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751 Hearing Conservation Program Management
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How Sound is Measured

Sound is measured in two ways: decibels and frequency.

How Old Are Your Ears

The Decibel (dB) is a measure of the amount of sound pressure. The dB is measured on a logarithmic scale which means that a sound with an intensity that is twice that of a reference sound corresponds to an increase of little more than 3 decibels.

Frequency (f) is a measure of the number of vibrations (i.e., sound pressure cycles) that occur per second. It is measured in hertz (Hz), where one Hz is equal to one cycle per second. The pitch of a sound - how high or low it seems - is how you perceive its frequency; the higher the pitch, the higher the frequency. High-frequency sounds are generally more annoying than low-frequency sounds and can be more harmful to hearing.

Human speech frequencies are in the range of 500 Hz to 4,000 Hz and is most sensitive to frequencies between 3,000 and 4,000 Hz. That's why people with damaged hearing have difficulty understanding higher-pitched voices and other sounds in the 3,000 to 4,000 Hz range.

Take this free online hearing test to see if you have hearing loss.

More comprehensive information on the various qualities of sound from OSHA's Technical Manual, Section III, Chapter 5.

Knowledge Check Choose the best answer for the question.

1-4. Human hearing is most sensitive to frequencies between _____.