195').

11
Ardvidsson and Lindvall (1976) demonstrated an association between reported feelings of annoyance evoked by noise, the performance efficiency, and the subject's personal experiences of the influence of noise performance.
Their results indicated that the annoyance-inclined individuals in a community may constitute a special risk group that will suffer more from the adverse effects of noise than others will. Boggs and Simon (1968) reported that noise has many effects on people working in industry, such as annoyance, decrease in working efficiency, physiologic changes in heart rate and blood pressure, and psychological distress.
\/-^ In December, 1971, The Environmental Protection
Agency reported that there was some evidence that workers exposed to high levels of noise have a higher incidence of cardiovascular disease, ear-nose-and-throat disorders, and equilibrium disorders than do workers exposed to lower levels of noise (Kavaler, 1975). Reaction to noise alters the emotions and the general health and stability of human organisms. According to Cohen (1969), such reactions contribute to feelings of fatigue, irritability, or tension.
Stress-Prone Personality Types
From the research thus far presented, it seems apparent that noise is considered more harmful, disagreeable, or aversive to some persons than to others.

According to Kryter (1970), the general finding is that the performance of the more anxious personality types is
12 more affected by noise than that of the nonanxious types.
Bryan (1973) states that there is strong evidence that individuals are divided into two groups, the "noise sensitives" and the "imperturbables." He defines the "noise sensitives" as progressively becoming more and more disturbed by the annoying noise while the "imperturbables" rapidly adapt or become used to the noise. Jerger (1965) also makes a distinction between "tough" and "tender" ears and the susceptibility to hearing loss.
There is a wide range of difference in the threshold of annoyance of different individuals. In a group of twenty people, the range in noise level which is necessary to produce annoyance may range from 40 dBHL to 80 dBHL.
This range is the result in part of the differences in personality traits of various individuals (Davis and
Silverman, 1962). Harris (1979) states that generally, extroverts, whose principal interests are turned outwards toward the external world of real things and people, have a higher annoyance rate than introverts, who concentrate more closely on their thoughts and inner feelings, and their achievements and fantasies.
Cohen (1969) reported that subjects who showed the poorest performance under high levels of noise were those

15 revealing greater anxiety and neurotic tendencies, determined by a personality questionnaire. In addition he reported that psychological reactions can be related to the noxious aspect of the sound source, the displeasure an individual is experiencing at the onset of the noise, the person's basic anxiety level, or his evaluation of his situation at the time the noise occurs. Some persons who are not psychologically well adjusted, tend to react to sudden loud noises with feeling of extreme anger or frustration (Lipscomb, 1974).
Bryan (1973) reports that sensititivy to noise correlates significantly with some personality traits.
He states that many noise sensitive people are those who possess the qualities of eagerness, drive, competitiveness, and a high anxiety level, and who are usually artistic or highly creative, intelligent people, who show a great deal of empathy for others.
In 1979, Ickes, Espili, and Glorig reported that stress-prone males were more sensitive to high intensity noise levels. They classified those considered stress prone as having some of the following characteristics: aggressive behavior, very competitive, impatient, hard driving, ambitious, and always rushed.
Jansen (1969) reported that testing vegetative reactions to loud noises indicated individual differences

14 in the degree of disturbance, and suggested that personality dimensions influenced reaction to noise. In addition, he stated that subjects with the emotional factors of nervousness, annoyance, tension, and neurotic attributes, suffer more from noise than do others. In testing persons with 90 dB(A) of white noise, he found changes in peripheral vegetative function, such as the circulatory function.
Tests for Pattern A Assessment
Rosenman, £_t aJ (1964) related personality types according to stress-prone behavior and the central nervous system in the study of coronary heart disease. They established the complicity of the central nervous system and a certain emotional complex in the pathogenesis of coronary heart disease (CHD). They designated the behavior as Pattern A behavior, composed of competitiveness, excessive drive, and an enhanced sense of urgency. Type
B behavior was defined as being the opposite of Type A behavior.
Bortner and Rosenman (1967) defined Pattern A personality as an objective measure made up of performance measures and a questionnaire which included characteristics of a Pattern A personality type. Traits of a Pattern A personality included such features as the desire for

15 recognition and advancement, an eagerness to compete, a need to accelerate physical and mental functions, a sustained drive to achieve, involvement in multiple function with deadlines to meet, and an overt behavior pattern.
Jansen (1969) reported that individuals with these types of personality traits suffered more from noise than others, and reacted physiologically to the noise with vasoconstriction.
In 1969, Bortner devised "A Short Rating Scale as a Potential Measure of Pattern A Behavior," including in it all of these traits of Pattern A behavior, with the opposite extremes included for Pattern B personalities.
Bortner's rating scale can be found in Appendix B. Bortner (1969) reported that by using his scale to rate personality types, he could select 75 per cent of the men that were previously rated type "A" or type "B" by the interview technique.
Ickes, Espili, and Glorig (1979) found that noxious noise can be a factor in producing vasoconstriction and that persons tested with Bortner's personality test demonstrate this vasoconstriction more often that Pattern
B personality types. They also state that there are multiple and complex factors which account for Pattern A behavior, and that if a person possesses enough of these

