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Title: Perceptual constancy for reverberation : loudness asymmetry, loudness context effects, binaural de-reverberation and cross-frequency effects
Author: Raimond, Andew
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2013
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Room reverberation adds slowly-decaying 'tails' at the end of sounds, yet listeners do not perceive these strongly. This is evinced by loudness judgements of stimuli shaped with 'reverberant tail-like' slow offsets being quieter than their reversed counterparts. This study investigates whether a perceptual 'constancy' mechanism is responsible, accounting for reverberation effects and maintaining constant perception despite changes to the sound's physical characteristics. Such a mechanism might take account of reverberation by separating sounds with decaying rails into source characteristics and effects from reverberation, then dismissing energy within tails from listeners' loudness judgements. The process appears to be informed by preceding contexts because loudness differences are enhanced following 'standard' stimuli with similar tail• like decays. This study found that this 'loudness context effect' is more pronounced when using stimuli with real• reverberant tails than artificially-shaped offsets, indicating the effect is sensitive to more than simplified slow offsets. Additionally, reverberation decorrelates sounds at a listener's two ears. When binaural and monaural conditions are examined, a 'binaural de-reverberation' occurs whereby perception of uncorrelated binaural tails is further reduced, causing a decrease in the loudness context effect. However, the loudness context effect is only apparent in situations where both standard and test stimuli occupy the same narrow frequency band and is markedly reduced in widely separated cross-band conditions. These monaural and within• band loudness effects are similar to a constancy for reverberation found in speech perception in which reverberant tails are also dismissed. The underlying processes causing these effects are explored. While models of the early auditory system can account for some of these loudness differences, such models are insensitive to additional influence from contexts. It seems a further, higher-level process may be having an effect: one that uses information from previously heard stimuli, such as the presence of similarly tailed decays, binaural comparisons, and stimuli sharing a common frequency
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available