Ecological Momentary Assessment to Obtain Signal Processing Technology Preference in Cochlear Implant Users.

Background: To assess the performance of cochlear implant users, speech comprehension benefits are generally measured in controlled sound room environments of the laboratory. For field-based assessment of preference, questionnaires are generally used. Since questionnaires are typically administered at the end of an experimental period, they can be inaccurate due to retrospective recall.

A wavelet-based noise reduction algorithm and its clinical evaluation in cochlear implants.

Noise reduction is often essential for cochlear implant (CI) recipients to achieve acceptable speech perception in noisy environments. Most noise reduction algorithms applied to audio signals are based on time-frequency representations of the input, such as the Fourier transform. Algorithms based on other representations may also be able to provide comparable or improved speech perception and listening quality improvements.

An adaptive Australian Sentence Test in Noise (AuSTIN).

Objectives: The aim of this research is to describe the development of an adaptive Australian Sentence Test in Noise and to validate the test in terms of test-retest reliability and efficiency using data obtained from its clinical application.

Design: The relative intelligibility of 1264 Bamford-Kowal-Bench (BKB)-like sentences in the presence of competing four-talker babble was assessed with cochlear implant recipients. Intensity adjustments to the babble segments were made to reduce intersentence variability.

A beamformer post-filter for cochlear implant noise reduction.

Cochlear implant users have limited ability to understand speech in noisy conditions. Signal processing methods to address this issue that use multiple microphones typically use beamforming to perform noise reduction. However, the effectiveness of the beamformer is diminished as the number of interfering noises increases and the acoustic environment becomes more diffuse.

Combining directional microphone and single-channel noise reduction algorithms: a clinical evaluation in difficult listening conditions with cochlear implant users.

Objectives: This study tested a combination of algorithms designed to improve cochlear implant performance in noise. A noise reduction (NR) algorithm, based on signal to noise ratio estimation was evaluated in combination with several directional microphone algorithms available in the Cochlear CP810 sound processor.

Design: Fourteen adult unilateral cochlear implant users participated in the study.

Perceptually optimized gain function for cochlear implant signal-to-noise ratio based noise reduction.

Noise reduction in cochlear implants has achieved significant speech perception improvements through spectral subtraction and signal-to-noise ratio based noise reduction techniques. Current methods use gain functions derived through mathematical optimization or motivated by normal listening psychoacoustic experiments. Although these gain functions have been able to improve speech perception, recent studies have indicated that they are not optimal for cochlear implant noise reduction.

Clinical evaluation of signal-to-noise ratio-based noise reduction in Nucleus® cochlear implant recipients.

Objective: The aim of this study was to investigate whether a real-time noise reduction algorithm provided speech perception benefit for Cochlear™ Nucleus® cochlear implant recipients in the laboratory.

Design: The noise reduction algorithm attenuated masker-dominated channels. It estimated the signal-to-noise ratio of each channel on a short-term basis from a single microphone input, using a recursive minimum statistics method.

Frequency-compression outcomes in listeners with steeply sloping audiograms.

Previous investigation of an experimental, wearable frequency-compression hearing aid revealed improvements in speech perception for a group of listeners with moderately sloping audiograms (Simpson et al, 2005). In the frequency-compression hearing aid, high frequencies (above 1600 Hz) were amplified in addition to being lowered in frequency. Lower frequencies were amplified without frequency shifting.

Improvements in speech perception with an experimental nonlinear frequency compression hearing device.

The performance of an experimental frequency compression hearing device was evaluated using tests of speech understanding in quiet. The device compressed frequencies above a programmable cut-off, resulting in those parts of the input signal being shifted to lower frequencies. Below the cut-off, signals were amplified without frequency shifting.