DSL v5.0 for Clinicians - Phonak

DSL ® v5.0: The New DSL Method for Hearing
Instrument Fitting in Children and Adults
Richard Seewald
National Centre for Audiology
University of Western Ontario
London Ontario Canada

Acknowledgements
Marlene Bagatto
Steve Beaulac
Leonard Cornelisse
Jillian Drake
Judith Gravel
Martyn Hyde
Lorienne Jenstad
Brenda Hoover
Diana Laurnagaray
Rachel Lui
Shane Moodie
Sheila Moodie
John Pumford
Patricia Roush
Susan Scollie
David Stapells
Jane Steinberg

Some Helpful Websites
• DSL Website: http://www.dslio.com (English, Spanish,
German and French)
• Ontario Infant Hearing Program Protocols:
http://ihp.mtsinai.on.ca/english/HealthProfessionals.htm
•Phonak Website:
* Conference Proceedings:
http://www.phonak.com/professional/informationpool/proceedings.htm
* VideoFocus Series:
http://www.phonak.com/professional/pediatrics/focus.htm

Is it time for a new version of the DSL Method?
1. Early hearing detection programs: Ensure seamless
interface between diagnostic data and prescription;
2. Provision of amplification by 6 months: Update RECD
values for young infants;
3. Advances in hearing instrument technology;
4. Study and account for adult/child differences with
regard to amplification preferences and requirements.

History of The DSL Method
• Work on the algorithm began in 1979
• Version 1 was completed in 1984 (pencil and paper)
• The first software system (DSLv3.0) was released in 1991
(DSL for fitting linear gain instruments)
• DSL[i/o] for Windows was released in 1996
(DSL[i/o] v4.0 for linear and WDRC instruments)
• DSL m[i/o] v5.0 for fitting multi-channel digital instruments
was released to hearing instrument manufacturers
in 2006

The DSL Method
Assessment
Electroacoustic
Prescription
Electroacoustic
Verification

The DSL Method v5.0
Assessment
• Compatibility with ABR
Assessment Data
• Updated RECD Norms
Electroacoustic
Prescription
• The DSL m [i/o] Algorithm
• Multi-channel Compression
• Targets for Children & Adults
• Targets for Quiet & Noise
• Modifications for Conductive
Losses and Binaural Fittings
Electroacoustic
Verification
• Signal Types & Levels
• Multi-Level Targets

Assessment Considerations for Fitting
Infants with Amplification using DSL v5.0

Early Hearing Detection and
Communication Development Programs
• Goal: To identify infants with hearing loss and define
the impairment by 3 months of age.
• Intervention (amplification) to be initiated by 6
months.

Two new developments in DSL
1) Improved the interface between ABR
threshold estimations (in dB nHL) and data
that are required for hearing aid prescription
by DSL.
2) Developed a more comprehensive data set for
predicting RECD values in infants and young
children.

Background
• Estimates of hearing sensitivity are derived from
FS-ABR measurements
• Hearing aid selection and fitting proceeds using
ABR threshold estimates
– Intervention is not postponed for collection of
behavioral data

2k 50dB nHL
0.5k 60dB nHL
2k 40dB nHL
0.5k 50dB nHL
2k 30dB nHL
0.5k 40dB nHL
0 5 10 15 20 25
msec
0 5 10 15 20 25
msec

Behavioral vs. Electrophysiological Assessment Procedures
• dB HL
• entire auditory system
• long duration pure tones
• standard calibration
• dB nHL
• measured from the brainstem
• brief tone bursts or clicks
• non-standard calibration

Some Issues……
…….
• For some ABR protocols (e.g., Stapells 2000),
frequency-specific ABR threshold estimates (nHL)
are not equivalent to behavioral thresholds (HL).
• Fitting algorithms (e.g., DSL m[i/o]) use threshold
information in HL or eHL to calculate prescription.

A Sizable Gap in our Procedures….
ABR
Thresholds
(nHL)
Threshold
Estimates for
Hearing Aid
fitting(eHL)

ABR Threshold Estimation: nHL
ABR
500 Hz 60 dB nHL
2000 Hz 40 dB nHL
Can I enter my
ABR results
directly into
DSL?

Fitting Hearing Aids from
eHL Data
• For some ABR protocols, corrections from nHL to
Estimated Hearing Level (eHL) are needed before
the hearing aid prescription can be calculated.