factors, then he could be classified as Pattern A person-
16 ality type.
Measurements of Vasoconstriction
Exposure to noise, extending over a range level of
90 dB(A) appear to produce a moderate, short-latency rise in heart rate, and thereafter a return to the prestimulus level. However, should the person remain aggravated or annoyed by the noise, then their heart rate would not return to normal but would continue to constrict. The description of peripheral circulation changes is used often to detect changes in the diameter of small blood vessels in response to stimuli, such as noise. Such changes in the circulation in the finger are often used, giving a response from the skin vessels. These include
1) the mean volume of the blood in the finger (BV) , and
2) the magnitude of volume changes (PV) due to the individual's pulse waves in the blood vessel. These are commonly measured by photoelectric transducers, and the results of the stimuli, such as noise, on the blood circulation, are determined. A reduced percentage of amplitude in pulse volume implies vasoconstriction (Harris, 1979).
Jansen (1969) found that by using a plethysmographic recorder, not only blood volume in the skin was reduced because of the vasoconstrictive effect, but also a

decrease was noted in the amplitude of the stroke volume of the heart beat with pulse-induced vasoconstriction.
Purpose and Scope of Thesis
Based on the findings of the research by Ickes,
Espili, and Glorig (1979), there is a need for further research which correlates the factors of noise-induced hearing loss as related to 1) noise intensity in the work environment, 2) amount of noise exposure time, and 3) stress patterns as related to personality. Therefore, the purpose of this thesis is to undertake an investigation among industrial workers to determine if a relationship exists for the amount of noise-induced hearing loss they exhibit and such other factors as personality type, length of time (in years) of noise exposure, and susceptibility to vasoconstriction in the presence of noise.

CHAPTER II
METHODS AND PROCEDURES
This chapter will be concerned with the discussion of the subjects, equipment, and procedure used in this experimentation, and the analytic procedure for the data found.
Subj ects
The subjects used in this study were obtained through the Texas Tech University Maintenance Department. All subjects were working in industrial noise settings at the time of the investigation. They included 35 males, ranging in age from twenty-three years to sixty-one years with a mean age of forty years. Sixteen of the subjects worked in the
TTU Power Plant #1, containing loud machinery, such as boilers,-pumps, turbines, chillers, and generators. Twelve subjects worked in the TTU Power Plant #2, containing the same type of equipment as in Plant #1, along with a very loud emergency back-up generator (which reportedly is only run for a five-minute period twice a month). Seven subjects worked in the TTU Cabinet Shop, containing power tools and hand tools. Daily exposure time to the noise ranged from two hours to eight hours.
18

Noise measurements were taken in these working areas prior to this research with a B ^ K Sound Level
Pressure Meter. All areas in which the noise exceeded
90 dB(A) were marked and signs were posted requiring workers to wear hearing protection in these areas.
Both the TTU Power Plant #1 and the TTU Power Plant #2 required the use of hearing protection in all working areas, except the offices, since the noise levels exceeded the critical 90 dB(A) level. The cabinet shop did not require the use of hearing protection as noise levels were not loud enough to damage hearing.
19
Equipment
Audiometer
A Maico-24 dual channel audiometer was used for the audiological assessment, including pure tone air conduction testing, speech reception threshold testing, and word discrimination testing. This audiometer consists of dual channels which contain a frequency selection dial in the frequency range from 125 Hz to 8000 Hz. Intensity range of the audiometer is from -5 dBHL to 115 dBHL. The iMaico-24 audiometer was also used as the white noise generator, coupled to a Teledyne TDH-59 earphone. The TDH-59 earphones were used also to perform the audiological assessment. All testing was performed in a sound-treated

20 room (Industrial Acoustics Corporation Model #403SP Sound
Suite). A B § K Sound Pressure Level Meter, utilizing a
#4145 microphone attached to a 2cc coupler, was used to calibrate the white noise to 100 dBSPL.
Graphic Recorder
A Grass Model 79 D Polygraph connected to a Grass
PTTI Photoelectric Transducer was used to record vasoconstriction of the subjects. The photoelectric transducer operates on the principle that light is absorbed in tissue in relation to the amount of blood contained in its vascular bed. The reflecting optical system of the device directs a ring of light into the tissue which is dispersed, with a portion of it being reflected out again.
The returning light changes the electrical resistance of the photosensitive surface of the photocell. Any variation in blood content is exhibited in a change in photocell resistance, producing a change in the voltage drop across the photocell. These voltage changes are regulated by the pulsatile blood flow in the tissue under observation (Grass Instruments Instruction Manual, 1972).
Four inch, single channel polygraph chart paper was used. The chart speech was 2.5 mm per second. An alligator clip, serving as a ground and as a protection against static charge, was attached to a piece of loose clothing on each subject. A twelve-inch square of black

21 cloth was placed over the hand to which the photoelectric transducer was attached. This cloth was used to eliminate any ambient light in the testing environment.
Procedure
Each subject was scheduled for one hour sessions.
No subject was told the extent or purpose of the study prior to testing. Subjects were required to avoid noise exposure 24 hours prior to testing. Thirty minutes prior to the start of each session, the audiometer and polygraph unit were switched on to allow adequate warm-up prior to experimentation.
The following outline shows the experimental sequence followed:
1. Case History
2. Bortner's Personality Scale
3. Speech Reception Thresholds
4. Speech Discrimination Scores
5. Pure Tone Air Conduction Testing
6. Plethysmograph Recording
Medical Case History
A complete medical and environmental case history was obtained from each subject. The medical history included information concerning diseases, ototoxic medication, and ear pathologies. Each individual was questioned as to any past medical history which could

