System and method for detecting interference

Abstract

A method for detecting interference between a transducer of acoustic signals and a sensor having a mechanical resonance frequency with a frequency band that includes transmitting an acoustic signal within a known range of frequencies, in a sequence during a predetermined time window, monitoring the output signal from the sensor within said time window, comparing the transmitted signal with the sensor output signal and detecting deviations in the sensor output signal corresponding to frequencies in the acoustic signal, and determining the acoustic frequencies interfering with the sensor signal. A system for detecting interference including a transducer, configured to emit a sequence of acoustic signals, and a sensor configured to produce an output signal, an analysis unit adapted to monitor said output signal with the acoustic signal.

Description

[0001] SYSTEM AND METHOD FOR DETECTING INTERFERENCE

[0002] INTRODUCTION

[0003] The present invention concerns a system and method for detecting interference in an electronic device. The interference may be caused by acoustic signals emitted by components of the electronic device resonating with other sensors with at least one mechanical resonance frequency inside the band of the acoustic signal. The present invention further relates to systems and methods for minimizing or avoiding interference in an electronic device.

[0004] More specifically, the present invention relates to electronic devices with MEMS accelerometers and gyroscopes and, more particularly, to methods and systems for minimizing interference from ultrasound signals emitted to such sensors.

[0005] BACKGROUND

[0006] In electronic devices transmitting an ultrasound output signal for a specific usecase, the frequency band of the ultrasound signal is important for signal to noise ratio (SNR) and use-case functionality and performance. If the frequency band is limited due to sampling rate restrictions or performance limitations (e.g. frequency filtering), the ultrasound signal may have a limited frequency range in which to operate. The invention discussed here will focus on two sensors in the same device, but the invention can easily be transferred to systems consisting of several electronic devices.

[0007] Gyroscopes in electronic devices usually operate in and around a resonance frequency. Thus, gyroscopes can experience interference from use-case specific ultrasound signals affecting their performance. Specifically, the gyroscopic sensors can display erroneous readings when the emitted ultrasound frequency or frequency band overlaps with the resonance frequency of the gyroscope. Although mitigation strategies such as damping / isolation, shielding, filtering, calibration, etc may be in use for the gyroscope, an ultrasound signal may still cause erroneous readings from the gyroscope. The impact of the ultrasound signal on the sensor data from the gyroscope depends on several factors including distance between the acoustic transmitter and the gyroscope, the amplitude of the ultrasound signal and the overlap in frequency ranges. Usually, the longer the distance between the speaker and the gyroscope is, the lower the amplitude and thereby the impact of the ultrasound signal is on the gyroscope data. Similarly, the lower the amplitude of the ultrasound signal, the lower the impact on the gyroscope data will be. The amount of overlap in the frequency range between the operating frequency of the gyroscope and the ultrasound signal will also matter. In general, the more overlap in the frequency range, the more impact on the gyroscope data. Since different use-cases may emit different ultrasound signals, the solution and specific thresholds or parameters can vary from use-case to use-case mandating use-case specific solutions.

[0008] US11598751 B2 discloses a resonance detection system which includes a vibration simulation mechanism and a vibration audio analysis device. The vibration simulation mechanism includes a mechanism body that accommodates a peripheral interface device, such as a notebook computer key input mechanical structure. The vibration simulation mechanism generates a vibration wave to the peripheral interface device which generates a vibration audio signal in response to the vibration wave. The vibration simulation mechanism further includes a patchtype audio collector, such as a miniature auscultation radio patch, which is connected with the vibration audio analysis device. The patch-type audio collector is attached on the mechanism body containing the peripheral interface device. The vibration audio signal is collected by the patch-type audio collector. The vibration audio analysis device judges whether there is an abnormal resonance phenomenon in the vibration audio signal, which may be used for fabrication quality control of peripheral interface devices.

[0009] However, the predetermination of the mechanical resonance frequency of a sensor as a separate component during the fabrication process may not be accurate and / or adequate. This is because the mechanical resonance frequency of components may be impacted by the way the components are mounted inside an electronic device, or because further mechanical resonance frequencies may appear due to a coupling with other components or after damage of the electronic device.

