Abstract: A digital, three-level output driver (7) of the H-bridge variety for a hearing aid (20) obtains a reduced capacitive interference by providing a primary voltage (3) and a secondary voltage (8) for the output driver (7) and applying the secondary voltage (8) to both sides of the output driver (7) whenever the middle level of the three-level output driver (7) is present in the input signal for the output driver (7). The output driver (7) may be controlled from a pulse-width modulated signal, a sigma-delta pulse-density modulated signal, or a combination of those signals. The output driver (7) produces a clocked output signal consisting of a positive level, a negative level, and a zero level for driving an acoustic output transducer of the hearing aid (20). The invention provides a hearing aid (20) and a method of driving an output stage (7) of a hearing aid (20).

Abstract: A hearing aid comprising a frequency shifter (20) has means (22) for detecting a first frequency and a second frequency in an input signal. The frequency shifter (20) transposes a first frequency range of the input signal to a second frequency range of the input signal based on the presence of a fixed relationship between the first and the second detected frequency. The means (34, 35, 36) for detecting the fixed relationship between the first and the second frequency is used for controlling the frequency transposer (20). A speech detector (26) configured for detecting the presence of voiced and unvoiced speech is provided for suppressing the transposition of voiced-speech signals in order to preserve the speech formants. The purpose of transposing frequency bands in this way in a hearing aid is to render inaudible frequencies audible to a user of the hearing aid while maintaining the original envelope, harmonic coherence and speech intelligibility of the signal.

Abstract: A hearing aid comprises a wireless Frequency-Shift-Keying (FSK) receiver. The receiver has an antenna receiving an FSK signal, a first amplifier stage amplifying the FSK signal, a limiter stage limiting the amplified FSK signal, a plurality of parallel phase detection stages and a lookup table block. Each phase detection stage comprises a local oscillator, a mixer stage, a filter stage, and a comparator stage. The output of each of the respective comparator stages is provided to the input of the look-up table block. The invention also relates to a method for processing a wireless FSK signal for providing a signal for a hearing aid, and a wireless FSK receiver.

Abstract: A hearing aid (50) comprises means (55, 56, 57, 58) for reproducing frequencies above the upper frequency limit of a hearing impaired user. The hearing aid (50) according to the invention comprises means (55, 57) for transposing higher bands of frequencies from outside the upper frequency limit of a hearing impaired user down in frequency based on a detected frequency in order to coincide with a lower band of frequencies within the frequency range perceivable by the hearing impaired user. The transposing means (55, 57) comprise an adaptive notch filter (15) for detecting a dominant frequency in the lower band of frequencies, adaptation means (16) controlled by the adaptive notch filter (15), an oscillator (3) controlled by the adaptation means (16), and a multiplier (4) for performing the actual frequency transposition of the signal. The invention further provides a method for processing a signal in a hearing aid.

Abstract: A hearing aid (40) comprises a frequency-shift-keying (FSK) receiver (30) comprising a first amplifier stage (13), a limiter stage (14) and a plurality of phase detection stages. Each phase detection stage comprises a local oscillator (15a, 15b, 15c, 15d, 15e), a mixer stage (16a, 16b, 16c, 16d, 16e), a filter stage (17a, 17b, 17c, 17d, 17e), and a comparator stage (18a, 18b, 18c, 18d, 18e), respectively. The number of phase detection stages is greater than two. The output of each comparator stage (18a, 18b, 18c, 18d, 18e) is commonly connected to the input of a look-up table (28). The invention also provides an FSK receiver for use in a hearing aid and a method for processing an FSK signal.

Abstract: A hearing aid (50) comprises means (55, 56, 57, 58) for reproducing frequencies above the upper frequency limit of a hearing impaired user. The hearing aid (50) according to the invention comprises means (55, 57) for transposing higher bands of frequencies from outside the upper frequency limit of a hearing impaired user down in frequency based on a detected frequency in order to coincide with a lower band of frequencies within the frequency range perceivable by the hearing impaired user. The transposing means (55, 57) comprise an adaptive notch filter (15) for detecting a dominant frequency in the lower band of frequencies, adaptation means (16) controlled by the adaptive notch filter (15), an oscillator (3) controlled by the adaptation means (16), and a multiplier (4) for performing the actual frequency transposition of the signal. The invention further provides a method for processing a signal in a hearing aid.

Abstract: A hearing aid is provided having a capacitor with a large capacitance coupled in parallel with the energy source for transient current supply. The operating period of the battery is prolonged compared to prior art digital hearing aids. Further, the smaller variations in supply voltage lead to less distortion of the output signal of the hearing aid signal processor. In a hearing aid with a telecoil, a well defined current path for the current transients generating the high magnetic fields picked up by the telecoil is established. This facilitates the design of a compensating current path that is substantially independent of battery type and position.

Abstract: A hearing aid is provided having a capacitor with a large capacitance coupled in parallel with the energy source for transient current supply. The operating period of the battery is prolonged compared to prior art digital hearing aids. Further, the smaller variations in supply voltage lead to less distortion of the output signal of the hearing aid signal processor. In a hearing aid with a telecoil, a well defined current path for the current transients generating the high magnetic fields picked up by the telecoil is established. This facilitates the design of a compensating current path that is substantially independent of battery type and position.

Abstract: A hearing aid includes a microphone (1), a signal-transmission unit (2, 3,) for forming or otherwise processing the signal, an output amplifier (4) to which an earphone (10) is connected, and a battery as the power supply. The output amplifier (4) is implemented essentially as a .SIGMA.-.DELTA. amplifier and is connected to a pulse generator (8) which produces a high-frequency pulsed clock signal in the 1 MHz region. A series-connected low-pass filter (15) is also provided. The input signal to the signal converter is a representation, produced by signal processing in the transmission unit, of the low-frequency input signal to the hearing aid, this signal being converted in the signal converter into a binary signal. The output signal (14) thus appears, after passing through the low-pass filter, essentially as an amplified copy of the low-frequency input signal.