22 have attributed to a hearing loss. A copy of the medical and environmental case history may be found in Appendix A.
Average High Frequency Hearing Loss
Each subject was given an audiological evaluation which included pure tone air conduction testing, establishment of speech reception thresholds, and word discrimination scores. An ascending Hughson-Westlake approach (Katz, 1978) was used to establish thresholds.
Particular attention was given to frequencies between
3000-6000 Hz.
An average high frequency hearing loss measure was calculated for each subject by taking the audiometric pure tone thresholds obtained at 3K, 4K, and 6K Hz, bilaterally, adding them together, and dividing the total by 6 (three frequencies in each of two ears).
Noise Exposure History
A complete noise exposure and work history was obtained from each subject. Each individual was questioned as to past working environments which may have included noise exposure. He was questioned extensively regarding noise, such as machinery noise, gunfire and/or artillery noise. In addition, each subject was asked about the number of years of exposure to the various type of noise and whether hearing protection was used.

23
An estimate of the loudness of the noise to which he was exposed was determined by asking the subject if he had to shout in order to hear someone talking.
A subjective noise exposure rating was derived from the reported noise exposure history of each subject and represents a figure on a scale from one to 100. This rating took into account the number of years each individual worked around noise, the type of noise, and any other possible contributing factor, such as gunfire or artillery noise. Since this score was a subjective rating, a test of validity was made by obtaining ratings from two independent judges and correlating the results. The correlation shows an r of .91 and suggests a high degree of validity for the procedure.
Noise Exposure Quotient
A noise exposure quotient was obtained for each subject by using the following formula:
NEQ =
Average High Frequency Hearing Loss
Subjective Noise Exposure Rating
The idea behind the NEQ was to better equate the high frequency hearing loss scores with noise exposure history. For example, if three men all have 20 dB average high frequency hearing loss, but their number of years of noise exposure are one year, five years, and twenty years, respectively, it can be seen that noise

24 susceptibility appears to be greater for subject one since he acquired as much hearing loss in one year as was acquired by the other two subjects in five and twenty years. The NEQ would reflect this by providing scores in this illustration of 20 (high noise susceptibility), 4 (moderate noise susceptibility), and one (low noise susceptibility).
Personality Typing
Each subject filled out Bortner's (1969) "Short
Rating Scale as a Potential Measure of Pattern A Behavior" to determine personality type. The scale as employed here varied from Bortner's original only in terms of the way the subject recorded his score. The scale is composed of fourteen items. Each item is composed of two phrases which consist of contrasting attitudes or personality traits.
The phrases are separated by a line of blocks, with each block counting two points. The subjects were instructed as follows:
Each of us belongs somewhere along the line between the two extremes indicated below. For example, most of us are neither the most competitive person we know. Put an X on the line where you think you belong between the two extremes. Of course, if you feel you belong at the extreme right or extreme left for any of these attributes, then so indicate.
A copy of the rating scale can be found in Appendix B.
Each of the items may yield a possible 24 points. The possible range is from 28 to 336 points. The means of

25 the subject scores in Bortner's study was 211.51 for the
Pattern A group with a a of 30.28, while the mean for the
Pattern B personality group was 178.21 with a a of 55. "9.
Methods of Obtaining Data
Plethysmographic Recordings
During plethysmographic testing, each subject was seated in a sound-proof room with his back to the equipment, so that he could not observe the graphic recorder.
The photoelectric transducer of the graphic recorder was attached to the index finger of the left hand. The hand was covered with a black cloth. A TDH-39 headphone was placed on the better ear of each subject. The alligator clip was attached to a piece of loose clothing. When everything was ready, the subject was instructed as follows:
Please remain as still and as quiet as possible. There will be a five-minute period of silence which will be followed by a fiveminute period of a loud hissing noise. Are there any questions?
Obtaining Data from the
Plethysmographic Recordings
Raw data was obtained from a count made of the recordings of pulsatile blood flow. The operational measure was the number of millimeters of excursion made by the recording pen of the graphic recorder.

26
Every third ascending excursion was counted, totaled, and averaged. The chart was divided into two sections: recordings obtained in noise, and recordings obtained in quiet.
The subjects were divided into two groups according to the results of their plethysmographic recording. The first group consisted of those subjects with significant vasoconstriction and the second group consisted of those subjects with non-significant vasoconstriction. Determination of significant or non-significant vasoconstriction was decided by means of a t test performed on the scores obtained from the graphic recordings. Out of the thirtyfive subjects, sixteen were found to have significant vasoconstriction and were called the Type A group. Nineteen did not have significant vasoconstriction and were called the Type B group. These two groups formed the basis for a statistical comparison between Bortner's
(1969) groups and the groups in this study.
Analysis of Data
There were two major statistical interpretations applied to these data. The first consisted of exploring the relationship between each two factors included in this study by means of a correlational matrix. These factors included:

27
1) personality type
2) high frequency hearing loss
3) magnitude of difference between the average amplitude of excursion in quiet and the average amplitude of excursion in noise
4) subjective noise exposure history
A series of Pearson's Correlations (Cornett, 1975) were performed between these variables. The five per cent level of confidence was chosen as the level of significance .
The correlational matrix of these factors resulted in six individual correlations. The hypotheses were:
1) There will be a significant correlation between difference scores for vasoconstriction in noise and quiet when compared to personality type. 2) There will be a significant correlation between difference scores for vasoconstriction in noise and in quiet when compared to average high frequency hearing loss. 3) There will be a significant correlation between difference scores for vasoconstriction in noise and in quiet when compared to the subjective noise exposure scores. 4) There will be a significant correlation between personality type and the average high frequency hearing loss. 5) There will be a significant correlation between the personality type and the subjective noise exposure score. 6) There will be a

