Page 398 - Industrial Ventilation Design Guidebook

REFERENCES 353

5,4.7 Exposure Limits
The link between the experience of disturbance and the dB(A) level, which has
been analyzed in various studies, indicates that 40 dB(A) would be equivalent
to a degree of disturbance immediately below "somewhat disturbing/' This re-
sult indicates that the ventilation noise in offices should lie beneath this level.
When assessing noise, however, it is necessary to take into account the fact that
the reaction to disturbance is influenced by many noise characteristics other
than the noise level, and also by working environment factors other than the
noise environment. The tolerance to noise is also reduced when working on
8
particularly challenging tasks. Under conditions of exposure and working sit-
uations of this kind, the noise level should not exceed 35 dB(A). Concerning
the dB(A) weighting of the ventilation noise, it should be pointed out that this
alternative can exhibit a very poor correlation to the experience of disturbance
8
by the noise in question. Previous analyses indicate, however, that the correla-
tion of the A-weigh ting procedure is no poorer than that of other weightings,
8
for example dB(B), dB(C), or dB(D). The most reliable conclusions with re-
spect to the negative influence of ventilation noise on exposure are obtained
from an analysis of the actual symptoms of inconvenience.

References
1. Kingsbury, H. F. (1991). In Handbook of Noise Control C. M. Harris (Ed.). McGraw-Hill
New York.
2. Landstrom, U., Kjellberg, A., and Soderberg, L. (1991). Spectral character, exposure levels and
adverse effects of ventilation noise in offices. /. Low Frequency Noise and Vibration 10(3).
3. Paakkonen, R. (1988). Low frequency noise and complaints about indoor climate. Proceedings
of Nordic Acoustical Meeting, 15-17 June, Tampere.
4. Landstrom, U., Soderberg, L., Nordstrom, B., and Kjeliberg, A. (1994). Measures against ven-
tilation noise—Which tone frequencies are least and most annoying. /, Low Frequency Noise
and Vibration 13(3).
5. Landstrom, U., Holmberg, K., Kjellberg, A., Soderberg, L., and Tesarz, M. (1996). Exposure time
and its influence on noise annoyance at work./. Low Frequency Noise and Vibration 14(4),
6. Holmberg, K., Landstrom, U., and Kjellberg, A. (1993). Effects of ventilation noise due to fre-
quency characteristics and sound level./. Low Frequency Noise and Vibration 12(4).
7. Landstrom, U., Kjellberg, L., Soderberg, L., and Nordstrom, B. (1991). The effects of broad-
band, tonal and masked ventilation noise on performance, wakefulness and annoyance. /. Low
Frequency Noise and Vibration 10(4).
8. Landstrom, LI. (1995). Exposure parameters involved in low frequency noise annoyance. Pro-
ceeding "Assessing and Controlling Community Noise with Low Frequency Components,"
Copenhagen, December.
9. Sharlancl, I. (1972). Woods Practical Guide to Noise Control. Woods of Colchester. Ltd.