Sound recognition depends on real-world sound level
Sam Norman-Haignere, Josh H. McDermott · The Journal of the Acoustical Society of America · 2016
How does the auditory system recognize instances of the same sound class with distinct acoustic properties? As a case study, we investigated the recognition of environmental sounds at different levels. In principle, level-invariant recognition could be achieved by a normalization mechanism that removes variation in level from listeners’ representation of sound identity. Alternatively, listeners could use level as a cue to aid their recognition, taking advantage of the fact that different sound classes are typically heard at different levels. The latter hypothesis predicts that sounds heard at atypical levels should be more difficult to recognize. We tested this prediction by asking human listeners to identify 300 environmental sounds, each presented at seven different sound levels between 30 and 90 dB SPL. We grouped these 300 sounds into those typically heard at low (e.g. salt-shaker) and high sound levels (e.g., jackhammer) using ratings collected via Mechanical Turk. For typically loud sounds, recognition accuracy improved monotonically with increasing experiment level. But for typically quiet sounds, recognition accuracy declined at high experiment levels (above 60 dB). These results are consistent with the hypothesis that listeners recognize individual sounds by internalizing the unique distribution of acoustic features that characterize them.