WesPac IX

The values of the comfort maximum gain values are usually expressed in dB values that will be very amiliar to people who have fitted hearing aids then calculate initial Comfortable Levels for
the our stereo. The fitting software will probably have an in-situ measurement
Average CUNY sentence scores in quiet at 3 input levels, and in noise for 19 listeners in a blind trial comparison of ADRO and WDRC.ADRO was also evaluated with speech in background noise.ADRO than for WDRC. A paired t-test (t = 3.81, df = 18, p < 0.01) showed that this difference
was statistically significant. This advantage of ADRO over WDRC in noise was achieved
without additional noise reduction algorithms, showing that noise reduction is “built in” to
ADRO.They have a clear and intuitive interpretation: larger values indicate louder output, and
smaller values indicate softer output sounds. There is no need to predict complex cross-over
frequencies, kneepoints, and compression ratios.
There are four easy steps to fitting an ADRO hearing aid:
Enter the audiogram. The fitting program will next step.
Balance loudness across frequencies at a comfortable level. This is like setting the graphics
equalizer on facility to generate narrow-band noises with controlled level and frequency inside the hearing aid. The audiologist (or the listener) should adjust these until they are in the comfortable range and equally loud across frequencies. This should take no more than a few minutes per ear.

There is no need to establish the Maximum Comfortable Level or to do Loudness Scaling. The
fitting software will automatically calculate the initial ADRO fitting from the audiogram and the
Comfortable Levels.
Adjust the overall volume to the preferred level for conversational speech. This is like
adjusting the volume on your stereo – one adjustment makes everything louder or softer.
nd noises are too loud, the maximum
igure 4. Steps required to fit an ADRO hearing aid illustrated with screen
shots from the Configure™ software used in the clinical trials of ADRO.
SUMMARY
The introduction of digital signal proce
aids has enabled the development of
new algorithms such as the ADRO amplifier. ADRO is easy to fit to any hearing loss, from
mild to severe, in an interactive and intuitive manner with the client. Once the hearing aid has
Different clients will have different preferences, even if they have the same audiogram. Just
turn on the hearing aid and have a natural two-way conversation with the client while you are
adjusting the volume. It is much easier for clients to choose the best volume setting this way
than to rely on loudness scaling with beeps and pure tones.
Fine tune Maximum Gains and Maximum Output Levels (if necessary). The Maximum
Gains control the loudness of soft sounds. If soft backgroud should be reduced at the appropriate frequencies. If soft speech is too soft, the maximum gain should be increased. The low-frequency maximum gain settings can also be used to change the sound of the client’s own voice. The high-frequency maximum gain settings can be reduced to avoid feedback if necessary. The Maximum Output Levels (MOLs) control the loudness of sudden loud sounds. If loud sounds sound distorted, then the MOLs should be raised. If sudden loud sounds are uncomfortable, then the MOLs should be reduced at the appropriate frequencies

In quiet. The ADRO amdigital signal processing hearing aids and evaluated in several hearing aid trials [6, 7, 8]. Each trial has compared the mented in a BT corresponds to low level background noise, and the higher one to speech.ADRO processing with an alternative amplifier in the same hearing aid hardware.
Figure 3 shows perception scores for the City University of New York (CUNY) sentences
[18] from a comparison study of ADRO with WDRC. Both amplifiers were imple
E hearing aid especially for the trial. The WDRC amplifier had three channels and was fitted
with the NAL-NL1 prescribed gains. The WDRC attack and release time constants were 10 ms
and 80 ms respectively. Nineteen people with pure-tone-average hearing thresholds from 33 to
97 dB HL were tested with both amplifiers in the same hearing aid hardware without knowing
which program was ADRO and which was WDRC after 8 weeks of take-home experience in
which they could switch between the two programs at will. At the end of the trial, 16 people
had an overall preference for ADRO, and 3 had an overall preference for WDRC. Figure 3
indicates that there was a significant (p<0.01) speech intelligibility benefit in quiet across the
range from low to normal levels (53, 60, and 66 dB). This benefit for speech perception in
quiet has been replicated in every evaluation of ADRO with hearing aids and cochlear implants.
The speech intelligibility results indicate that the ADRO rules provided good speech

