Siemens Audiologische Technik Gmbh

Gerhard Pfannenmueller

Raimund Martin

In a hearing aid having an input transducer (2), a useful signal processor (4 through 9) having an output stage (9), and an output transducer (11), whereby a first time-discrete useful signal processing is provided preceding the output stage (9), and controlled by a sampling signal, a second time-discrete useful signal processing different therefrom is simultaneously employed without disturbing influences. To that end, a second time-discrete useful signal processing with a pulse-duration modulation is provided in the output stage (9), this being formed by a delta signal, whereby the sampling signal and the delta signal are derived from only one oscillator (12).

Hearing aid

In a circuit arrangement having a switching amplifier (10), particularly for hearing aids, for limiting a pulse-width-modulated signal (S3) that is formed for a low-frequency signal (S1) and a higher-frequency delta signal (S2), a limitation of the output signal from the switching amplifier is achieved without a reduction in gain given only slight distortions. To that end, the pulse-width-modulated signal (S3) is supplied to a circuit (5; 14; 18) which modifies the width (D1, D2, D4) of individual pulses in the pulse-width-modulated signal (S3), whose width (D1, D2, D4) is longer or/and shorter than a maximum or minimum pulse width D3; D5) prescribable by the circuit (5; 14; 18). The pulse-width-modulated signal (S5; S6) modified by the circuit (5; 14; 18) can be supplied to the switching amplifier (10) as an input signal.

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Oberasbach, Germany

Gerhard Pfannenmueller