Audio Frequencies and Sound
Audio Frequencies are only audible to humans across a range of around 20 to 20,000 hertz. This does depend on the individual to an extent, and as we get older the range gets smaller due to over exposure. Frequencies below 20 Hz can usually be felt rather than heard, as long as it is loud enough, where as frequencies above 20,000 Hz are not able to be picked up by our receptors.
| Frequency (Hz) | Octave | Description |
|---|---|---|
| 16 to 32 | 1st | The human threshold of feeling, and the lowest pedal notes of a pipe organ. |
| 32 to 512 | 2nd to 5th | Rhythm frequencies, where the lower and upper bass notes lie. |
| 512 to 2048 | 6th to 7th | Defines human speech intelligibility, gives a horn-like or tinny quality to sound. |
| 2048 to 8192 | 8th to 9th | Gives presence to speech, where labial and fricative sounds lie. |
| 8192 to 16384 | 10th | Brilliance, the sounds of bells and the ringing of cymbals. In speech, the sound of the letter “S” (8000-11000 Hz) |
(http://en.wikipedia.org/wiki/Audio_frequency)
All notes and sounds have a frequency spectrum, clearing showing harmonics visible as distinct peaks and spikes, showing us the components of the sound or signal (http://en.wikipedia.org/wiki/Frequency_spectrum). A sound can have many different frequencies to it, and is picked up by different length receptors in our ears. When one note or tone is active, one length is predominantly stimulated. To gain a full and rounded audio track you need to spread your sound as widely and as equally across the frequency spectrum as possible.
Sound is a vibrating wave that travels through solids, liquids and gases, and is composed of frequencies within our hearing range. Sound waves are characterised by their properties, which are frequency, amplitude, wavelength, intensity, period, speed and direction, or velocity (http://en.wikipedia.org/wiki/Sound). There are many different types of wave, sine waves, square waves, triangular and saw tooth being the most widely used.
Digital recording and production allows music to be stored and transferred across a much wider range of media. They are stored as a series of binary numbers representing samples of the audio signal at equal time intervals, at a rate so fast the human ear perceives it as continuous (http://en.wikipedia.org/wiki/Sound_recording_and_reproduction). The rate an audio file is recorded at can matter hugely when playing out on a big system, and it is advised not to go below 320 kbps in mp3 format. Digital recordings are considered to be higher quality then analog recordings not only because they have a wider frequency response, but because a digital copy will not lose sound quality as it gets used.
