7.08  filter nominal midband frequency. For a set of contiguous one-third octave bandpass filters, frequency of a specified series such as the preferred-frequency series that includes 100, 125, 160, 200, 250, 315, 400, 500, 630, 800, and 1000 hertz, extended by successive multiplication or division by 10. For a set of contiguous octave bandpass filters, the nominal midband frequency is one of a series such as the preferred frequency series that includes 16, 31.5, 63, 125, 250, 500, 1000, 2000, 4000, and 8000 hertz, extended by successive multiplication or division by 103. Unit, hertz (Hz).

Annotation 1          Preferred frequencies are defined in ANSI/ASA S1.6-1984 (R 2011) American National Standard Preferred Frequencies, Frequency Levels, and Band Numbers for Acoustical Measurements. The reference frequency for Band Numbers is 1 Hz.

Annotation 2          Over any 1:10 range of frequency the average difference between exact and nominal midband frequencies for the G10frequency ratio is –0.047%; the maximum difference is –0.944%. Over the usual audio range of frequency from 20 Hz to 20,000 Hz the average difference between exact and nominal midband frequencies for the G2frequency ratio is –0.202%; the maximum difference is 0.825%.

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