Method for operating a hearing aid and hearing aid
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- WS AUDIOLOGY AS
- Filing Date
- 2024-08-16
- Publication Date
- 2026-07-01
AI Technical Summary
Hearing aids experience significant crosstalk due to the close proximity of input and output signal lines, which is exacerbated by the tight integration of components within a small housing.
A method is implemented in the hearing aid that involves setting a phase offset between the sampling frequency and the switching frequency to prevent crosstalk from being passed to the conversion unit, thereby reducing unwanted noise in the input signal.
The phase offset effectively reduces crosstalk by ensuring that sampling occurs only when the input signal is free of noise induced by the switching amplifier, leading to improved performance and reduced audio noise in the hearing aid.
Smart Images
Figure EP2024073056_27022025_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Method for operating a hearing aid and hearing aid
[0003] The invention concerns a method for operating a hearing aid and a corresponding hearing aid. In particular, the invention relates to reducing crosstalk in a hearing aid.
[0004] A hearing aid generally comprises an input transducer, a signal processing unit and an output transducer. The input transducer is typically a microphone and the output transducer is typically a receiver, also referred to as a speaker. A hearing aid is regularly assigned to an individual user and is only used by this user. A hearing aid is used, for example, to care for a hearing-impaired user and to compensate for a hearing loss of the user. The input transducer generates an input signal, which is fed to a signal processing unit. The signal processing unit modifies the input signal and thereby produces an output signal which is thus a modified input signal. To compensate for a hearing loss, the input signal is amplified with a frequency-dependent amplification factor, for example according to an audiogram of the user. The output signal is finally output to the user by means of the output transducer. In a hearing aid with a microphone and receiver, the microphone generates the input signal from sound signals in the environment and the receiver generates another sound signal from the output signal. The input signal and the output signal are electrical signals, which are therefore also referred to as signals for short. In contrast, the sound signals from the environment and the sound signal that may be emitted by the receiver are acoustic signals.
[0005] By its nature, a hearing aid is a particularly small electronic device, in which several electrical components and connecting lines are arranged inside a housing with a small volume. The resulting proximity of components and lines may lead to undesired crosstalk. In particular, the coupling between the lines for the input and output signal is very sensitive to crosstalk. In other words: crosstalk is difficult to manage in the design of a hearing aid due to the tight integration and proximity between input line and output line. This problem becomes more severe in hearing aids which additionally comprise an input transducer oriented towards the ear canal, e.g., an inner microphone, which then is particularly close to the receiver also directed in the same direction.
[0006] In view of this, it is an object to reduce crosstalk between an input line and an output line of a hearing aid. To this end, a suitable method and a corresponding hearing aid shall be provided.
[0007] The object is solved according to the invention by a method with the features according to claim 1 and by a hearing aid with the features according to claim 9. Advantageous embodiments are the subject of the dependent claims. Any explanations in connection with the method also apply to the hearing aid and vice versa. Insofar as steps of the method are described implicitly or explicitly, advantageous embodiments for the hearing aid result are obtained by the hearing being configured to carry out one or more of these steps. For this, the hearing aid comprises a correspondingly configured control unit.
[0008] The method is a method for operating a hearing aid. The hearing aid comprises an input transducer, outputting an input signal, a sampling unit, and an input line, for transmitting the input signal from the input transducer to the sampling unit. Hence, the input signal is generated by the input transducer during operation of the hearing aid and transmitted along the input line to the sampling unit. The sampling unit preferably is an A / D-converter. The sampling unit is part of a signal processing unit of the hearing aid and samples the input signal for subsequent signal processing inside said signal processing unit.