28 significant correlation between the average high frequency hearing loss and the subjective noise exposure score.
The second major means of evaluating this data was to determine how closely the Type A and Type B subjects in this study compared to the Pattern A and
Pattern B subjects in Bortner's (1969) groups which he used to construct his "Short Rating Scale as a Potential
Measure of Pattern A Behavior." A comparison of the means of each personality type group was made. A standard error of difference was obtained and from this a critical ratio was determined.
Then a t test was applied to the means of each personality group in this study relative to their Noise
Exposure Quotients to see if there were a significant difference between the groups. The hypothesis of this evaluation is that the Type A personality group will show a greater Noise Exposure Quotient than will the
Type B personality group.

CHAPTER III
RESULTS AND DISCUSSION
The results of the statistical analysis, along with appropriate tables to aid in interpretation and explanation of the findings, will be found in this chapter. A summary for the raw data for each subject can be found in Appendix
C and Appendix D. A discussion of these findings is included and follows the presentation of results.
Correlations
A number of correlations were computed to determine the relationship between personality type, high frequency hearing loss, noise-induced vasoconstriction, and subjective history of noise exposure. Table 1 is a correlational matrix which summarizes these relationships.
TABLE 1
CORRELATIONAL MATRIX
2 3 4
1 .18 .06 .00
2 .22 .19
3 .69*
*Significant at the 5 per cent level
1= Difference scores for vasoconstriction in quiet and noise
2= Type A - Type B personality score
3= Average high frequency hearing loss
4= Subjective noise exposure history
29

30
Significant Correlations
The only significant correlation was obtained between the amount of high frequency hearing loss of the subjects in this study and their subjective noise exposure score (F- .69, p>.05). Therefore the hypothesis that there will be a significant correlation between the average high frequency hearing loss and the subjective noise exposure score cannot be rejected. This was expected as research supports the fact that noise exposure of sufficient intensity and duration can cause hearing loss (Katz, 1978; Martin, 1975; Northern, 1976).
Insignificant Correlations
Those correlations found to be insignificant at the predetermined 5 per cent level of confidence were between the following factors: 1) the amount of vasoconstriction and the personality type, 2) the amount of vasoconstriction and the amount of high frequency hearing loss, 3) the amount of vasoconstriction and the subjective noise exposure score, 4) the personality type and the amount of hearing loss, and 5) the personality type and the subjective noise exposure score. Therefore, the hypothesis pertaining to these factors are rejected.

31
Bortner's Subjects Compared to
Subjects of tnis Study
The subjects of this study were divided into two groups, those with significant vasoconstriction and those with nonsignificant vasoconstriction, by means of a t test as described in the preceding chapter. Those with significant vasoconstriction were called the Type A personality group, and those with insignificant vasoconstriction were called the Type B personality group.
Using the available data from this study and comparing it with the available data from Bortner (1969) , it was possible to obtain a standard error of difference ( cr j^) .
From this, a critical ratio could also be determined
(CR = D^/a T^) . This procedure provided a means of determining whether Bortner's groups (Pattern A and Pattern B) were drawn from the same or different populations than were the two groups (Type A and Type B) designated in this study. As Table 2 shows, the small, critical ratio between
Bortner's Pattern A group and the Type A group of this study indicate no significant difference and further indicate that the two samples are drawn from the same population. Both are A groups as defined by Bortner. Whereas the large critical ratios between Bortner's Pattern B and the Type B group of this study, as well as between the Type A and Type B groups of this study, indicate

32 significant differences and suggest that the subjects in these comparisons were not drawn from similar populations.
TABLE 2
CRITICAL RATIO
COMPARISONS CRITICAL RATIO
Bortner's A group compared to the Type A group of this study .64
Bortner's B group compared to the Type B group of this study 3.82*
Type A and Type B groups of this study compared to each other 5.22*
These results are further clarified by an inspection of the means of Bortner's subjects when compared to the means of the subjects of this study. Table 3 shows this comparison. In looking at the means of Bortner's subjects compared to the subjects in this study, it is evident that both A personality groups are similar.
However, a comparison of the B groups of both studies show that the mean of the Type B group of this study is consider ably higher. Therefore, it seems that the Type B group of this study most likely contains both Pattern A and Pattern
B subjects. Intuitively it is felt that Pattern B subjects rarely show significant vasoconstriction and therefore the

33
Type A group of this study (significant vasoconstriction) compares favorably with Bortner's Pattern A group. It is further felt that some Pattern A subjects may fail to show significant vasoconstriction and would therefore fall into the B category by the determination of nonsignificant vasoconstriction.
TABLE 3
MEANS OF THE PERSONALITY TYPES
A B
Bortner's means 211.51 178.21
The means of this study 209.56 192.05
Comparison of NEQ Scores for
Type A and Type B^ Subjects
Next, a t test was used to compare the means of the two personality groups (Type A and Type B) in this study relative to their Noise Exposure Quotient scores. The mean
NEQ score for the Type A group was 56.31 and the mean NEQ score for the Type B group was 83.94. The t score between these two means was 5.36 which is significant beyond the
.05 level of confidence. This indicates that the Type B group appears to be the most susceptible to noise exposure.

