5[1][1].compression of dilon
TRANSCRIPT
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 1/63
Concepts of Compression
Harvey Dillon
National Acoustic Laboratories.
CRC for Cochlear Implant and Hearing Aid Innovations
ASA
Brisbane, 2001
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 2/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Outline: Concepts of Compression
Basics
Rationales for using compression
Evidence for the benefit of compression
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 3/63
Why do we need compression, andwhat is it ?
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 4/63
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 5/63
Whole Range
0
1
2
3
4
5
6
7
O u t p u t L e v e l
WeakModerate
Intense
0
1
2
3
4
5
6
7
O u t p u t L e v e
l
WeakModerate
Intense
High Level
0
1
2
3
4
5
6
7
O u t p u t L e v e l
WeakModerate
Intense
Low Level
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 6/63
Feedback point
OutputInput
Level detecting
device
Variable gain
amplifier
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 7/63
Feedback point
OutputInput
Rules
Variable gain
amplifier
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 8/63 Audiology Research Team Pierce Lee/이 원
육프로그램
50
60
70
80
90
100
110
30 40 50 60 70 80 90 100 110
Input (dB SPL)
O u t p u t ( d B
S P L )
Compression, Expansion, Gain and Attenuation
0102030
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 9/63 Audiology Research Team Pierce Lee/이 원
육프로그램
50
60
70
80
90
100
110
30 40 50 60 70 80 90 100 110
Input (dB SPL)
O u t p u t ( d B
S P L )
0102030
Compression, Expansion, Gain and Attenuation
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 10/63 Audiology Research Team Pierce Lee/이 원
육프로그램 Seven Rationales for Using Compression
1. Avoiding discomfort and distortion
2. Increasing comfort
3. Reducing inter-syllabic level differences
4. Reducing long term level differences
5. Normalising loudness
6. Empirical evidence
7. Maximising speech intelligibility
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 11/63 Audiology Research Team Pierce Lee/이 원
육프로그램
Avoid Discomfort, Damage, and
Distortion
byControlling maximum output (SSPL)
using compression limiting
Rationale 1:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 12/63
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 13/63 Audiology Research Team Pierce Lee/이 원
육프로그램 Avoid Discomfort, Damage and Distortion
AGCo, not AGCi
High compression ratio (>10 ?)
Fast attack time (<5 ms)
Fast, or adaptive , release time (<100 ms)
Peak clipping for very profound losses
Compression parameters:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 14/63 Audiology Research Team Pierce Lee/이 원
육프로그램
Increase comfort
byhigh level gradual comression
Rationale 2:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 15/63 Audiology Research Team Pierce Lee/이 원
육프로그램 Increase comfort
Increase comfort
Decrease need for volume control
Aims:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 16/63 Audiology Research Team Pierce Lee/이 원
육프로그램
O u t p u t d B
S P L
Input dB SPL65
linear
Compression
Increasing comfort
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 17/63
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 18/63 Audiology Research Team Pierce Lee/이 원
육프로그램 Increased comfort
Decreased signal to noise ratio for
sequential signal and noise
(Distorted envelope cues)
Disadvantages:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 19/63 Audiology Research Team Pierce Lee/이 원
육프로그램
Increase Audibility of Soft Phonemes
by
fast acting wide dynamic range
compression
Rationale 3:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 20/63 Audiology Research Team Pierce Lee/이 원
육프로그램 Increase audibility of soft phonemes
Increase intelligibility
Decrease need for volume control
Aims:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 21/63 Audiology Research Team Pierce Lee/이 원
육프로그램 Effect of compression on waveform
Linear
time
Compressed
time
CVR increased
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 22/63
Audiology Research Team Pierce Lee/이 원
육프로그램
O u t p u t d B
S P L
Input dB SPL65
Increasing audibility
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 23/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Increase audibility of soft phonemes
AGCi (not AGCo)
Release time < 50 ms
Low (enough) compression threshold
Single channel or multi-channel
compression
Compression parameters:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 24/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Increased audibility of soft phonemes
Increased risk of feedback
Decreased signal to noise ratio for
sequential signal and noise
(Distorted envelope cues)
Disadvantages:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 25/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Preferred Threshold
40 dB
SPL
66 dB
SPL
don't
know
0
2
4
6
8
10
12
14
40 dB
SPL
66 dB
SPL
don't
know
N o o f p e o p l e
statistically
significant
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 26/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Preferred Threshold
46 dB
SPL
62 dB
SPL
don't
know
0
10
20
30
40
5060
70
80
90
46 dB
SPL
62 dB
SPL
don't
know
60%
31%
9%
N o o f p e o p l e
statistically
significant
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 27/63
CT6
2
65
Summary: High CT preferred to a low CT
because its “clearer”
O u t p u t d B
S P L
Input dB SPL
CT46
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 28/63
Summary: High CT preferred to a low CT
because its “clearer”
2:1 compression preferred to linear because it’s more “comfortable”
O u t p u t d B
S P L
Input dB SPL
CT46
CT62
linear
65
R ti l 4
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 29/63
Audiology Research Team Pierce Lee/이 원
육프로그램
Reduce Long Term Level
Differences
by
slow acting automatic volume control
Rationale 4:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 30/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Reduce Long Term Level Differences
To avoid (or reduce) the need for volume
control adjustments
To improve intelligibility in quiet
environments(compared to linear amplifier with no volume
control)
Aims:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 31/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Reduce Long Term Level Differences
Slow acting compression
Release time > 1 sec ?