A Clinical Solution . . . .
• Apply a correction to ABR thresholds (nHL) to
obtain the Estimated Hearing Level (eHL)
• The corrected nHL value represents a behavioral
threshold (eHL) for the purposes of prescription.

Ontario Infant Hearing Program:
Assessment Protocol
Corrections for FS-ABR Measures:
500 1000 2000 4000
AC -15 -10 -5 0
AC correction for 250 Hz = 25*

Sample Findings
-10
0
Frequency (Hz)
250 500 1000 2000 4000 6000
8000
Hearing Threshold Level (dB)
10
20
30
40
50
60
70
80
90
100
110
120
X
X X
X X X

What about ear canal acoustics?
• Large variability in ear canal SPL across infants
and young children
– Kruger 1987, Feigin et al 1989, Bagatto et al
2002
• Must account for this variability in both
audiologic assessment and in hearing instrument
fitting.

What about ear canal acoustics?
35
30
25
20
RECD (dB)
15
10
5
0
-5
-10
100 1000 10000
Frequency (Hz)

The SPLogram
140
130
120
110
100
90
80
70
60
50
X
X
X
40
30
20
10
0
125 250 500 1000 2000 4000 6000 8000
Frequency (Hz)

Getting from nHL to dB SPL in the ear canal
ABR dB nHL
+
Correction x
Frequency
=
Threshold
dB eHL
+
RECD
How well does this work ??
+
RETSPL
=
Real Ear
dB SPL

Accuracy of Predicting Behavioural
Thresholds from ABR Threshold
Estimations in RESPL
Bagatto, Seewald, Scollie, Liu, & Hyde
Trends in Amplification (2005)

Procedure
• Subjects
– 15 children & young adults with SNHL
– 15 young adults with normal hearing
• RECD measures
• Behavioural audiometry
– .5, 1, 2, 4kHz
• FS-ABR threshold estimations
– .5, 1, 2, 4kHz
• Insert earphones used

HL
nHL
-correction
eHL
+ RECD
+ RECD
+ RETSPL
+ RETSPL
Real-ear SPL
Real-ear SPL

120
500 Hz
120
1000 Hz
Behavioural Thresholds
(dB SPL)
100
80
60
40
20
0
0 20 40 60 80 100 120
ABR Thresholds (dB SPL)
Behavioural Thresholds
(dB SPL)
100
80
60
40
20
r = 0.91 r = 0.98
0
0 20 40 60 80 100 120
ABR Thresholds (dB SPL)
120
2000 Hz
120
4000 Hz
Behavioural Thresholds (dB
SPL)
100
80
60
40
20
0
0 20 40 60 80 100 120
ABR Thresholds (dB SPL)
Behavioural Thresholds
(dB SPL)
100
80
60
40
r = 0.98
20
r = 0.99
0
0 20 40 60 80 100 120
ABR Thresholds (dB SPL)

Summary of Results
• Average difference between ABR and behavioral
thresholds was 5.6 dB
• 83 to 98% of variance accounted for
• Standard deviation ranged from ± 3 to ± 6
– Reduced from previous studies

Conclusions
• When certain variables are considered, it is possible
to use ABR threshold estimates to accurately predict
behavioral thresholds in RESPL
– nHL to eHL corrections
– Ear canal acoustics
• DSL m[i/o] 5.0 will facilitate the application of nHL to
eHL corrections and do all of the math for you !

DSL m[i/o] v5.0 : Developments
New RECD Values for Infants and Young Children

Predicted RECDs
Predicted RECD values in previous
versions of DSL:
- foam tip coupling only
- based on 12 month age ranges
Newly developed predictions:
- foam tip and earmold coupling
- calculated to the nearest month

Updated Average RECD Values
Real-Ear
Ear-to-Coupler Difference (RECD)
Predictions as a Function of Age for Two
Coupling Procedures
Bagatto, Scollie, Seewald, Moodie,& Hoover
JAAA, 13, 2002

Predicted RECD Values
Subjects
- 392 infants & children
- ages 1 month to 16 years
- 141 ears used immittance tips
- 251 ears used earmolds
- normal otoscopic and immittance findings

Predicted RECD Values
Primary Result:
- High between-subject variability in
RECD measures for children of
the same age
35
30
25
20
RECD (dB)
15
10
5
0
-5
-10
100 1000 10000
Frequency (Hz)

RECD values for earmolds

RECD values for earmolds

Predicted RECD Values
Limitations:
– all subjects had normal middle ear
function
– high variability in RECD measures
associated with children of the same
age
Therefore, whenever possible, predicted values
should NOT replace the more precise RECD
measurement.

