Frequency
The number of complete vibration cycles per second, measured in hertz (Hz), which sets a sound's pitch.
Also called: frequencies, pitch frequency, hertz, Hz
Frequency is the number of complete vibration cycles a sound makes per second, measured in hertz (Hz). A tone at 440 Hz completes 440 cycles each second. Doubling the frequency raises the pitch by an octave, so 220 Hz and 440 Hz sound an octave apart. The equal-tempered semitone is a frequency ratio of about 1.0595, so each step up multiplies the frequency rather than adding to it. Frequency is distinct from amplitude, which is the size of the vibration. A note can be loud or soft at the same frequency. Intervals are measured in cents from the frequency ratio, using 1200 times the base-2 logarithm of that ratio.
Related terms
- PitchThe perceived highness or lowness of a sound, which for most sounds follows its fundamental frequency.
- AmplitudeThe size of a sound wave's vibration, measured as its greatest displacement from rest, which determines loudness.
- CentA unit for small pitch differences: 1/100 of an equal-tempered semitone, so an octave is 1200 cents.
- A440 (concert A)The A above middle C tuned to 440 Hz, the most widely used reference pitch for tuning ensembles and instruments.