meggido a écrit :
Ca dépend de la méthode/filtre utilisée pour la mesure. La plus représentative pour l'oreille humaine est la "A weighted" mais il y a aussi la B et la C :
Human hearing is not equally sensitive at all audio frequencies . The ear is most sensitive to
frequencies in the 1 kHz to 5 kHz range. Weighting filters try and give readings that roughly
correspond to the way humans respond to sound. Sound pressure level measurements use
weighting filters based on three curves: A, B, and C. The curve selected was based on the
loudness of the sound. The C-weighting curve is generally flat over most of the audio band (FR =
+0, -3 dB from 30 Hz to 8 kHz) and used for loud signals. The B-weighting curve is used for
intermediate level sounds and has the same upper corner as the C-weighting, but the lower
amplitude corner is 120 Hz. The A-weighting curve is used for measuring low level signals such
as background noise. This curve, shown in Figure 13, has become a standard for acoustic noise
measurements of all signal levels for the Occupational Safety and Health Administration (OSHA).
|