Download Evaluating the Sound Quality Advantages of Beltone First through

Beyond Stethosets: Evaluating the
Sound Quality Advantages of Beltone
First through Clinical Assessment
Stephen A. Hallenbeck, Au.D.
Natural, comfortable or otherwise pleasant hearing aid sound quality has been reported by end users as critical
Whistle Stop efficiently removes feedback through phase
for success with amplification. At the same time, these subjective descriptors highlight the innate ambiguity of
cancellation and situation-specific temporary gain reduc-
FACTORS INFLUENCING SOUND
QUALITY
sound quality and the tremendous challenge associated with quantifying these characteristics to ensure the best-
tion, often before feedback is even audible to the client.
There are several areas which exert an influence over
sounding hearing aid is chosen for each client.
AFX Music Mode promotes the most accurate feedback
sound quality. The first and possibly most important com-
cancellation for music without additional sound distortion.
ponent of sound quality is related to the primary function of
Prospective hearing aid users generally expect that hearing healthcare practitioners will employ their expertise to
In sum, the signal processing and advanced directional
a hearing aid; specifically, providing the user with audibility
efficiently guide them through the decision-making process of which hearing aid will be best suited to them. Fur-
and hearing comfort features of Beltone First provide a
through prescriptive gain. A common problem encoun-
ther, they may not expect to have to try several different hearing aids to determine the best-sounding ones. Given
state-of-the-art sound quality experience for users.
tered in initial hearing aid fittings is that clients can have
1
adverse immediate reactions to even minimal levels of am-
the importance of sound quality and the inherent difficultly with quantifying it, how can professionals effectively
and rapidly evaluate hearing aid sound quality to better serve their clients? And do real differences in sound quality
across hearing aid manufacturers’ products truly exist?
ATTRIBUTES OF BELTONE FIRST
QUALITY FOR CLIENTS
TM
THAT PROMOTE BETTER SOUND
QUANTIFYING DIFFERENCES IN
HEARING AID SOUND QUALITY
ACROSS MANUFACTURERS
plification, simply because sounds are perceived differently
The hearing aid industry has recognized that the sound
the least amount of gain without occluding the ear canal
quality of a hearing aid is a major component which influ-
would always be judged as the most natural sounding.
as compared to their natural, impaired hearing. As such,
it could be argued that the hearing aid which provides
Beltone hearing aids have always been designed with
come the inherent low-cut in amplification from directional
ences the acceptance of amplification. Further, manufac-
Of course, this strategy is absolutely counterproductive
sound quality in mind. Rapid 17 signal processing, which
processing while maintaining a purer sound quality. This
turers have also recognized that hearing professionals may
to rehabilitation through use of amplification, and should
models the input signal and applies amplification analo-
omnidirectionality in the low frequencies may also permit
benefit from more objective methods of evaluating sound
be avoided. However, differences in both generic and pro-
gous to the ear’s natural processing of sounds, provides
an easier listening experience, as clients experience audi-
quality, if these objective methods can indeed be derived.
prietary prescriptive fitting rules, coupled with the first-fit
Beltone with a clear advantage from the start over other
tory awareness to all directions for the low frequencies,
To address this need, listening panels consisting of individ-
strategies designed to provide lower gain at the first-fit,
manufacturers who use less-sophisticated compression
regardless of the directional pattern. In other words, clients
uals with hearing loss were assembled to evaluate sound
can influence the sound quality of the instrument being
strategies. The selection of three time constants – Syllabic,
do not feel as if they are listening “in a tunnel” because off-
quality across hearing aid manufacturers. The results of
fit. Thus, when evaluating sound quality across manufac-
Normal and AVC – enables the professional to personalize
axis sounds are inaudible, as occurs with a traditional full
these listening panels revealed significant, validated differ-
turers, it may be optimal to evaluate sound quality at the
the compression characteristics to the client’s needs. Two
directional setting. The Mixing Point between this omnidi-
ences in sound quality across a variety of manufacturers’
first-fit gain settings as well as at equivalent gain settings
types of output compression ensure that very loud sounds
rectional and directional processing is adjustable for top-
hearing aids (Figure 1). Given that these differences are
to ensure a fair and even test.
