Showing papers on "Digital hearing aid published in 1993"

Real-time multiband dynamic compression and noise reduction for binaural hearing aids.

Abstract: A multi-signal-processor set-up is introduced that is used for real-time implementation of digital hearing aid algorithms that operate on stereophonic (i.e., binaural) input signals and perform signal processing in the frequency domain. A multiband dynamic compression algorithm was implemented which operates in 24 critical band filter channels, allows for interaction between frequency bands and stereo channels, and is fitted to the hearing of the individual patient by a loudness scaling method. In addition, a binaural noise reduction algorithm was implemented that amplifies sound emanating from the front and suppresses lateral noise sources as well as reverberation. These algorithms were optimized with respect to their processing parameters and by minimizing the processing artifacts. Different versions of the algorithms were tested in six listeners with sensorineural hearing impairment using both subjective quality assessment methods and speech intelligibility measurements in different acoustical situations. For most subjects, linear frequency shaping was subjectively assessed to be negative, although it improved speech intelligibility in noise. Additional compression was assessed to be positive and did not deteriorate speech intelligibility as long as the processing parameters were fitted carefully. All noise reduction strategies employed here were subjectively assessed to be positive. Although the suppression of reverberation only slightly improved speech intelligibility, a combination of directional filtering and dereverberation provided a substantial improvement in speech intelligibility for most subjects and for a certain range of signal-to-noise ratios. The real-time implementation was very helpful in optimizing and testing the algorithms, and the overall results indicate that carefully designed and fitted binaural hearing aids might be very beneficial for a large number of patients.

Digital hearing aid with microcomputer - uses acoustic sensor to pick up oto-acoustic reaction of inner ear to tones measured by electro-acoustic transducer

Abstract: In addition to the acoustic sensor and a digital signal processing microcomputer, the hearing aid contains an electro-acoustic transducer and a correction device for sequential generation of measuring tones. In dependence on the objective reaction of the user as compared with a stored hearing standard, a correction of the respective transmission data is carried out. The acoustic sensor (11) of the hearing aid (10) picks up the oto-acoustic reaction of the user's inner ear (25) to the measuring tones from the transducer (16). According to the respective sensor voltage, the microcomputer (13) carries out the comparison and correction. ADVANTAGE - Objective testing of hearing vol. and adaptation of transmit function.

Digital signal processing (DSP) applications for multiband loudness correction digital hearing aids and cochlear implants.

Abstract: Single-chip digital signal processors (DSPs) allow the flexible implementation of a large variety of speech analysis, synthesis, and processing algorithms for the hearing impaired. A series of experiments was carried out to optimize parameters of the adaptive beamformer noise reduction algorithm and to evaluate its performance in realistic environments with normal-hearing and hearing-impaired subjects. An experimental DSP system has been used to implement a multiband loudness correction (MLC) algorithm for a digital hearing aid. Speech tests in quiet and noise with 13 users of conventional hearing aids demonstrated significant improvements in discrimination scores with the MLC algorithm. Various speech coding strategies for cochlear implants were implemented in real time on a DSP laboratory speech processor. Improved speech discrimination performance was achieved with high-rate stimulation. Hybrid strategies incorporating speech feature detectors and complex decision algorithms are currently being investigated.

Behavioral assessment of adaptive feedback equalization in a digital hearing aid.

Abstract: An evaluation was made of the efficacy of a digital feedback equalization algorithm employed by the Central Institute for the Deaf Wearable Adaptive Digital Hearing Aid. Three questions were addressed: 1) Does acoustic feedback limit gain adjustments made by hearing aid users? 2) Does feedback equalization permit users with hearing-impairment to select more gain without feedback? and, 3) If more gain is used when feedback equalization is active, does word identification performance improve? Nine subjects with hearing impairment participated in the study. Results suggest that listeners with hearing impairment are indeed limited by acoustic feedback when listening to soft speech (55 dB A) in quiet. The average listener used an additional 4 dB gain when feedback equalization was active. This additional gain resulted in an average 10 rationalized arcsine units (RAU) improvement in word identification score.