Similar term(s): audio frequency, sound frequency, sound wave.
Frequency is the measurement of the number of times that a
repeated event occurs per unit of time.
The frequency of wave-like patterns including sound,
electromagnetic waves (such as radio or light), electrical signals, or other
waves, expresses the number of cycles of the repetitive waveform per second.
In SI units, the result is measured in Hertz (Hz), named
after the German physicist, Heinrich Rudolf Hertz. 1 Hz means one cycle (or
wave) per second.
Frequency has an inverse relationship to the concept of
wavelength (the distance between two peaks) such that the
frequency is equal to the velocity divided by the wavelength.
For humans, hearing is limited to frequencies between about 20 Hz and 20 000
Hz, with the upper limit generally decreasing with age. Other species have a
different range of hearing.
Humans are particularly sensitive to intermediate frequencies (3 000 to 4 000
Hz), while lower and higher-pitched sounds appear less loud. As a reference the
lowest and the highest note on a grand piano are 27 Hz and 4 000 Hz.