[0009] The sampling unit comprises a conversion unit and an input sampler, wherein said input sampler operates with a sampling frequency, for periodically generating a sample from the input signal and passing said sample to the conversion unit. That is, the actual sampling of the input signal is performed by the input sampler, which, e.g., cuts out certain pieces of the input signal during defined time intervals and transmits these or signals derived therefrom as samples to the conversion unit. Due to the periodic sampling, several subsequent samples are created over time. A sample is also denoted as “sampling signal”. The conversion unit, then, converts the sample into a proper signal for the subsequent signal processing. The details of the conversion and of the subsequent signal processing are not important here. In fact, at least the signal processing, while beneficial, is optional and may be omitted, such that the signal processing unit only performs an amplification with the switching amplifier. More important is, that the input sampler periodically generates samples from the input signal, which automatically means that during some periods of time (i.e., during first time intervals) a sample is generated, while during other periods of time (i.e., during second time intervals) no sample is generated, i.e., the input signal is rejected by the input sampler during these other periods of time. The samples are generated at a frequency corresponding to the sampling frequency. For example, if the sampling frequency is 20 kHz, then samples are generated at a rate of 20,000 per second. The sampling frequency naturally defines the bandwidth of the sampling performed by the sampling unit and the length of the time intervals.
[0010] The hearing aid further comprises an output transducer, a switching amplifier, which switches with a switching frequency, and an output line, which connects the switching amplifier with the output transducer. In analogy to the input signal, an output signal is transmitted along the output line from the switching amplifier to the output transducer and subsequently output by said output transducer during operation of the hearing aid. The switching amplifier preferably is a class D amplifier. The switching amplifier is part of the signal processing unit. The output signal is generated by the switching amplifier based on a signal derived from the input signal and any signal processing performed thereon. Said signal is amplified by the switching amplifier and, thus, the output signal is generated.
[0011] The switching amplifier operates by switching back and forth between a finite number of (e.g., two or three) defined states, e.g., using pulse-width modulation, pulse-density modulation, or related techniques to produce a pulse train. For example, the switching amplifier during operation generates a train of pulses, in particular rectangular pulses, of fixed amplitude but with varying width and separation, or varying number per unit time, representing amplitude variations of the signal which is input to the switching amplifier. Preferably, said pulses or pulse train are / is subsequently passed through a suitable low-pass filter (e.g., integrated into the switching amplifier) to generate the output signal as an analog signal, which is suitable for being processed by the output transducer. To be precise, the output signal as a function of time is a sum of subsequent steps, wherein a minimum length of the steps (i.e., minimum duration) is defined by the switching frequency. The switching is defined by the switching frequency, which, preferably, is provided by a suitable clock of the hearing aid. The switching frequency defines the fastest possible switching of the switching amplifier and, hence, in analogy to the sampling unit, may be regarded as a sampling frequency of the switching amplifier.
[0012] The input signal is an input signal to the signal processing unit and the output signal is an output signal of the processing unit. The input transducer, input line, and sampling unit belong to an input side of the hearing aid. Correspondingly, the output transducer, the output line, and the switching amplifier belong to an output side of the hearing aid. The output line and the input line are particularly close to each other, in a spatial sense, such that crosstalk may occur between the input line and the output line. For example, the input line and output line are spaced apart from each other by less than 1 mm. Crosstalk primarily occurs from the output line to the input line, i.e., the output signal induces noise in the input line, since the output signal is usually much stronger than the input signal. This, in particular, is the result of the amplification by the switching amplifier.
[0013] In any case, a coupling path is formed between the input line and the output line. Crosstalk occurs along the coupling path. Said coupling path is not an actual electrical connection, but may be modelled by a stray capacitance, i.e., a virtual capacitor connecting the input line and output line. The exact value of the stray capacitance is heavily dependent on the exact design and application context and, hence, may vary accordingly. Unfortunately, during operation, the switching of the switching amplifier also generates high levels of out-of-band quantization noise that may be picked up by the input line as crosstalk and aliased by the sampling unit to audio noise. The crosstalk, i.e. , noise, induced in the input line by the output signal adds to the original input signal generated by the input transducer and the input signal comprising said noise (noisy input signal) is transmitted along the input line towards the sampling unit. Correspondingly, if a sample is generated based on the input signal including noise, said noise is also converted by the conversion unit leading to an undesirable performance of the hearing aid. Of particular importance in the present case is, that the switching of the switching amplifier possibly leads to undesirable crosstalk. Hence, a phase offset between the sampling frequency and the switching frequency is used to prevent crosstalk from being passed to the conversion unit, wherein said crosstalk - as described - occurs between the output line and the input line as a result of switching of the switching amplifier.