Summary: What we need to fit amplification
• Ear specific and frequency specific threshold estimates
(eHL) for air and bone conduction stimuli (tone-burst
ABR, ASSR, VRA).
• Account for external ear acoustics in the assessment
process (RECD).
• Using RECD measures, predict the ear canal SPL at
threshold across frequencies.
• We can then move on to the prescription and fitting of
amplification.

The SPLogram
140
130
120
110
100
90
80
70
60
50
X
X
X
40
30
20
10
0
125 250 500 1000 2000 4000 6000 8000
Frequency (Hz)

The DSL Method v5.0
Electroacoustic
Prescription
• The DSL m [i/o] Algorithm
• Multi-channel Compression
• Targets for Children & Adults
• Targets for Quiet & Noise
• Modifications for Conductive
Losses and Binaural Fittings

Prescriptions for Infants and Children

DSL Prescriptions for Use with Children
• Much of the work in developing DSL 5.0
has been aimed at preserving most of the
prescriptive characteristics for infants and
children applied in previous versions of the
DSL Method.

Preferred Listening Levels of Children
who Use Hearing Aids:
Comparison to Prescriptive Targets
Scollie, Seewald, Moodie and Dekok
JAAA 2000

Scollie et al. (2000)
• N = 18 Mean age = 10 years
Mild to Profound SN hearing loss
• The subjects listened to average
conversational speech and adjusted their VC
to the level they preferred.
• The subjects preferred VC setting, for an
average speech input, was compared to DSL
& NAL prescribed settings.

Preferred Listening Levels in Children
PLL / DSL Comparison
Recommended Listening Level (dB)
80
60
40
20
0
DSL
0 20 40 60 80
Preferred Listening Level (dB)

Preferred Listening Levels in Children
PLL / DSL Comparison
• On average, the children’s preferred
listening level was 2 dB above the DSL
v4.1 prescribed setting.

Prescriptions for Adults

Adult / Child Preferred Listening Levels
Laurnagaray & Seewald
Trends in Amplification (2005)

Procedure
• Subjects (n=72)
– 24 children who were full-time hearing aid users
– 24 adults with experience wearing hearing aids
– 24 adults who were new hearing aid users
• Prescriptive targets DSL[i/o]
• New users provided with 15 to 20 day period of hearing
instrument use
• Volume control wheel set to minimum
• Speech (RMS 60 dB SPL) via a loudspeaker in soundfield
• Participant set VCW until talker sounded the best (repeated
measure)

Adult/Child Preferred Listening Levels
70
60
□ Children
New Adult Users
• Experienced Adult Users
Preferred Listening Level
50
40
30
20
10
0
0 10 20 30 40 50 60 70
Recommended Listening Level

Implications for DSL v5.0
• DSL v5.0 acknowledges that adults and children not only
require, but also prefer different listening levels, thus:
DSL v5.0 is the first generic hearing instrument
prescription algorithm to prescribe different sensation
levels of amplified speech for children with congenital or
early onset hearing loss versus adults with late onset
hearing loss.

Electroacoustic Verification

Hearing Aid Verification
The responsible clinician should want to know about the levels of
sound that a hearing instrument delivers into the ear of an infant
or young child. Consequently, comprehensive electroacoustic
verification is an essential stage in the pediatric hearing
instrument fitting process.
Verification test signals are now available that can be used with
modern DSP instruments in a valid way.
To verify that audibility and appropriate output limiting have been
achieved for a wide range of input signals it is imperative that
real-ear measurements of hearing instrument performance be
made.

Hearing Instrument Verification
• In DSL v5.0 we continue to recommend a simulated (ie. 2cc
coupler + RECD) approach to electroacoustic verification –
targets will be available on hearing instrument test systems
for soft speech, average speech, loud speech and hearing
instrument output limiting.
• Clinicians are advised to use speech-based verification test
signals whenever possible. If speech is not available as a
test signal, the use of speech-weighted modulated noise is
recommended.

Conclusion
• In this presentation I have described some features
of the new DSL Method v.5.0.
• The developments incorporated into this version still
reflect the original goals of the DSL Method we
described mid-80’s:
AUDIBILITY, COMFORT AND SAFETY
SYSTEMATIC, SCIENTIFIC
CLINICALLY FEASIBLE

Thank you !