Calibration of sound analyserSP verifies sound analysers and band filters to their specified standard, IEC 61260 or IEC 60225.
Sound analysers are also verified to relevant requirements for sound level meters. Sound intensity analyserers are verified with a special method.
When measuring the spectral contents of sound, the signal is devided into frequency bands with a constant relative band width. Constant relative band width means that the width of the band (number of Hz included in the band) is proportional to the centre frequency of the band. The most common relative band widths are 1/1 and 1/3 octave band. The FFT analyzer, e.g., has another distribution of the frequency bands; it works with a constant absolute band width, i.e. each band contains an equal number of Hz.
Characteristics for the frequency bands are specified in an international standard, IEC 61260. In this standard, three classes of accuracy are stated, 0 to 2, where class 0 is the best. However, up to 1995 an old standard, IEC 60225, applied and many of those instruments specified to this standard are still in use.