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Carel Ostendorf 1 TENTH INTERNATIONAL CONGRESS ON SOUND AND VIBRATION, ICSV10 THE DUTCH DILEMMA Carel Ostendorf Cauberg-Huygen Raadgevende Ingenieurs Postbus 480 6200 AL Maastricht, The Netherlands [email protected] Abstract In 1993 the Dutch Stichting Bouwresearch SBR (Foundation for Building Research) published a guideline about the measuring and evaluation of vibrations in relation to nuisance (guideline 2). In the period between 1993 and 1995, guideline 2 conquered the Netherlands and in 1996 it was generally accepted. In 1998 this clear world was disturbed by the publication of the Dutch "Handreiking industrielawaai en vergunningverlening" (directions for industrial noise and legislation) by the ministry of VROM (ministry of Housing, Spatial Planning and Environment). This publication contains a chapter about vibrations. It gives limits for vibrations that could be used in legislation. The limits differ from guideline 2, however. In 2002, guideline 2 was revised. The limits in the new guideline have changed compared to the publication of 1993, but they still differ from the Handreiking. So, the Dutch now have two documents (Guideline and Handreiking) which are different in use and limits. The State Council has approved the use of both documents in cases of legislation. The choice of document can be crucial for the legislation. Making the choice can cause a dilemma. This paper will discuss the differences between Guideline and Handreiking, the historic background of the differences and the latest opinions of the State Council. Carel Ostendorf 2 INTRODUCTION Until 1993 the evaluation of vibrations in relation to nuisance was done in the Netherlands according to a German standard called DIN 4150 part 2 from 1975. This choice was made simply because no Dutch standard was available. In 1993 the Dutch Stichting Bouwresearch SBR (Foundation for Building Research) published three guidelines about the measuring and evaluation of vibrations in relation to: ¾ Damage (Guideline 1). ¾ Nuisance (Guideline 2). ¾ Equipment (Guideline 3). Guidelines 1 and 3 will not be discussed in this paper. In the period between 1993 and 1995, Guideline 2 conquered the Netherlands and in 1996 it was generally accepted. In 1998 this clear world was disturbed by the publication of the Dutch “Handreiking industrielawaai en vergunningverlening” (directions for industrial noise and legislation, in this paper called “Handreiking”) by the ministry of VROM (ministry of Housing, Spatial Planning and Environment). Although the main subject of this publication was noise and its regulations, the publication contains a chapter about vibrations. It gives limits for vibrations that could be used in legislation. The limits, however, differ from Guideline 2, but for the method of measuring and evaluation the Handreiking is similar to the Guideline. In September 2002, SBR published the revisions of the Guidelines. Guideline 2 is now called Guideline B to make clear that it is the new edition of the Guideline. The limits in the Guideline have changed compared to the publication of 1993, but they still differ from the Handreiking. So, instead of no standard, the Dutch now have two, which are different in use and limits. Which standard has to be chosen? VIBRATION PARAMETER In both Guideline and Handreiking the vibration parameter that has to be evaluated is called Vmax. Before this parameter is obtained, the vibration signal has to be manipulated in 3 ways: ¾ the frequency range is limited from 1 to 80 Hz; ¾ the vibration signal is weighted; ¾ from the weighted signal, the effective value (rms value) is calculated. By weighting the vibration signal, the difference in the sensitivity of humans for vibrations with a different frequency is considered. This is also done in the German standard DIN 4150. Guideline and Handreiking use the same weighting function as used in the German standard. The weighting of the vibration signal depends on the type of signal: acceleration or velocity. Both functions result in the same weighted vibration signal. Carel Ostendorf 3 For acceleration the weighting follows the function: Ha ( f ) = 1 1 1 • • v 0 2π ( f 0 ) 1 + ( f / f0 )2 [1] In case vibration velocity is measured, the weighting follows: Hv ( f ) = 1 1 • v0 1 + ( f0 / f )2 [2] In these formulas is: ¾ f frequency, in Hz; ¾ f0 5.6 Hz; ¾ v0 1 mm/s. By using the factor 1 in the weighting functions, the weighted vibration V0 signal has lost its unit. This is done to make clear that the vibration signal is weighted. From the weighted signal the effective value (rms value) is calculated according to: t veff (t ) = 1 g (ξ )v 2 (t − ξ )dξ ∫ τ 0 [3] g(ξ) = exp[- ξ/τ]; τ = 0.125 s. ξ = time in e-function The value for τ (0.125 seconds) is the same as used in sound level meters with the time weighting set to “FAST”. For harmonic and periodical vibrations with a frequency over 10 Hz, the value of veff(t) is almost constant and equal to veff. For frequencies below 10 Hz, the value of veff(t) varies around the value of veff. This variation increases for lower frequencies. During the measurement, for every interval i, of 30 seconds, the highest value of veff(t) is determined. This value is called veff,max,30,i. In figure 1 an example of the relation between veff(t) and veff,max,30,i is given. Finally Vmax can be obtained: this is the highest value of veff,max,30,i. Although