TOP MENUWhat is octave analysis? Difference from FFT analysis |
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・Frequency analysis ・Calculate the Fourier transform ・Detrending method ・Sampling theorem ・DC component ・Bilinear transform ・Floating point number ・Resolution, sampling period ・Fixed point number ・Digital Filter ・Octave analysis |
・In Japanese
■What is an octave?
An octave is the interval of eighths from one "C" to the next "C" in music. One octave higher is a pitch with twice the frequency.
Below are the scales and frequencies of an 88-key keyboard.
■What is octave analysis? Difference from FFT analysis
Octave analysis is a method of frequency analyzing the loudness of a sound.
The difference from FFT analysis, which is another frequency analysis method, is that the range of frequencies to be analyzed is different.
FFT analysis has frequencies that are evenly spaced and is more detailed than octave analysis, but octave analysis has equal frequency intervals and is often coarser than FFT analysis.
Both methods use fast Fourier transform for frequency analysis. ■Overview of octave analysis
The flow of octave analysis is as follows.
The raw sound pressure (unit: Pa) obtained with a measuring instrument is passed through an octave band filter to separate the components by frequency.
Frequency analysis is then performed using fast Fourier transform.
Analysis results can be obtained by performing decibel conversion and auditory correction on the results. ＜What is an octave band filter?＞
An octave bandpass filter has the characteristic of attenuation as it deviates from the center frequency.
The following are the characteristics of class 1 in a 1/3 octave band filter. ＜What is auditory correction?＞
Auditory correction is a correction value for sound pressure level according to frequency.
This expresses the characteristic that humans are less sensitive to sound at low frequencies. The characteristics are as follows.
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