One of the main differences between ADRO and other nonlinear amplifiers is that ADRO is
linear most of the time, and only becomes nonlinear when the output levels are no longer in the
optimum range for the listener. ADRO uses fuzzy logic rules to optimize the output signal of
the hearing aid in each narrow frequency channel. A “fuzzy” logic rule is one that is not always
true or false, but can be true for part of the time (see the description of the comfort and
audibility rules below). The rules ensure the comfort and audibility of sounds by keeping the
output level between a comfort target and an audibility target. If a sound falls below the
audibility target, it is made louder. If it rises above the comfort target, it is made softer. While
the sound is within the optimized range, the hearing aid gain does not change. Instead, it
operates in a linear fashion. This approach is quite different from the alternative compression
strategies that continuously vary gain according to fixed input/output functions in a smaller
number of broader overlapping frequency bands.

The dynamic range of hearing is usually considered to be the range between the hearing
threshold at the softer end, and the discomfort level, or uncomfortable level at the louder end.
It is well-known that this dynamic range varies with frequency in listeners with normal hearing
[11], and that the dynamic range is reduced in listeners with impaired hearing [12]. One of the
goals of a hearing aid is to place sounds within this reduced dynamic range for listeners with
impaired hearing in order to achieve audibility and comfort levels similar to those of a person
with normal hearing in normal listening environments. In 1937, Fletcher and Munson [12]
suggested that compression of the output signal would be an appropriate way to achieve this
goal. The first successful compression hearing aids appeared in the 1980’s, and wide dynamic
range compression (WDRC) is now used in almost all hearing aids to achieve the goals of
comfort and audibility. The type and amount of compression is usually determined with a
prescription such as NAL-nonlinear [13], Desired Sensation Level i/o [14], or CamFit [15].
Although WDRC is used in most hearing aids, linearity is a desirable quality for amplifiers
used by people with normal hearing because it provides the best sound quality. Compression
would usually be considered a distortion of the sound in most high fidelity sound systems.
WDRC hearing aids must therefore make a compromise between sound quality, which requires
long time constants and compression ratios close to one [16], and comfort and audibility which
may require short time constants and high compression ratios [17].
In addition to linearity, frequency response is also a factor in subjective judgments of sound
quality amongst listeners with normal hearing. People will often adjust the base or treble, or
the graphics equalizer, as well as the volume control on their sound system to suit their own
preferences with regard to sound quality and loudness. In effect, they are optimizing the
frequency response and the volume of the linear sound system, taking into account the sound
they are listening to, the environmental noise, and their own preferences.
The fundamental idea behind ADRO is to produce a linear amplifier that automatically
optimizes its frequency response and output levels for any sound, in any environment, and is
fitted taking into account the preferences and hearing loss of the listener

Modern hearing aids are changing very rapidly. The market has changed from 80% analog in
2000 to 83% digital devices in 2004 [1]. This trend has enabled a new generation of digital
signal processing algorithms [2, 3] that are revolutionizing many aspects of the hearing health
industry. One of these new algorithms is the digital amplification strategy known as Adaptive
Dynamic Range Optimization (ADRO™) [4, 5]. The ADRO amplifier is intrinsically digital
and would have been extremely difficult to implement as an analog circuit. It uses statistical
analysis of the output signal in many narrow frequency bands (usually 32 or 64 bands) and
fuzzy logic rules to control the gain independently in each frequency band. Several clinical
trials have confirmed that the ADRO strategy provides benefits over conventional linear and nonlinear amplifiers for hearing aids [6, 8, 8] and cochlear implants [9, 10]. The scientific
evidence supporting these benefits, and the underlying reasons for the benefits are reviewed
here.

Clinical trials of the adaptive dynamic range optimization (ADRO) amplifier
show that it produces more comfortable sound, higher speech recognition in quiet
at low input levels, higher speech recognition in background noise, and improved
sound quality relative to conventional wide dynamic range compression (WDRC)
hearing aids. Instead of attempting to compress a wide range of input sounds
into a narrower range of hearing, ADRO uses statistical rules to select the most
informative parts of the intensity range and presents it at a comfortable level for
the listener. Typically, ADRO uses a higher number of narrow frequency
channels and slower adaptation rates than WDRC. First used in cochlear
implants, ADRO is particularly well-suited to bimodal and hybrid stimulation
which combine electric and acoustic stimulation in opposite ears, or in the same
ear respectively.

Welcome To Acoustics Congress