34
Discussion
In general the findings of this study are not what the hypothesis would have predicted. The analysis of the data failed to show significance for the hypothesis that stress-prone (Type A) personality types are more susceptible to noise-induced hearing loss. To the contrary, results show that it is the Type B personality group which appears to be more susceptible to the harmful effects of high intensity noise.
In addition, the results did not support the inference that vasoconstriction occurring with the Type A group contributes to noise-induced hearing loss by adding anoxia to the effects of noise itself. If the data reported here are valid, doubts may be raised regarding the validity of the assumption that increased noise susceptibility is the result of increased vasoconstriction with resultant anoxia within the inner ear.
The major area of concern regarding validity pertains to the method by which the NEQ scores were computed.
Is the procedure valid or is it not? Do NEQ scores truly reflect noise susceptibility or are these scores so contaminated with other factors, such as pathological ear conditions, as well as the subjectivity employed in assigning scores to the noise-exposure history, as to

35 render the NEQ concept useless? The author thinks not and she would remind the reader that there is really no other way to adequately assess susceptibility among industrial workers who have already acquired noiseinduced hearing loss. The variables are too numerous and too difficult to control independently except in terms of a subjective judgment as to their significance.
Further, the high correlation between two qualified judges (r = .91) adds further validity to this procedure.
Apparently judges can agree.
It would also have been possible to make a direct comparison between the means of the average high frequency hearing loss scores for the two groups by treating hearing loss as a random variable. However, the small sample size employed in this study would not make hearing loss truly random and would be less defensible than the NEQ scores.
A major question raised by this study concerns the physiological mechanism of Pattern A individuals which serves to protect them, while allowing B type individuals to acquire additional hearing loss. There are at least two hypotheses to consider. First, the "allocation of attention" hypothesis by Matthews and Brunson (1979), which suggests that Pattern A subjects are selectively able to focus attention on a task at hand while filtering out extraneous stimuli. How such filtering of

56 auditory stimuli could take place is not clear, but worthy of investigation. Second, there is the possibility that the auditory reflex phenomenon serves as an additional inner-ear protector for Pattern A subjects, by occurring earlier (at a lower sound pressure level) than in B subjects, or by creating impedance of greater magnitude for the A subjects than for the B subjects. Further research into the relationship of stress patterns and noise-induced hearing loss is obviously needed.

CHAPTER IV
SUMMARY AND CONCLUSIONS
This chapter represents an attempt to summarize the entire study in such a way that a person could come to a basic understanding of the general course of the research undertaken in this study. For this reason, the results and conclusions are enumerated in an abstract form.
Purpose
The purpose of this study was to investigate if a relationship exists between industrial noise-induced hearing loss and such other factors as personality type, length of time (in years) of noise exposure, and susceptibility to vasoconstriction in the presence of noise.
Procedure
Thirty-five subjects, all adult males, were used in this study. They ranged in age from twenty-three years to sixty-one years, with a mean age of forty years.
A complete medical and environmental case history was obtained from each subject. The medical history included information concerning diseases, ototoxic medication, and ear problems. The environmental case history
57

38 included noise exposure and work history. Each individual was questioned as to previous noise exposure, and to any past medical history which could have attributed to a hearing loss. A subjective rating on a scale of 0-100 was assigned to each individual.
Each subject completed Bortner's (1969) "Short
Rating Scale as a Potential Measure of Pattern A Behavior" to determine personality type. The results of this test determined which subjects were stress prone.
An audiometric evaluation, which included pure tone air conduction thresholds, speech reception thresholds, and word discrimination scores, was obtained for each subject. Particular attention was given to frequencies between 3000-6000 Hz. An average high frequency hearing loss measure was calculated for each subject by adding the pure tone thresholds at 3000-6000 Hz bilaterally and dividing the total by 6.
Each subject's noise exposure history was subjectively rated on a scale from 1 to 100. A Noise
Exposure Quotient was obtained for each subject by dividing the amount of each individual's average high frequency hearing loss by their subjective noise exposure rating. The idea behind the NEQ was to better equate the high frequency hearing loss scores with noise exposure history.

59
The index finger of the left hand of each subject was attached to a photoelectric transducer connected to a Grass Model 79 D Polygraph recording unit, to measure blood volume. Eacfi subject received 5 minutes of quiet followed by 5 minutes of 100 dBA white noise. Physiological measurements of vasoconstriction were recorded on four-inch, single channel polygraph chart paper, which was marked according to quiet periods and noise presentation periods. The operational measure was the number of millimeters of excursion made by the recording pen. Every third excursion was counted, totaled, and averaged.
The statistical design of this study consisted of two major statistical interpretations. The first explored the relationship between each of two factors included in this study by means of a correlational matrix. The second consisted of a t test applied to the means of each peraonality group (Type A and Type B) in this study relative to their Noise Exposure Quotients to see if there were a significant difference between the groups, hypothesizing that the Type A personality group would show a greater
Noise Exposure Quotient than would the Type B personality group. Then, a comparison was made between the Type A and Type B subjects in this study and the Pattern A and
Pattern B subjects in Bortner's C1969) study. A standard error of difference was obtained and from this a critical

40 ratio was determined. Then, a comparison of the means of each personality type group was made. This was done in an attempt to see how closely the designated Type A group in this study compared to Bortner's Pattern A subjects, which he employed in standardizing his personality test.
Results
Pearson's correlational results indicated no significant vasoconstriction between 1) the amount of vasoconstriction and the personality type, 2) the amount of vasoconstriction and the amount of high frequency hearing loss, 3) the amount of vasoconstriction and the subjective noise exposure score, 4) the personality type and the amount of hearing loss, and 5) the personality type and the subjective noise exposure score.
The correlation between the amount of high frequency hearing loss of the subjects and their subjective noise exposure score was significant at the 5 per cent level of confidence.
The t test used to compare the means of the two personality groups (Type A and Type B) in this study relative to their Noise Exposure Quotient scores showed a significant difference between the two personality groups. Unexpectedly, the Type B personality group showed a greater Noise Exposure Quotient than did the expected Type A personality group. Due to these results.

