3. What are current sound protection limits?
The SCENIHR opinion states:
For long term (e.g. workplace) exposure, the level of 85 dB(A) was regarded as the critical intensity; at exposures below 85 dB(A) the hearing losses were significantly lower than for exposures exceeding this value (Welleschik 1979). International standards (ISO 1999:1990; NIOSH revised criteria, 1998) recommended the equivalent sound pressure level (Lequ, 8h) of 85 dB(A) (A filter-weighted, 8-hour working day-weighted average) as the exposure limit for occupational noise (ISO 1999:1990; NIOSH revised criteria, 1974). However, this limit did not guarantee the safety for the auditory system of workers. Therefore, the new EC Directive on the minimum health and safety requirements regarding exposure of workers to the risks arising from physical agents (noise) introduces lower exposure action value at Lequ, 8h = 80 dB(A) (Directive 2003/10/EC).
Noise at Work Regulations (Directive 2003/10/EC, came into force in 2006) recommend three action levels for occupational settings depending on equivalent noise level for 8-hour working day. If these values are converted using the time-intensity trade-off of 3 dB increase for halving the time then the equivalent levels are shown, for example in a night club with sounds of 104 dB(A) 2 minutes of exposure is equivalent to 80 dB(A) Lequ, 8h. Thus, listening to a PMP player at 95 dB(A) for 15 minutes a day would equate to the first action level, under the assumption of this exposure repeated over a long period.
Although the above regulations and limits apply to the workplace, the fact that they rely on the exposure level and duration means that they can equally be applied to other situations where sound has a detrimental effect such as that from personal music players; whether use in workplace, or under leisure situations.
For the purposes of this mandate “noise” has been defined as any unwanted sound. The word “sound” is used consequently throughout this opinion to clarify that the concern is the voluntary listener of personal music players and not the observer of the listening situation. Noise exposures and sound exposures at high sound pressure level may result in similar damage to hearing.
The fundamental unit of noise exposure measurement is A-weighted decibel [dB(A)]. This unit corresponds well with the physiological sensitivity of human and it has been generally adopted in scientific literature.
Sound levels of signals presented through headphones are usually measured by artificial ears. In the link of sound transfer from the open field to the ear, the head and torso effects are usually determined by using a manikin.
The risk for hearing damage, as expressed in Noise at Work Regulations, depends on level and exposure time (“equal energy principle”). This regulation (Directive 2003/10/EC) came into force in 2006 and establishes a minimal action level of hearing protection to the limit of 80dB(A) for an 8-hour working day, equivalent to 89 dB(A) for 1 hour, assuming that below this level the risk to hearing is negligible. The 8-hour equivalent level (Lequ, 8h) is a widely used measure for the risk of hearing damage.
Source & ©: SCENIHR,
Note: The European Directive 2003/10/EC on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (noise) is available at:
The criteria issued by the U.S. National Institute for Occupational Safety and Health (NIOSH) are available at: www.cdc.gov/niosh/topics/noise/