[0014] The phase offset is an operating parameter of the hearing aid. The phase offset may be set as part of the method or separate therefrom. The phase offset may be set once and remain fixed afterwards or may be changed as required during operation, e.g., via a suitable user interface.
[0015] The use of the phase offset is based on the notion, that crosstalk - as the result of the switching - occurs at defined points of time, namely points of time defined by the switching frequency. At the same time, the sampling frequency defines, at which points of time a sample is generated from the input signal. According to the invention, a phase offset between the sampling frequency and the switching frequency is now set (also: adjusted) such, that at those points of time, during which noise is created in the input line from switching of the switching amplifier, no sampling by the input sampler occurs. Correspondingly, the input signal at those points of time, where it includes crosstalk, is rejected by the input sampler and prevented from being passed to the conversion unit. As a result, crosstalk is not converted and, thereby, reduced, which leads to an improved performance of the hearing aid. The expression “crosstalk is reduced” is understood to mean, that the amount of crosstalk entering the signal processing unit is reduced, and not, that crosstalk from the output line to the input line is prevented.
[0016] In a preferred embodiment, the hearing aid comprises a phase adjustment unit for adjusting the phase offset. Advantageously, the phase offset is also measured by the phase adjustment unit.
[0017] In a preferred embodiment, the phase offset is set such that crosstalk is blocked by the input sampler from being passed to the conversion unit. In other words: the phase offset is set such, that the input sampler rejects the input signal during those periods of time, during which the input signal comprises crosstalk. Correspondingly, generation of the samples is based exclusively on the input signal at those periods of time, during which the input signal is free of crosstalk. The mentioned periods of time are known, since the switching frequency and the phase offset are known.
[0018] In a preferred embodiment, the phase offset is set such that the switching amplifier performs a switching operation immediately after the input sampler stops generating the sample. In addition or in the alternative, the phase offset is set such that the switching amplifier performs a switching operation immediately after the input sampler starts passing the sample to the conversion unit. A “switching operation” is understood as a switching of the switching amplifier according to its working principle. Both alternatives ensure, that crosstalk is rejected by the input sampler and not transmitted to the conversion unit. This is based on the notion, that the crosstalk will only last for a short period of time, which is determined by a time constant defined by an output impedance on the output line and the stray capacitance. It is therefore advantageous for the switching amplifier to switch (i.e. , update the output signal) immediately after the input sampler has switched from generating a sample to passing said sample to the conversion unit. This provides a maximum period of time for the noise to fade out before the input sampler again switches back for generation of a subsequent sample. In reality, there may be multiple unintended coupling paths from the output line into the input line and ultimately into the sampling unit. Therefore, it is not possible to provide a simple rule for the optimal phase offset between the sampling frequency and the switching frequency. Instead, the optimal phase offset is preferably determined by way of experiment given a specific hearing aid design. The optimal phase offset is that one, which reduces crosstalk reaching the conversion unit, which can be assessed by observing the output from the conversion unit.
[0019] In a preferred embodiment, the input sampler comprises a sampling capacitor and a switch, said switch having a sampling state and a passing state. In the sampling state, the switch connects the input transducer with the sampling capacitor, but not with the conversion unit. In the passing state the switch connects the sampling capacitor with the conversion unit, but not with the input transducer. In both states, the conversion unit is not directly connected to the input transducer. The working principle of such an input sampler is as follows: the input sampler is switched to the sampling state, in which the sampling capacitor is charged to a voltage level determined by the input signal generated by the input transducer (sampling phase). The input sampler is then switched from the sampling state to the passing state, in which the charge from the sampling capacitor is passed, i.e. , transmitted, as a sample to the conversion unit for conversion (conversion phase). The sampling phase and the conversion phase mutually exclude each other and the input sampler periodically switches between the sampling state and the passing state. The switching occurs at the sampling frequency, such that a single period according to the switching frequency comprises exactly one sampling phase and one conversion phase.
