EP1406468B1 - Hearing-aid device or hearing-aid system with a clock signal generator - Google Patents

Abstract

The method involves generating frequency fluctuations in the clock signal generated by the clock generator (6). The frequency fluctuations are produced by modulating an internal clock signal produced by the clock generator with a further signal. The internal clock signal can be modified by a sinusoidal signal or with a noise signal. AN Independent claim is also included for the following: (a) a hearing aid device or system.

Description

The invention relates to a hearing aid or hearing aid system and a method for operating a hearing aid or hearing aid system having at least one input transducer for receiving an input signal and conversion to an electrical signal, an A / D converter for converting the electrical input signal into a digital signal, a digital signal processing unit for processing the digital signal, a clock generator for generating a clock signal with predefined properties for controlling the digital signal processing unit, an output transducer and a transmitting and / or receiving unit for wireless signal transmission between the hearing aid or hearing aid system and another device.

A modern hearing aid offers the possibility of wireless signal transmission between the hearing aid and another device, such as another hearing aid, a programmer or an external transceiver. For transmitting and / or receiving, the hearing aid device comprises a transmitting and / or receiving unit. However, hearing aid systems with a hearing aid device and a transmitting and / or receiving unit are also known, in which the transmitting and / or receiving unit is designed as an independent external unit with respect to the hearing aid, which can be detachably connected to the hearing aid for transmitting and / or receiving connected is. Preferably, the transmitting and / or receiving unit is then plugged onto the hearing aid and electrically connected via contact and conduit means with this. But it is also possible that the transmitting and / or receiving unit is not attached directly to the hearing aid, but is worn as a separate device on the body or clothing of a hearing aid wearer. The connection to the hearing aid then consists only of electrical contact and conduit means.

The transmitting and / or receiving units of the devices in question are often designed as so-called "FM systems", so that the transmitted signal is frequency-modulated. However, modulation of the transmitted signal is not necessarily required nor limited to frequency modulation.

From the US 5,721,783 is a hearing aid with a remote from the hearing aid processor is known, which has a wireless connection between the hearing aid and the processor.

From the DE 693 27 951 T2 a hearing aid is known in which, among other things, a digital noise signal is added to the microphone signal to compensate for acoustic feedback.

From the Laid-open publication DE 199 41 859 A1 a network-independently operable medical device is known in which the clock frequency of at least one digital component can be changed and, in particular, adapted to specific conditions. For example, the clock frequency can be reduced with a far advanced discharge of the voltage source to increase the "remaining term".

From the Patent US 6,411,151 B1 For example, a circuit for reducing instabilities in the clock signal (jitter) is known.

From the Publication WO 02/07479 A1 is a hearing aid system with two portable on the head of a user hearing aids for binaural care of a user known. By one of the two hearing aids, the clock frequency of the hearing aid system is specified and for this purpose also transmitted to the other hearing aid in particular by means of a wireless connection. In modern hearing aids, signal processing is digital. To control the necessary digital circuits, a clock signal is required. The clock signal of a digital hearing aid is usually not very stable. Oscillating crystals for stabilizing the clock generator can not be used because of their size. Consequently, the clock frequency is slightly temperature and supply voltage dependent. It is therefore only quasi-stable. Nevertheless, the clock signal can also be considered as a uniform, stable signal with a constant period and pulse width for a hearing aid for a period of a few minutes.

Due to the clocked operation of the hearing aid device, the hearing aid device and in particular a clocked output stage emit an electromagnetic interference signal with precisely this clock frequency. Furthermore, interference signals occur at multiples of this clock frequency, also called harmonics or harmonics. Thus, it may happen that the receiving unit of the hearing aid device or hearing aid system detects a signal caused by harmonics, although no real received signal for the receiving unit is present. The frequency band in which the received signal is located is normally chosen so that no harmonics of the clock frequency fall into it. A slowly drifting clock frequency of the clock generator can now lead to harmonics of the clock frequency being within the frequency band of the received signal. As a result, the reception is disturbed by the receiving unit.

