Decibel Meter

30 a) a) a) a) MN ._ ... . latiamitgarde 0 VI threshol I 10 10 20 kHz 12 140 dB 120 100 60 60 40 20 0 ...ram :Ph- En102 dB .10 -F 1 111M DECIBEL METER This portable instrument, designed by ELV GmbH, gives an accurate indication of the sound pressure level (SPL). The three SPL ranges, three response modes, and linear or A-weighted filtering provided by the meter enable many types of measurement to be carried out, from the tracing of ambient noise sources to establishing the sensitivity of a loudspeaker. Depending on their physical and mental state, human beings respond subjectively to ambient noise. Objective, absolute sound pressure level measurements therefore invariably require a specially designed test instrument, the decibel meter, of which a design is discussed here. Two weighting methods and associ- ated standard curves have been de- veloped and are widely used for sound pressure level (SPL) measurements. One of these methods yields the A-curve, which gives roughly the inv...