EP1624723A2 - Stabilisation of the system-clock pulse in a hearing aid - Google Patents

Abstract

A clock generator (8) generates a system clock hearing frequency varying within a specific range from a predetermined target value. A receiving unit (14) receives a periodic electromagnetic signal from a remote controller (9) including a quartz crystal (13), to stabilize frequency of the system clock by reducing variation in frequency of the system clock from the target value. Alternatively, the quartz crystal may be in a timepiece, or signals from a standard time transmitter may be employed. An independent claim is also included for operation method of hearing aid.

Description

The invention relates to a hearing aid with an input transducer for receiving an input signal and conversion to an electrical input signal, a signal processing unit for processing and frequency-dependent amplification of the electrical input signal, an output transducer for generating a perceptible by a user as an acoustic signal output signal and a clock element for generating a system clock wherein the actual system clock frequency deviates from a predetermined system clock frequency due to the component within a certain fluctuation range from the predetermined system clock frequency. Furthermore, the invention relates to a hearing aid system with such a hearing aid and an external transmitter. Furthermore, the invention relates to a method for operating such a hearing aid.

In behind or in the ear portable digital hearing aids, the system clock can not be generated with a quartz, but only with an oscillator due to the desired miniaturization, as a quartz control would take up too much space. Due to higher, sometimes temperature-dependent component tolerances, the fluctuation range within which the clock frequency of the hearing aid can deviate from a predetermined target value, therefore +/- 5%, that is, at a nominal 20 KHz clock frequency, the actual value between 19 KHz and 21 KHz , This is a problem, especially for filters, which are intended to modify purely acoustic / physical phenomena, for example, receiver resonance, effects through the sound tube and the like. The parameters of these filters, such as the frequency response, are directly dependent on the sampling rate of the input signal and thus of the clock frequency in a digital implementation. If, for example, a narrow receiver resonance is to be attenuated with a digital filter given physical 8 kHz by the listener, then For example, an inaccurate sampling rate would only allow for a target frequency range of 8 KHz +/- 5%, that is 7.6 KHz to 8.4 KHz. However, this is too inaccurate. For the above reason, such filters are not used yet.

From DE 100 48 341 C1, a hearing aid is known, in which an automatic selection of the active hearing program takes place as a function of the time of day. The hearing aid is equipped with an internal clock for this purpose. For accurate and convenient setting of the current time, the hearing aid is preferably designed to receive an external time signal (e.g., DCF 77) of a time signal transmitter. A manual setting of the time, z. For example, to switch between summer time and winter time, it eliminates.

A hearing device with a microphone, a signal processing unit, a receiver and a detector element for detecting electromagnetic interference signals is known from EP 1 104 645 B1, wherein a filter element which can be configured as a function of the detected interference signals is present for suppressing the interference signals. The known hearing aid is implemented in digital circuit technology and has a clock generator for this purpose. In a detected, clocked interference signal, the previous clock frequency is replaced by the clock frequency of the interference signal or a multiple of this clock frequency. The clock frequency is thus determined by the clock frequency of the interference signal.

The object of the present invention is to reduce the fluctuation range of a predetermined clock frequency in a digital hearing aid device.

This object is achieved in a hearing aid to an input transducer for receiving an input signal and conversion to an electrical input signal, a signal processing unit for processing and frequency-dependent amplification of the electrical input signal and an output transducer for generating a user as an acoustic signal perceptible output signal and with a clock element for generating a system clock, wherein the actual system clock frequency deviates from a predetermined system clock frequency due to the component within a certain range of variation from the predetermined system clock frequency, solved by an externally generated, in the hearing aid device receivable, periodic electromagnetic signal for stabilizing the actual system clock frequency, the is usable such that the deviation of the actual system clock frequency from the predetermined system clock frequency decreases.

• Empfang eines periodischen elektromagnetischen Signals eines externen Senders, dessen Periode bekannt ist,
• Zählen der tatsächlichen Taktimpulse des Systemtaktes des Hörhilfegerätes während wenigstens einer Periode des von dem externen Sender abgegebenen Signals,
• Vergleich des Zählergebnisses mit einem Sollwert
• Nachjustieren des Systemtakts zur Angleichung der tatsächlichen Anzahl der Taktimpulse während einer Periode des von dem externen Sender abgegebenen Signals mit dem Sollwert.

The object is further achieved by a method for operating a hearing aid with an input transducer for receiving an input signal and conversion to an electrical input signal, a signal processing unit for processing and frequency-dependent amplification of the electrical input signal and an output transducer for generating a perceptible by a user as an acoustic signal output signal and with a clock element for generating a system clock, wherein the actual system clock frequency deviates from a predetermined system clock frequency for a specific component within a certain fluctuation width from the predetermined system clock frequency, with the following steps:

• Receiving a periodic electromagnetic signal from an external transmitter whose period is known
• Counting the actual clock pulses of the system clock of the hearing aid during at least one period of the signal output from the external transmitter,
• Comparison of the counting result with a setpoint
• Readjusting the system clock to equalize the actual number of clock pulses during a period of the signal output from the external transmitter with the setpoint.

