Fractional-Octave Analysis
- Updated2024-06-07
- 2 minute(s) read
Fractional-Octave Analysis
Fractional-octave analysis is a technique for analyzing audio and acoustic signals. Fractional-octave analyses, especially 1/3 and 1/12 octave, exhibit characteristics analogous to the response of the human ear. Many industry standards, such as ANSI and IEC, require fractional-octave analysis.
The following steps summarize fractional-octave measurement:
- Send a time-domain signal through a bank of N bandpass filters.
- Compute the instantaneous square value for the outputs of the N filters.
- Average the instantaneous square values according to a selected averaging mode.
- Display the averaged values in a bar graph.
The type of fractional-octave measurement you perform, 1/1 through 1/24 octave, determines the number of filters to apply, as well as the passband of those filters. The filters used are known as constant Q filters.
The following example is an illustration of full-octave analysis. In the example, an input signal acquired by a microphone is sent through 10 bandpass filters centered at the frequencies listed in the following illustration.
Related Information
- Bandwidth
The bandwidth of a filter denotes the range of frequencies the filter allows to pass through. Calculating the bandedge frequencies informs you of the bandwidth's characteristics.