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

Temporal loudness weights: Primacy effects, loudness dominance and their interaction

Loudness judgments of sounds varying in level across time show a non-uniform temporal weighting, with increased weights assigned to the beginning of the sound (primacy effect). In addition, higher weights are observed for temporal components that are higher in level than the remaining components (loudness dominance). In three experiments, sounds consisting of 100- or 475-ms Gaussian wideband noise segments with random level variations were presented and either none, the first, or a central temporal segment was amplified or attenuated. In Experiment 1, the sounds consisted of four 100-ms segments that were separated by 500-ms gaps. Previous experiments did not show a primacy effect in such a condition. In Experiment 2, four- or ten-100-ms-segment sounds without gaps between the segments were presented to examine the interaction between the primacy effect and level dominance. As expected, for the sounds with segments separated by gaps, no primacy effect was observed, but weights on amplified segments were increased and weights on attenuated segments were decreased. For the sounds with contiguous segments, a primacy effect as well as effects of relative level (similar to those in Experiment 1) were found. For attenuation, the data indicated no substantial interaction between the primacy effect and loudness dominance, whereas for amplification an interaction was present. In Experiment 3, sounds consisting of either four contiguous 100-ms or 475-ms segments, or four 100-ms segments separated by 500-ms gaps were presented. Effects of relative level were more pronounced for the contiguous sounds. Across all three experiments, the effects of relative level were more pronounced for attenuation. In addition, the effects of relative level showed a dependence on the position of the change in level, with opposite direction for attenuation compared to amplification. Some of the results are in accordance with explanations based on masking effects on auditory intensity resolution.

Temporal Loudness Weights Are Frequency Specific

Previous work showed that the beginning of a sound is more important for the perception of loudness than later parts. When a short silent gap of sufficient duration is inserted into a sound, this primacy effect reoccurs in the second sound part after the gap. The present study investigates whether this temporal weighting occurs independently for different frequency bands. Sounds consisting of two bandpass noises were presented in four different conditions: (1) a simultaneous gap in both bands, (2) a gap in only the lower frequency band, (3) a gap in only the higher frequency band, or (4) no gap. In all conditions, the temporal loudness weights showed a primacy effect at sound onset. For the frequency bands without a gap, the temporal weights decreased gradually across time, regardless of whether the other frequency band did or did not contain a gap. When a frequency band contained a gap, the weight at the onset of this band after the gap was increased. This reoccurrence of the primacy effect following the gap was again largely independent of whether or not the other band contained a gap. Thus, the results indicate that the temporal loudness weights are frequency specific.

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.