do not exceed the client’s uncomfortable levels, and also
level models, allowing the professional greater abilities to
present, and that sound quality influences a client’s ac-
control the output in each of the processing channels. This
fine-tune per the client’s needs.
ceptance of amplification, sound quality should definitely
Other areas of hearing aid processing which influence
be included in the decision-making process of which hear-
sound quality include the contributions of hearing aid fea-
ing aid is best.
tures, such as feedback suppression and directionality. A
processing, occurring largely behind-the-scenes, is largely
2
responsible for the sound quality advantages enjoyed by
Finally, Beltone’s features designed to maximize hearing
Beltone First.
comfort round out the sound quality experience. Smart
good feedback suppression system will be transparent to
Gain Pro enables the listener to move through varied
the listener, effectively preventing feedback without add-
In addition to superior signal processing, Beltone’s array
sound environments throughout the day, with built-in ad-
ing any sound distortions or artifacts as byproducts of this
of advanced directional features are designed to maintain
justments to Sound Cleaner and gain levels. Sound Shifter
feedback cancellation. Of course, additional sounds such
the integrity of the sound while improving different attrib-
enables certain clients to access high-frequency sounds
as squeaks and squeals produced by the hearing aid but
utes of the signal received by the client. CrossLink Direc-
that were previously inaudible to them. Silencer reduces
not present in the actual input signal are generally regard-
tionality affords every possible binaural directional pattern
the gain for low-input sounds in every channel, ensuring
ed as detrimental to sound quality by the user. Directional-
– bilateral omnidirectional, bilateral directional and asym-
that internal processing and external fans and low-level
ity can affect sound quality as well, depending on how it is
metric directional – in one automatic program, depending
motor sounds are not over-amplified. Wind Noise Reduc-
implemented by the manufacturer. If low-frequency equali-
on the classification of the environment and the location
tion reduces amplification of turbulent wind flow around
zation of gains is not achieved for directionality, users can
of speech sources. However, every directional option pro-
the microphones. Synchronized SATISFY gradually and
often perceive a difference in loudness when they switch
vides split-band processing, with omnidirectionality for low
comfortably transitions clients to the optimal levels of gain
frequencies and directionality for high frequencies, to over-
for best speech intelligibility. And Feedback Eraser with
Figure 1. Preference ratings for current hearing aids.2 Error bars indicate 95% confidence intervals.
from an omnidirectional to a directional mode, thereby affecting the sound quality. For these reasons, it is usually
desirable to clinically assess sound quality with features
clinic with a quick change of coupling to the professional’s
If the “listen in” option is selected, the following steps can
tings. Use coupler or probe microphone measures to
enabled, as they would be during the client’s everyday use
ears. Alternately, a “listen in” feature available in some
help a hearing professional systematically compare sound
match the prescribed target outputs, using the same
of the hearing aids.
verification equipment through the test box or through
quality across different hearing aid manufacturers, both at
modulated speech signal. Fine tune gains as neces-
probe microphone measurements can help the profes-
proprietary first-fit and equalized gain settings.
sary to achieve matched outputs across the frequency
HOW TO ASSESS SOUND QUALITY
IN THE CLINIC
sional evaluate sound quality in a wider range of controlled
sound environments than can be achieved in a typical clin-
1. Program each hearing aid with its proprietary first-fit
Due to expectations of end users that hearing profession-
ic. The “listen in” feature may also be useful when evaluat-
gain settings for a typical sloping hearing loss, with de-
als recommend the best-sounding hearing aids for them,
ing sound quality for high gain levels, as in some cases the
fault feature settings.
it is advantageous to evaluate sound quality of different
equipment may allow for the “listen in” volume level to be
hearing aids at different settings before dispensing them
decreased for the professional’s comfort.
range.
7. At each of these levels, “listen in” to the hearing aid response. How is the sound quality at each level? Bright
or dull? Tinny? Distorted in any way?
