Effect of Reverberation on Spatial Unmasking for Nearby Speech Sources

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Effect of Reverberationon Spatial Unmaskingfor
Nearby Speech Sources

• Barbara Shinn-Cunningham,
• Lisa Mraz, and Norbert Kopão
• Hearing Research Center
• Boston University

Supported by AFOSR
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Motivation

• Spatial unmasking arises when target and masker
  are spatially separated
• changes in energy at the ear
• changes in binaural cues

• What is tradeoff of including reverberation?
• should alter spatial unmasking

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Previous Study(Shinn-Cunnningham, et. al., in
press)

• Nearby speech/masker sources
• large interaural level difference
• big differences in target/masker ratios at the
  two ears

• Zurek model predicts many results, but not when
  large ILDs in masker

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Conditions

• 3 listening conditions
• binaural, left, right

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Reverberant Head-Related Impulse Responses
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• 2 room conditions
• anechoic
• reverberant

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Impulse Response Pressure
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• reverberant

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Methods

• T clear speech sentences (thanks to K. Payton)
• M speech-shaped noise

• Remove overall level effects at better ear
• fix masker (M) level at better ear
• adaptively vary target (T) level to 50 correct
• Block by listening/room condition
• Repeat 3 or more runs to get std. err. lt 1 dB

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Speech T _at_ (0, 15 cm)
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Better-Ear Advantage

• Difference between monaural thresholds at better
  and worse ears

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Better-Ear Advantage

• Predict no significant difference

• M masker
• T target

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Better-Ear Advantage

• Predict ordinary head-shadow difference

• M masker
• T target

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Better-Ear Advantage

• Predict larger-than-normal difference

• M masker
• T target

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Better-Ear Advantage

• Predict very large difference

• M masker
• T target

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Better-Ear Advantage
Better Ear - Worse Ear Threshold (dB)
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Better-Ear Advantage
Better Ear - Worse Ear Threshold (dB)
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Better-Ear Advantage
Better Ear - Worse Ear Threshold (dB)
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Better-Ear Advantage
Better Ear - Worse Ear Threshold (dB)
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Better-Ear AdvantageReverberant Conditions

• If anything, expect reduced better-ear advantage

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Better-Ear Advantage
Better Ear - Worse Ear Threshold (dB)
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Binaural Advantage

• Difference between binaural and better
  ear thresholds

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Binaural Advantage

• Predict little binaural advantage

• M masker
• T target

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Binaural Advantage

• Predict binaural advantage

• M masker
• T target

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Binaural Advantage

• Predict same binaural advantage

• M masker
• T target

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Binaural Advantage
Binaural - Better Ear Threshold (dB)
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Binaural Advantage
Binaural - Better Ear Threshold (dB)
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Binaural Advantage
Binaural - Better Ear Threshold (dB)
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Binaural AdvantageReverberant Conditions

• If anything, expect reduced binaural gain

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Binaural Advantage
Binaural - Better Ear Threshold (dB)
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Binaural Advantage
Binaural - Better Ear Threshold (dB)
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Conclusions

• Better-ear advantage can be very large

• Reverberation reduces the better-ear advantage
• Binaural-processing advantage only present if
• T and M in different directions
• Masker ILD is not extraordinarily large
• Reverberation reduces binaural gain

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