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CLINICAL GUIDANCE | SECTION ONE

The channel gains adapt so as to optimize the loudness of the signal into the

recipient’s dynamic range. For low intensity sounds, the gain is increased while

for high intensity sounds, the gain is reduced to keep the signal level below the

C-level (see Figure 10). The channel gains are adaptively adjusted to maintain

the signal in each channel within the upper region of the dynamic range

of hearing. ADRO responds slowly and smoothly to changes in signal level.

Continual adjustment of channel gains using ADRO provides improved sound

quality and improved speech perception performance in quiet at soft levels,

without affecting performance in noise. ADRO will override manual gains to

channel gains.

Studies with ADRO in both adults and children

1,2

have shown that ADRO

improves performance in quiet with no decrement in speech understanding in

noise.

ADRO is used alone and in combination with other input processing algorithms

for the SmartSound

™

Everyday environment and also in combination for

the SmartSound Noise, Focus and Music environments. See section 1.13

SmartSound for more information.

References

1. James, C.J., Blamey, P.J., Martin, L., Swanson, B., Just, Y., Macfarlane, D. (2002). Adaptive

dynamic range optimization for cochlear implants: a preliminary study. Ear & Hearing.

23, 49S-58S.

2. Dawson, P.W., Decker, J.A., Psarros, C.E. (2004). Optimizing dynamic range in children

using the Nucleus cochlear implant. Ear & Hearing.25, 230-41.

1.12.2 Whisper

™

Whisper

™

provides recipients with greater access to soft signals, such as the

softer elements of some music. It was developed by Prof. Hugh McDermott at

the University of Melbourne

Whisper uses fast time constants operating at the front end of the automatic

gain control (AGC). Whisper compresses the more intense portions of the

input signal and processes softer parts of the signal that would typically not

be heard. This is very analogous to wide dynamic range compression. Using

Whisper, signals above the 52 dB SPL compressor knee-point are compressed

at a 2:1 ratio, while softer signals below the knee-point are not compressed and

maintain a 1:1 relationship between input and output (see Figure 11).

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