Download RESOUND ENYATM OFFERS CLEAR SPEECH AND QUALITY

RESOUND ENYATM OFFERS CLEAR SPEECH AND QUALITY SOUND
Jennifer Groth, MA, ReSound Global Audiology
ABSTRACT
ReSound Enya offers clients a superior value hearing solution that delivers excellent sound quality and speech
understanding in noisy environments, both indoors and out. With ReSound Warp-based amplification at its core,
enhanced features such as Adaptive Directionality, NoiseTrackerTM II, WindGuardTM and DFS UltraTM II provide meaningful user benefits that drive satisfaction. With a built-in tinnitus sound generator, ReSound Enya is also an element
in the comprehensive ReSound Tinnitus program.
Figure 1 shows the impact of different hearing aid related characteristics on user satisfaction. The top three
drivers are “Enhanced features”, “Value”, and “Sound
quality”. In fact, these three elements are highly interrelated. “Enhanced features” refers to capabilities
beyond basic amplification, but in reality, enhanced
features have no inherent value as determinants of
satisfaction. In other words, features do not influence
user satisfaction per se; the benefits that can come
with features influence user satisfaction. Benefits that
go far in solving hearing-related problems per money
spent lead to a high perception of value. For ReSound
Enya, sound processing and product capabilities were
carefully selected and combined to provide users with
clear speech and quality sound at superior value.
Impact on user satisfaction
Although hearing is a primary sense, it can be difficult to appreciate its true significance because - unlike
eyesight - hearing is always “on”. An individual’s daily
existence is so interwoven with the sense of hearing
that it is nearly impossible to imagine the complex issues that damaged hearing can bring. Hearing is essential for one’s awareness of what is happening in
the environment, it is the primary mode of human
communication and interaction, and it provides enjoyment and entertainment. In fact, hearing can be well
described as priceless. In order to provide maximum
value for hearing instrument users of all means, ReSound followed this idea as a guiding principle in the
development of the ReSound Enya family of hearing
instruments. In this process, it was crucial to determine what aspects of hearing instruments would be
most important for user satisfaction.
Appearance Out-of- Maintenance Ease of
pocke
effort
use
price
Physical
comfort/
Fit
Product Enhanced
quality features
Value
Sound
quality
Figure 1. MarkeTrak 91 revealed key drivers of user satisfaction.
CLEAR SPEECH
The main complaint of most individuals with hearing
loss and those who wear hearing aids is hearing difficulties in noisy backgrounds. The first task of a hearing
instrument is to improve audibility for speech and other sounds in high quality without exceeding loudness
tolerance levels. ReSound Enya is built with established technologies based on the Surround Sound by
ReSoundTM strategy for sound processing. Following
this approach, the ear and natural hearing processes
inspire ReSound designs. The foundation of the ReSound Enya is the WarpTM compression system, which
emulates the way frequencies are analyzed by the
natural ear. The Warp processor uses a mathematical warping function to map frequency components
logarithmically to a scale closely corresponding to the
critical bandwidth of the auditory filters2.
ADAPTIVE DIRECTIONALITY
Even with the clear, undistorted amplification for audibility that the Warp compression system provides,
difficulties hearing well in background noise often persist. The best way to improve speech understanding
in background noise is to increase the signal-to-noise
ratio (SNR). An increased SNR can be achieved using directional microphones. Commonly used directional microphone systems assume the desired signal
is located in front of the listener. Sounds originating
from other directions are considered noise, and the
amplification for these signals is decreased relative to
signals from in front. ReSound Enya features Adaptive
Directionality, a sophisticated directional algorithm that
is able to track and cancel the loudest sounds behind
the user. It provides various directional characteristics
that adapt based on the intensity and direction of the
noise. The directional response cancels the strongest
noise source behind the user, and can cancel multiple noise sources in different spatial locations simultaneously when the frequency contents of the noise
sources differ.
Figure 2. Adaptive Directionality changes directional patterns to most effectively reduce sound from behind the user.
SOFTSWITCHING™
While specific directional characteristics should be
preferred in specific situations, research has shown
that over 30% of individuals with manually switchable
omnidirectional/directional hearing aids do not change
between these modes 3. Reasons for this include the
user not knowing when to switch, and/or not wanting to make these manual adjustments in their daily
hearing aid use. SoftSwitching uses knowledge about
directional preferences along with acoustic analysis of
the listening environment to control whether the hearing aid processes in an omnidirectional or directional
mode. SoftSwitching uses sound level and speech
detection algorithms to decide when directionality is
likely to be advantageous in a certain listening environment. It switches the microphone mode to Adaptive
Directionality whenever there is noise in the environment and speech is detected from in front of the user.
