Acoustical Society of America, Chicago 7 June 2001
Effect of Reverberationon Spatial Unmasking
for Nearby Speech Sources
Barbara Shinn-Cunningham,Lisa Mraz, and Norbert Kopão
Hearing Research CenterBoston University
Supported by AFOSR
Acoustical Society of America, Chicago 7 June 2001
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
Acoustical Society of America, Chicago 7 June 2001
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
Acoustical Society of America, Chicago 7 June 2001
Conditions
3 listening conditions• binaural, left, right
8 spatial configurations masker (M) target (T)
M T
M @ (90 deg, 15 cm)
MT
MT
M @ (0 deg, 15 cm)
T in Mdirection
T
M
MT
MT
MT
T
M
T at15 cm
T at1 m
T at15 cm
T at1 m
T 90 degfrom M
direction
Acoustical Society of America, Chicago 7 June 2001
Reverberant Head-Related Impulse Responses
4 6 8 10 12 14 16 18 20-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Time (ms)
Impu
lse
Res
pons
e P
ress
ure
anechoic
reverberant
2 room conditions• anechoic
• reverberant
Acoustical Society of America, Chicago 7 June 2001
T “clear speech” sentences (thanks to K. Payton)
M speech-shaped noise
Methods
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. < 1 dB
Acoustical Society of America, Chicago 7 June 2001
Speech: T @ (0˚, 15 cm)
Anechoic
Reverberant
Acoustical Society of America, Chicago 7 June 2001
Better-Ear Advantage
Difference between monaural thresholds at better and worse ears
Acoustical Society of America, Chicago 7 June 2001
Better-Ear Advantage
Predict no significant difference
M @ (90 deg, 15 cm)
MT
M @ (0 deg, 15 cm)
T in Mdirection
T
MMT
T at15 cm
T at1 m
T at15 cm
T at1 m
M = masker
T = target
Acoustical Society of America, Chicago 7 June 2001
MT
M @ (0 deg, 15 cm)
T at1 m
T 90 degfrom M
direction
Better-Ear Advantage
Predict ordinary head-shadow difference
M = masker
T = target
Acoustical Society of America, Chicago 7 June 2001
M T
M @ (90 deg, 15 cm)
T in Mdirection
T at1 m
Better-Ear Advantage
Predict larger-than-normal difference
M = masker
T = target
Acoustical Society of America, Chicago 7 June 2001
M @ (90 deg, 15 cm)M @ (0 deg, 15 cm)
MT M
T
T
M
T at15 cm
T at15 cm
T at1 m
T 90 degfrom M
direction
Better-Ear Advantage
Predict very large difference
M = masker
T = target
Acoustical Society of America, Chicago 7 June 2001
0
10
20
30
MT
TM
MT
Better-Ear Advantage
x-sub mean
ind. sub
Bet
ter
Ear
- W
ors
e E
ar T
hre
sho
ld (
dB
)
T = targetM = masker
Acoustical Society of America, Chicago 7 June 2001
0
10
20
30
0
10
20
30
MT
MT
TM
MT
Better-Ear Advantage
x-sub mean
ind. sub
Bet
ter
Ear
- W
ors
e E
ar T
hre
sho
ld (
dB
)
T = targetM = masker
Acoustical Society of America, Chicago 7 June 2001
0
10
20
30
0
10
20
30
MT
MT
TM
MT M T
Better-Ear AdvantageB
ette
r E
ar -
Wo
rse
Ear
Th
resh
old
(d
B)
x-sub mean
ind. sub
T = targetM = masker
Acoustical Society of America, Chicago 7 June 2001
0
10
20
30
0
10
20
30
MT
MT M
T
T
M
MT
TM
MT M T
Better-Ear Advantage
x-sub mean
ind. sub
Bet
ter
Ear
- W
ors
e E
ar T
hre
sho
ld (
dB
)
T = targetM = masker
Acoustical Society of America, Chicago 7 June 2001
Better-Ear AdvantageReverberant Conditions
If anything, expect reduced better-ear advantage
Acoustical Society of America, Chicago 7 June 2001
0
10
20
30
0
10
20
30
MT
MT M
T
T
M
MT
TM
MT M T
Better-Ear Advantage
x-sub mean
ind. sub
Bet
ter
Ear
- W
ors
e E
ar T
hre
sho
ld (
dB
)
T = targetM = masker
Acoustical Society of America, Chicago 7 June 2001
Binaural Advantage
Difference between binaural and better ear thresholds
Acoustical Society of America, Chicago 7 June 2001
Binaural Advantage
Predict little binaural advantage
M T
M @ (90 deg, 15 cm)
MT
M @ (0 deg, 15 cm)
T in Mdirection
T
MMT
T at15 cm
T at1 m
T at15 cm
T at1 m
M = masker
T = target
Acoustical Society of America, Chicago 7 June 2001
MT
M @ (0 deg, 15 cm)
MT
T at15 cm
T at1 m
T 90 degfrom M
direction
Binaural Advantage
Predict binaural advantage
M = masker
T = target
Acoustical Society of America, Chicago 7 June 2001
M @ (90 deg, 15 cm)
MT
T
M
T at15 cm
T at1 m
T 90 degfrom M
direction
Binaural Advantage
Predict same binaural advantage
M = masker
T = target
Acoustical Society of America, Chicago 7 June 2001
Binaural Advantage
x-sub mean
ind. sub
Bin
aura
l -
Bet
ter
Ear
Th
resh
old
(d
B)
T = targetM = masker
Acoustical Society of America, Chicago 7 June 2001
-2
0
2
4
6
8
-2
0
2
4
6
8
MT
TM
MT M T
MT
MT
Binaural Advantage
x-sub mean
ind. sub
Bin
aura
l -
Bet
ter
Ear
Th
resh
old
(d
B)
T = targetM = masker
Acoustical Society of America, Chicago 7 June 2001
Binaural Advantage
x-sub mean
ind. sub
Bin
aura
l -
Bet
ter
Ear
Th
resh
old
(d
B)
T = targetM = masker
Acoustical Society of America, Chicago 7 June 2001
Binaural AdvantageReverberant Conditions
If anything, expect reduced binaural gain
Acoustical Society of America, Chicago 7 June 2001
Binaural Advantage
x-sub mean
ind. sub
Bin
aura
l -
Bet
ter
Ear
Th
resh
old
(d
B)
T = targetM = masker
Acoustical Society of America, Chicago 7 June 2001
Binaural Advantage
x-sub mean
ind. sub
Bin
aura
l -
Bet
ter
Ear
Th
resh
old
(d
B)
T = targetM = masker
Acoustical Society of America, Chicago 7 June 2001
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
Acoustical Society of America, Chicago 7 June 2001
Acoustical Society of America, Chicago 7 June 2001
-25
-20
-15
-10
-5
-25
-20
-15
-10
-5
L R B L R B L R B L R B L R B L R B L R B L R B
M T
M @ (90 deg, 15 cm)
MT
MT
M @ (0 deg, 15 cm)
T in Mdirection
T
M
MT
MT
MT
T
M
T at15 cm
T at1 m
T at15 cm
T at1 m
T 90 degfrom M
direction