Up to now, extensive attempts at filtering have largely failed to eliminate or even localize the narrow-band interfering components already present in the hearing aid device, which extend in particular over the harmonic components of the final fundamental frequency into the frequency range of a few hundred MHz. Nevertheless, a high-frequency radiation is not complete avoid, which sometimes leads to disruptions in the operation of a receiving unit. Furthermore, suitable shielding measures on the hearing aid remedy this high-frequency radiation. All these measures are very complex and expensive.

Object of the present invention is therefore to avoid electromagnetic interference at multiples of the clock frequency of a hearing aid in a simple and cost-effective manner.

This object is achieved by a method for operating a hearing aid or hearing aid system having at least one input transducer for receiving an input signal and conversion into an electrical signal, an A / D converter for converting the electrical input signal into a digital signal, a digital signal processing unit for processing the digital signal, a clock generator for generating a clock signal with predefined properties for controlling the digital signal processing unit, an output transducer and a transmitting and / or receiving unit for wireless signal transmission between the hearing aid or hearing aid system and another device, wherein the clock signal originating from the clock generator is destabilized to a limited extent by frequency fluctuations produced by a jitter unit.

Furthermore, the object is achieved by a hearing aid or hearing aid system having at least one input transducer for receiving an input signal and conversion into an electrical signal, an A / D converter for converting the electrical input signal into a digital signal, a digital signal processing unit, a clock generator for generating a Clock signal with predefined properties for controlling the digital signal processing unit for processing the digital signal, an output transducer and a transmitting and / or receiving unit for wireless signal transmission between the hearing aid or hearing aid system and another device, wherein the clock generator is associated with a jitter unit for generating frequency fluctuations that destabilize the clock signal to a limited extent.

The hearing aid according to the invention is, for example, a hearing aid worn behind the ear, a hearing aid worn in the ear, an implantable hearing aid or a pocket hearing aid. Furthermore, the hearing aid according to the invention may also be part of a plurality of devices for supplying a hearing aid comprising comprehensive hearing aid system, e.g. Part of a hearing aid system with two worn on the head hearing aids for binaural care, part of a hearing aid with a head-worn hearing aid and a portable external processor unit, part of a fully or partially implantable hearing aid system with multiple components, part of a hearing aid system with external additional components such as remote control unit or external microphone unit, etc.

A hearing aid generally includes one or more input transducers for receiving an input signal. The input transducer is designed for example as a microphone which receives an acoustic signal and an electrical signal converts. As input transducers but also come into consideration, which have a coil or an antenna and receive an electromagnetic signal and convert it into an electrical signal. Furthermore, a hearing aid usually includes a signal processing unit for processing and frequency-dependent amplification of the electrical signal. For signal processing in the hearing aid, a preferably digital signal processor (DSP) is used, whose operation can be influenced by means of programs or parameters which can be transmitted to the hearing aid. As a result, the mode of operation of the signal processing unit can be adapted both to the individual hearing loss of a hearing device wearer and to the current hearing situation in which the hearing aid device is currently being operated. The thus changed electrical signal is finally fed to an output transducer. This is usually designed as a handset, which converts the electrical output signal into an acoustic signal. However, other embodiments are also possible here, for example, an implantable output transducer, which is directly connected to a ossicle and this stimulates to vibrate.

For wireless signal transmission between the hearing aid device and another device, the hearing aid device according to the invention may comprise a transmitting and / or receiving unit. However, it can also be part of a hearing aid system with at least one hearing aid device and a transmitting and / or receiving unit, which is arranged as an independent structural unit outside the housing of the hearing aid device.

To operate a digital hearing aid with a digital signal processing unit and a digital power amplifier, a clock generator is required, which outputs a clock signal with predefined properties. The invention provides that the clock signal is destabilized to a limited extent, ie, even over a short observation period of a few seconds, changes occur in the clock signal. It can so that no longer be regarded as a periodic sequence of successive, equal clock pulses.

There are different options for changing the clock signal. Thus, e.g. the period may vary or the pulse width may vary. Furthermore, the edge steepness of the clock pulses may be subject to short-term fluctuations.

The destabilization of the clock signal causes both the energy components of the noise generated in the hearing aid with the clock frequency and its harmonics are distributed over a larger frequency band and thus the frequency-specific energy is lower. This in turn means that with appropriately sized fluctuations of the clock signal, the amplitude of an interference signal caused by the harmonics is below the reception threshold of the receiving unit. Harmonics of the clock frequency therefore no longer interfere with the wireless reception of a signal from an external device. In general, the invention offers the advantage that a hearing aid in conjunction with a signal transmission system for wireless signal transmission allows trouble-free communication.