With smooth transitions between microphone modes
and Directional MixTM processing, Softswitching offers
users the convenience of directional benefit in noisy
situations without having to switch programs.
DIRECTIONAL MIX
By applying an omnidirectional response to low-frequency sound inputs, Directional Mix solves audibility
and sound quality issues that traditionally have been
inherent in directional hearing aid use, and that would
complicate automatic switching such as SoftSwitching. One of these issues is noise resulting from the
equalization, or “bass boost,” of the low-frequency
roll-off of directional amplification. This roll-off occurs
because low-frequency sounds arriving at the front
and rear microphones of the hearing aid have similar
phase relationships. This means that they tend to be
cancelled regardless of their direction of arrival. To accommodate for this decrease in audibility while in the
directional mode, a boost in low-frequency amplification is typically applied. However, this may result in an
audible noise floor, and detract from the overall hearing
benefit4. Using omnidirectional processing in the low
frequencies avoids this problem, while still providing
improved SNR for the important speech frequencies.
The frequency at which the processing of the input
signal changes between omnidirectional and directional is automatically calculated by the AventaTM fitting software depending on the low frequency hearing
thresholds and the microphone spacing of the device.
It provides the best balance between improved SNR
and sound quality for each individual. Figure 3 shows
the smooth transition between the omnidirectional and
directional signals resulting in noise-free directionality.
Noise free directionality
Omnidirectional
Directional
Figure 3. Directional Mix ensures a smooth transition between omnidirectional
low frequency processing and directional high frequency processing.
QUALITY SOUND
Virtually all hearing instrument manufacturers claim
excellent sound quality in their products. Such claims
easily go unchallenged due to the lack of methods for
impartially assessing sound quality in hearing instruments. ReSound, however, can rightly claim top-rated
sound quality across generations of products as determined by an impartial method agreed upon by hearing aid manufacturers5. Using the same technologies,
ReSound Enya brings this superior sound quality to
the basic hearing instrument segment.
Enhancing sound quality with NoiseTracker II
Apart from the WARP compression system, one of
the most significant contributing technologies to the
superior sound quality proven with ReSound hearing instruments is NoiseTracker II. Benefits of noise
reduction may include ease of listening and listening
comfort6, better sound quality7, and reduced cognitive
load8. Many hearing care professionals consider noise
reduction systems to be equivalent across manufacturers and there is little information to substantiate differences. More recently, the varying acoustic effects of
different systems have been demonstrated, and subjective measures have also revealed that these differences lead to perceptual differences, in both normalhearing and hearing-impaired listeners.9,10 Although, it
was found that noise reduction systems could reduce
noise annoyance and preserve speech naturalness,
the degree to which this was achieved with the systems tested differed. These results have important implications for product selection. The effect of the specific noise reduction system should be a consideration
in hearing instrument fitting.
The NoiseTracker II system uses spectral subtraction11, one of the most widely used methods for enhancement of speech in noise in audio applications.
The concept of spectral subtraction is to subtract the
short-term noise spectrum from the total signal, leaving
only the speech portion. Although the concept is easy,
the implementation is not because the success of this
strategy depends on being able to precisely characterize the noise. In other words, the system must be
able to effectively separate speech from background
noise. Considering that the background noise often
consists of speech, this is quite a challenge. An additional challenge is to keep up with the dynamic speech
and noise make-up of real listening environments. Fi-
nally, it is important for hearing instrument users that
not all noise be removed from the signal, and that the
noise characteristics be preserved. If all ambient noise
is removed or if the spectrum of the noise background
was altered, this would create an unnatural-sounding
experience. Background sounds do need to be audible to the degree that users can recognize and orient
themselves in their listening environments. Ultimately,
the goal is undistorted speech at the prescribed gain,
and undistorted noise at lower level.
The accuracy of NoiseTracker II in reducing background noise was tested by recording speech in a
crowd noise background at a 0 dB SNR. This environment is very challenging for a noise reduction system.
