alan kan , corey stoelb , matthew goupell , ruth litovsky
DESCRIPTION
Possible Implications of Interaural Mismatch in the Place-of-Stimulation on Spatial Release from Masking in Cochlear Implant Listeners. Alan Kan , Corey Stoelb , Matthew Goupell , Ruth Litovsky. Cochlear Implants (CI) restore hearing. Source: http://www.cochlear.com/uk/node/6858. - PowerPoint PPT PresentationTRANSCRIPT
Binaural Hearing and Speech Laboratory
Possible Implications of Interaural Mismatch in the Place-of-Stimulation
on Spatial Release from Masking in Cochlear Implant Listeners
Alan Kan, Corey Stoelb, Matthew Goupell, Ruth Litovsky
Binaural Hearing and Speech Laboratory
Cochlear Implants (CI) restore hearing
Source: http://www.cochlear.com/uk/node/6858
Binaural Hearing and Speech Laboratory
Binaural cues tells us where sounds come from
Bang!
Interaural time difference (ITD)
Interaural level difference (ILD)
Binaural Hearing and Speech Laboratory
Spatial Release from Masking (SRM)
The improvement in speech-in-noise understanding gained from a separation
between target and masker sources
TargetMasker
Binaural Hearing and Speech Laboratory
Loizou et. al. (2009)
SRM
(dB)
SRM
(dB)
CI users Normal hearing listeners
Binaural Hearing and Speech Laboratory
Interaural place-of-stimulation mismatch
Base Apex
Left
Right
Electrode # 2 4 6 8 10 12 14 16 18 20 22
2 4 6 8 10 12 14 16 18 20 22Electrode #
20000 Hz 20 Hz7000 Hz 4000 Hz
Binaural Hearing and Speech Laboratory
Mismatch affects SRM
Binaural Hearing and Speech Laboratory
What is the effect of mismatch on sound image fusion?
Base Apex
Left
Right
Electrode # 2 4 6 8 10 12 14 16 18 20 22
2 4 6 8 10 12 14 16 18 20 22Electrode #
20000 Hz 20 Hz
Binaural Hearing and Speech Laboratory
Find a matched pair via pitch matching
Base Apex
Left
Right
Electrode # 2 4 6 8 10 12 14 16 18 20 22
2 4 6 8 10 12 14 16 18 20 22Electrode #
20000 Hz 20 Hz
Δ=0
Binaural Hearing and Speech Laboratory
Mismatch conditions
Base Apex
Left
Right
Electrode # 2 4 6 8 10 12 14 16 18 20 22
2 4 6 8 10 12 14 16 18 20 22Electrode #
20000 Hz 20 Hz
Δ=0Δ=-2 Δ=-4 Δ=-8Δ=2Δ=4Δ=8
Right higher in frequency Left higher in frequency
1.5 mm
Binaural Hearing and Speech Laboratory
What do you hear?
Binaural Hearing and Speech Laboratory
Mismatch affects where a sound is perceived
Left higher in frequency
Right higher in frequency
Binaural Hearing and Speech Laboratory
Mismatch affects people differently
Left higher in frequency
Right higher in frequency
Left higher in frequency
Right higher in frequency
Binaural Hearing and Speech Laboratory
Increasing mismatch leads to more split sound images
Binaural Hearing and Speech Laboratory
Most people lateralize towards high frequencies
Binaural Hearing and Speech Laboratory
Possible Implications
Target
Lateralized sound image
TargetTarget
Split sound image
Binaural Hearing and Speech Laboratory
How does mismatch affect sounds off the mid-line?
Typical values:•ILD = 0; ±2; ±5; ±10 CU•ITD = 0; ±100; ±200; ±400; ±800 µs•Negative values mean sound is to the left.
Binaural Hearing and Speech Laboratory
Good lateralization at no mismatch
Binaural Hearing and Speech Laboratory
Mismatch affect ILDs
Binaural Hearing and Speech Laboratory
Mismatch affect ILDs
Binaural Hearing and Speech Laboratory
Mismatch affect ITDs even more
Binaural Hearing and Speech Laboratory
Non-midline crossings increase with mismatch
L
C
R
Binaural Hearing and Speech Laboratory
Possible Implications
Lateralized sound image Split sound image
Masker MaskerMasker
Binaural Hearing and Speech Laboratory
Possible implications on SRM
Target
Masker
TargetMaskersLateralized Image
Binaural Hearing and Speech Laboratory
Possible implications on SRM
Target
Masker
Target MaskersLateralized Image
TargetMaskersLateralized Image
Binaural Hearing and Speech Laboratory
Possible implications on SRM
Target
Masker
TargetMaskersTargetMaskers
Split Image
Target MaskersLateralized Image
TargetMaskersLateralized Image
Binaural Hearing and Speech Laboratory
Summary
• Interaural place-of-stimulation mismatch leads to lateralized or split sound images which affects perceived location of sounds
• Depending on location of target and masker, interaural mismatch might increase or hinder spatial release from masking
Binaural Hearing and Speech Laboratory
Thank you
• We’d like to thank our research participants for participating in our experiments, and Cochlear Ltd. for supplying the equipment and technical support.
• This work is supported by NIH-NIDCD R01003083 (Litovsky) and in part by a core grant to the Waisman Center from the NICHD (P30 HD03352).
