frequency level

3.05  frequency level. Logarithm of the ratio of a given frequency to an appropriate reference value. The base of the logarithm and reference value should be indicated.

Annotation 1          If the base of the logarithm is 2, the unit of frequency level is the octave. The reference value is approximately equal to 16.352 Hz for musical acoustics.

Annotation 2          If the base of the logarithm is 2^1/12, the unit of frequency level is the semitone. The reference value is approximately equal to 16.352 Hz for musical acoustics (see 12.23).

Annotation 3          If the base of the logarithm is 10, then the unit of frequency level is the decade; e.g., 20,000 Hz is three decades above 20 Hz.