Octave band

Analyzing a source on a frequency by frequency basis is possible but time consuming. The whole frequency range is divided into set of frequencies called bands. Each band covers a specific range of frequencies. For this reason, a scale of octave bands and one-third octave bands has been developed. A band is said to be an octave in width when the upper band frequency is twice the lower band frequency. A one-third octave band is defined as a frequency band whose upper band-edge frequency (f2) is the lower band frequency (f1) times the cube root of two.

Octave Bands

Calculation

%% Calculate Octave Bands in Matlab
fcentre = 10^3 * (2 .^ [-6:4])
fd = 2^(1/2);
fupper = fcentre * fd
flower = fcentre / fd

Naming

Band Number Quoted Frequency Calculated Frequency A-Weighting Adjustment
1 16 Hz 15.625 Hz
2 31 Hz 31.250 Hz -39.4 dB
3 63 Hz 62.500 Hz -26.2 dB
4 125 Hz 125.000 Hz -16.1 dB
5 250 Hz 250.000 Hz -8.6 dB
6 500 Hz 500.000 Hz -3.2 dB
7 1k Hz 1000.000 Hz 0 dB
8 2k Hz 2000.000 Hz 1.2 dB
9 4k Hz 4000.000 Hz 1 dB
10 8k Hz 8000.000 Hz -1.1 dB
11 16k Hz 16000.000 Hz -6.6 dB

Third Octave Bands

Calculation

%% Calculate Third Octave Bands in Matlab
fcentre  = 10^3 * (2 .^ ([-18:13]/3))
fd = 2^(1/6);
fupper = fcentre * fd
flower = fcentre / fd


See also


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