Figure 4 shows the spectrogram of the background
noise by itself. Time is on the horizontal axis, and frequency is on the vertical axis. The most intense levels
appear pink, while the less intense levels are blue. It
is clear from Figure 4 that the background noise has
the most energy in the low frequencies, but also considerable energy in the mid frequency range. Figure 5
shows the difference between NoiseTracker II off and
on. If the spectral subtraction noise reduction system
can accurately follow, estimate and subtract the noise
spectrum, Figure 4 and Figure 5 should look similar,
which in fact they do. This is in contrast to a noise
reduction system set to a moderate level in another
manufacturer’s high-end hearing instrument, which
is shown in Figure 6. The pattern of reduction does
not resemble the background noise spectrogram very
closely. Not only is little reduction applied where there
is most energy in the background noise, but discrete
bands of identifiable reduction appear in the spectrogram. Although both systems may result in less annoyance of the background noise, the NoiseTracker
II system is likely to preserve a more natural sounding
outcome.
Figure 4. Spectrogram of the background noise only.
Listening comfort outdoors with WindGuard
Wind noise can create a frustrating listening experience for hearing aid users. Even at low wind speeds,
high levels of turbulent noise can be created at the
hearing aid microphones, adding high levels of noise
to distort the desired sounds. Wind noise is even more
problematic for dual-microphone hearing instruments
than for those with single microphones12, 13, because
wind noise is spectrally low-frequency and spatially
uncorrelated. When wind is present, distinct air vortexes are created at each microphone of the hearing
instrument. Since each of these vortexes is unique, so
is the signal at each microphone, and the signals are
thereby uncorrelated. Combining uncorrelated inputs
at the 2 microphones or ports of a directional hearing instrument results in an increase of the signal level.
Thus, in a traditional directional hearing instrument
with low-frequency equalization, wind noise is amplified relatively more than it would be in a single microphone instrument. Directional Mix, which assigns an
omnidirectional response to low frequencies, already
alleviates some of the wind noise problem in ReSound
dual microphone hearing instruments. WindGuard
provides a second line of defense against wind noise
in both directional and omnidirectional microphone
modes, keeping sound levels comfortable in outdoor
listening situations.
The goal of WindGuard is to apply enough gain reduction in the frequency bands where wind is detected
to provide listening comfort for the hearing instrument
user, without disrupting the gain levels of the frequen-
The second component of WindGuard is the wind
reduction module. When the system determines that
wind noise is present and greater than 70 dB SPL (the
level at which wind noise typically becomes a problem
for hearing instrument users), gain reduction is applied
to specific frequency bands. Figure 7 shows a highly
simplified schematic of the 2 modules of WindGuard.
WIND DETECTION MODULE
1
2
Comparing
microphone
input signals
Calculating
wind-tosound ratic
WIND REDUCTION
MODULE
Figure 7. Simplified schematic of dual-microphone input and WindGuard. The
grey circles represent the two hearing instrument microphones.
WindGuard ensures the optimum solution is provided
regardless of the environment. Obviously, when no
wind noise is detected, no gain reduction is applied.
However, the system continually analyzes and stores
information about the current environment for use in
calculating the wind-to-sound ratio. Figure 8 illustrates
the three different states of WindGuard processing. In
panel a, no wind noise is detected. In this situation,
the level of environmental sound is continually updated
for use in calculating wind-to-sound ratio in case wind
Frequency
Frequency
Frequency
Figure 8. States of WindGuard processing. Bars depict the power per each
band. Solid bars indicate the minimum power level within a certain period of
time, and dotted bar extensions indicate the maximum power level within that
same time period. The horizontal solid jagged line shows the average power
level per band of the acoustic sound. The (a) scenario depicts the situation
where there is no wind, when the average power level is calculated. Scenario
(b) illustrates the presence of wind noise, when wind noise is less than 70
dB SPL. No gain reduction occurs in this scenario since the wind noise is
detected at a low level. In Scenario (c), wind noise is detected above 70 dB
SPL. Gain reduction, shown as down-arrows, is applied to bring the levels of
the wind noise to the average power levels previously stored by the system.
Be untroubled by feedback with DFS Ultra II
Acoustic feedback is largely responsible for giving
hearing aids a bad reputation. This is in part because
others may easily hear the whistling caused by acoustic
feedback even in cases when the hearing instrument
user does not. Feedback cancellation processing can
drastically reduce the occurrence of acoustic feedback and is available in nearly all modern hearing aids.