41 the opposite of what the hypothesis predicted was found.
Instead of the Type A personality types being more susceptible to noise, it was found that it is the Type B personality group which appears to be more susceptible to the harmful effects of high intensity noise.
A statistical comparison made between the Type A and Type B subjects in this study compared to the
Pattern A and Pattern B subjects in Bortner's (1969) study revealed a small critical ratio between Bortner's
Pattern A group and the Type A group of this study, indicating no significant difference between the two groups and further indicating that the two samples were drawn from the same population, and therefore both are
A groups as defined by Bortner. A large critical ratio was found between Bortner's Pattern B group and the
Type B group of this study, as well as between the
Type A and Type B groups of this study, indicating significant differences and suggesting that the subjects in these comparisons were not drawn from similar populations .
Conclusions
Within the limitations of this study, the following conclusions were reached:
1. The findings of this study are not what the hypothesis would have predicted. It was

42 expected to find that stress-prone (Type A) personality types are more susceptible to noise-induced hearing loss. However, the opposite was found, and results showed that the Type B personality group appears to be more susceptible to noise-induced hearing loss.
2. The results of this study did not support the inference that vasoconstriction occurring with the Type A group contributes to noise-induced hearing loss by adding anoxia to the effects of noise itself, and raised doubts regarding the validity of the assumption that increased noise susceptibility is the result of increased vasoconstriction with resultant anoxia within the inner ear.
3. Inasmuch as the Type A group of this study
(significant vasoconstriction) appears to be drawn from the same population as were Bortner's subjects, this study provides replication of the premise originally suggested by Ickes:
Pattern A subjects show significantly more vasoconstriction in the presence of noise than do
Pattern B subjects.

43
4. A major question raised by this study concerned the physiological mechanism of
Pattern A individuals which serves to protect them, while allowing Type B individuals to acquire additional hearing loss.
5. Further research into the relationship of stress patterns and noise-induced hearing loss is obviously needed.

BIBLIOGRAPHY
Arvidsson, 0. and Lindvall, T. "Subjective annoyance from noise compared with some directly measurable effects." Archives of Environmental
Health, 33, 159-165 (1968).
Boggs, D. H. and Simon, J. R. "Differential effects of noise on tasks of varying complexity." Journal of Applied Psychology, 52, 148-153.'
Bohne, B. Noise-induced hearing loss. Hearing Instrumentation, 28 (3), 1976, 14-15.
Bortner, R. "A short rating scale as a poetntial measure of Pattern A behavior," Journal of Chronic Diseases, 22, 87-91 (1969).
Bortner, R. and Rosenman, R. "The measurement of Pattern
A behavior." Journal of Chronic Diseases, 20,
525-533 (1967).
Broadbent, D. E. and Little, E. A. J. "Effects of noise reduction in a work situation," Occup. Psych.,
133-140 C1960).
Bryan, Michael. "Noise laws don't protect the sensitive."
New Scientist, 59, 738-740 (1973).
Cohen, A. "Noise-induced hearing loss--exposures to steady-state noise," presented at the American
Medical Association Sixth Congress on Environmental Health, 22-29 April 1969, Chicago, 111.
Cornett, J. and Beckner, W. Introductory Statistics for the Behavioral Sciences. Columbus^! Ohio: Charles
E. Merrill Publishing Co., 1975.
Davis, Hallowell, and Silverman, S. Richard. Hearing and
Deafness. New York: Holt, Rinehart, and Winston,
Inc., 1960.
Eldridge, A. and Miller, H. Effects of high intensity noise on retention. J. Appl. Psychology 41: 570-
72 (1968). ~ ^ ^
44

Faulkner, L. L. Handbook of Industrial Noise Control. New York:
Industrial Press Inc., 1976.
Fornwalt, Nevin. Investigation into the Effect of Intermittent
Noise of Constant Periodicity vs. Random Periodicity on the Performance of an Industrial Task. Masters Thesis,
Texas Tech University, Lubbock, Texas, 1965.
Friedman, M., and Rosenman, R. "Association of specific overt behavior pattern with blood and cardiovascular findings,"
Journal of the American Medical Association, 169, 1286-
1295, 1959.
Friedman, M., and Rosenman, R. Type A Behavior and Your Heart.
New York: Alfred A. Khopf7~l'^74.
Glorig, A. Noise and Your Ear. New York: Grune and Stratton,
1958.
Guild, S. R. Observations on the pathology of high-tone deafness,
Bui. John Hopkins Hosp., 54, 315-379, 1952.
Gulick, W. Hearing Physiology and Psychophysics. New York:
Oxford University Press, 197T.
Harris, Cyril. Handbook of Noise Control. New York: McGraw-
Hill Book Company, 1979.
Hawkins, J. "The role of vasoconstriction in noise-induced hearing loss." Annals of Otology, Rhinology and
Laryngology, 80, 903-915, 1971.
Hines, W. A. Noise Control in Industry. London: Business
Publications Limited, 1966.
Ickes, W., Espili, J. and Glorig, A. "Pattern A personality and noise-induced vasoconstriction," Journal of Speech and
Hearing Research, 22, 334-342, 1979.
International Wrought Copper Council. Noise in Industry.
London: Unwin Brothers Limited, 1968.
Jansen, G. Effects of noise on the physiological state. Noise as a public health hazard. ASHA Rep 4: 89-98, 1969.
Jerger, James. Modem Developments in Audiology. New York:
Academic Press Inc., 1963.
45

