On the modeling of the vent path in hearing aid systems.
Explore the source record for details and available documents.
Acoustic Stimulation↗
Biomedical subjects
B Rafaely
Publications and source records attributed to B Rafaely.
Feedback path variability modeling for robust hearing aids.
Acoustic feedback is a common problem in hearing aids with vented earmolds. Hearing aids designed to work under normal conditions become unstable when the feedback path varies under changing conditions. A comprehensive study of the variability of the feedback path under various conditions and for different users is presented in this paper. A multiplicative uncertainty bound widely used in H-infinity robust control is suggested to model the variations, which is then used to formulate a robust stability condition for the hearing aid. The upper limit of the closed-loop acoustic gain of the hearing aid for maintaining robust stability is also derived. Examples of robust constant amplification hearing aids, which maintain stability in the face of the given variations in the feedback path, are presented. The robust stability condition is also suggested as a tool to design more robust digital, hearing aids.
Acoustic Stimulation↗
Spatial-temporal correlation of a diffuse sound field
The spatial correlation function of the sound in a diffuse field is a quantity widely used in many reverbrant room acoustic applications. Although results for the spatial and temporal correlation for pure-tone and band-limited diffuse fields have already been developed, these have not been generalized for other signal types. This work presents a generalized derivation of the diffuse field spatial-temporal correlation which can be used for stationary random signals with given power spectral density. It is shown that the spatial-temporal correlation depends entirely on the temporal correlation of the signal exiting the diffuse field, or alternatively on its power spectral density. A simulation using the plane wave model is presented for tonal and broadband diffuse sound fields.
Journal Article↗
Broadband performance of an active headrest.
This paper presents a study of the attenuation of broadband random acoustic disturbances, when using a feedback active headrest system, as originally suggested by Olson and May. Previous studies showed that a practical active headrest can be designed for tonal disturbances using feedforward controllers. However, many applications, such as jet aircraft and cars, require feedback systems to control random disturbances over a wide frequency bandwidth. In this work, robust feedback controllers are designed to control broadband random disturbances in the low-frequency range based on measured data from a laboratory headrest system. The results show that a practically useful performance can be achieved, but only if the controller is designed to minimize the pressure at a "virtual microphone" close to the listener's ears, and that the performance is maintained reasonably well with movements of the listener's head. The paper emphasizes the importance of both the acoustics and the control in the design of broadband active headrest systems.
Acoustics↗
The effect of steroid hormones on buccal mucosa of menopausal women.
The effects of local application of estrone and progesterone on the oral mucosa was studied in sixty-one patients. These included forty-one postmenopausal women with various subjective oral complaints, ten postmenopausal women with no oral complaints, and ten normally menstruating women. Subjective complaints (dryness, bad taste, burning sensation, and viscous saliva), quantity of saliva, and histologic changes in buccal mucosa were evaluated before and after treatment. Treatment comprised three modalities: an ointment containing estrone alone; another ointment of estrone and progesterone; and a third with a placebo base. These were massaged three times daily over the gingivae and oral mucosa for 30 days. A significant increase in secretion of saliva was observed with all three treatment modalities. Biopsies showed marked proliferative changes with all three types of ointment. A moderate improvement in subjective complaints followed all types of medication. These results indicate no specific effect of female sex hormones on the factors considered in this study. It appears that simple, repeated massage with any suitable ointment base is an effective method of inducing proliferative changes in atrophic buccal mucosa, increasing salivary secretion, and alleviating some of the subjective oral complaints of postmenopausal women.
Administration, Topical↗