As a test, we altered our model in three respects: (1) removing cochlear compression, (2), altering the bandwidths of the “cochlear” filters, and (3) altering the bandwidths of the modulation filters (rows four, two, and six of Figure 1). In the latter two cases, linearly spaced filter banks were substituted for the log-spaced filter banks found in biological auditory systems (Figure 6C). We also included a condition with all three alterations. Each altered model was used both to measure the Selleck BYL719 statistics

in the original sound signal, and to impose them on synthetic sounds. In all cases, the number of filters was preserved, and thus all selleck screening library models had the same number of statistics. We again performed an experiment in which listeners judged which of two synthetic sounds (one generated from our biologically inspired model, the other from one of the nonbiological models) more closely resembled the original from which their statistics were measured. In each condition, listeners preferred synthetic sounds produced by the biologically inspired model (Figure 6D; sign tests, p < 0.01 in all conditions), supporting the notion that the auditory system represents textures

using statistics similar to those in this model. To illustrate the overall effectiveness of the synthesis, we measured the realism of synthetic versions of every sound in our set. Listeners were presented with an original recording followed by a synthetic signal matching its statistics. They rated the extent to which the synthetic signal was a realistic example of the original sound, on a scale of 1–7. Most sounds yielded average ratings above 4 (Figures 7A and 7B; Table S1). The sounds with low ratings, however, are of particular interest, as they are statistically matched to the original recordings and yet do not sound like them. Figure 7C Topotecan HCl lists the sounds with average ratings below 2. They fall into three general classes—those involving pitch (railroad crossing, wind chimes, music, speech, bells),

rhythm (tapping, music, drumming), and reverberation (drum beats, firecrackers); see also Figure S5. This suggests that the perception of these sound attributes involves measurements substantially different from those in our model. We have studied “sound textures,” a class of sounds produced by multiple superimposed acoustic events, as are common to many natural environments. Sound textures are distinguished by temporal homogeneity, and we propose that they are represented in the auditory system with time-averaged statistics. We embody this hypothesis in a model based on statistics (moments and correlations) of a sound decomposition like that found in the subcortical auditory system.