46
Johnson, L., and Hawkins, J. Sensory and neural degeneration with aging seen in micro-disections of a human inner ear.
Annals of Otology, Rhinology, and Laryngology, 81, 1^9-194,
1976.
^^^y J Handbook of Clinical Audiology. Baltimore: Williams and
Wilkins Company, 1978.
Kavaler, Lucy. Noise the New Menace. New York: The John Day
Conpany, 1975.
Kryter, K. D. "The effects of noise on man," Journal of Speech and Hearing Disorders, Monograph Supplement 1, 1950.
Kryter, Karl. Tlie Effects of Noise on Ito. New York: Academic
Press, Inc., 1970.
Lipscomb, David. Noise: The Unwanted Sounds. Cliicago: Nelson-
Hall Company, 1974.
Martin, F. Introduction to Audiology. Englewood Cliffs: Prentice
Hall, Inc., 1975.
Matthews, K. A., and Brunson, B. I. "Alloaation of attention and the type A coronary-prone behavior pattern." Journal of
Personal and Social Psychology, 37, 2081-2090, 1979.
May, Daryl, Handbook of Noise Assessment. New York: Van Nostrand
Reinhold (Company, 1978.
Newby, Hayes. Audiology. New York: Appleton-Century-Crofts,
1972.
Northern, J. Hearing Disorders. Boston: Little, Brown, and
Company, 1976.
Olishifski, B., and Harford, R. Industrial Noise and Hearing
Conservation. Chicago: National Safety Council, 1975.
Poulton, E. C. "A new look at the effects of noise: a rejoinder,"
Psychological Bulletin, 85, 1064-1079, 1978.
Rawson, R. Models PTTI, PTTN, and RPT Photoelectric Transducers:
Instruction Manual. Quincy, Mass.: Grass Medical Instruments, 1969.

47
Rosenman, A., Friedman, M., Straus, R., Wumer, M., Losttchok, R. ,
Hann, W., and Werthessen, A. A predictive study of coronary heart disease. Journal of the American Medical
Association. 189, 15-22, 1964.
Thiessen, G. J. Effects of Noise on Man. Ottawa, Ontario:
National Research Council, 1976.
The University of Michigan School of Public Health and the Institute of Industrial Health. Noise: Causes, Effects,
Measurement, Costs, Control. Ann Arbor, Michigan: The
University of Michigan Press, 1952.
Summerfield, A., Glorig, A., and Wheeler, D. E. Is there a suitable industrial test of susceptibility to noise-induced hearing loss? Noise Control, 4, 40-46, 54, 1958.
Ward, Dixon, and Fricke, James. Noise as a Public Health Hazard.
Washington: The American Speech and Hearing Association,
1969.
Welch, Bruce, and Welch, Annemarie. Physiological Effects of Noise
New York: Plenum Press, 1970.

APPENDIX
A. MEDICAL AND ENVIRONMENTAL CASE HISTORY
B. BORTNER'S (1969) "SHORT RATING SCALE AS A
POTENTIAL MEASURE OF PATTERN A BEHAVIOR"
C. SUMMARY OF RAW DATA
D. SUMMARY OF THE AUDIOGRAMS OF EACH SUBJECT
48

APPENDIX A: MEDICAL AND ENVIRONMENTAL CASE HISTORY
Hearing Difficulty
Onset Progression
Difficulty now: RE LE Understanding Speech in Noise in a Group
Ear Aches:
RE LE
Cause
Duration
Treatment
How often
Effect on Hearing
Last Occurrence
ENT Treatment:
When, By Whom, Results
49
Problem
Any Type of Surgery on the Head or Ears, such as myringotomy, mastoidectomy, etc.
5. Tinnitus:
RE LE
Frequency
Description
Effect on Hearing_
6. Vertigo:
Duration
Description Duration
Frequency Duration
Tinnitus
Precipitating Factors

50
7. Other ENT Complaints:
Colds__ Tonsilitis Sinusitis
Ear Fullness
Headaches Other
8. Familial Hearing Loss:
Relation to Pt.
Age of Onset Etiology
9. Drugs or Medication:
Types of Medication taken or taking
Amount of Intake For What Problem
Aspirin Quinine
Streptomycin ^Mycin drugs
Other Antibiotics
10. Diseases or Serious Illness:
When Relation to Hearing
Ears
Mumps Age Measles Age
Meningitis Influenza
Pneumonia High Fevers
Other
11. Head Trauma or Concussion:
Have you ever had a concussion or hit your head very hard?

Did it bleed?
Did you black out?
How was it medically treated?
12. Noise Exposure:
Where
Type of Noise
Hours of Daily Exposure
Number of Years of Exposure
Past Noise Exposure (work, military, farm, gunfire)
51
Hearing Effect_
Tinnitus
Was hearing protection used?
Was the noise so loud that you had to shout to hear someone talking?

