Perception of sound: Audible frequency spectrum
We have said how the frequencies audible by the human ear go from 20Hz to 20KHz. Lets now try and label these frequencies so as to have a better idea of where to place the sounds we listen to.
Table 2.2. The Frequency Spectrum
| Name | Range | Extension (octave extension) | Comments |
|---|
| Subsonic Frequencies | 1Hz-20Hz | 4 |
They are not audible by the human ear. They are generated by earthquakes for example, or by large reed organs in churches
| | Very low frequencies | 20Hz-40Hz | 1 |
It is the lowest octave audible to the human ear. The Bass-drum in a drum-kit and the low notes on a piano as well as the sound of thunder or air-conditioning are within this range
| | Low frequencies | 40Hz-160Hz | 2 | Almost all low frequencies in music are within this range | | Middle-low frequencies | 160Hz-315Hz | 1 | The Central (C) note on the piano (216 Hz) is within this range. This range contains many of the sound signal informations that can be potentially altered by poor equalizing | | Middle frequencies | 315Hz-2.5KHz | 3 | The ear's sensitivity is at its highest in this range. This band's sound-quality, if taken individually, is similar to that of telephones. | | Middle frequencies | 2.5KHz-5KHz | 1 |
In this range the isophonic curve
[Isophonic Curves (Equal Loudness Contours)
]
has its highest peak and is therefore the range the ear is most sensitive to. To equalize an instrument in this range increases its presence in the mix bringing it in front of the other sounds (this is true if you want to obtain the opposite too: if you want to hide an off-key voice you've been forced to keep in the recording because the singer is the record label's boss' friend's son-in-law, take away the frequencies at 3KHz and drown it in reverb...it'll become a distant, almost metaphysical presence!).
| | High Frequencies | 5KHz-10KHz | 1 |
It is the range in which we perceive the sparkle of sounds because it contains much of the harmonic content of the notes generated in the previous ranges. The acoustic energy levels are very low here and the consonants ‘s', ‘t' and ‘c' belong to this range.
| | Very high frequencies | 10KHz-20KHz | 1 |
Even less acoustic energy is to be found in this range. Only the highest harmonics of certain instruments are here. If we were to eliminate the latter however (with an equalizer for example) the mix would become dull
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See also:
Related topics on Wikipedia
