Adverse health effects of noise : Sources with low-frequency components. Disturbances may occur even though the sound pressure level during exposure is below 30 dBA. The evidence on low-frequency noise is sufficiently strong to warrant immediate concern. Various industrial sources emit continuous low-frequency noise (compressors, pumps, diesel engines, fans, public works); and large aircraft, heavy-duty vehicles and railway traffic produce intermittent low-frequency noise. Low-frequency noise may also produce vibrations and rattles as secondary effects. Health effects due to low-frequency components in noise are estimated to be more severe than for community noises in general (Berglund et al. 1996). Since A-weighting underestimates the sound pressure level of noise with low-frequency components, a better assessment of health effects would be to use C-weighting. When prominent low-frequency components are present, measures based on A-weighting are inappropriate. However, the difference between dBC (or dBlin) and dBA will give crude information about the presence of low-frequency components in noise. If the difference is more than 10 dB, it is recommended that a frequency analysis of the noise be performed.
See WHO - Guideline Values: Section 4.3 Specific Environments - Chapter 4. In residential populations heavy noise pollution will most certainly be associated with a combination of health effects. For example, cardiovascular disease, annoyance, speech interference at work and at home, and sleep disturbance. Therefore, it is important that the total adverse health load over 24 hours be considered and that the precautionary principle for sustainable development is applied in the management of health effects.
See WHO - Guideline: Adverse health effects of noise - Chapter 3.
Low frequency noise and stress:
Stresses may be grouped into three broad types: cataclysmic stress, personal
stress and background stress. Cataclysmic stress includes widespread and
devastating physical events. Personal stress includes bereavements and
similar personal tragedies. Cataclysmic and personal stresses are evident
occurrences, which are met with sympathy and support, whilst their impacts
normally reduce with time. Background stresses are persistent events, which
may become routine elements of our life. Constant low frequency noise has
been classified as a background stressor (Benton, 1997b; Benton and
Leventhall, 1994). Whilst it is acceptable, under the effects of cataclysmic and
personal stress, to withdraw from coping with normal daily demands, this is not
permitted for low level background stresses. Inadequate reserves of coping
ability then leads to the development of stress symptoms. In this way,
chronic
psychophysiological damage may result from long-term exposure to low-level
low frequency noise.
Changes in behaviour also follow from long-term exposure to low frequency
noise. Those exposed may adopt protective strategies, such as sleeping in
their garage if the noise is less disturbing there. Or they may sleep elsewhere,
returning to their own homes only during the day. Others tense into the noise
and, over time, may undergo character changes, particularly in relation to
social orientation, consistent with their failure to recruit support and consent
that they do have a genuine noise problem. Their families and the investigating
EHO may also become part of their problem.
The claim that their "lives have
been ruined" by the noise is not an exaggeration, although their reaction to the
noise might have been modifiable at an earlier stage. See section 10 of Report for Defra by Dr Geoff Leventhall:
A Review of Published Research on Low Frequency Noise and its Effects (PDF file).
Noise annoyance from wind turbines - a review (PDF file)
(Annoyance caused by diesel trains decreases when the modulation depth was reduced)
Low Frequency Noise - Technical Research Support for DEFRA Noise Programme (PDF file)
(Extracts of this publication may be made for non-commercial in-house use, subject to the source being acknowledged)
A Review of Published Research on Low Frequency Noise and its Effects (PDF file)
(Report for Defra by Dr Geoff Leventhall Assisted by Dr Peter Pelmear and Dr Stephen Benton)
The above publication (excluding the logo) may be reproduced free of charge in any format or medium
provided that it is reproduced accurately and not used in a misleading context. The material must be
acknowledged as Crown copyright with the title and source of the publication specified.
Note: Low frequency noise causes extreme distress to a number of people who are
sensitive to its effects. Such sensitivity may be a result of heightened sensory
response within the whole or part of the auditory range or may be acquired.
The noise levels are often low, occurring in the region of the hearing threshold,
where there are considerable individual differences. There is still much to be
done to gain a fuller understanding of low level, low frequency noise, its
effects, assessment and management. Survey papers of low frequency noise
and its occurrence include (Backteman et al., 1983a; Backteman et al., 1983b;
Backteman et al., 1984a; Backteman et al., 1984b; Berglund et al., 1996;
Broner, 1978a; Hood and Leventhall, 1971).
Example of the Impact of Modulation: At the
highest modulation depth at 2.0Hz modulation frequency, the level was
reduced by 12.9dB averaged over the subjects. This work confirms the
importance of fluctuations as a contributor to annoyance and the limitation of
those assessment methods, which do not include fluctuations in the
assessment. (See: Report for Defra by Dr Geoff Leventhall Assisted by Dr Peter Pelmear and Dr Stephen Benton)