An embodiment of the invention provides a jitter unit by which small frequency fluctuations (frequency jitter) are applied to the clock signal. To generate the frequency fluctuations in the clock signal, a stable internal clock signal of the clock generator is preferably modulated with a further signal, that is, superimposed on a further signal. The modulation is preferably carried out with a sine or noise signal, wherein the frequency components are advantageously well above the audio frequency range and thus cause no additional distortions or an increased noise in this. The signal modulated with the internal clock signal is preferably selected such that the frequency of the resulting clock signal is centered at a frequency fluctuates. This center frequency can thus still be regarded as the clock frequency of the system, wherein the real clock frequency is then in sliding transition alternately for a few periods above the center frequency and for some periods below the center frequency. Advantageously, the frequency of the clock fluctuations is above the audible audio frequency range, so that the clock fluctuations do not lead to audible distortions in the output of the hearing aid.

• Figur 1 das Blockschaltbild eines digitalen Hörhilfegerätes mit einer Jitter-Einheit,
• Figur 2 ein ungestörtes Empfangssignal,
• Figur 3 ein Empfangssignal mit überlagertem Störspektrum,
• Figur 4 das Störspektrum und
• Figur 5 das Störspektrum unter dem Einfluss der Jitter-Einheit.

Further details of the invention will become apparent from the following description of an embodiment. Show it:

• FIG. 1 the block diagram of a digital hearing aid with a jitter unit,
• FIG. 2 an undisturbed received signal,
• FIG. 3 a received signal with superimposed interference spectrum,
• FIG. 4 the interference spectrum and
• FIG. 5 the interference spectrum under the influence of the jitter unit.

FIG. 1 shows an embodiment of a hearing aid according to the invention in the block diagram. For sound recording is a microphone 1, which receives an acoustic input signal and converts it into an electrical input signal. The electrical input signal is first supplied to a preamplifier and A / D converter unit 2. This converts the analog input signal into a digital input signal. For further processing and frequency-dependent amplification of the digital input signal is the digital signal processing unit 3. This includes the final amplification of a class D amplifier. Finally, the processed and amplified signal by means of a receiver 4 in an analog acoustic Output signal converted and delivered. To power the hearing aid components, a battery 5 is present. Furthermore, the digital signal processing unit of the hearing aid is connected to a clock generator 6. In the hearing aid device in the embodiment according to FIG. 1 is next to the microphone 1 as a further signal input a telecoil 7 is provided, through which an electromagnetic input signal can be recorded. The hearing aid device further comprises an MTO switch 8, which can be operated by a hearing aid wearer, for selecting the operation via the microphone (switch position M), via the telecoil (switch position T) or for switching off the hearing aid device (switch position O). In addition, the hearing aid comprises a programming socket 9 for wired connection with a programming device and a situation button 10 for switching between different hearing programs by the hearing aid wearer. As a further control element, a VC-controller 11 is provided, through which the volume can be adjusted manually on the hearing aid.

The hearing aid according to the invention is connected to the wireless signal transmission between the hearing aid and another device, such as another hearing aid, with a transmitting and / or receiving unit 12 which includes an antenna 13. In this case, the transmitting and / or receiving unit 12 can be integrated directly into the housing of the hearing aid and thus be part of the hearing aid. However, the transmitting and / or receiving unit 12 can also have its own housing and form a hearing aid unit as a separate external unit together with the hearing aid. In this case, for the operation of such a hearing aid system attachment of the external transmitting and / or receiving unit may be provided on the housing of the hearing aid, but the external transmitting and / or receiving unit can also be worn separately on the body, eg as a chest or pocket device, and be connected only via electrical connection means with the hearing aid.

