An excess of sound, whether in intensity or duration, can generate adverse effects or permanent damage to the hearing. Hearing can be damaged to the point of clinical deafness, and short- or long-term ringing in the ears (tinnitus) can result. This can be brought about either by exposure to continuous sound or by short-lived sound peaks. Such high levels of sound are not only found in the workplace, but also in leisure activities, for example, in listening to loud music. Sound levels in discotheques can approach those in noisy workplaces, where protective measures for the affected workers are prescribed by law. Sound measurements taken on a random sample basis in discotheques and at live-music events have recorded music noise levels of between 90 and 110 a-decibels (dB(A)).
The Health and Safety at Work Act ( Arbeitsstättenverordnung - ArbStättV, 2004 ) decrees that the criterion sound level in places of work, when taken over an 8 hour period, may not exceed 85 dB(A). This requirement was made binding under German law on 09.03.2007 in the course of the implementation of the EU Directive 2003/10/EC for the protection of workers from adverse noise effects ( Health and Safety Ordinance on Noise and Vibration - LärmVibrationsArb SchV ). In comparison to earlier regulations, the prevention and protection values (“upper” and “lower” threshold values) have been reduced by 5 dB (A). In accordance therewith the employer is under obligation to provide the workforce with ear protection when the criterion level reaches or exceeds 80 dB(A) (peak value 135 dB(Cpeak). From a level of 85 dB(A) (peak value 137 dB(Cpeak)), the employer is obliged to ensure that ear protection equipment made available is being used according to law. Quantitative estimations in respect of risk of hearing damage can be undertaken on the basis of the ISO 1999 guideline or guideline 2058 of the Association of German Engineers (VDI), section 2: ( Assessment of noise in the working area with regard to the risk of hearing damage ).
In addition, “noisy“ toys (such as cap pistols, whistles, and football rattles), portable music players, and fireworks, can have adverse impacts on hearing. Portable music players with headphones can generate music sound levels of up to 110 dB(A). This corresponds to the noise level generated by a pneumatic hammer. Toy pistols have given rise to short-lived peak levels of 160 dB(A) and more when fired close to the ear.
Noise related damage to hearing is irreversible
In the cases of both lasting exposure to high levels of sound and short-lived, very intense sound peaks, the hair cells in the inner ear with their very fine hairs (stereocilia) can be permanently damaged. Their function is to transform sound vibrations into electrical signals, which are conducted via the nervous system. Loss of hearing due to noise occurs especially through exposure to high-pitched sounds (with frequencies of around 4,000 Hertz). The ability to understand speech and general communication in the presence of other background noise (such as in restaurants) can be affected. Longer-term exposure can also serve to reduce the ability to hear lower pitched sounds. Hair cells once destroyed do not grow back, which means that noise related damage to hearing is irreversible.
Unusual noises in the ears after exposure to loud noise, for example after listening to loud music, should be seen as a warning signal from the body. Damage to hearing can, however, also occur without such attendant noises in the ear.
Hearing loss in growing children
In the course of the German Environmental Survey 2003/06 (GerES IV) for Children, the Federal Environment Agency ( Umweltbundesamt – UBA ) investigated around 1,000 children between the ages of eight and fourteen for exposure to noise. In addition, hearing tests were carried out in the children’s homes between 2003 and 2006. These screening tests showed that around 13% of the children surveyed demonstrated hearing loss at at least one test frequency of more than 20 dB(A), with 2.4 % showing an even higher loss of more than 30dB(A). This meant in practice that they required a volume of 20 to 30 dB(A) more than the other children in order to be able to hear the test tone. Noise exposure from leisure activities could be one of the causes of this hearing loss.
Protecting the hearing
In order to protect one’s own hearing earplugs should be used at loud concerts or in discos. Music through headphones should be listened to at a moderate volume, and only devices with a built-in volume regulator should be purchased. Parents buying sound emitting toys should make sure by means of comparison that they choose quieter toys. The CE seal of product safety alone is not a sufficient guarantee.
The Federal Environment Agency recommends the avoidance as far as possible of high levels of sound in leisure activities, or, if this is not possible, the wearing of ear protectors. The ears can, of course, cope with individual instances of higher volume, but it is then important to allow them sufficient recovery time at sound levels of under 70 dB(A). Regular exposure to higher levels of noise without ear protectors should be avoided.