Figures for Chapter 8
Candidacy
Dillon (2001)
Hearing Aids
Speech audibility in quiet and in noise
100
80
Threshold
60
40
20
0
125
(b)
(a)
Level (dB SPL)
Level (dB SPL)
100
80
60
40
Threshold
20
Noise
0
250
500
1000 2000 4000 8000
125
250
Frequency (Hz)
500 1000 2000 4000 8000
Frequency (Hz)
Figure 8.1 The long-term 1/3 octave speech spectrum for a) speech at 55 dB SPL
in a quiet place, and b) speech at 85 dB SPL in a noisy place. Each speech
spectrum includes the 30 dB dynamic range from the weakest useful elements of
speech to the most intense elements (shown as the vertical lines). The portion of
the speech range that is audible above noise and hearing thresholds is thickly
shaded. The normal threshold of hearing is shown as the lower dotted line.
Source: Dillon (2001): Hearing Aids
Frequency (Hz)
125 250 500 1k
2k
4k
0
Speech sounds and
the speech spectrum
Hearing threshold (dB HL)
20
f
40
p
m
60
8k
ee
or
ar
k
sh
th
t
s
80
100
120
Figure 8.2 The speech spectrum, including a 30 dB dynamic
range at each frequency, for speech at a long- term level of
65 dB SPL. The approximate locations of the spectral centre
of a few speech sounds are indicated.
Source: Dillon (2001): Hearing Aids
Cochlear implant speech-score probability
Probability (%)
100%
CUNY sentences
in 10 dB SNR
80%
CUNY sentences
in quiet
60%
40%
20%
CNC
words
0%
0
20
40
60
80
100
Speech test score (%)
Fig 8.3 Probability of implanted adults exceeding the indicated
speech score for CNC (consonant-nucleus-consonant) words,
CUNY/SIT sentences (City University of New York speech intelligibility
test) in quiet, and CUNY/SIT sentences in noise with a 10 dB SNR.
Source: Dillon (2001): Hearing Aids
Implant versus hearing aid probability
100
CUNY in noise
Probability (%)
80
IMSPAC
60
CUNY in quiet
40
20
CNC words
0
60
80
100
120
PTA Threshold (dB HL)
Figure 8.4 Probability of a speech identification score for an
implanted adult or child being greater than the anticipated score
obtained with hearing aids, as a function of pure tone hearing levels.
Source: Dillon (2001): Hearing Aids
Implant improvement re hearing aids
Likely score increase (% points)
60
40
CUNY in noise
20
IMSPAC
0
CUNY in quiet
-20
-40
CNC words
-60
60
80
100
120
PTA Threshold (dB HL)
Figure 8.5 Average increase in scores (implant minus hearing
aids) as a function of pre-implant hearing threshold.
Source: Dillon (2001): Hearing Aids