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| Year : 2004
| Volume
: 6 | Issue : 23 | Page
: 1-2 |
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| Introduction to the special issue on low frequency noise |
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C Maschke
FeMueller-BBM GmbH, Berlin, Germany
Click here for correspondence address
and email
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How to cite this article:
Maschke C. Introduction to the special issue on low frequency noise. Noise Health 2004;6:1-2 |
Historically, early work on low frequency noise and its effects on health and performance were stimulated by the American and Russian space programs, sources of very high levels of low frequency noise and vibration. Animal experiments in the last 50 years have shown that high levels of low frequency noise and vibration can influence the respiratory rate, the heart functions, the stomach and intestine functions and the function of the central nervous system, as well as increase the rate of abnormal mitosis. The increase of low frequency noise and vibrations in the everyday environment is a new challenge for industrialized nations. This special issue draws attention to these problems.
The frequency range below 200 Hz is often called low frequency noise. The boundary is not fixed, but the range from 10 Hz to 200 Hz is of great interest regarding health. Low frequency noise contains both infrasound and some socalled audible noise. Despite the general understanding that infrasound is not audible, it is possible for humans to perceive infrasound if the sound level is high enough, although there is a change in the aural detection process at which the tonality of the auditory sensation is lost. The phenomena of human perception of low frequency noise is reviewed in the first contribution by Moller and Pedersen (Department of Acoustics, Aalborg University, Denmark).
Low frequency noise is part of the everyday acoustic environment. The noise levels of low frequency noise often lie in the area of the perception threshold where there are considerable individual differences. Noises with a dominant part in the area of low frequency are issued by many technical sources. Vehicles like lorries, busses, trains, airplanes and helicopters are major sources. However, low frequency noises are also issued by stationary sources associated with the heating, cooling or ventilation of buildings. Low frequency noise can spread a very far distance with a low attenuation in the open air and pass through walls and windows with low attenuation, too.
It is difficult for residents to protect themselves against low frequency emissions. The effects of low frequency noise are therefore of great interest to public health. Conventional methods of assessing annoyance, typically based on Aweighted equivalent sound level, are inadequate for low frequency noise and lead to incorrect decisions by regulatory authorities. This is the conclusion of the contribution by Leventhall (Noise and Vibration Consultant, Ashtead, United Kingdom). The known effects according to selected physiological parameters, subjective complaints and performance is reviewed by Schust (Federal Institute for Occupational Safety and Health, Germany).
Low frequency noise in the living environment can represent an extreme distress for persons who are sensitive to low frequency sound. Such sensibility can be the result of a natural highsensitivity level or one which can be brought on in the course of the life. The association between low frequency noise and stress as viewed through stress hormone excretion as well as respiratory system impairment in children is discussed by Ising (Berlin Centre of Public Health, Germany) and colleagues. The findings suggest that great attention must be given to nightly sound exposure. The disturbing effect of nightly noise on sleep is recognized generally. There are a large number of studies in which the effect of nightly traffic noise on sleep and wellbeing was examined. However, there is usually little known about what percentage of that noise is low frequency noise. Only the A-weighted sound pressure level is indicated in many publications. The special effect of low frequency noise on sleep is reviewed by Persson Waye (Department of Acoustics, Aalborg University, Denmark).
Low frequency noise frequently appears together with vibrations. Sound in air with a low frequency character can activate vibrations in housing structures. Conversely, low frequency sounds also arise as a result of vibrations in housing structures (secondary sound in air). Room resonance can highly increase the low frequency sound. The disturbing effect of low frequency immission and vibration in residential buildings is presented by Findeis and Peters (Department Noise and Vibration Protection, Brandenburg, Germany).
The isolated assessing of air sound or vibrations is only valid provided that no (noteworthy) interactions occur. There are only few experimental examinations on this topic. One of the few studies was carried out by Sueki et al. (1989) in Japan. In the experiments the vibration perception thresholds and the threshold of adverse effects of vibrations (e.g. languor) was examined with and without low frequency noise. The experiments showed, for example, that audible low frequency sound can reduce the perception threshold for vibrations. The adverse effects of vibrations were stronger with the presence of low frequency noise.
The effect of low frequency noise and vibrations on health is described by Branco (Center for Human Performance, Alverca, Portugal) and his colleagues as vibroacoustic disease (VAD). VAD was first documented in people employed as airplane technicians, commercial and military pilots, mechanical engineers, restaurant workers and disc jockeys. In the meantime, VAD has been seen in populations which were exposed to low frequency noise that is part of everyday environments.
Experiments with both animals and humans have shown that the vibroacoustic stressor causes thickening of cardiovascular structures (cardiac muscle and blood vessels). The pericardial thickening without inflammatory process and in absence of diastolic dysfunction (pathological changes of the diastolic blood pressure function; second value of the blood pressure measurement) is therefore the clinical characteristic of VAD. Depression, increased irritability and aggression, a tendency for isolation and decreased cognitive skills (flexibility of thinking) are additional parts of the clinical picture of VAD.
One of the future challenges of noise effect research is to quantify the effect of environmental low frequency noise in combination with vibration, according to annoyance, performance and health indicators. The state of knowledge as to the extra aural effects of low frequency noise is altogether still unsatisfactory. Some investigations give evidence that the effect of low frequency noise in the environment is highly underestimated today. It is hoped that this special issue of Noise & Health brings more attention to the problem of low frequency noise in the living environment.
Correspondence Address:
C Maschke
FeMueller-BBM GmbH, Zweigbuero Berlin Nollendorfplatz 3-4, Berlin 10777
Germany
 Source of Support: None, Conflict of Interest: None  | Check |
PMID: 15273019 
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