Considerations for the Development and Fitting of Hearing-Aids for Auditory-Visual Communication
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Transcript of Considerations for the Development and Fitting of Hearing-Aids for Auditory-Visual Communication
Considerations for the Development and Fitting of Hearing-Aids for Auditory-Visual Communication
Ken W. Grant and Brian E. Walden
Walter Reed Army Medical Center
Army Audiology and Speech Center
Washington, DC 20307-5001
Typical Listening Environments for Multi-Memory Hearing Aids
• Quiet
• Background Noise– Low-frequency– High-frequency– Multiple Talkers
• Reverberation
• Music and Environmental Sounds
• Face-to-face communication is the most common of all listening environments.
• Should hearing aids be programmed differently when visual speech cues are available?
Auditory-Visual Listening Environments
• If we improve auditory-only speech recognition, do we necessarily improve auditory-visual speech recognition?
• What speech information is provided by speechreading?
• What speech information is provided by hearing aids?
• To what extent is the information provided by speechreading and by hearing aids redundant?
• What frequency regions best convey information that is complementary to speechreading?
If we improve auditory-only speech recognition, do we
necessarily improve auditory-visual speech recognition?
• Recognition of medial consonants (/C/) spoken by a female talker and recorded on optical disk.
• Manipulated the auditory intelligibility by band-pass filtering.
• Compared A and AV speech recognition scores for normal-hearing subjects.
70
80
90
100
30 40 50 60 70 80 90 100
Auditory Consonant Recognition (%)
r = 0.38
Au
di t
or y
- Vis
ual
Co
nso
na
nt
Re
cog
ni t
i on
(%
)
What speech information is provided by speechreading?
• Recognition of medial consonants (/C/) spoken by female talker and recorded on optical disk.
• Speechreading only.
• Measured percent information transmission of voicing, manner, and place cues.
0% 3%4%Voicing
Manner
Place
Other
Visual Feature Distribution%Information Transmitted re: Total Information Received
93%
HYPOTHESIS: The amount of benefit obtained from the combination
of visual and auditory speech cues depends of the degree of redundancy between the two modalities.
• Speechreading provides information primarily about place-of-articulation.
• Hearing aids that provide primarily (redundant) place information will result in small AV benefit.
• Hearing aids that provide (complementary) voicing and manner information will result in large AV benefit.
0
10
20
30
40
50
60
60 70 80 90 100Auditory Voicing+Manner Information (re: Information Received)
0
10
20
30
40
50
0 5 10 15 20 25 30Auditory Place Information (re: Information Received)
r = -0.87
r = 0.88
AV
Ben
efit
(A
V-A
)A
V B
enef
it (
AV
-A)
What speech information is provided by hearing aids?
• Twenty-five patients fit with the ReSound BT2 multi-band wide dynamic range compression hearing system.
• Recognition of medial consonants (/C/) under four receiving conditions (speech level at 50 dB SPL):– Unaided Listening (without hearing aid or visual cues)– Aided Listening (with hearing aid, no visual cues)– Unaided Speechreading (without hearing aid)– Aided Speechreading (with hearing aid)
E
E
E E
EE
EE
E E
I
I
II
II
II I I
100
90
80
70
60
50
40
30
20
10
0
100 1000 10000
Frequency (Hz)
E Right (N=25)
I Left (N=25)
NU-6Right: M=86.1% (sd: 6.7%)Left: M=85.1% (sd: 6.8%)
Hea
rin
g T
hre
sho
ld (
dB
HL
)
0102030405060708090
100
Voicing
Manner
Place
0102030405060708090
100
0102030405060708090
100
0 10 20 30 40 50 60 70 80 90 100Consonant Recognition Without Hearing Aid (%)
Listening With Hearing Aid
Listening With Speechreading
Hearing Aid Plus Speechreading
To what extent is the information provided by speechreading and by hearing aids redundant?
• Amplification and speechreading provide somewhat redundant information.
– Hearing aid provided information primarily about place-of-articulation. Smaller gains over unaided hearing were achieved for voicing and manner cues.
– Speechreading provided substantial improvement over unaided hearing for place and some improvement for manner. No benefit for voicing.
What frequency regions best convey information that is complementary to speechreading?
• Auditory recognition of medial consonants (/C/) by normal hearing subjects.
• Band-pass filtered speech conditions with equal Articulation Index.
• Analyzed confusions for information transmission of voicing, manner, and place features.
0
10
20
30
40
50
60
70
80
90
100
200 1000 6000
Center Frequency (Hz)
Place
Manner
Voicing
V
M
P
AI=0.1
Per
cen
t In
form
atio
n T
ran
smit
ted
0
10
20
30
40
50
60
70
80
90
100
200 1000 6000
Center Frequency (Hz)
Place
Manner
Voicing
V
M
P
AI=0.2
Per
cen
t In
form
atio
n T
ran
smit
ted
0
10
20
30
40
50
60
70
80
90
100
200 1000 6000
Center Frequency (Hz)
Place
Manner
Voicing
V
M
P
AI=0.3
Per
cen
t In
form
atio
n T
ran
smit
ted
SUMMARY
• Improving auditory speech recognition does not necessarily improve AV speech recognition.
• To improve AV speech recognition A and V cues should be maximally complementary.
• Speechreading provides information about place-of-articulation.
• Hearing aids tend to provide mostly place information, making them somewhat redundant with speechreading.
• Complementary cues to speechreading (voicing and manner) are best conveyed by low-frequencies.
Recommendations for designing hearing aids for Auditory-Visual speech communication
• Programming should focus on improving the recognition of voicing information, and to a lessor extent, manner-of-articulation information.
• Since voicing and manner information are primarily low frequency information, extend frequency response to include this region.
• May need to consider effects of compression on low-frequency amplitude envelope.
• Traditional concerns about upward spread of masking may not be warranted under auditory-visual conditions.
Acknowledgement
• NIH Grant DC00792
• ReSound Corporation, Redwood City, CA
• Department of Clinical Investigation, Walter Reed Army Medical Center, Washington, DC