In a hearing aid, an input signal is recorded by means of an input transducer and converted into an electrical input signal. Usually serves as an input transducer at least one microphone, which is an acoustic input signal receives. Modern hearing aids often comprise a microphone system with a plurality of microphones in order to achieve a direction dependent on the direction of arrival of acoustic signals reception, a directional characteristic. However, the input transducers may also include a telecoil or antenna for receiving electromagnetic input signals. The input signals converted by the input transducer into electrical input signals are fed to a signal processing unit for further processing and amplification. The further processing and amplification takes place to compensate for the individual hearing loss of a hearing aid wearer, as a rule, as a function of the signal frequency. The signal processing unit outputs an electrical output signal, which is supplied via an output transducer to the hearing of the hearing aid wearer, so that the latter perceives the output signal as an acoustic signal. As output transducers usually listeners are used, which generate an acoustic output signal. However, output transducers for generating mechanical vibrations are also known, which directly excite certain parts of the ear, such as the ossicles, to vibrate. Furthermore, output transducers are known which directly stimulate neurons of the ear.

The hearing aid according to the invention is implemented in digital circuit technology and therefore comprises a clock element for generating the system clock. Since quartz can not be used due to the intended miniaturization of hearing aids, the hearing aid according to the invention uses a common oscillator. However, this has the disadvantage that a predetermined system clock frequency can actually only be achieved with a deviation of about +/- 5% of the predetermined value. Since this deviation is not acceptable for the application of certain filters, it is proposed according to the invention to use a more precise, for example stabilized with a quartz, external clock signal for stabilizing the internal system clock. This clock signal is generated in an external device, such as a remote control for the hearing aid, and as electromagnetic Transfer the signal wirelessly to the hearing aid. If the clock frequency of this external clock is known, then the clock frequency of the hearing aid can be compared and readjusted. The deviation from the specified value is thereby significantly less than +/- 5%, for example, only +/- 0.5%. Due to the stabilized clock with the achieved thereby, small deviation of the clock frequency of the setpoint then realized in the hearing aid digital filters can be set much more accurate.

For generating the clock, a so-called ring oscillator is often used in hearing aids, which is characterized in particular by a low power consumption. This is composed essentially of several series-connected inverters, wherein the output of the last inverter of the chain is fed back to the input of the first inverter. The fine adjustment of the clock is done via an adjustable power source, which supplies the inverter with power. The current of this power source is usually set once after the production of a hearing aid. Due to the ambient temperature, aging influences, component tolerances, etc., however, during operation of the hearing aid device, the abovementioned deviations of up to +/- 5% from the set desired value occur. In connection with the invention, the current source is readjusted during the operation of the hearing aid in this method of clock generation.

The invention is not limited to the exemplified ring oscillator for clock generation. Rather, the person skilled in a variety of other methods for clock generation in hearing aids known. In the known further methods, the clock frequency can generally be readjusted by controllable current or voltage sources, resistors, capacitances or inductances.

An embodiment of the invention provides a quartz wristwatch as an external transmitter, which is additionally provided with a transmitting unit. This requires compared to a conventional one Quartz wristwatch with only minor modifications and can be worn inconspicuously in the distance to the hearing aid for this application.

In a preferred embodiment of the invention, a time signal for radio clocks sent out in many countries, in Germany the DCF77 time signal, is used as an external clock signal in order to stabilize the hearing aid device-internal system clock. Such a time signal is broadcast in many countries nationwide and with very high accuracy of the clock periods. Also corresponding receivers are available at low cost.

A development of the invention provides to readjust the system clock an averaging over several counts of the actual clock pulses of the hearing aid clock during at least one period of the external clock signal and perform the corresponding comparisons with the setpoint. This allows an even more accurate adjustment of the system clock. Disturbances in the reception of the external signal are thereby compensated.

The invention will be explained in more detail with reference to an embodiment. The figure shows a hearing aid 1 with a microphone 2 for receiving an acoustic input signal and conversion into an electrical signal, a signal processing unit 3 for processing and frequency-dependent amplification of the electrical signal and a receiver 4 for converting the processed and amplified signal into an acoustic output signal. which is supplied to the hearing of a hearing aid wearer. The signal processing unit 3 in the embodiment is implemented in digital circuit technology and therefore comprises an A / D converter 5 for converting the electrical input signal into a digital input signal and a D / A converter 7 for converting the processed digital signal into an analog output signal. In between, the signal processing takes place in a digital circuit technology realized signal processing unit 6.

