How is Sound Measured?
Sound is measured in two ways: decibels and frequency.
- Decibels indicate the pressure of sound. Sound waves transfer that pressure from place to place and are expressed in units on a logarithmic scale.
- Frequency is related to a sound's pitch and is measured in units called hertz (Hz), or cycles per second. The pitch of a sound - how high or low it seems - is how you perceive its frequency.
The higher a sound's pitch, the higher its frequency. Generally, high-frequency sounds are more annoying than low-frequency sounds and can be more damaging to hearing. Human hearing is most sensitive to frequencies between 3,000-4,000 Hz. That's why people with damaged hearing have difficulty understanding higher-pitched voices and other sounds in the 3,000-4,000 Hz range.
Children typically have the best hearing and can often distinguish frequencies ranging from the lowest note on a pipe organ (about 20 Hz) to the trill of a dog whistle (up to 20,000 Hz).
Knowledge Check Choose the best answer for the question.
7-3. The _____ a sound's pitch, the ______ its frequency.
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