Comparisons of Spectra 22 Performance in Noise with and without an Additional Noise Reduction Preprocessor

Abstract

This paper describes a two-microphone, software-programmable noise-reduction device that was interfaced to the Nucleus Spectra 22 speech processor to act as a front-end noise-reduction preprocessor. The development for the portable processor and the noise-reduction algorithm, more formally known as beamforming, was originally motivated by complaints from individuals who use hearing aids. These individuals complain about a deterioration in performance with increasing levels of background noise. Since individuals who use cochlear implants have similar complaints, it was a natural extension to pose the question: "What benefit, if any, would the beamforming algorithm provide to individuals who use cochlear implants?" To arrive at an answer, the audio interface to the noise reduction device was modified (to make it compatible to the Nucleus Spectra 22 speech processor), and a set of precursory subject experiments were performed. 1 The precursory studies were specific to the Nucleus 22 Channel Cochlear Implant and the Spectra 22 speech processor, both manufactured by Cochlear Corporation and Cochlear Limited. The noisereduction device used in the precursory studies is known as the Alpha II and is developed by AudioLogic Inc.Eleven English-speaking subjects participated in a series of sessions during which they were tested with their own Spectra 22 speech processor and with the Alpha II beamforming algorithm acting to preprocess the input data to their device. The beamforming algorithm was configured for a beam width of ±15° (15° on either side of the listener). Five of the 11 subjects were tested with a no beam algorithm. The no beam program was used to demonstrate that any improvements measured with the Alpha II were caused by the beamforming algorithm and not by the addition of the second microphone.The subjects were tested at signal-tonoise ratios (SNRs) strong enough to degrade their Spectra alone scores in noise relative to their scores in quiet. The average noise score was 29.3% (SD:10.9) with the Spectra alone and 55.5% (SD:27.5) with the Spectra plus the Alpha II beam program. The average scores in noise for the five 1 This data is a subset of data originally submitted to and pending publication in Ear and Hearing. It is offered with the understanding that the manuscript is tutorial and not intended as a forum for results.

Otimização da percepção da fala em deficientes auditivos usuários do sistema de implante coclear multicanal

“…O processador de fala codifica o sinal acusticamente processado para um padrão de estimulação do eletrodo. Nesse caso, a integridade do processador e seus algoritmos têm um fator determinante na habilidade do usuário de separar o sinal alvo de outros sinais 3 . O objetivo deste trabalho foi realizar um estudo clínico avaliando a percepção da fala em usuários do IC multicanal Nucleus 24, nas diferentes estratégias de codificação disponíveis neste dispositivo (SPEAK, CIS e ACE), em diferentes situações de audição (silêncio e ruído), a fim de verificar os benefícios advindos da tecnologia atual para cada usuário e determinar quais estratégias e quais combinações de parâmetros foram mais apropriadas para serem fornecidas aos mesmos.…”

Two-microphone spatial filtering provides speech reception benefits for cochlear implant users in difficult acoustic environments

“…Kollmeier and colleagues (Kollmeier et al, 1993;Kollmeier and Koch, 1994) developed and evaluated a spatial-filtering algorithm, using binaurally-situated microphones, which provided an SRT gain of roughly 2 dB relative to an omni-directional reference in background noise. Margo et al (1997) evaluated a similar strategy using a real-time device and observed mixed results. Specifically, in a sound-proof room with straightahead target speech and noise at 90 , 3 of 11 listeners showed worse performance with the processing, while the remaining 8 had speech-reception improvements ranging from 20 to 77 percentage points.…”

Avaliação da percepção da fala com ruído competitivo em adultos com implante coclear

“…To subjects that use the cochlear implant, the authors describe that a speech processor codifies the acoustically processed signal to an electrode stimulation pattern. In this case, integrity of the speech processor and its algorithm has been a determining factor for the users' skills to separate the target signal from other signals 5 .…”

“…The negative influence of noise in speech perception of cochlear implant users may be justified by the following factors: the speech processor codifies the signal to a stimulation pattern of electrodes in quiet that is different from it in noise 6 ; signal processing in the cochlear implant system reduces information and signal redundancy 3 ; monoaural input to the hearing system that consists in one single microphone connected to the speech processor, does not allow processing of noise reduction that is possible in the binaural auditory system 3,5 .…”

“…The studies have been carried out to develop new strategies for speech codification 7 , new noise reducing circuits 3 , and other supporting devices, such as Beamformer, binaural microphone, which preserves the sound originated from the front and attenuates the sound originated from the side and behind the patient 5 , modulated frequency systems 8 , and indication of use of hearing aids in the nonimplanted ear 9 . These technological resources aim at fundamentally promoting improvement in understanding speech in noise.…”