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LO o vO o
(Nl
LO r-^
O
^
LO r-^
O
U-)
O
LO
LO
<—t
LO to
(NJ r-{
O
O
LO t^ o
00 r>-
LO
55
LO LO 00 LO to rH n- rH t o cr> t~- ^ LO
LO CM ' ^
LO LO LO LO LO
O O L O l O O O O L O O O t O L O v O t O to rH to rj- rH CM rH C^ rH 00 oo
LO
LO
(Nl
(NJ o to rH o vO rH
" ^
CT» rH o
(NJ
(NJ
"«* to
(NJ
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CM
CM 00
(NJ o
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00
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00
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( N l t O r ^ f L O O I ^ O O C O ^ O i — I
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(Nl to " ^ LO \ 0 rH — ) r H rH rH
C N J f M ( N J ( N i r v I C M C N J ( N J ( S J ( V 4 f v q ( N | ( N j r s l ( N | ( N | p Q P Q p q p Q p Q p Q p Q e Q q q p Q q q p Q f f l P Q X i P Q
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I U B O T J I U S T S - U O M
= ^g

APPENDIX D: SUMMARY OF THE AUDIOGRAMS OF EACH SUBJECT
56
4
•H
4H
7)
G
O
CJ
O
11>
03
>
P
G
03
CJ
• H
M H
5
6
7
(30
• P-1 cn p>
•H
8
75
4->
CJ
0
•r->
3 cn
9
1 0
Hearing Threshold at Each Frequency in dBHL
Subject Ear
No. Tested 250 500 1000 2000 3000 4000 6000 8000Hz
1 RE
LE
5
5
5
10
5
10
10
15
70
70
75
75
55
65
60
70
2
3
RE
LE
RE
LE
RE
LE
0
0
0
0
5
0
5
10
0
0
0
5
0
0
0
5
0
0
0
0
5
0
0
0
25
25
15
15
10
5
10
0
10
15
15
20
15
20
5
20
5
20
15
30
0
0
15
0
1 1
RE
LE
RE
LE
RE
LE
RE
LE
RE
LE
RE
LE
RE
LE
5
5
5
5
5
5
20
15
85
80
95
95
NR
90
NR
NR
0
0
0
5
0
0
0
10
0
10
10
10
5
15
0
5
0
10
0
0
0
5
10
15
5
20
5
20
0
5
10
20
0
0
5
5
5
5
0
10
5
20
20
25
25
20
20
10
5
5
15
15
15
15
20
10
20
35
30
55
75
30
45
20
5
0
0
5
15
10
10
10
5
10
10
25
15
10
10
10
5
0
5
5
10
10
55
15
40
35
50
35
55
45
50
35

Subject Ear
12 RE
LE
0
0
5
5
10
10
10
10
15
15
15
15
10
15
25
20
13 RE
LE
10
5
15
15
15
10
15
20
35
30
35
40
25
30
25
25
14
15
RE
LE
RE
LE
5
5
5
5
10
5
10
10
20
25
10
25
15
40
20
15
25
20
15
20
15
20
10
5
15
10
15
20
25
5
30
5
16 RE
LE
10
10
5
5
15
10
20
25
35
45
50
45
55
40
70
55

58 o
2 eshold at each Frequency in dBHL
No.
Ear
Tested
250 500 1000 2000 3000 4000 6000 8000 Hz
17 RE
LE
10
5
10
5
0
0
0
10
5
5
5 0
10 5
0
0
18 RE
LE
5
5
5
5
5
5
50
30
65
55
65
60
70
60
65
65
19 RE
LE
20 RE
LE
0
10
0
10
0
15
5
20
15
25
30
25
25
45
15
65
5
5
10
15
10
10
25
25
40
45
50
55
40
55
25
20
21 RE
LE
0
0
0
5
5
5
10
10
20
10
15
20
15
10
0
0
22
23
24
25
Xi
3 t/J
26
27
RE
LE
RE
LE
RE
LE
RE
LE
RE
LE
RE
LE
5
5
5
5
0
10
5
5
25
45
15
60
10
75
30
65
5
5
5
5
10
5
5
5
5
20
15
20
5
0
10
0
5
5
5
5
10
10
5
15
10
10
10
5
10
10
:5
15
5
5
5
10
15
20
25
45
25
55
25
45
15
25
20
25
10
5
15
15
15
5
10
5
30
30
40
45
55
45
60
35
10
5
10
10
10
10
15
15
15
20
20
25
15
10
5
10

59
Hearing Threshold at Each Frequency in dBHL
Subject Ear
No. Tested 250 500 1000 2000 3000 4000 6000 8000 Hz
28 RE
LE
15
10
10
15
10
10
5
5
20
20
20
25
20
20
30
20
29 RE
LE
15
10
10
5
10
5
5
5
15
5
20
20
30
20
10
25
30
31
RE
LE
RE
LE
5
5
0
5
5
10
10
5
25
60
90
100
80
NR
NR
NR
10
10
5
15
10
15
15
25
10
30
15
35
0
10
10
50
32
33
34
35
RE
LE
RE
LE
RE
LE
RE
LE
5
5
5
10
15
15
10
15
85
85
90
95
80
90
65
70
0
0
0
0
10
10
20
20
7 5-
65
70
75
65
70
45
30
10
10
15
15
15
15
25
30
30
40
25
40
20
55
25
30
10
5
10
10
0
10
20
15
25
20
50
25
55
30
60
20