Temporal integration of loudness

Only recently have models of stationary loudness been extended to handling non-stationary sounds. Some of this modelling is based on preliminary assumptions and may require further experimentation. With the ultimate goal of probing and extending existing loudness models a series of experiments has been carried out, which investigate the temporal weighting listeners implicitly use when judging the overall loudness of sounds fluctuating in level. Results of the first experiment show that listeners do not employ an averaging strategy as assumed in conventional noise-evaluation algorithms, for example. Rather, the onset of the sound is perceptually emphasized, though large individual differences exist. This suggests that the judgement of the integrated loudness is accomplished at a high level of cognition. If this is indeed the case, it questions the way integration is handled by the majority of loudness models. In a second experiment it was found, that a salient change on the middle of a sound, causes the salient segment of the sound to be more heavily weighted as well. This also indicates that loudness integration occurs at a relatively high level of cognition. The effects found are incompatible with existing loudness models. In the core of loudness models is a time-coefficient which describes the temporal integration. Typically such a time-coefficient is found in gap detection experiments, temporal masking and amplitude modulation detection experiments. The validity of this approach was tested in two experiments. In the first listeners had to identify sounds with different temporal properties, but with the same spectrum. The temporal extend of the sounds was varied, and in this way measures of the temporal resolution obtained. In some conditions of the experiment non-informative noise was surrounding the temporal pattern the listener had to identify. The added noise severely reduced the performance of the listeners, much more than would be expected from traditional integration models (sliding window integrator). Again this suggests that higher level cognitive effects may have an effect not normally considered in experiments measuring temporal resolution of the auditive sensory system. In a second experiment extremely short (~0.06 ms) time coefficients were found if the temporal pattern possessed certain properties. This suggests that different stages of the sensory system, with different critical time coefficients, are involved in the perception.