2. Through coupler or probe microphone measures, run
to clients. The manner in which sound quality is assessed
output or Speech Mapping curves with a modulated
8. Select a music input or a “live microphone” on the veri-
can vary. A stethoset can be used by the professional to
However, each of these three listening test options has its
speech signal at soft (55-60 dB SPL), moderate (65-70
fication equipment, and “listen in” on the sound qual-
listen to the hearing aid response in the clinic. Along these
inherent benefits and drawbacks. Table 1 lists these con-
dB SPL) and loud (75-80 dB SPL) levels. Through fine
ity produced. Is the sound tinny or distorted? How
same lines, behind-the-ear (BTE) or receiver-in-the-ear
siderations along with the author’s subjective ranking of
tuning of gains, match the prescribed target outputs
are loud and soft dynamics reproduced in the hearing
(RIE) hearing aids can be worn by the professional in the
the quality of these listening test options.
(according to manually-entered targets on the verifica-
aids? Are any additional squeals produced by the hear-
tion equipment, or through visual approximation (“eye-
ing aid in response to musical tones?
Option
Listening Check-Stethoset
Wearing the Devices
“Listen in” options using
the test box and/or probe
microphone equipment
Table 1. Clinical Sound Quality Testing Options
Strengths
Weaknesses
Overall Quality of Test
Quick, easy,
simple to complete
Unknown input levels;
high gain may limit the
number of real world cases
you can accurately evaluate
Good
Provides a real-world sound
experience with more
accurate coupling to the ear
than a stethoset provides
Difficult to evaluate performance
at high gain if the clinician
has normal or near normal
hearing thresholds; Difficulties
coupling to the ear in the case
of custom devices
Better
Controlled environment
to systematically and
objectively evaluate input
signal variations and the
hearing aid response
Expensive equipment that may
not be readily available
balling”) of the output targets on the fitting software).
9. (Optional) Systematically turn the various hearing aid
3. At each of these levels, “listen in” to the hearing aid response. How is the sound quality at each level? Bright
features on and off to evaluate any impact they have
on sound quality.
or dull? Tinny? Distorted in any way?
Best
fication equipment, and “listen in” on the sound qual-
FINAL THOUGHTS ON SOUND
QUALITY
ity produced. Is the sound tinny or distorted? How
Sound quality is an elusive, highly individualized, but vital
are loud and soft dynamics reproduced in the hearing
aspect of hearing aid use. Professionals are challenged to
aids? Are any additional squeals produced by the hear-
become connoisseurs of hearing aid sound quality, amidst
ing aid in response to musical tones?
a wide range of hearing aid manufacturers and options.
4. Select a music input or a “live microphone” on the veri-
The protocol outlined above is provided as a guideline for
5. Next, choose a prescriptive rule that can be imple-
evaluating the sound quality of newly-introduced products
mented across all manufacturers. Since many first-fit
on the market, as well as for comparisons among current
settings employ the manufacturer’s proprietary pre-
and older products. Thorough evaluation of sound quality
scriptive rule, a generic rule such as NAL-NL2 or DSL
can provide a valuable, deeper insight into the technical
may be optimal. Program each hearing aid for the
possibilities available with hearing aids today. In turn, these
same sloping hearing loss with its respective default
insights can be used to help counsel clients on realistic ex-
feature settings.
pectations, and to help troubleshoot user complaints in a
more efficient manner. With greater understanding of the
6. Select the chosen generic prescriptive rule in the verifi-
quality of sound produced through hearing aid technology,
cation equipment and display targets for the same soft,
hearing professionals can gain further expertise to provide
medium and loud inputs as used with the first-fit set-
the best outcomes for their clients.
REFERENCES
1. Kochkin S. (2010). Marke trak VIII: Consumer satisfaction with hearing aids is slowly increasing. The Hearing
Journal, 63(1), 19-27.
2. Jespersen C. Sound quality in high end hearing instruments. In preparation.
M201063-GB-14.02-Rev.A
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