desired sensation level (dsl v5)
DESCRIPTION
Arab Audiology JournalTRANSCRIPT
Desired Sensation Level
(DSL-V5)
National Acoustic Lab NL 2
(NAL-NL2)
Goal of Fitting Formula
DSL [i/o]/v5
Goal is to provide the wearer with an audible and
comfortable signal in each frequency region
Does not attempt to make sounds equally loud in each
frequency region
Goal of Fitting Formula
NAL/NL2
Goal is to maximize speech intelligibility at the listening
level preferred by the wearer
Intelligibility is assumed to be maximized when all
bands of speech are perceived to have the same
loudness (loudness equalization)
Desired Sensation Level
The DSL Method makes use of HL audiometric data
and converts it to SPL at the eardrum (using the Real-
Ear-To-Coupler-Difference (RECD) measurement)
Like other prescriptive measures, the goal is to select
hearing aid frequency and gain characteristics that place
as much as possible of the long-term speech spectrum
(LTASS) into the amplified range
DSL version 5.0
New version prescribes a higher level of gain and output
in the pediatric/congenital prescription than in the
adult/acquired prescription
Motivation Behind Development
First, children with hearing loss are being identified at
birth and amplification is being provided to infants by 6
months of age
(Joint Committee on Infant Hearing, 2000; American Academy of
Audiology, 2003)
Secondly, improvements in auditory brainstem response
(ABR) testing procedures, and significant advances in
hearing instrument technology make continued
development both desirable and necessary
Finally, clinicians still desire access to generic
prescriptive algorithms relative to manufacturer-specific
proprietary fitting algorithms, especially for their
pediatric clients
Given all these considerations, work was initiated in the
late 1990s on a new version of the DSL Method (DSL
v5.0) which includes the DSL multi-stage input/output
algorithm, referred to as DSL m[i/o]
DSL v5
•Audible and comfortable speech cues in all listening
situations is the main goal.
• Less overall gain than in the previous DSL
• Offers output limiting that is more appropriate for the
speech signal.
• Channel-matching to the specific instrument
DSL v5
• Supports severe-to-profound hearing losses
• Corrections for mixed and conductive hearing losses
• Supports binaural fittings
Has four different prescriptions
•Kids in quiet
•Kids in noise
•Adults in quiet
•Adults in noise
DSL v5 Child
DSL v5 Child targets are formulated for congenital
hearing loss, regardless of age
An adult that has a congenital hearing loss has likely
been provided with amplified levels of sound that are
more consistent with what the DSL v5 Child target
criteria provide
DSL v5 Child
The goal was to keep the DSL v5 Child targets as close
to the DSL [i/o] targets as possible
However, for more severe hearing losses, the targets for
average conversational speech are lower. This is due to
a correction that aims to ensure that the peaks of speech
are within the patient's auditory area and not saturating
the hearing aid
DSL v5 Adult
DSL v5 Adult targets are formulated for those who have
acquired hearing loss. The Adult targets are
approximately 7 dB lower than the targets for children
DSL v5 Adult
The difference between the adult and child prescription
decreases for people with a severe-to-profound hearing
loss, which is a desired effect because it maintains
audibility of speech
NAL-NAL2
NAL-NL2, like NAL-NL1, is a threshold-based
procedure that prescribes gain-frequency responses for
different input levels, or the compression ratios at
different frequencies, in wide dynamic range
compression hearing aids
NAL-NAL2
The goal of NAL- NL2 remains to maximize speech
intelligibility for any input level of speech above the
compression threshold, while keeping the overall
loudness of speech at or below normal overall loudness
NAL-NL2 stages
Motivation behind NAL-NL2
NAL-NL1 was often perceived as too loud
NAL-NAL2
• Changed the intelligibility modeling so that new target
gain provides more speech intelligibility
More gain for soft sounds (more compression) less
gain for low frequencies
NAL-NAL2
Considers additional individual factors:
• Age: More gain for children than adults
• Experience: More gain for more experienced users
• Gender: More gain for male users
• Language: More low frequency gain & less high
• frequency gain for tonal languages
• Dead regions of the cochlea
• Cognitive ability
• Frequency selectivity
Comparison between DSL V.5.0 and
NAL-NLNAL- NLDSL version 5.0
Thresholds obtained via
headphones, insert
phones,
Thresholds obtained via
headphones, insert
phones, sound field and
electrophysiologic
measures
Audiometric data that
can be used to derive
targets
Yes Yes Adjustment for
conductive/mixed loss
Yes Yes Adjustment for binaural
fitting
Yes, RECDYes, RECD, REDD and
REUR
Individual specific data
can be entered and used
in deriving targets
NAL- NLDSL version 5.0
Yes NoDesensitization factor
Choose between 1 and 4
channels
YesAccounts for number of
channels
Prescription designed to
amplify speech such
that at a given level
intelligibility is
maximized with the
constraints of
normalizing overall
loudness. Resulting
targets similar to those
of LE approach
Loudness normalization,
placement of acoustic
cues available to normal
hearing listener into
dynamic range of
listener with hearing
loss (given certain
constraints)
Underlying rationale/
goal
Yes but recommends
midlevel CT
Yes but recommends
choice of CT based on
degree of loss
Allows for choice of CT
Yes Yes Adjustment for
venting/tubing
Audiology: Treatment
By Michael Valente, Holly Hosford-Dunn, Ross J. Roeser
NAL- NLDSL version 5.0
Yes Yes Adjustment for
venting/tubing
Yes Yes Age related adjustments
for ear canal
characteristics
No Yes Age related adjustments
for audibility
No Yes Adjustment for hearing
aid experience
Coupler targets, real ear
gain targets, REIG,
aided threshold targets,
SPL-O-GRAMS and
hearing aid parameters
(CT, CF, C…. etc.,)
Coupler targets, real ear
aided targets, real ear
gain targets, aided
threshold targets, SPL-
O-GRAMS and hearing
aid parameters (CT, CF,
C…. etc.,)
Fitting information
provided