Requirements for low-frequency sound reproduction, Part I: The audibility of changes in passband amplitude ripple and lower system cutoff frequency and slope

The audibility of changes in passband amplitude ripple and lower system cutoff frequency and slope has been investigated for a loudspeaker system for two situations: a real loudspeaker in an anechoic chamber and a simulated system reproduced via headphones. The signals were standard program material, selected to ensure a sufficient energy content at the relevant frequencies. The experiments were conducted with six subjects with normal hearing using a paired-comparison procedure. The subjects assessed the attributes "lower bass" and "upper bass" in relation to a fixed reference condition. The first experiment investigated the influence of high-pass filter order (second, fourth, and sixth) and lower cutoff frequency (20, 35, and 50 Hz) at three reproduction levels and for four program items. The second experiment examined the influence of amplitude ripple corresponding to four reverberation times at three reproduction levels and for four program items. The results of the first experiment showed that the lower cutoff frequency has a significant influence on the perceived level of lower bass reproduction if the reproduction level is above the hearing threshold in the relevant frequency bands. The influence of high-pass filter order was not significant for the conditions investigated. The results of the second experiment showed that the amplitude ripple has a significant influence on the perceived level of lower and upper bass reproduction. The results also showed that there were no significant differences between the data produced by the two reproduction methods.