EP1624723B1 - Stabilisation of the system-clock pulse in a hearing aid - Google Patents

Description

The invention relates to a hearing aid system according to the preamble of the first claim. Furthermore, the invention relates to a method for operating such a hearing aid device system.

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 nominal 20 KHz clock frequency, the actual value between 19 KHz and 21 KHz , This is a problem especially for filters which are purely acoustic / physical phenomena, e.g. Hörerresonanzen, to modify effects through the sound tube and the like. The parameters of these filters, e.g. the frequency response, in a digital implementation directly dependent on the sampling rate of the input signal and thus of the clock frequency. Should e.g. a narrow receiver resonance at physically 8 KHz given by the listener are attenuated with a digital filter, so an inaccurate sampling rate would only allow information for a target frequency range of 8 KHz +/- 5%, ie 7.6 KHz to 8.4 KHz , However, this is too inaccurate. For the above reason, such filters are not used yet.

From the DE 100 48 341 Cl is a hearing aid is known in which an automatic selection of the active hearing program depending on the time of day. The hearing aid is equipped with an internal clock for this purpose. For accurate and comfortable setting of the current time, the hearing aid is preferably for receiving an external time signal (eg 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.

From the EP 1 104 645 B1 a hearing device with a microphone, a signal processing unit, a receiver and a detector element for detecting electromagnetic interference signals is known, wherein a configurable depending on the detected interference signal filter element for suppressing the interference signals is present. 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.

From the publication US 2004/00037442 A1 a hearing device system with a first and a second hearing aid for binaural care of a user is known in which a clock signal generated in the first hearing aid is transferable to the second hearing aid and the clock signal is thus relevant for both hearing aids.

From the publication US 6,768,802 B1 is a hearing aid system with a first and a second hearing aid for binaural care of a user known in which by the wireless transmission of a signal between the hearing aids a "synchronization" of the two hearing aids can be reached, including the settings of both hearing aids in the same "transfer mode", ie the same hearing program to adapt the hearing aids to different listening environments is to understand.

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 by a hearing aid system with the features according to claim 1.

Furthermore, the object is achieved by a method for operating such a hearing aid system with the method steps specified in claim 6.

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 fed 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 (7)

1. Hearing aid system (1, 9), including:

   - a hearing aid (1) with an input converter (2) for recording an input signal and converting said signal into an electrical input signal, a signal processing unit (3) for processing and frequency-dependent amplification of the electrical input signal and an output converter (4) for generating an output signal which can be perceived by a user as an acoustic signal, and a clock element (8) for generating a system clock, whereby the clock element (8) has no quartz and an actual system clock frequency of a predetermined system clock frequency varies within a specific variation range from the predetermined system clock frequency, in a component-specific manner,

   - an external transmitter (9) for generating a periodic electromagnetic signal, whereby the external transmitter includes a quartz crystal for generating the periodic electromagnetic signal,

   and whereby the electromagnetic signal generated by the external transmitter (9) can be received in the hearing aid device (1) and can be used to stabilize the actual system clock frequency, such that the variation of the actual system clock frequency from the predetermined system clock frequency reduces.
2. Hearing aid system (1, 9) according to claim 1, whereby the external transmitter (9) for generating the periodic electromagnetic signal is designed as a remote controller (9) for the hearing aid (1) with additional functionality.
3. Hearing aid system (1, 9) according to claim 1 or 2, whereby the external transmitter comprises a quartz watch with additional functionality.
4. Hearing aid system (1, 9) according to claim 1, whereby the external transmitter is configured as a time signal-transmitter for radio-controlled clocks.
5. Hearing aid system (1, 9) including:

   - a hearing aid (1) with an input converter (2) for recording an input signal and converting said signal into an electrical input signal, a signal processing unit (3) for processing and frequency-dependent amplification of the electrical input signal and an output converter (4) for generating an output signal which can be perceived by the user as an acoustic signal, and a clock element (8) for generating a system clock, whereby the clock element (8) has no quartz and an actual system clock frequency of a predetermined system clock frequency varies within a specific variation range from the predetermined system clock frequency, in a component-specific manner,

   - an external transmitter (9) for generating a periodic electromagnetic signal, whereby the external transmitter is configured as a time signal transmitter for radio-controlled clocks and outputs a DCF77 time signal,

   - and whereby the electromagnetic signal generated by the external transmitter (9) can be received in the hearing aid (1) and can be used to stabilize the actual system clock frequency such that the variation of the actual system clock frequency from the predetermined system clock frequency reduces.
6. Method for operating a hearing aid system (1,9), including

   - a hearing aid (1) with an input converter (2) for recording an input signal and converting said signal into an electrical input signal, a signal processing unit (3) for processing and frequency-dependent amplification of the electrical input signal and an output converter (4) for generating an output signal which can be perceived by a user as an acoustic signal and a clock element (8) for generating a system clock, whereby the clock element (8) has no quartz and an actual system clock frequency of a predetermined system clock frequency varies within a specific variation range from the predetermined system clock frequency, in a component-specific manner,

   - an external transmitter (9) for generating a periodic electromagnetic signal, whereby the external transmitter includes a quartz to generate the periodic electromagnetic signal,

   having the following steps:

   - receiving the periodic electromagnetic signal by means of the hearing aid (1)

   - 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),

   - comparing the counter result with a target value (S)

   - readjusting the system clock to adapt the actual number of clock pulses during a period of the signal emitted by the external transmitter (9) with the target value (S).
7. Method according to claim 6, whereby a notification takes place via several counts and comparisons for re-adjustment purposes.

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