Feedback cancellation has the potential to increase
the amount of gain available for a particular fitting by
15 dB or more in a static situation where there are no
dynamic variations in the feedback path due to client
movement or changes in the acoustics of the environment. However, feedback cancellation systems are
limited in their ability to operate effectively in dynamic
real-world situations. Factors such as room reverberation and nonlinearities of the hearing instrument can
cause the very whistling and chirping that the processing is intended to eliminate. To complicate matters further, most systems cannot distinguish between actual
feedback and external sounds that may be correlated
with feedback. Such sounds include tones, beeps and
musical notes, and the failure of the feedback cancellation system to recognize these sounds often results
in disturbing echoing or ringing artifacts. As a result,
they must compromise on balancing performance in
terms of gain, sound quality and critical situations such
as phone usage. For example, providing the desired
amplification means the wearer may have to tolerate
poor sound quality as the system erroneously attacks
non-feedback sound inputs.
ReSound Enya users are protected against feedback
by industry-leading feedback management technology. ReSound has long led the field in feedback cancellation with no compromise in sound quality with its
unique use of two cancellation filters, adaptive filter
constraints and separate cancellation filters for dual
microphone instruments. DFS Ultra II adds input signal modeling, which maintains a representation of the
sound entering the hearing instrument. The advantage
of this component is that the system can more easily distinguish between feedback and non-feedback
sounds, vastly improving the dynamic behavior of the
system. Important everyday sounds like phone rings,
alarm beeps and music can be amplified to desired
levels without being mistaken for feedback.
DFS Ultra II also incorporates WhistleControlTM to ensure feedback-free performance in all daily life situations, including when a phone is held up to the hearing
instrument. Because the feedback cancellation is constrained to not adapt to signals that are very different
from the feedback pathway model, it is possible for
intermittent feedback to occur in situations like this.
WhistleControl restores the desired response when
feedback is imminent (Figure 9). What this means to
hearing instrument users is that they can enjoy the
most advanced, effective feedback control on the
market today while experiencing the superior sound
quality that ReSound has always provided.
Real ear SPL (dB)
Figure 6. Spectrogram showing the difference between another manufacturer’s noise reduction system off and on under the same test conditions. The reduction has a different pattern than the spectrogram of the background noise.
WindGuard consists of two components: a wind detection module and a wind reduction module. In the
detection stage, the amount of wind noise with respect to other sounds is calculated across both microphones by correlating the signal from each microphone. Wind noise is likely to be present when the
signals from each microphone are not correlated. In
the final stage of wind detection, the level of wind noise
is compared to the level of other sounds in the environment to determine a wind-to-sound ratio, which is
used by the wind reduction module to determine how
much to reduce gain.
noise appears. Panel b shows the state where wind
noise is detected, but where it is below 70 dB SPL.
No gain reduction is applied in this case. Panel c illustrates how gain is reduced in low-frequency bands
if wind noise is detected and exceeds 70 dB SPL.
The amount of gain reduction is based on the windto-sound ratio, and is intended to bring the level of
wind noise to the average sound level of the user’s
environment.
Sound Level
Figure 5. Spectrogram showing the difference between NoiseTracker II off
and on. The reduction corresponds well to the background noise spectrogram in Figure 4.
cy bands that are unaffected by wind. The amount of
gain reduction applied varies with the environment and
the level of the wind noise, making the reduction as
personalized as possible to the situation without sacrificing audibility for other sounds. The end result: the
hearing instrument user has a very natural sounding
experience, with soft wind noise in the background
and preserved audibility for other sounds in the environment.
Desired amplification
Feedback due to phone
Response restored by DFS
Ultra with built-in Whistle
Control
Frequency (Hz)
Figure 9. DFS Ultra II with built-in Whistle Control eliminates feedback in critical situations like phone use. The feedback which occurred without DFS Ultra
and Whistle Control (dotted line) was eliminated and the response restored to
the desired amplification when this feature was activated.
Flexible, personalized solutions for tinnitus
Tinnitus is a concern for many people, and affects
approximately 10-15% of the overall population, with
approximately 3-5% of the population suffering from
clinically treatable tinnitus14. Many persons with hearing loss in fact have tinnitus as their primary complaint.