[0020] Preferably, the sampling frequency and the switching frequency are identical. In other words: the same frequency is used as switching frequency on the output side and as sampling frequency on the input side. This does not prevent the already mentioned crosstalk between the output line and the input line, but it prevents out-of-band-noise as part of the output signal to leak as crosstalk into in- band audible frequencies. In detail: the switching amplifier generates the output signal, which has a specific frequency spectrum. Said frequency spectrum basically comprises two frequency components (intervals), namely a first component, which is an audible spectrum (intended audio spectrum) from DC to an upper frequency as defined by a pre-selected bandwidth, and a second frequency component, which comprises unintended and unavoidable quantization noise above the upper frequency, generated by the switching amplifier.
[0021] Fortunately, the quantization noise is inaudible, because it is - by design - outside the audible spectrum and because the output transducer advantageously does not respond well to the corresponding frequencies. However, because the output signal is sampled by way of the switching of the switching amplifier, said frequency components are replicated at higher frequencies of the frequency spectrum according to the switching frequency. In case of insufficient isolation between the input line and the output line, a part of the frequency spectrum may leak into the input line, i.e., crosstalk is produced. Now, if the sampling frequency differs from the switching frequency and when aliased in the sampling unit with the sampling frequency higher than the switching frequency, the replicated parts of the output signal’s frequency spectrum above the sampling frequency are downshifted and potentially reproduced (at least partly) inside the audible spectrum. This negative effect, however, is avoided, when the sampling frequency is identical to the switching frequency, because above mentioned second frequency component will always and automatically only be aliased to frequencies outside the audible spectrum.
[0022] In addition, it is particularly easy to set a certain phase offset if the sampling frequency and the switching frequency are identical, since the phase offset can then be kept constant and does not have to be periodically readjusted.
[0023] Preferably, the input transducer is a microphone and / or the output transducer is a receiver. In a first suitable embodiment, the microphone is an outer microphone, directed outwards from the ear canal of a user when said user is wearing the hearing aid. Such an outer microphone is used to capture sounds from the environment of the user, said sounds then being processed by the signal processing unit and subsequently output by the receiver for the user’s benefit. In a second suitable embodiment, however, the input transducer is an inner microphone, i.e. , a microphone which is directed inwards into the user’s ear canal to capture sounds from within the ear canal. Such an inner microphone is advantageously used as an occlusion microphone, to reduce the occlusion effect.
[0024] Preferably, the signal processing unit is configured for digital signal processing. Correspondingly, the signal from the sampling unit preferably is a digital signal as is the signal (incoming signal) which is input to the switching amplifier. The signal processing is then, advantageously, performed on digital signal. The switching of the switching amplifier is preferably synchronized with the incoming signal, in particular, by way of a corresponding adjustment of the switching frequency.
[0025] Some or all of the sampling unit, the switching amplifier, the entire signal processing unit, and the control unit may be realized as part of a common chip, but may also be distributed among different chips.
[0026] In a possible embodiment, the input line and the output line each are a conductor and run inside a housing of the hearing aid. In such an embodiment, the input line and the output line may be tracks on a PCB (printed circuit board) of the hearing aid arranged inside the housing. Said PCB may also accommodate any of the various components mentioned above.
[0027] An inventive hearing aid is configured for being operated according to a method as described above.
[0028] The invention is described in detail below and with reference to the following figures, showing preferred embodiments of the invention:
[0029] Fig. 1 a hearing aid,
[0030] Fig. 2 the hearing of Fig. 1 in a different representation,
[0031] Fig. 3 two frequencies and a phase offset, Fig. 4 a frequency spectrum.
[0032] An exemplary hearing aid 2 is shown in Fig. 1 , a schematic representation of this hearing aid 2 is shown in Fig. 2. These Figs. 1 and 2 are also used to illustrate a method for operating the hearing aid 2. The hearing aid 2 comprises an input transducer 4, here a microphone, outputting an input signal 6, a sampling unit 8, and an input line 10, for transmitting the input signal 6 from the input transducer 4 to the sampling unit 8. Hence, the input signal 6 is generated by the input transducer 4 during operation of the hearing aid 2 and transmitted along the input line 6 to the sampling unit 8. The sampling unit 8 here is an A / D-converter. The sampling unit 8 is part of a signal processing unit 12 of the hearing aid 2 and samples the input signal 6 for subsequent signal processing (not shown) inside said signal processing unit 12. The microphone may be an outer microphone or an inner microphone, examples for both cases are shown in Fig. 1 .
