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Amplitude Compression: Timing is Everything Andrea Pittman Arizona State University Funded by a grant from Oticon A/S © 2013 Andrea Pittman All Rights Reserved
Amplitude Compression:
Timing is Everything
Andrea Pittman
Arizona State University
Funded by a grant from Oticon A/S© 2013 Andrea Pittman All Rights Reserved
20 40 60 80 100
Input (dB SPL)
60
80
100
40
Ou
tpu
t (d
B S
PL)
Wide Dynamic Range Compression
© 2013 Andrea Pittman All Rights Reserved
Wide Dynamic Range Compression
20 40 60 80 100
Input (dB SPL)
60
80
100
40
Ou
tpu
t (d
B S
PL)
© 2013 Andrea Pittman All Rights Reserved
The Problem with Slow-Acting Compression
SLOW:
FAST:
© 2013 Andrea Pittman All Rights Reserved
The Problems with Fast-Acting Compression
30
50
70
90
110
Level (d
B S
PL)
-20
0
20
Gai
n (d
B)
Time
Fast Compression
© 2013 Andrea Pittman All Rights Reserved
The Problems with Fast-Acting Compression
30
50
70
90
110
Level (d
B S
PL)
-20
0
20
Gai
n (d
B)
Time
Slow Compression
30
50
70
90
110
Level (d
B S
PL)
-20
0
20
Ga
in (
dB
)
Time
© 2013 Andrea Pittman All Rights Reserved
The Problems with Fast-Acting Compression
20 40 60 80 100
60
80
100
40
Input (dB SPL)
Ou
tpu
t (d
B S
PL)
NO
ISE
SPEE
CH
SNR: 20 dB
© 2013 Andrea Pittman All Rights Reserved
The Problems with Fast-Acting Compression
20 40 60 80 100
60
80
100
40
Input (dB SPL)
Ou
tpu
t (d
B S
PL)
NO
ISE
SPEE
CH
NO
ISE
SNR: 10 dB
© 2013 Andrea Pittman All Rights Reserved
Adaptive Compression (SpeechGuard)
• Slowly follows gradual input changes
• Quickly reacts to large increases in input
• Quickly reacts to large decreases in input
Slow SlowFast
© 2013 Andrea Pittman All Rights Reserved
Adaptive Compression (SpeechGuard)
• Rapidly reduce gain for high-level sounds
• Rapidly re-establish gain for lower-level sounds
• Better preserve the shape ofthe acoustic waveform
• Optimize the signal-to-noise ratio
© 2013 Andrea Pittman All Rights Reserved
Purpose
Determine the benefits of adaptive compression to children’s and adult’s ability to manage complex listening environments.
Complex Environments:
– Speech perception
– Perception of environmental sounds
– Visual task
© 2013 Andrea Pittman All Rights Reserved
Participants
Children
20 with normal hearing7-12 years
15 with hearing loss7-12 years
Adults
21 with normal hearing21-30 years
26 with hearing loss50-65 years
66-78 years
© 2013 Andrea Pittman All Rights Reserved
Amplitude Compression Parameters
• Single compression model
• 4 channels
• Compression ratio = 3:1
• Knee point of 40 dB SPL
• Timeconstants– Slow: attack ~20ms, release ~800ms
– Fast: attack ~10ms, release ~40ms
– Adaptive: Speech Guard
© 2013 Andrea Pittman All Rights Reserved
Auditory Stimuli
Target
Playground Noise
+10 dB
+4 dB
Trigger
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Non-overlapping Overlapping
Auditory Stimuli
Target
Playground Noise
Trigger
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Door
Cough
“Apple”
Auditory Stimuli
“Dog” Target
Playground Noise
Trigger
Words Environmental Sounds
© 2013 Andrea Pittman All Rights Reserved
Complex Task
ThingAnimal Person ??
Person AnimalFood ??
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ADAPA: VarR: Var
FASTA: 10 msR: 40 ms
SLOWA: 20 msR: 800 ms
FASTSLOWADAP
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Listening Conditions
SPEECHENVIRONMENTAL
SOUNDS
FAST SLOW ADAP FAST SLOW ADAP
NON-OVERLAPPING
18 18 18 18 18 18
OVERLAPPING 18 18 18 18 18 18
36 36 36 36 36 36
© 2013 Andrea Pittman All Rights Reserved
RESULTS
© 2013 Andrea Pittman All Rights Reserved
NORMAL HEARING
HEARING LOSS
Words
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
© 2013 Andrea Pittman All Rights Reserved
NORMAL HEARING
HEARING LOSS
Words
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
© 2013 Andrea Pittman All Rights Reserved
Sounds NORMAL HEARING
HEARING LOSS
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
© 2013 Andrea Pittman All Rights Reserved
NORMAL HEARING
HEARING LOSS
Sounds
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
© 2013 Andrea Pittman All Rights Reserved
Words Sounds
NORMAL HEARING
HEARING LOSS
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
FAST
AD
AP
SLO
W
© 2013 Andrea Pittman All Rights Reserved
Conclusions
Listeners with hearing loss had difficulty with:
– Partial acoustic information
– Fast-acting compression
– Environmental sounds
Adaptive compression
– Improved recognition of speech and environmental sounds
© 2013 Andrea Pittman All Rights Reserved
Funding– Oticon
Professional Assistance– Kamilla Angelo
– Thomas Behrens
– Michael Nilsson
Research Assistants– Ashley Pederson
– Madalyn Rash
– Amanda Willman
– Tia Mulrooney
Local Facilities– Phoenix Children’s Hospital
– Children’s Rehabilitative Services
– Mesa School District
– ASU Speech and Hearing Clinic
Thanks to…
© 2013 Andrea Pittman All Rights Reserved
