FFT Analyzer Basic FAQ

Modern FFT analyzers are equipped with acoustic filters in their input sections. The characteristics of these filters are clearly defined in sound level meter standards (JISC 1509-1 and IEC 61672-1).

Frequency weighting A (A-weighting) is a characteristic originally devised to approximate the characteristics of human hearing (pure tone loudness characteristics). The sound pressure level filtered using this method (i.e., A-weighted sound pressure level) is also called the noise level in Japan and is a basic measurement for noise measurement. Frequency weighting C (C-weighting) has a relatively flat characteristic compared to A-weighting and is used when measuring impact noise, for example.

When analyzing the AC output (the filtered signal) of a sound level meter by inputting it into an FFT analyzer, the important thing to remember is to avoid double filtering during the analysis.

	8-3 Frequency Correction Circuit (What is a Sound Level Meter?)