Low compression threshold
< 55 dB SPL ?
Single channel or multi-channelcompression
Method:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 32/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Reduce Long Term Level Differences
Noise increases during long gaps
May not react sufficiently quickly to sudden
changes in overall level
Disadvantages:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 33/63
Audiology Research Team Pierce Lee/이 원
육프로그램
Normalise Loudness
by
compressing most at low levels
and high frequencies
Rationale 5:
N li l d
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 34/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Normalise loudness
Achieve normal overall loudnessperception
Achieve normal balance of loudnessacross frequencies
Hence to improve intelligibility andnaturalness of sound
Aims:
L d S l
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 35/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Loudness Scale
Uncomfortable
Very Loud
Loud
Loud but ComfortableComfortable
Soft but Comfortable
SoftVery soft
Inaudible
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 36/63
20 30 40 50 60 70 80 90 100
Hearing
Impaired
(individual)
Normal
Hearing
(average)
Inaudible
Very Soft
Soft
Comfortable
Loud
Very Loud
Uncomfortable
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 37/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Input-output curve to normalise loudness
40
60
80
100
20 40 60 80 100
Input (dB SPL)
O u t p u t ( d B
S P L )
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 38/63
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 39/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Loudness normalisation - procedures
FIG6
DSL[i/o]
IHAFF (Contour test and VIOLA)
Scaladapt
LGOB
N li l d
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 40/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Normalise loudness
+
-10
0
10
20
30
40
50
60
0.1 0.2 0.5 1.0 2.0 5.0
Frequency (kHz)
G a i n ( d B )
50
90
TILL
Normalise loudness
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 41/63
Audiology Research Team Pierce Lee/이 원
육프로그램
+
1
2
3
4
Normalise loudness
Normalise loudness
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 42/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Normalise loudness
Greatest compression ratio at low levels
Greatest compression ratio at high
frequencies (for most losses)
Release times fast or slow
Two or more channels (or even one)
Compression parameters
Normalise loudness
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 43/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Normalise loudness
Increased risk of feedback
Increased noise in gaps (if fast
compression)
Sub-optimal intelligibility
Disadvantages:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 44/63
Audiology Research Team Pierce Lee/이 원
육프로그램
Empirically Determined Compression
byusing whichever compression
works best in experiments
Rationale 6:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 45/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Empirically determined compression
To use the form of compression that givesthe best intelligibility or quality, as indicated
by empirical experiments.
Conclusion: WDRC for the LFs, especially forpeople with sloping losses and big dynamic
ranges
Aim:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 46/63
Audiology Research Team Pierce Lee/이 원
육프로그램
Speech intelligibility maximization
byNAL-NL1
Rationale 7:
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 47/63
Experimental evidence: The effect
of compression on intelligibility
Conclusions
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 48/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Conclusions
1. Fast acting compression probably does
not significantly increase intelligibility
compared to linear at optimal level.
2. Fast acting compression probably does
not significantly decrease intelligibility
compared to linear at optimal level.