[0033] The sampling unit 8 comprises a conversion unit 14 and an input sampler 16, wherein said input sampler 16 operates with a sampling frequency f1 , for periodically generating a sample 18 from the input signal 6 and passing said sample 18 to the conversion unit 14. That is, the actual sampling of the input signal 6 is performed by the input sampler 16, which, e.g., cuts out certain pieces of the input signal 6 during defined time intervals and transmits these or signals derived therefrom as samples 18 to the conversion unit 14. Due to the periodic sampling, several subsequent samples 18 are created over time. The conversion unit 14, then, converts the sample 18 into a proper signal for the subsequent signal processing. The input sampler 16 periodically generates samples 18 from the input signal 6, which automatically means that during some periods of time a sample 18 is generated, while during other periods of time no sample 18 is generated, i.e. , the input signal 6 is rejected by the input sampler 16 during these other periods of time. The samples 18 are generated at a frequency corresponding to the sampling frequency f1 .
[0034] The hearing aid 2 further comprises an output transducer 20, a switching amplifier 22, which switches with a switching frequency f2, and an output line 24, which connects the switching amplifier 22 with the output transducer 20. In analogy to the input signal 6, an output signal 26 is transmitted along the output line 24 from the switching amplifier 22 to the output transducer 20 and is subsequently output by said output transducer 20 during operation of the hearing aid 2. The switching amplifier 22 here is a class D amplifier and is part of the signal processing unit 12. The output signal 26 is generated by the switching amplifier 22 based on a signal derived from the input signal 6 and any signal processing performed thereon. Said signal is amplified by the switching amplifier 22 and, thus, the output signal 26 is generated.
[0035] The switching amplifier 22 operates by switching back and forth between a finite number of (e.g., two or three) defined states. For example, the switching amplifier 22 during operation generates a train of pulses of fixed amplitude but with varying width and separation, or varying number per unit time, representing amplitude variations of the signal which is input to the switching amplifier 22. Optionally, said pulse train is subsequently passed through a suitable low-pass filter (not shown) to generate the output signal 26 as an analog signal. The output signal 26 as a function of time is a sum of subsequent steps, wherein a minimum length of the steps is defined by the switching frequency f2. The switching frequency f2 defines the fastest possible switching of the switching amplifier 22 and, hence, in analogy to the sampling unit 8, may be regarded as a sampling frequency of the switching amplifier 22.
[0036] The input signal 6 is an input signal to the signal processing unit 12 and the output signal 26 is an output signal of the processing unit 12. The input transducer 4, input line 10, and sampling unit 8 belong to an input side of the hearing aid 2. Correspondingly, the output transducer 20, the output line 24, and the switching amplifier 22 belong to an output side of the hearing aid 2. The output line 24 and the input line 10 are particularly close to each other, in a spatial sense, such that crosstalk C may occur between the input line 10 and the output line 24. Crosstalk C primarily occurs from the output line 24 to the input line 10. A coupling path is formed between the input line 10 and the output line 24 and crosstalk C occurs along the coupling path. Said coupling path is not an actual electrical connection, but may be modelled by a stray capacitance, i.e. , a virtual capacitor 28 connecting the input line 10 and output line 24. The exact value of the stray capacitance is heavily dependent on the exact design and application context and, hence, may vary accordingly.
[0037] During operation, the switching of the switching amplifier 22 generates high levels of out-of-band quantization noise that may be picked up by the input line 10 as crosstalk as described and may subsequently be aliased by the sampling unit 8 to audio noise. The crosstalk C, i.e., noise, induced in the input line 10 by the output signal 26 adds to the original input signal 10 generated by the input transducer 4 and the input signal 10 comprising said noise (i.e., the crosstalk C) is transmitted along the input line 10 towards the sampling unit 8. Correspondingly, if a sample 18 is generated based on the input signal 6 including noise, said noise is also converted by the conversion unit 14. To avoid this, a phase offset p between the sampling frequency f1 and the switching frequency f2 is used to prevent crosstalk C from being passed to the conversion unit 14. This is illustrated in Fig. 3, showing an example for the two frequencies f1 , f2 and the phase offset p in the time domain (amplitude a versus time t).
