effect of reverberation on spatial unmasking for nearby speech sources

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


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


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


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


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


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


Speech: T @ (0˚, 15 cm)

Anechoic

Reverberant


Better-Ear Advantage

Difference between monaural thresholds at better and worse ears



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


MT

M @ (0 deg, 15 cm)

T at1 m

T 90 degfrom M

direction


Predict ordinary head-shadow difference

M = masker

T = target


M T

M @ (90 deg, 15 cm)

T in Mdirection

T at1 m


Predict larger-than-normal difference

M = masker

T = target


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


Predict very large difference

M = masker

T = target


0

10

20

30

MT

TM

MT


x-sub mean

ind. sub

Bet

ter

Ear

- W

ors

e E

ar T

hre

sho

ld (

dB

)

T = targetM = masker


0

10

20

30

0

10

20

30

MT

MT

TM

MT


x-sub mean

ind. sub

Bet

ter

Ear

- W

ors

e E

ar T

hre

sho

ld (

dB

)



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



0

10

20

30

0

10

20

30

MT

MT M

T

T

M

MT

TM

MT M T


x-sub mean

ind. sub

Bet

ter

Ear

- W

ors

e E

ar T

hre

sho

ld (

dB

)



Better-Ear AdvantageReverberant Conditions

If anything, expect reduced better-ear advantage


0

10

20

30

0

10

20

30

MT

MT M

T

T

M

MT

TM

MT M T


x-sub mean

ind. sub

Bet

ter

Ear

- W

ors

e E

ar T

hre

sho

ld (

dB

)



Binaural Advantage

Difference between binaural and better ear thresholds


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


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


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


Binaural Advantage

x-sub mean

ind. sub

Bin

aura

l -

Bet

ter

Ear

Th

resh

old

(d

B)



-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)



Binaural Advantage

x-sub mean

ind. sub

Bin

aura

l -

Bet

ter

Ear

Th

resh

old

(d

B)



Binaural AdvantageReverberant Conditions

If anything, expect reduced binaural gain


Binaural Advantage

x-sub mean

ind. sub

Bin

aura

l -

Bet

ter

Ear

Th

resh

old

(d

B)



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


-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

effect of reverberation on spatial unmasking for nearby speech sources

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