Evaluation of a portable two-microphone adaptive beamforming speech processor with cochlear implant patients

Abstract

A two-microphone noise reduction technique was tested with four cochlear implant patients. The noise reduction technique, known as adaptive beamforming (ABF), used signals from only two microphones--one behind each ear--to attenuate sounds not arriving from the direction directly in front of the patient. The algorithm was implemented in a portable digital signal processor, and was compared with a strategy in which the two microphone signals were simply added together (two-microphone broadside strategy). Tests with the four patients were conducted in a soundproof booth with target speech arriving from in front of the patient and multitalker babble noise arriving at 90 deg to the left. Results at 0-dB signal-to-noise level (S/N) showed large improvements in speech intelligibility for all patients, when compared to the two-microphone broadside strategy. Precautions were taken to avoid cancellation of the target speech, and, accordingly, subjective tests showed no deterioration in performance for the adaptive beamformer in quiet. Physical measurement of the directional characteristics of the ABF was made with the microphones placed behind the ears of a KEMAR manikin and in the same acoustic environment as used with the patients. Results showed directional gain of approximately 10 dB when the angle of incidence for interfering noise was shifted more than 20 to 30 deg from directly in front of or behind the manikin.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a method for enhancing interaural level differences at low frequencies

“…Further evaluations are necessary to assess how well such schemes may work in everyday situations. There is some evidence that such schemes may be effective for people with cochlear implants (van Hoesel and Clark, 1995;Hazrati and Loizou, 2013).…”

Use of a sigmoidal-shaped function for noise attenuation in cochlear implants

“…A number of preprocessing noise-reduction algorithms have been proposed for cochlear implants over the years (Yang and Fu, 2005;Loizou et al, 2005;Loizou, 2006;Van Hoesel and Clark, 1995;Wouters and Vanden Berghe, 2001). The preprocessing approach to noise reduction, however, has three main drawbacks: (1) preprocessing algorithms sometimes introduce unwanted distortion in the signal, (2) some algorithms (e.g., subspace algorithms) are computationally complex (and consequently power hungry) and do not integrate well with existing CI strategies, and (3) it is not easy to optimize the operation of a particular algorithm to individual users.…”

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

“…However, performance deteriorates as acoustic conditions degrade due to complicating factors such as reverberation and moving or multiple noise sources (Greenberg and Zurek, 1992;van Hoesel and Clark, 1995;Hamacher et al, 1997;Wouters and Vanden Berghe, 2001).…”