How do we measure sound waves?

Sound energy travels in waves and is measured in frequency and amplitude.

The energy in a sound wave can be measured using Decibels. The Decibel Meter shows examples of things that make noise and measurements in decibels.

Amplitude measures how forceful the wave is. It is measured in decibels or dBA of sound pressure. 0 dBA is the softest level that a person can hear. Normal speaking voices are around 65 dBA. A rock concert can be about 120 dBA.

Sounds that are 85 dBA or above can permanently damage your ears. The more sound pressure a sound has, the less time it takes to cause damage. For example, a sound at 85 dBA may take as long at 8 hours to cause permanent damage, while a sound at 100 dBA can start damaging hair cells after only 30 minutes of listening.


Frequency is measured in the number of sound vibrations in one second. A healthy ear can hear sounds of very low frequency, 20 Hertz (or 20 cycles per second), to a very high frequency of 20,000 Hertz. The lowest A key on the piano is 27 Hertz. The middle C key on a piano creates a 262 Hertz tone. The highest key on the piano is 4186 Hertz.


Decibel Exposure Time Guidelines

Continuous dB

Permissible Exposure Time

85 dB

8 hours

Accepted standards for recommended permissible exposure time for continuous time weighted average noise, according to NIOSH and CDC, 2002. For every 3 dBs over 85dB, the permissible exposure time before possible damage can occur is cut in half.

88 dB

4 hours

91 dB

2 hours

94 dB

1 hour

97 dB

30 minutes

100 dB

15 minutes

103 dB

7.5 minutes

106 dB

3.75 min (< 4min)

109 dB

1.875 min (< 2min)

112 dB

.9375 min (~1 min)

115 dB

.46875 min (~30 sec)