Evaluation of a model of temporal weights in loudness judgments

The effect of silent gaps on temporal weights in loudness judgments

Human loudness judgments of time-varying sounds show a non-uniform temporal weighting pattern with increased weights at the beginning of a sound. Four experiments were conducted to investigate whether this primacy effect reoccurs after a silent gap of an appropriate duration that is inserted into a level-fluctuating sound. In three of the experiments, contiguous sounds as well as sounds containing silent gaps of different durations were presented. The temporal loudness weights were compared between the sounds that contained a gap and the sounds without a gap. The data showed that with increasing gap duration an increasingly pronounced primacy effect reoccurred on the second sound part in the sense that a) the weights assigned to the first segments after the gap were increased compared to the conditions without a gap, and that b) the following weights again showed a decrease over time. This effect was statistically significant for gap durations of 350 ms and above. To investigate whether an attenuation in level can lead to the same results as a silent gap, segments in the middle part of a sound were attenuated in the fourth experiment, and the resulting weights were compared to conditions in which the middle segments were unattenuated or where a 700 ms silent gap was presented instead of the middle segments. An attenuation of 15 dB resulted in a significant reoccurrence of the primacy effect, although the effect was more pronounced for an attenuation of 30 dB and the silent gap. The results are discussed in the light of auditory nerve responses, masking effects on intensity resolution, and assumptions based on evidence integration processes.

Temporal weights in loudness: Investigation of the effects of background noise and sound level

Previous research has consistently shown that for sounds varying in intensity over time, the beginning of the sound is of higher importance for the perception of loudness than later parts (primacy effect). However, in all previous studies, the target sounds were presented in quiet, and at a fixed average sound level. In the present study, temporal loudness weights for a time-varying narrowband noise were investigated in the presence of a continuous bandpass-filtered background noise and the average sound levels of the target stimuli were varied across a range of 60 dB. Pronounced primacy effects were observed in all conditions and there were no significant differences between the temporal weights observed in the conditions in quiet and in background noise. Within the conditions in background noise, there was a significant effect of the sound level on the pattern of weights, which was mainly caused by a slight trend for increased weights at the end of the sounds ("recency effect") in the condition with lower average level. No such effect was observed for the in-quiet conditions. Taken together, the observed primacy effect is largely independent of masking as well as of sound level. Compatible with this conclusion, the observed primacy effects in quiet and in background noise can be well described by an exponential decay function using parameters based on previous studies. Simulations using a model for the partial loudness of time-varying sounds in background noise showed that the model does not predict the observed temporal loudness weights.