[0038] The phase offset p is an operating parameter of the hearing aid 2. The phase offset p maybe set as part of the method or separate therefrom. The phase offset p may be set once and remain fixed afterwards or may be changed as required during operation, e.g., via a suitable user interface.
[0039] The phase offset p between the sampling frequency f1 and the switching frequency f2 is now set (also: adjusted) such, that at those points of time, during which noise is created in the input line 10 from switching of the switching amplifier 22, no sampling by the input sampler 16 occurs. Correspondingly, the input signal 10 at those points of time, where it includes crosstalk C, is rejected by the input sampler 16 and prevented from being passed to the conversion unit 14. As a result, crosstalk C is not converted and, thereby, reduced. The hearing aid 2 shown here comprises a phase adjustment unit 30 for adjusting the phase offset p. Optionally, the phase offset p is also measured by the phase adjustment unit 30.
[0040] In the embodiment shown here, the phase offset p is set such that crosstalk C is blocked by the input sampler 16 from being passed to the conversion unit 14. Correspondingly, generation of the samples 18 is based exclusively on the input signal 6 at those periods of time, during which the input signal 6 is free of crosstalk C. The mentioned periods of time are known, since the switching frequency f2 and the phase offset p are known.
[0041] Presently, the phase offset p is set such that the switching amplifier 22 performs a switching operation immediately after the input sampler 16 stops generating the sample 18 as well as immediately after the input sampler 16 starts passing the sample 18 to the conversion unit 14. Thereby, crosstalk C is rejected by the input sampler 16 and not transmitted to the conversion unit 14.
[0042] In the exemplary embodiment shown here, the input sampler 16 comprises a sampling capacitor 32 and a switch 34, said switch 34 having a sampling state (shown in Fig. 2 as the arrow with the solid line) and a passing state (shown in Fig. 2 as the arrow with the dashed line). In the sampling state, the switch 24 connects the input transducer 4 with the sampling capacitor 32, but not with the conversion unit 14. In the passing state the switch 32 connects the sampling capacitor 32 with the conversion unit 14, but not with the input transducer 4. In both states, the conversion unit 14 is not directly connected to the input transducer 4. The working principle of such an input sampler 16 is as follows: the input sampler 16 is switched to the sampling state, in which the sampling capacitor 32 is charged to a voltage level determined by the input signal 6 generated by the input transducer 4 (sampling phase). The input sampler 16 is then switched from the sampling state to the passing state, in which the charge from the sampling capacitor 32 is passed as a sample 18 to the conversion unit 14 for conversion (conversion phase). The input sampler 16 periodically switches between the sampling state and the passing state and the switching occurs at the sampling frequency f1 .
[0043] Presently, the sampling frequency f1 and the switching frequency f2 are identical. This does not prevent the crosstalk C between the output line 24 and the input line 10, but it prevents out-of-band-noise as part of the output signal 26 to leak as crosstalk C into in-band audible frequencies. In detail and with reference to Fig. 4, schematically showing a frequency spectrum of the output signal 26 (amplitude a versus frequency f): the switching amplifier 22 generates the output signal 26, which has a specific frequency spectrum, which basically comprises two frequency components 36, 38, namely a first component 36, which is an audible spectrum (intended audio spectrum) from DC to an upper frequency fbw as defined by a preselected bandwidth, and a second component 38, which comprises unintended and unavoidable quantization noise above the upper frequency fbw, generated by the switching amplifier 22. Fortunately, the quantization noise is inaudible.
[0044] However, because the output signal 26 is sampled by way of the switching of the switching amplifier 22, said frequency components 36, 38 are replicated as replicated parts 40 at higher frequencies of the frequency spectrum according to the switching frequency f2. In case of insufficient isolation between the input line 10 and the output line 24, crosstalk C is produced. Now, if the sampling frequency f1 differs from the switching frequency f2 and when aliased in the sampling unit 8 with the sampling frequency f1 higher than the switching frequency f2, the replicated parts 40 of the output signal’s 26 frequency spectrum above the sampling frequency f1 are downshifted and potentially reproduced (at least partly) inside the audible spectrum 36, as illustrated in Fig. 4. This negative effect, however, is avoided, when the sampling frequency f1 is identical to the switching frequency f2, because above mentioned second frequency component 38 will always and automatically only be aliased to frequencies outside the audible spectrum 36.