the determination of Vmax seems to be complicated, it is actually quite simple. Apart from weighting, every sound level meter with the possibility of measuring the rms value using the “Fast”-integration time and a “max hold” function is suitable to do the job. Of course its frequency Carel Ostendorf 4 range for the lower frequencies should be sufficient (1-80 Hz). Figure 1 gives an example of the relation between veff, veff,max,30,i and Vmax. Example Vmax 0.18 0.16 0.14 Veff(t) --->[-] 0.12 0.1 0.08 0.06 0.04 Veff(t) 0.02 Veff,max,30,i 0 0 30 60 90 120 150 180 210 240 270 Time --->[sec] Figure 1: relation between veff, veff,max,30,i and Vmax. EVALUATION OF VMAX General Both Guideline and Handreiking use the same principle of evaluating Vmax using three limiting values called A1, A2 and A3. The evaluation is done in three steps: ¾ If Vmax < A1, then nuisance needs not be expected. ¾ If Vmax > A2, nuisance has to be expected. ¾ If A1 < Vmax < A2 a new parameter (Vper) has to be calculated and compared to A3. In Vper the duration of the vibrations is considered. Note that the first two steps of the evaluation are based on the maximum value (Vmax). One peak in the vibration signal can be enough to exceed the limits of A1 and/or A2. The use of two limits (A1 and A2) to evaluate Vmax has a reason. By not exceeding A1 it is almost certain that nuisance will be prevented. By exceeding A1 a little or not too often it is not sure that nuisance will occur. It depends on the level of the vibration and the duration. One high peak with a short duration can be acceptable. To limit the top level of the vibration A2 is used. Exceeding A2 means that nuisance can be expected even if the vibration lasts only for a few seconds. 300 Carel Ostendorf 5 If the vibration level (Vmax) exceeds A1 but does not exceed A2, the duration of the vibration level combined with the level itself is used to calculate Vper. To evaluate Vper, A3 is used. Calculation of Vper The calculation of Vper consists of two parts: ¾ the calculation of an averaged vibration level based on the measured veff,max,30,i; ¾ the calculation of a time correction factor in which the duration of the vibration is considered. The calculation of the averaged vibration level (vper,meet) is done according to: 1 n 2 v per ,meet = [ • ∑ veff [4] , max,30,i ] n i =1 In this formula, n is the number of 30 seconds intervals in the measurement period. The value of veff,max,30,i is the highest rms value of the weighted vibration signal for every 30 seconds. If veff,max,30,i < 0.1, the value of 0 has to be used in the calculation. The time correction factor depends on the period of time that is considered. In Dutch nuisance regulations about sound and vibrations, every 24 hours is divided into 3 periods: ¾ Day (07.00 – 19.00 hours or 12 hours); ¾ Evening (19.00 – 23.00 hours or 4 hours); ¾ Night (23.00 – 07.00 hours or 8 hours) These periods are used to determine the ratio between the duration of the vibrations and the duration of the period. In formula: Tb [5] T0 Tb represents the duration of the vibration and T0 the duration of the period (12, 4 or 8 hours). To finalise the calculation of Vper, both time correction factor and the averaged vibration level have to be multiplied: T Vper = v per ,meet • b [6] T0 Time correction: This system of evaluation (Vmax and Vper) ensures that limiting values are not used in a rigid way. For nuisance there are no definitive limits which are valid for all people. Carel Ostendorf 6 THE DUTCH DILEMMA To evaluate vibrations and nuisance in case of legislation, the Dutch have two documents available: ¾ Guideline B published by SBR. ¾ Handreiking published by VROM. In 2000 and 2001, the State Council has approved the use of both documents in cases of legislation. Both documents differ in limits, however. A very important difference between Guideline B and Handreiking is that the limits are not based on the same point of view. In the Guideline the function of a building (this is linked to the activity of people in this building) is the base for the limiting value. The way vibrations cause nuisance is affected by the activity of a person. Someone sleeping or reading will be annoyed sooner than someone working in a factory. The basic limits are given in table 1. Table 1: Basic limits according to Guideline B Building categories Day and evening A1 A2 A3 Healthcare and living 0.1 0.4 0.05 Office, education, meeting 0.15 0.6 0.07 Critical working area 0.1 0.1 - A1 0.1 0.15 0.1 Night A2 0.2 0.6 0.1 A3 0.05 0.07 - In the Handreiking, the limits are based on the location of the buildings and copied from the German standard DIN 4150 part 2. Five categories are used: 1. Houses in rural areas. 2. Houses in areas with agrarian activities, in residential areas and in city centres. 3. Houses in areas with an equal ratio between industrial and residential buildings. 4. Houses in areas with industrial activities. 