Evaluation of a real-time adaptive-beamforming hearing aid
Julie E. Greenberg, Patrick M. Zurek · The Journal of the Acoustical Society of America · 1989
A real-time two-microphone monaural hearing aid, based on the constrained adaptive beamformer proposed by Griffiths and Jim [IEEE Trans. Antennas Propag. AP-30, 27–34 (1982)], has been implemented and evaluated. The beamformer adapts to preserve the target signal (assumed to be straight ahead) and to minimize the power of jammer signals arriving from all other directions. The basic Griffiths-Jim algorithm is augmented with a method to inhibit adaptation in the presence of strong target signals [Greenberg et al., J. Acoust. Soc. Am. Suppl. 1 85, S26 (1989)]. The real-time system employs the Motorola DSP56001 and was evaluated using a speech target and a single jammer for a variety of free-space and head-mounted microphone configurations in anechoic and reverberant environments. The system demonstrates very good performance (30- to 40-dB gain from input to output in an intelligibility-weighted spectral average of target-to-jammer ratio) for several broadside microphone configurations in the anechoic environment. Adaptation inhibition provides a robust insensitivity to target misalignment at high-input target-to-jammer ratios. As expected, performance degrades with increasing reverberation; at the critical distance, the system provides 5- to 10-dB gain. In extreme reverberation, the system performs at least as well as a delay-and-sum beamformer. [Work supported by NIH.]