SOUND ANALYSER
Electroacoustics / Acoustics A machine comprised of a FILTER system and a system for indicating the relative energy passed through each part of the filter. This measurement gives the distribution of energy of the applied signal as a function of frequency called the SPECTRUM of the signal.
See: SONOGRAPHY, SPECTROGRAPH. Compare: FOURIER ANALYSIS, HELMHOLTZ RESONATOR, LEVEL RECORDER, OSCILLOSCOPE, SOUND LEVEL METER.
There are many types of analysers. An Octave Band Analyser measures the intensity level for each of a set of octave bands, centred on 31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000 and 16,000 Hz. A Third-Octave Band Analyser divides the frequency spectrum into three bands per octave, the Tenth-Octave Band Analyser into ten bands per octave.
See BROAD BAND NOISE, INFRASONIC, SPECTRUM, WHITE NOISE for examples of third-octave analyses. See: CENTRE FREQUENCY. Compare: CRITICAL BAND, Appendix E.
Other types of analysers include the Wave Analyser, which is a continuously variable analyser over the entire audio range; the Impact Noise Analyser for analysing IMPACT SOUNDs such as hammers or punch presses; and the Vibration Analyser, for analysing INFRASONIC VIBRATION.
STANDARD OCTAVE BAND FREQUENCIES
Centre Frequency (Hz) Effective Band (Hz) 31.5 22.1 - 44.2 63 44.2 - 88.4 125 88.4 - 177 250 177 - 354 500 354 - 707 1,000 707 - 1,414 2,000 1,414 - 2,828 4,000 2,828 - 5,657 8,000 5,657 - 11,314 CENTRE FREQUENCIES FOR THIRD-OCTAVE BANDS
Centre Frequency Centre Frequency Centre Frequency (Hz) (Hz) (Hz) 10 100 1,000 12.5 125 1,250 16 160 1,600 20 200 2,000 25 250 2,500 31.5 315 3,150 40 400 4,000 50 500 5,000 63 630 6,300 80 800 8,000
home