Technical Paper
Investigating Calculated Loudness ISO 532 for Evaluating Impulsive Sounds
1991-05-01
911088
Because of the multitude of impulsive sounds that can occur in automobiles it would be valuable to have a method for evaluating these sounds that relates well to customer response. Loudness Calculation based on ISO 532 Method B ( Zwicker' s method) was investigated for its potential as such a method. Problems occurred in obtaining valid 1/3 octave band spectra from conventional real time analyzers for the input to the calculation routine. A conflict arises between the short averaging times needed to track the impulse and the uncertainty principle (BT product rule) for the lower frequency bands. Since Zwicker' s method is based on critical bands, a four-pass analysis procedure was devised using an external filter set for the width of a critical band. The calculation routine was modified to directly accept critical band data.