Figure 4: Table showing the Ten Octaves of the Audio Spectrum, giving a few more particulars about the musical, acoustical and subjective qualities of each octave. Also, I’ve given the approximate wavelengths of frequencies in each octave. This, coupled with a basic knowledge of how diffraction and reflection work, is primary information for understanding acoustical problems in rooms.

Octave #	Octave Center Freq.	Octave Range	Physical Wavelengths	Musical Range	Subjective Character and key cues.
10	16000	10-20K	1.5"-.7"	extreme high overtones	Extreme highs, airiness, hiss, sizzle. Upper “edge.”
9	8000	5-10K	3"-1.5"	overtones	Highs, treble, metallic brightness, sibilance, brilliance
8	4000	2.5-5K	6"-3"	overtones	Presence, edge of consonance, brightness, speech recognition cues
7	2000	1.25-2.5K	1'-6"	overtones	Hardness, bite, intensity, loudness, definition. Phantom image cues
6	1000	640-1.25K	2'-1'	Soprano!	Upper pitches, major overtones for most instruments
5	500	320-640	4'-2'	Alto, Soprano	Body, richness, fullness, rounded. Warmth.
4	250	160-320	8'-4'	Middle C, Tenor, Alto	Mudrange. Thickness, tubbiness, thumpiness. Spaciousness in stereo reverb.
3	125	80-160	16'-8'	Baritone, Tenor	Upper bass, harmonic foundation octave.
2	62.5	40-80	32'-16'	Low C, Bass	Lower bass, bottom of musical pitches. Sonic foundation.
1	31.25	20-40	64'-32'	non-pitched bass sounds	Infrasound, unpitched lows, "big" natural sounds, i.e. thunder, earthquakes.

There’s a lot to talk about here. Musical functions exist in various ranges, overall apparent loudness is very much a function of how these octaves are treated, and both the specific tonal qualities of various instruments and the overall quality and character of the music is determined by the distribution of energy among these octaves.

This is where equalization comes from, of course. Equalization can be thought of as one of the primary applications of spectral management, and much or most of what you do in terms of spectral management will be done with equalizers. But before you grab for the Q control of your latest parametric equalizer, there are some other things to consider.

The first has to do with the nature of pitched musical sounds. Such sounds all have “pitches,” such as “G above Middle C.” The range of such pitches, in actual musical practice, is about the sum of human voice ranges, or from about Low C (approximately 65 Hz.) to High C (approximately 1044 Hz.). So the range of such pitches is four octaves. But, the musical sound identified as having a pitch of Middle C does not exist ONLY at 261 Hz. It exists as an array or range of frequencies whose lowest member is probably 261 Hz. and which stretches across all the audible octaves above 261 Hz. Probably, the bulk of the physical power of this musical sound lies in octave bands far from Octave 4.

The point about this is that although there is a range of pitches (as distinguished from frequencies), they are subjective mental constructs we use for organizing our own sense of the “highness” or “lowness” of a sound and patterns of highness and lowness (melody), and they don’t represent the frequencies present in those musical sounds. These frequencies include, as you probably know, the overtones or harmonics of the sound, while the assigned “pitch frequency” is called the “fundamental.” The physical power of that musical sound is the sum of the powers of all the harmonics, and that power is distributed across the spectrum as a function of the relative power of each of the various harmonics.