Speech understanding in background noise with the two-microphone adaptive beamformer BEAM in the Nucleus Freedom Cochlear Implant System.

Objective: This paper evaluates the benefit of the two-microphone adaptive beamformer BEAM in the Nucleus Freedom cochlear implant (CI) system for speech understanding in background noise by CI users.

Design: A double-blind evaluation of the two-microphone adaptive beamformer BEAM and a hardware directional microphone was carried out with five adult Nucleus CI users. The test procedure consisted of a pre- and post-test in the lab and a 2-wk trial period at home.

Factors affecting the use of noise-band vocoders as acoustic models for pitch perception in cochlear implants.

Although in a number of experiments noise-band vocoders have been shown to provide acoustic models for speech perception in cochlear implants (CI), the present study assesses in four experiments whether and under what limitations noise-band vocoders can be used as an acoustic model for pitch perception in CI. The first two experiments examine the effect of spectral smearing on simulated electrode discrimination and fundamental frequency (FO) discrimination. The third experiment assesses the effect of spectral mismatch in an FO-discrimination task with two different vocoders.

Improved music perception with explicit pitch coding in cochlear implants.

Music perception and appraisal is very poor in cochlear implant (CI) subjects partly because (musical) pitch is inadequately transmitted by the current clinically used sound processors. A new sound processing scheme (F0mod) was designed to optimize pitch perception, and its performance for music and pitch perception was compared in four different experiments to that of the current clinically used sound processing scheme (ACE) in six Nucleus CI24 subjects. In the F0mod scheme, slowly varying channel envelopes are explicitly modulated sinusoidally at the fundamental frequency (F0) of the input signal, with 100% modulation depth and in phase across channels to maximize temporal envelope pitch cues.

Effects of waveform shape on human sensitivity to electrical stimulation of the inner ear.

Psychophysical measures of the electrically stimulated human auditory system were obtained for different types of symmetric and asymmetric charge-balanced waveforms. Absolute detection thresholds of biphasic, pseudomonophasic, and 'alternating monophasic' current waveforms delivered by a bipolar intra-cochlear electrode pair were determined for four subjects implanted with the LAURA device. Thresholds for alternating monophasic stimuli, in which anodic and cathodic phases alternated every 5 ms, were 5-8 dB lower than for the biphasic waveforms for all four subjects.

Relative contributions of temporal and place pitch cues to fundamental frequency discrimination in cochlear implantees.

The effect of the filter bank on fundamental frequency (F0) discrimination was examined in four Nucleus CI24 cochlear implant subjects for synthetic stylized vowel-like stimuli. The four tested filter banks differed in cutoff frequencies, amount of overlap between filters, and shape of the filters. To assess the effects of temporal pitch cues on F0 discrimination, temporal fluctuations were removed above 10 Hz in one condition and above 200 Hz in another.

A flexible auditory research platform using acoustic or electric stimuli for adults and young children.

A user-friendly and versatile research platform for use in auditory experiments, referred to as APEX (Application for PsychoElectrical eXperiments), is described. The platform takes care of automatic stimulus presentation and collection of the subject's responses. Acoustical auditory, as well as electrical auditory experiments with CI recipients can be conducted.

Multichannel place pitch sensitivity in cochlear implant recipients.

Cochlear implant recipients perceive a rise in pitch when the site of stimulation is moved from the apex toward the base. The place pitch sensitivity is typically measured using the stimulation of single channels. However, all current cochlear implant devices stimulate multiple channels simultaneously or with pulses temporally interleaved.

Digital hearing aids and future directions for hearing aids.

In recent years many technical evolutions have been applied in hearing aids. In this paper differences between analog, programmable and fully digital hearing aids, the basic and supplementary functions of a hearing aid, and some important issues and future directions for digital hearing aids will be mentioned.