[0045] In a possible embodiment, the input line and the output line each are a conductor and run inside a housing 42 of the hearing aid 2. In such an embodiment, the input line 10 and the output line 24 may be tracks on a PCB (printed circuit board) of the hearing aid 2 arranged inside the housing 42.
[0046] The hearing aid 2 also comprises a control unit 44, configured to carry out the method as described above.
[0047] List of Reference Numerals
[0048] 2 hearing aid
[0049] 4 input transducer
[0050] 6 input signal
[0051] 8 sampling unit
[0052] 10 input line
[0053] 12 signal processing unit
[0054] 14 conversion unit
[0055] 16 input sampler
[0056] 18 sample
[0057] 20 output transducer
[0058] 22 switching amplifier
[0059] 24 output line
[0060] 26 output signal
[0061] 28 virtual capacitor, stray capacitance
[0062] 30 phase adjustment unit
[0063] 32 sampling capacitor
[0064] 34 switch
[0065] 36 first component (audible spectrum)
[0066] 38 second component
[0067] 40 replicated part
[0068] 42 housing
[0069] 44 control unit a amplitude
[0070] C crosstalk f frequency f1 sampling frequency (of sampling unit) f2 switching frequency (of switching amplifier) fbw upper frequency p phase offset t time
Claims
Claims1. Method for operating a hearing aid (2), a. wherein the hearing aid (2) comprises an input transducer (4), outputting an input signal (6), a sampling unit (8), and an input line (10), for transmitting the input signal (6) from the input transducer (4) to the sampling unit (8), b. wherein the sampling unit (8) comprises a conversion unit (14) and an input sampler (16), wherein said input sampler (16) operates with a sampling frequency (f1 ), for periodically generating a sample (18) from the input signal (6) and passing said sample (18) to the conversion unit (14), c. wherein the hearing aid (2) comprises an output transducer (20), a switching amplifier (22), which switches with a switching frequency (f2), and an output line (24), which connects the switching amplifier (22) with the output transducer (20), d. wherein a phase offset (p) between the sampling frequency (f1 ) and the switching frequency (f2) is used to prevent crosstalk (C) from being passed to the conversion unit (14), wherein said crosstalk (C) occurs between the output line (24) and the input line (10) as a result of switching of the switching amplifier (22).
2. Method according to claim 1 , wherein the phase offset (p) is set such that crosstalk (C) is blocked by the input sampler (16) from being passed to the conversion unit (14).
3. Method according to claim 1 or 2, wherein the phase offset (p) is set such that the switching amplifier (22) performs a switching operation immediately after the input sampler (16) stops generating the sample (18).
4. Method according to any one of claims 1 to 3,wherein the phase offset (p) is set such that the switching amplifier (22) performs a switching operation immediately after the input sampler (16) starts passing the sample (18) to the conversion unit (14).
5. Method according to any one of claims 1 to 4, wherein the input sampler (16) comprises a sampling capacitor (32) and a switch (34), said switch (34) having a sampling state and a passing state, wherein in the sampling state the switch (34) connects the input transducer (16) with the sampling capacitor (32), wherein in the passing state the switch (34) connects the sampling capacitor (32) with the conversion unit (14).
6. Method according to any one of claims 1 to 5, wherein the sampling frequency (f1 ) and the switching frequency (f2) are identical.
7. Method according to any one of claims 1 to 6, wherein the input transducer (4) is a microphone and wherein the output transducer (20) is a receiver.
8. Method according to any one of claims 1 to 7, wherein the input transducer (4) is an inner microphone.
9. Method according to any one of claims 1 to 8, wherein the input line (10) and the output line (24) each are a conductor and run inside a housing (42) of the hearing aid (2).
10. Hearing aid (2), which is configured for being operated according to a method according to any one of claims 1 to 9.