Basic FAQ for FFT Analyzer

Recent FFT analyzers are equipped with acoustic filters in their input section. The characteristics of these filters are clearly defined by the standards for sound level meters (JISC 1509-1 and IEC 61672-1).

Frequency weighting A (A characteristic) was originally devised to approximate human auditory characteristics (pure tone loudness characteristics), and the sound pressure level with this filter applied (i.e., A characteristic sound pressure level) is referred to as noise level in Japan, serving as a fundamental measurement for noise assessment. Frequency weighting C (C characteristic) has a relatively flat characteristic compared to A characteristic and is used when measuring impulsive noise.

When analyzing the AC output of the sound level meter (where the signal is output after filtering) with an FFT analyzer, it is important to ensure that double filtering is not applied during the analysis.

	8-3 Frequency Correction Circuit (What is sound level meter)