Both tinnitus sufferers and clinicians may struggle to
find truly flexible tinnitus treatment devices that support the individual needs of users. Sound preference
and acceptability can vary greatly from person to person, and therefore flexible sound therapy solutions are
critical to meet these personalized needs and wants.
ReSound Tinnitus is a complete package that includes
combination instruments like ReSound Enya along
with the ReSound ReliefTM app as well as valuable
counseling materials to support clinicians in tinnitus
management services.
REFERENCES
1. MarkeTrak 9: A New Baseline. Estimating hearing
loss and adoption rates and exploring key aspects
of the patient journey, Final Report, March 2014,
Hearing Industries Association.
A combination instrument
The ReSound Enya TSG (Tinnitus Sound Generator)
can be activated in any listening program and offers
pre-defined sounds as well as the possibility to customize the frequency content and modulation of the
tinnitus sound for the individual. In addition, ear-to-ear
communication in ReSound Enya 4 models synchronizes the modulation between ears for the most harmonious experience.
4. Ricketts T, Henry P. Low-frequency gain compensation in directional hearing aids. American Journal of Audiology. 2002; 11(1): 29-41.
Ultimate personalization
Not all people prefer to listen to broadband noises.
With the ReSound ReliefTM app, tinnitus sufferers can
introduce sounds beyond what is inside their hearing
instrument into their sound therapy. These include environmental sounds, music, personal imported sounds
as well as guided relaxation exercises. ReSound Relief
ultimately acts as a multisensory personal sound player (Figure 10). It allows the user to create personalized
soundscapes that integrate auditory, visual and tactile
cues to help distract them from focusing on their tinnitus. Each soundscape can be personalized by name,
mood color and a layering of multiple sounds. ReSound Relief also offers counseling information to help
support your clinical guidance through a tinnitus management program, which makes the Relief app unique
to other tinnitus apps available today. Sounds from
the Relief app can be wirelessly streamed to ReSound
Enya hearing instruments using the ReSound UniteTM
Phone Clip+ and 2.4GHz wireless streaming technology, or simply used by plugging in a set of headphones.
2. Moore BCJ & Glasberg BR. Suggested formulae
for calculating auditory filter bandwidths and excitation patterns. Journal of the Acoustical Society
of America. 1983; 74: 750-753.
3. Cord MT, Surr RK, Walden BE, Dyrlund O. Relationship between laboratory measures of directional advantage and everyday success with directional microphone hearing aids. Journal of the
American Academy of Audiology. 2004; 15(5):
353-64.
5. Jespersen CT. Independent study identifies a
method for evaluating hearing instrument sound
quality. Hearing Review. 2014; 21(3):36-40.
Figure 10. ReSound ReliefTM App Offers personalized soundscapes, helpful
tips and usage information.
6. Bentler R, Wu Y, Kettel J, Hurtig R. Digital noise reduction: outcomes from laboratory and field studies. Int J Audiol. 2008; 47:447-460.
7. Ricketts T, Hornsby B. Sound quality measures for
speech in noise through a commercial hearing aid
implementing “digital noise reduction”. J Acad Am
Audiol. 2005; 16:270-277.
8. Sarampalis A, Kalluri S, Edwards B, Hafter E.
Objective measures of listening effort: Effects of
background noise and noise reduction. J Speech
Lang Hear Res. 2009; 52: 1230-1240.
9. Brons I, Houben R, Dreschler W. Perceptual effects of noise reduction with respect to personal
preference, speech intelligibility, and listening effort. Ear Hear. 2013; 34(1): 29-41.
10. Brons I, Houben R, Dreschler W. Effects of noise
reduction on speech intelligibility, perceived listening effort and personal preference in hearing
impaired listeners. Trends in Hearing. 2014; 18:
1-10.
11. Boll SF. Suppression of acoustic noise in speech
using spectral subtraction. IEEE Trans Acoust
Speech Sig Proc . 1979; 27:113-120.
12. Thompson SC. Directional microphone patterns:
They also have disadvantages. Audiology Online.
2000. http://www.audiologyonline.com/articles/
directional-microphone-patterns-they-also-1294.
13. Kates J. Digital Hearing Aids. 2008. San Diego:
Plural Publishing.
14. McFadden, D. Tinnitus: facts, theories, and treatments. Report of Working Group 89, Committee on Hearing Bioacoustics and Biomechanics.
1982. Washington, DC: National Academy Press.
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