Subjective and Objective Measurement of the Loudness Level of Single and Repeated Impulses
W. Reichardt · The Journal of the Acoustical Society of America · 1970
The subjective measurement of impulsive sounds involves equal duration for the 1-kHz comparison tones and the same repetition rate as the impulses being measured. The loudness levels of the short 1-kHz tones and repeated short 1-kHz tones can be taken from nomograms presented. The objective measurement of impulses requires an impulse sould-level meter with an RC-integrating network following the squaring device. The RC time constant must simulate the inertia of the human ear. The rise time and decay time constant must be the same. This impulse SLM sound-level meter indicated the same effective value as the classical sound-level meter for steady noises or for rapidly repeated impulses. The value indicated for slowly repeated impulses is higher, and we have a continuous transition to this higher value. The decay time constant must correspond to the rate of decrease in loudness after the sound has stopped. This can be described as τ = 25 msec or as 60-dB reverberation time of 0.35 sec. The reading of such an impulse sound-level meter with A weighting is designated LAI. Loudness calculation by Niese's (1956. Hochfrequenztech. u. Elektroakust. 65, 4.) method, for either single or repeated impulses, requires a spectrum correction ΔLSP to be taken from a nomogram, LNI=LAI+ΔLSP. Stevens' (1961. J. Acoust. Soc. Amer. 33, 1957) and Zwicker's (1960. Acustica 10, 304) methods, for single impulses or impulses repeated less frequently than 2/sec, require the dynamic impulse level LCI to be measured in 1-oct or 13-oct bands. Impulses repeated more frequently than 2/sec are measured and calculated in the classical way, but need by this method another impulse correction ΔLI=LAI−LAS.