An instrument for “real-time” measurement of the decaying edge of transient signals

The problem of measuring the decaying edge of bandlimited transient signals in `real time´ is discussed for signals with a priori unknown arrival time, peak amplitude and envelope shape, whose decay time to rise time ratios are in excess of 50. An instrument is proposed to identify, measure and normalise the peak of the transient signal and thus permit measurement of the decaying edge to be made from a known reference. Signal envelope estimates made at the local maximum of the incoming transient are used to define the transient peak. The effects of noise on the peak detector operation are examined, noise produced peak position errors computed and a noise threshold monitor is incorporated into the proposed instrument. Measurements of the performance of a simplified transient peak detector/normaliser contained in an acoustic reverberation meter designed by the author are presented.