Biomedical subjects

W Soede

Publications and source records attributed to W Soede.

4 recordsLinked to original sources

PubMed1993

Development of a directional hearing instrument based on array technology.

A directional hearing aid might be beneficial in reducing background noise in relation to the desired speech signal. Conventional hearing aids with a directional cardioid microphone are insufficient because of the low directivity of cardioids. Research was done to develop microphone(s) with strong directional characteristics using array techniques. Particular emphasis was given to optimization and stability. Free-field simulations of several robust models show that a directivity index of 9 dB can be obtained at the higher frequencies. Simulations were verified with a laboratory model. The results of the measurements show a good agreement with the simulations. Based on simulations and measurements, two portable models were developed and tested with a KEMAR manikin. The KEMAR measurements show that the two models give an improvement of the signal-to-noise ratio of approximately 7.5 dB in a diffuse sound field. It may be concluded that the developed microphones have the capability to reach a significant improvement of speech intelligibility in noise under practical circumstances.

Acoustic Stimulation↗

PubMed1993

Assessment of a directional microphone array for hearing-impaired listeners.

Hearing-impaired listeners often have great difficulty understanding speech in surroundings with background noise or reverberation. Based on array techniques, two microphone prototypes (broadside and endfire) have been developed with strongly directional characteristics [Soede et al., "Development of a new directional hearing instrument based on array technology," J. Acoust. Soc. Am. 94, 785-798 (1993)]. Physical measurements show that the arrays attenuate reverberant sound by 6 dB (free-field) and can improve the signal-to-noise ratio by 7 dB in a diffuse noise field (measured with a KEMAR manikin). For the clinical assessment of these microphones an experimental setup was made in a sound-insulated listening room with one loudspeaker in front of the listener simulating the partner in a discussion and eight loudspeakers placed on the edges of a cube producing a diffuse background noise. The hearing-impaired subject wearing his own (familiar) hearing aid is placed in the center of the cube. The speech-reception threshold in noise for simple Dutch sentences was determined with a normal single omnidirectional microphone and with one of the microphone arrays. The results of monaural listening tests with hearing impaired subjects show that in comparison with an omnidirectional hearing-aid microphone the broadside and endfire microphone array gives a mean improvement of the speech reception threshold in noise of 7.0 dB (26 subjects) and 6.8 dB (27 subjects), respectively. Binaural listening with two endfire microphone arrays gives a binaural improvement which is comparable to the binaural improvement obtained by listening with two normal ears or two conventional hearing aids.

Acoustic Stimulation↗

PubMed1993

Directional hearing aid based on array technology.

The hearing impaired often have great difficulty understanding speech in surroundings with background noise or reverberation. A directional hearing aid might be beneficial in reducing background noise in relation to the desired speech signal. To this end microphone systems were developed with strongly directional characteristics, using array techniques. Considerable attention was paid to optimization and stability. Free-field simulations of several robust models showed that a directivity index of 9 dB can be obtained. Simulations were verified with a laboratory model. Based on simulations and measurements, two portable prototypes were developed and tested using a KEMAR-manikin. The KEMAR-measurements showed that the two prototypes gave an improvement of the signal to noise ratio of 7 dB in a fully diffuse sound field. The benefit of these microphone arrays for the hearing impaired was tested in a sound insulated room. One loudspeaker was placed in front of the listener simulating the partner in a discussion, and a diffuse background noise was produced by eight loudspeakers placed on the corners of a cube. The hearing impaired subject was seated in the centre of the cube. The speech-reception threshold in noise for simple Dutch sentences was determined with a normal single omni-directional microphone and with one of the prototypes. The results of the listening tests with 45 hearing impaired subjects showed an average improvement of the S/N-ratio of 7.0 dB for monaural fitting.

Acoustic Stimulation↗

PubMed1993

Development and assessment of two fixed-array microphones for use with hearing aids.

Hearing-impaired listeners often have great difficulty understanding speech in situations with background noise (e.g., meetings, parties). Conventional hearing aids offer insufficient directivity to significantly reduce background noise relative to the desired speech signal. Based on array techniques, microphone prototypes have been developed with strongly directional characteristics to be incorporated into the frame and the "temples" of a pair of eyeglasses. Particular emphasis was on optimization and electronic stability. Computer simulations show that a directivity index of more than 10 dB can be obtained at the higher frequencies. Simulations were verified with free-field measurements. To investigate the influence of the human head on directivity, two portable models were also tested with a KEMAR manikin. The measurements show that the two models give an improvement of the signal-to-noise ratio of approximately 7 dB in a diffuse background noise field compared with an omnidirectional microphone. For the clinical assessment of these microphone arrays in the diffuse noise field (simulating a cocktail party situation), the speech-reception threshold in noise for simple Dutch sentences was determined with a normal single omnidirectional microphone and with one of the microphone arrays. The results of monaural listening tests of 30 subjects with normal hearing and 45 subjects with hearing impairment show that the microphone arrays give a mean improvement of the speech reception threshold in noise of about 7 dB compared with an omnidirectional microphone.

Adult↗