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 49/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Comparison of linear and non-linear
Input level
O u t p u t l e v e l
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 50/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Comparison of linear and non-linear
Input level
O u t p u t l e v e l
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 51/63
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 52/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Comparison of linear and non-linear
Input level
O u t p u t l e v e l
3. Compression (many sorts) maintains intelligibility
as input level is decreased below typical levels.
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 53/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Comparison of linear and non-linear
Input level
O u t p u t l e v e l
4 Compression (many sorts) maintains loudness comfort
as input level is increased above typical levels.
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 54/63
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 55/63
Audiology Research Team Pierce Lee/이 원
육프로그램
Questions
References
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 56/63
Audiology Research Team Pierce Lee/이 원
육프로그램 References
Dillon, H. (1996). Compression? Yes, but for low or
high frequencies, for low or high intensities, and with
what response times? Ear & Hearing, 17, 287-307.
Byrne, D. (1997). Hearing aid selection for the 1990s:
Where to? J. Amer Acad Audiol, 7:377-395.
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 57/63
Dillon, H, Storey, L. The National Acoustic
Laboratories procedure for selecting the Saturated
Sound Pressure Level of Hearing Aids: Theoretical
derivation. Ear & Hearing , August, 1998.
Storey, L, Dillon, H, Yeend, I, Wigney, D. The National
Acoustic Laboratories procedure for selecting the
Saturated Sound Pressure Level of Hearing Aids:Experimental validation. Ear & Hearing , August,
1998.
Dillon, H, Storey, L, Grant, F, Phillips, A, Skelt, L,
Mavrias, G, Woytowych, W, and Walsh, M. Preferredcompression threshold with 2:1 wide dynamic
range compression in everyday environments.
Aust. J. of Audiol ., May, 1998.
Question and answer
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 58/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Question and answer
I am really looking forward to this stupid quiz: True/false
False
I will write my answers down anyway: True/False
True
Question and Answer
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 59/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Question and Answer
1. The major purpose of compression is to:
Fit a big dynamic range of sound into a small dynamic rangeof hearing
2. Compression is the opposite of gain: True or False?
False
3. Compression makes speech more intelligible than linearamplification when speech .....
is soft
4. Compression makes speech more comfortable than linearamplification when speech .....
is loud
5. TILL amplification makes feedback more likely: True or False?
True
Question and Answer (cont)
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 60/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Question and Answer (cont)
6. A gradual form of compression is significantly better than
linear amplification + compression limiting: True or False?True
7. Manual volume controls are not needed on automatic hearingaids: True or False?
False 8. Compression threshold should be as low as possible without
feedback occurring: True or False?
False
9. SSPL selection is more critical for people with a mild loss thanfor people with a profound loss: True or False?
False
10. Compression limiting is always better than peak clipping:T/F?
Question and Answer (cont)
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 61/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Question and Answer (cont)
6. A gradual form of compression is significantly better than
linear amplification + compression limiting: True or False?True
7. Manual volume controls are not needed on automatic hearingaids: True or False?
False 8. Compression threshold should be as low as possible without
feedback occurring: True or False?
False
9. SSPL selection is more critical for people with a mild loss thanfor people with a profound loss: True or False?
False
10. Compression limiting is always better than peak clipping:T/F? False
Question and Answer (cont)
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 62/63
Audiology Research Team Pierce Lee/이 원
육프로그램 Question and Answer (cont)
11. Measuring UCL or LDL is critical to accurate prescription of
SSPL: True or False?False
12. NAL-NL1 restores the normal loudness balance across
frequency: True or False?
False
13. Increasing audibility increases intelligibility except when:
.................
SL or SPL is too large
14. NAL-NL1 is the only validated non-linear selection
procedure:
True or False?
False
Question and Answer (cont)
8/13/2019 5[1][1].Compression of Dilon
http://slidepdf.com/reader/full/511compression-of-dilon 63/63
육프로그램 Question and Answer (cont)
11. Measuring UCL or LDL is critical to accurate prescription of
SSPL: True or False?False
12. NAL-NL1 restores the normal loudness balance across
frequency: True or False?
False
13. Increasing audibility increases intelligibility except when:
.................
SL or SPL is too large
14. NAL-NL1 is the only validated non-linear selection
procedure:
True or False?
False