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
- Noise Measurement
- A-weighting
- Weighting filter
- Weighting curve
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