Frequency describes how many times a vibration repeats itself in one second. Pitch is the perception of the frequency of sound with high pitches corresponding to high frequencies and low pitches corresponding to low frequencies. Frequency is measured in Hertz (Hz).
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Sound is produced when the molecules in the air are caused to vibrate. A sound can be described in terms of, for example, frequency or intensity. The sound intensity indicates the magnitude of the vibrations of the air molecules and frequency the number of vibrations per second.
Frequency is expressed in Hertz, which represents the number of vibrations per second. 440 Hz (pitch A) is a frequency of 440 vibrations per second.
The human ear can detect frequencies in the range from approximately 20 to 20,000 Hz. (From foghorn to piccolo). The lower the pitch, the lower the frequency. The higher the pitch, the higher the frequency.
Perception of the frequency of sound |
The ear is not equally sensitive to all frequencies. The human ear is most sensitive to sounds in the range from 1,000 to 4,000 Hz. The ear is less sensitive to low and high pitch tones, which need to be of higher intensity before they can be perceived by the ear.
Pure tones consist of one frequency. Most everyday sounds are not pure tones but a combination of many frequencies. Pure tones are used for some hearing tests, such as pure-tone audiometry.
Speech lies in the frequency range from 250 to 8,000 Hz, and is composed of many frequencies that need to be perceived very accurately. An ear with normal hearing can distinguish between frequencies that differ as little as 5 Hz or 0.5%.
SEE ALSO:
SoundSound intensityDecibel