The digital components of the hearing aid 1 are clocked by a clock generator 8. By Frequenzvervielfältiger individual components can be clocked at multiples of this clock frequency. Since the clock generator contains only a simply constructed oscillator and no quartz, the predetermined clock frequency can be maintained with a maximum deviation of +/- 5% from the predetermined setpoint. However, this fluctuation range is too high for certain digital filters included in the digital signal processing unit 6.

The clock frequency generated by the clock generator 8 will be stabilized according to the invention such that at least temporarily the deviation of up to +/- 5% from the setpoint is substantially limited. This includes in the embodiment, a remote control 9 for remote control of the hearing aid 1. This includes the labeled "1" to "4" program selection buttons 10 for adjusting the signal processing in the hearing aid 1 to different listening environments and a volume control rocker 11 to adjust the volume. In addition to these conventional components of a remote control, the remote control 9 in the exemplary embodiment comprises a clock generator 12, which comprises a quartz 13. The clock frequency can thus be kept very accurate. The period of the clock pulses which are generated and emitted by the remote control 1 is preferably very long, for example 10 seconds. As a result, hardly any energy is needed to send the clock signal. The hearing aid 1 in turn comprises a receiving unit 14 for receiving the output from the remote control 9 clock signal. The external clock signal is finally supplied to a counter 15 which counts the number of clocks of the clock generator 8 during a period of the external clock signal. For example, the counter 15 reaches a count of 210,000 during a period of the external clock signal of 10 seconds. At a nominal value of the system clock frequency of 20 KHz, the count would have after 10 sec, however, be 200,000. The clock frequency of the clock generator 8 is therefore readjusted accordingly. For this purpose, a comparison control unit 16 is present in the hearing aid 1, in addition to the count and a setpoint S received. From the comparison of the counter reading with the reference value, the comparison and control unit 16 generates a control signal for slowing the clock frequency of the clock generator 8.

In a preferred embodiment of the invention, the count is averaged over several periods of the external clock signal before a control signal for correcting the clock frequency of the clock generator 8 is generated. As a result, an even more accurate adjustment of the system clock of the hearing aid 1 is achieved. In particular, disturbances in receiving the external clock signal are compensated.

Claims (9)

Hearing aid (1) having an input transducer (2) for receiving an input signal and conversion to an electrical input signal, a signal processing unit (3) for processing and frequency-dependent amplification of the electrical input signal and an output transducer (4) for generating a perceived by a user as an acoustic signal Output signal and with a clock element (8) for generating a system clock, wherein the actual system clock frequency deviates from a predetermined system clock frequency due to the component within a certain range of variation from the predetermined system clock frequency, characterized in that an externally generated, in the hearing aid (1) receivable periodic electromagnetic signal for Stabilization of the actual system clock frequency is usable, such that the deviation of the actual system clock frequency from the predetermined system clock frequency decreases. Hearing aid system (1, 9) with a hearing aid (1) according to claim 1 and an external transmitter (9) for generating the periodic electromagnetic signal. Hearing aid system (1, 9) according to claim 2, wherein the external transmitter (9) for generating the periodic electromagnetic signal as a remote control (9) for the hearing aid (1) is formed with additional functionality. Hearing aid system (1, 9) according to claim 2 or 3, wherein the external transmitter comprises a quartz for generating the periodic electromagnetic signal. Hearing aid system (1, 9) according to claim 4, wherein the external transmitter is designed as a quartz wristwatch with additional functionality. Hearing aid system (1, 9) according to claim 2, wherein the external transmitter is designed as a time signal transmitter for radio-controlled clocks is. Hearing aid system according to claim 6, wherein the external time signal transmitter emits a DCF77 time signal. A method of operating a hearing aid (1) having an input transducer (2) for receiving an input signal and conversion to an electrical input signal, a signal processing unit (3) for processing and frequency dependent amplification of the electrical input signal, and an output transducer (4) for generating one of a user audible signal perceptible output signal and with a clock element (8) for generating a system clock, wherein the actual system clock frequency deviates from a predetermined system clock frequency due to the component within a certain fluctuation width of the predetermined system clock frequency, comprising the following steps: Receiving a periodic electromagnetic signal of an external transmitter (9) whose period is known Counting the actual clock pulses of the system clock of the hearing aid (1) during at least one period of the signal emitted by the external transmitter (9), - Comparison of the counting result with a setpoint (S) - readjusting the system clock to equalize the actual number of clock pulses during a period of the output from the external transmitter (9) signal with the set value (S). The method of claim 8, wherein an averaging over multiple counts and comparisons is carried out for readjustment.

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