Different FREQUENCIES affect the human ear in different WAYS. Equal loudness tests determined how each frequency affects the human ear and showed that the average human ear is most sensitive AROUND 4 kHz. A 100 dB signal will only feel like 70 dB at 50 Hz. This is why a guitar may sound louder than a bass drum, or a brake squeal is more annoying than an engine knock, when in fact they are the same decibel levels on a linear scale.

An A-weighting scale is basically a filtering SYSTEM, which provides the relative dB effect on a human ear, at each frequency. This can be accomplished in the software system, within a Sound Level Meter, or with an in-line filter.

Different frequencies affect the human ear in different ways. Equal loudness tests determined how each frequency affects the human ear and showed that the average human ear is most sensitive around 4 kHz. A 100 dB signal will only feel like 70 dB at 50 Hz. This is why a guitar may sound louder than a bass drum, or a brake squeal is more annoying than an engine knock, when in fact they are the same decibel levels on a linear scale.

An A-weighting scale is basically a filtering system, which provides the relative dB effect on a human ear, at each frequency. This can be accomplished in the software system, within a Sound Level Meter, or with an in-line filter.