Range of sound
Sound pressure is measured in decibels, or tenths of a Bel. Sound pressure level is indicated as dB SPL.
Since the human ear can detect sounds with an extensive range of amplitude, a decibel scale is used to
simplify the measurement results. For example, the ratio between the threshold of hearing and threshold
of pain in the human ear if measured in true energy is 10,000,000 times! The same range using the dB
scale is 0 - 140 dB referenced to 20 µPa (Micropascals).
The quietest sound that humans can hear has an amplitude of approximately 0 dB. Prolonged exposure
to sound pressure levels exceeding 85 dB can cause permanent damage to the ear. Sound levels in
excess of 130 dB are more than the human ear can safely withstand and can result in serious pain and
permanent damage.
What do the standards say?
Many organizations have studied and analyzed the effects of high sound exposure on hearing. As a
result, standards were developed to regulate personal noise exposure. In the United States, the
Occupational Safety and Health Administration (OSHA), the Mine and Safety and Health Administration
(MSHA), and the American Conference of Governmental Industrial Hygienists (ACGIH) have all created
regulations and limitations on total permissible noise exposure. International standards are specified by
the health and safety regulations such as the European Union (EU) Directive 2003/10/EC. Additionally,
the International Electrotechnical Commission (IEC) IEC-61252 has specific guidelines and regulations to
monitor noise in the workplace.
To access these copyrighted standards, please refer to the following:
OSHA - http://www.osha.gov
MSHA- http://www.msha.gov
NIOSH - http://www.cdc.gov/niosh/topics/noise
ACGIH - http://www.cdc.gov/niosh/topics/noise
IEC - http://www.iec.ch
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