Definition and Properties of Audio Frequency
– Audio frequency refers to a periodic vibration audible to the average human.
– The SI unit of frequency is hertz (Hz).
– It determines the pitch of sound.
– The accepted standard hearing range for humans is 20 to 20,000Hz.
– Frequencies below 20Hz are felt rather than heard, while frequencies above 20kHz are ultrasonic.
Sound Propagation and Frequency Components
– Sound propagates as mechanical vibration waves.
– Frequency components of sound determine its color and timbre.
– Higher pitches have higher frequency, while lower pitches have lower frequency.
– The audible frequency range for humans is typically between 20Hz and 20,000Hz.
– Different species, like some dog breeds, have different hearing ranges.
Frequencies and Descriptions
– Frequencies from 16 to 32Hz are the lower human threshold of hearing and lowest pedal notes of a pipe organ.
– Frequencies from 32 to 512Hz are rhythm frequencies and contain lower and upper bass notes.
– Frequencies from 512 to 2,048Hz define human speech intelligibility and give a horn-like or tinny quality to sound.
– Frequencies from 2,048 to 8,192Hz give presence to speech and contain labial and fricative sounds.
– Frequencies from 8,192 to 16,384Hz provide brilliance and are associated with sounds like bells and cymbals.
Examples of Frequency in Music and Instruments
– Middle C has a frequency of 261.625Hz.
– The lowest note for a tuba or large pipe organ is 16.3515625Hz.
– The highest note reproducible by the average female human voice is approximately 1,046.5Hz.
– The highest note on a standard 88-key piano is approximately 16,744Hz.
– A typical CRT television emits a tone around 16,744Hz while running.
Related Concepts and References
– Absolute threshold of hearing is a related concept.
– The hypersonic effect is a controversial claim for human perception above 20,000Hz.
– Loudspeakers are relevant to audio frequency.
– Musical acoustics is a field related to audio frequency.
– Piano key frequencies and scientific pitch notation are relevant in music theory. Source: https://en.wikipedia.org/wiki/Audio_frequency
An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch.
| Sound measurements | |
|---|---|
Characteristic | Symbols |
| Sound pressure | p, SPL, LPA |
| Particle velocity | v, SVL |
| Particle displacement | δ |
| Sound intensity | I, SIL |
| Sound power | P, SWL, LWA |
| Sound energy | W |
| Sound energy density | w |
| Sound exposure | E, SEL |
| Acoustic impedance | Z |
| Audio frequency | AF |
| Transmission loss | TL |
The generally accepted standard hearing range for humans is 20 to 20,000 Hz. In air at atmospheric pressure, these represent sound waves with wavelengths of 17 metres (56 ft) to 1.7 centimetres (0.67 in). Frequencies below 20 Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. Sound frequencies above 20 kHz are called ultrasonic.
Sound propagates as mechanical vibration waves of pressure and displacement, in air or other substances. In general, frequency components of a sound determine its "color", its timbre. When speaking about the frequency (in singular) of a sound, it means the property that most determines its pitch. Higher pitches have higher frequency, and lower pitches are lower frequency.
The frequencies an ear can hear are limited to a specific range of frequencies. The audible frequency range for humans is typically given as being between about 20 Hz and 20,000 Hz (20 kHz), though the high frequency limit usually reduces with age. Other species have different hearing ranges. For example, some dog breeds can perceive vibrations up to 60,000 Hz.
In many media, such as air, the speed of sound is approximately independent of frequency, so the wavelength of the sound waves (distance between repetitions) is approximately inversely proportional to frequency.