Finally, the hearing aid according to the invention has a jitter unit 14 connected to the clock generator 6. The jitter unit 14 effects a frequency jitter of the clock signal output from the clock generator 6. The frequency jitter may e.g. caused by the superposition of a stable internal clock signal of the clock generator with a sine signal or with a noise signal. Advantageously, the frequency of the superimposed signal is above the audio frequency range, so that no perceptible interference in the output signal of the hearing aid is produced by the overlays. The frequency fluctuations in the clock signal produced in this way ensure that both the energy components of interference signals with the clock frequency and their harmonics are distributed over a larger frequency band and thus the frequency-specific energy is reduced. Interference signals caused by the clocked mode of operation of the hearing aid device at the clock frequency used and its harmonics can still be detected by the antenna 13 or the telecoil 7, but they are now below the input threshold of the transmitting and / or receiving unit 12 or of the preamplifier A / D converter 2 and thus no longer lead to disturbances of one of the transmitting and / or receiving unit or the telecoil 7 received or delivered useful signal.

FIG. 2 shows the frequency spectrum of a received by the transmitting and / or receiving unit 12 electromagnetic signal with a carrier frequency of 1 MHz. The received signal according to FIG. 2 is not disturbed by a clock signal. Otherwise, the signal according to FIG. 3 , In this signal is clearly visible superimposed on a noise signal, which is composed of the harmonics of the clock frequency of the hearing aid. For clarity shows FIG. 4 the interference spectrum without the received signal. If a frequency jitter is now generated at the clock signal in the last-mentioned starting situation according to the invention, then, as in FIG FIG. 5 illustrates the interference spectrum smoothed again. The interference signals are now below a receiving threshold of the transmitting and / or receiving unit 12, whereby a trouble-free signal transmission between the hearing aid and another device is possible.

Claims (14)

1. Method for operating a hearing aid device or hearing device system comprising at least one input converter for receiving an input signal and converting said signal into an electrical signal, an A/D converter for converting the electrical input signal into a digital signal, a digital signal processing unit (3) for processing the digital signal, a clock generator (6) for generating a clock signal with predefined properties for controlling the digital signal processing unit (3), an output converter and a transmit and/or receive unit (12) for wireless signal transmission between the hearing aid device or hearing device system and a further device, characterised in that the clock signal, which emanates from the clock generator (6) is destabilised to a restricted degree by frequency oscillations generated by a jitter unit.
2. Method according to claim 1, characterised in that an internal clock signal generated by the clock generator (6) is modulated with a further signal in order to generate the frequency oscillations.
3. Method according to claim 2, characterised in that the internal clock signal is modulated with a sinusoidal signal.
4. Method according to claim 2, characterised in that the internal clock signal is modulated with a noise signal.
5. Method according to one of claims 2 to 4, characterised in that the frequency of the further signal lies above the audible frequency range.
6. Method according to one of claims 1 to 5, characterised in that the frequency of the clock signal oscillates around an average frequency.
7. Hearing aid device or hearing device system comprising at least one input converter for receiving an input signal and converting said signal into an electrical signal, an A/D converter for converting the electrical input signal into a digital signal, a digital signal processing unit (3) for processing the digital signal, a clock generator (6) for generating a clock signal with predefined properties for controlling the digital signal processing unit (3), an output converter and a transmit and/or receive unit (12) for wireless signal transmission between the hearing aid device or hearing device system and a further device, characterised in that a jitter unit (14) is assigned to the clock generator (6) in order to generate frequency oscillations, which destabilise the clock signal to a restricted degree.
8. Hearing aid device or hearing device system according to claim 7, characterised in that an internal clock signal of the clock generator (6) can be modulated with a further signal in order to generate the frequency oscillations of the clock signal.
9. Hearing aid device or hearing device system according to claim 8, characterised in that the internal clock signal can be modulated with a sinusoidal signal.
10. Hearing aid device or hearing device system according to claim 8, characterised in that the internal clock signal can be modulated with a noise signal.
11. Hearing aid device or hearing device system according to one of claims 8 to 10, characterised in that the frequency of the further signal lies above the audible frequency range.
12. Hearing aid device or hearing device system according to one of claims 7 to 11, characterised in that the frequency of the clock signal oscillates around an average frequency.
13. Hearing aid device according to one of claims 7 to 12, characterised in that the transmit and/or receive unit (12) is integrated into the hearing aid device.
14. Hearing device system according to one of claims 7 to 12, characterised by
    a hearing aid device and an external transmit and/or receive unit (12) connected to the hearing aid device.

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