Torsten Dr. Niederdränk

Hearing aid and method for adjusting a hearing aid

The process of adapting a hearing aid to its wearer is to be simplified. To this end the acoustic conditions in the auditory canal, especially the acoustic impedance, are estimated by measuring the input impedance of the earpiece on the hearing aid. For adjusting the hearing aid it is worthwhile using the mechanical resonance of the system of hearing aid and auditory canal which can be detected with the aid of the input impedance. This is produced by a simplified equivalent circuit diagram from which the corresponding acoustic variables can be obtained.

Experimental investigations of the acoustic backscattering of a single cavitation bubble

There is great interest in the oscillation of a single cavitation bubble in a sound field. The dynamic bubble behavior is investigated by means of the acoustic backscattering of a high‐frequency ultrasonic field. An experimental setup for generating single bubble cavitation is used. In addition to the driving sound field of low frequency (25 kHz) for generating the single cavitation bubble in a piezoelectric tube, a second high‐frequency image sound field is radiated into the cavitation cell by a focusing PVDF transducer. The high‐frequency components are scattered by the bubble and can be received by the same PVDF transducer, assuming that the bubble is placed in the focus of the transducer. For the image excitation, bursts have been used with a frequency of 30 MHz and a burst length of 20 μs. The amplitude of the scattered sound depends on the temporary bubble radius. In the backscattered signal, a slight shift appears in the frequency due to the fast motion of the bubble wall. After considering the sca...