How human listeners make sense of crowded acoustic scenes

The notion that sensitivity to the statistical structure of the environment is pivotal to perception has recently garnered considerable attention. I will discuss a series of recent experiments in which we investigated this sensitivity in the context of crowded acoustic scenes. Stimuli are artificial ‘soundscapes’ populated by multiple (up to 14) simultaneous streams (“auditory objects”) comprised of tone-pip sequences, each with a distinct frequency and pattern of amplitude modulation. Sequences are either temporally regular or random. We show that listeners’ ability to detect abrupt appearance or disappearance of a stream is facilitated when scene streams were characterized by a temporally regular fluctuation pattern and that this ability is preserved during healthy aging. Remarkably, listeners benefit from regularity even when they are not consciously aware of it. These findings establish that perception of complex acoustic scenes relies on the availability of detailed representations of the regularities automatically extracted from multiple concurrent streams.