5. Houses on industrial sites. Table 2 gives an overview of the limits used in the Handreiking. Table 2: Category 1 2 3 4 5 Limits used in the Handreiking Limits day and evening (07.00-23.00 uur) A1 A2 A3 day evening 0.1 2 1 0.05 0.15 2.5 1.5 0.07 0.2 4 2 0.1 0.3 5.5 3 0.15 0.4 6 4 0.2 night (23.00-07.00 uur) A1 A2 A3 0.1 0.1 0.15 0.2 0.3 0.15 0.2 0.3 0.4 0.5 0.05 0.05 0.07 0.1 0.15 Carel Ostendorf 7 When evaluating noise in cases of legislation, the rule that the limits depend on the location of the house has been in use for a long time. Furthermore, the State Council has stated that in special cases it is allowed to differ from the limits in the Guideline; for example if the vibration level due to other sources is already higher. Both these opinions are used in the limits in the Handreiking. Table 2 shows that for higher categories, higher vibration limits are used. For a house on an industrial site, A1 is 0.4 while for a house in a city A1 is 0.15. Because of this difference in limits, it is important to make the right choice of category. Unfortunately, this is not always obvious. The descriptions of the categories are not included in Dutch legislation but copied from the German standard DIN 4150 part 2. So, a discussion about the category that has to be used is possible. However, in December 2001, the State Council concluded that the categories 1, 2 and 3 could be used because the limits are severe enough to prevent or restrict nuisance. The limits in category 4 and 5 must not be used without the motivation that these limits will prevent or restrict nuisance. Category 2 is recommended in general in the Handreiking. The corresponding limits are compared to the limits in Guideline B for the category “living”. Table 3 contains all limits for both Guideline B and Handreiking. Table 3: Comparison of limits used in Guideline B and Handreiking Document Day Evening Night A1 A2 A3 A1 A2 A3 A1 A2 A3 Guideline B 0.1 0.4 0.05 0.1 0.4 0.05 0.1 0.2 0.05 (Living) Handreiking 0.15 2.5 0.07 0.15 1.5 0.07 0.1 0.2 0.05 (cat. 2) For the night there is no difference between Guideline and Handreiking. For the day and evening there is. The value of A1 and A3 is the lowest in the Guideline although the difference is not that big. Striking is the difference for A2. According to the Guideline a vibration level over 0.4 (day) causes possible nuisance. The Handreiking, however, permits a vibration level of 2.5! Note that this is a level that can damage the construction of a building. The vibration level of 2.5 is only allowed to happen one period of 30 seconds or Vper will be over A3. To explain the difference in limits and its consequences, two examples are given. ¾ A vibration level Vmax of 0.12 exceeds A1 in the Guideline but is under A2 in the day, evening and night. This means that Vper has to be calculated and compared to A3. If the vibration level veff,max,30,i is constant (0.12) and constantly present, Vper will be 0.12 as well because the averaged value vper,meet is 0.12 and there is no time correction. A value of 0.12 for Vper exceeds A3 in all periods so nuisance Carel Ostendorf 8 needs to be expected. According to the Guideline, the constant vibration level of 0.12 is too high to be legalized. The company which causes this level, has to take measures to reduce the vibrations to less than 0.1, or must limit the time. When the vibration level is present during 2 hours in the day, 0.67 hours in the evening and 1.3 hours in the night, Vper will be under A3. According to the Handreiking a vibration level Vmax of 0.12 is no problem during the day and evening because it is under A1. Only in the night there is a problem because Vper exceeds A3. For the day and evening, it is possible to legalize a vibration level of 0.12. ¾ A vibration level Vmax of 0.5 exceeds A2 in the Guideline and cannot be legalized even if this level only occurs once a day. According to the Handreiking, Vmax exceeds A1 but is under A2 in the day and evening. Vper has to be calculated and compared to A3. If the vibration level occurs twice every hour and no other vibrations are caused (veff,max,30,i < 0.1), vper,meet over 1 hour will be 0.064. If the company is active from 07.00 till 21.00 hours, the time correction will be 0 during the day and 0.71 during the evening. So Vper will be 0.064 in the day and 0.046 in the evening. These values do not exceed A3 in the day and evening and can be legalized. When the Guideline is used a vibration level of 0.5 cannot be legalized. Using the Handreiking this vibration level can be legalized when the time is limited to 14 minutes in the day and 4.7 minutes in the evening. CONCLUSION In cases of legislation, the Dutch authorities have two documents that can be used regarding the evaluation of vibrations. The Handreiking allows higher vibration levels compared to the Guideline and makes it easier for a company to get legislation. On the other hand, the government has to protect its civilians against nuisance by vibrations. The Guideline offers more protection but makes it harder (or even impossible) for a company to get legislation. The choice of the document is free and can be crucial for the result of the legislation. It is a dilemma. REFERENCES Standard: Deel B “Hinder voor personen in gebouwen”, meet- en beoordelingsrichtlijn, (Part B “nuisance for people in buildings” guideline for measurements and evaluation of vibrations), Stichting Bouwresearch (Foundation for Building Research), Rotterdam, September 2002 (in Dutch). Standard: “Handreiking industrielawaai en vergunningverlening” (directions for industrial noise and legislation), by the ministry of VROM (ministry of Housing, Spatial Planning and Environment), Den Haag, 1998 (in Dutch). Proceedings 10th international Meeting on Low Frequency Noise and Vibration and its Control: Ostendorf C.J., “Nine years of Dutch experience in evaluation of vibration in relation to nuisance”, page 111 to 122, York (GB) 2002 .