[0010] DE102018202995A1 discloses a method for automatically checking at least one function of an electronic device, which has a touch screen and a vibration device, using a handling machine. The method includes the step of transmitting a characteristic signal from the electronic device to the handling machine, in that the electronic device generates a mechanical vibration using a vibration device of the electronic device, which comprises a carrier signal and a useful signal characterizing the characterizing signal and modulated onto the carrier signal, and this mechanical vibration is transmitted to the handling machine and demodulated there in order to record the characterizing signal by the handling machine.

[0011] CN1 13068100A discloses a closed-loop automatic detection vibration reduction method. The method comprises the steps of controlling a loudspeaker of equipment to be detected to play a detection sound source, controlling a microphone of the to-be-tested device to record and collect an audio signal when a loudspeaker plays the detection sound source, analyzing the audio signal to obtain test analysis data, and suppressing the amplitude of the loudspeaker in the resonant frequency range according to the test analysis data. According to the closed-loop automatic detection vibration reduction method, the resources of the electronic equipment are fully utilized, closed-loop detection is realized, and the obtained audio signal is more real; meanwhile, the real resonance state of the equipment is determined according to the audio signals of the loudspeaker on the electronic equipment, then resonance noise is correspondingly suppressed according to different resonance frequency ranges of the electronic equipment, the resonance problem of the electronic equipment is solved in a targeted mode, and better sound listening experience is brought to a user.

[0012] Such systems and methods, however, require the finished electronic device to be tested and optimized at a testing facility, and in case the mechanical resonance frequency changes overtime, the detection and optimization may be a cumbersome procedure due to the need for accessing said testing facility.

[0013] Hence, there is a need for a system and method for efficiently and dynamically detecting, minimizing or even eliminating such mechanical resonances in the finished electronic device. This is obtained with a method and system according to the accompanying claims.

[0014] According to the invention, interference caused by the limited frequency band allocated to the ultrasound signal may interfere with other sensors operating in the same frequency band in the same electronic device. It is even conceivable that the ultrasound signal emitted by one electronic device can impact the gyroscope included in another device.

[0015] SUMMARY OF THE INVENTION

[0016] The invention relates to a method for detecting interference between a transducer of acoustic signals and a sensor having a mechanical resonance frequency with a frequency band. The method comprises the step of transmitting an acoustic signal within a known range of frequencies, in a sequence during a predetermined time window. The method further comprises the step of monitoring the output signal from the sensor within said time window. The method further comprises the step of comparing the transmitted signal with the sensor output signal and detecting deviations in the sensor output signal corresponding to frequencies in the acoustic signal. The method further comprises the step of determining the acoustic frequencies interfering with the sensor signal.

[0017] The transducer of acoustic signals and the sensor may be comprised in an electronic device. The transducer of acoustic signals may be comprised in a first electronic device, and the sensor may be comprised in a second electronic device.

[0018] The acoustic signal may be transmitted from a plurality of transducers. Frequency components of the acoustic signal may be transmitted by the plurality of transducers. Frequency components may be split between the plurality of transducers.

[0019] The method may further comprise the step of reducing interference by producing a periodic signal using the transducer, and selecting a period of the periodic acoustic signal, the acoustic signal having a frequency band with one or more frequencies with a distance between them being larger than the resonance frequency band of the sensor, such that any frequency selected from the one or more frequencies falls outside the resonance frequency band of the sensor.

[0020] The method may further comprise the step of reducing interference by selecting an amplitude of the periodic acoustic signal to be smaller than a threshold amplitude value.

[0021] The method may further comprise the step of reducing interference by producing a periodic acoustic signal using the transducer, the periodic acoustic signal being composed of one or more harmonics each having a frequency and a phase, such that harmonics with frequencies in the vicinity of the resonance frequency band of the sensor are removed.

[0022] The method may further comprise the step of reducing interference by reducing interference by producing a periodic acoustic signal using the transducer, the periodic acoustic signal having a gap in its frequency spectrum which corresponds to the mechanical resonance frequency of the sensor.

[0023] The method may further comprise notifying the transducer if the sensor is active or not, for proceeding or ceasing, respectively, with creating a gap in its frequency spectrum.

[0024] The method may further comprise notifying the transducer if requirements regarding accuracy of the sensor are met or not, for proceeding or ceasing, respectively, with creating a gap in its frequency spectrum. The invention relates to a system for detecting interference between a transducer of acoustic signals and a sensor having a mechanical resonance frequency with a frequency band, comprising a transducer of acoustic signals, configured to emit a sequence of acoustic signals. The system further comprises a sensor having a mechanical resonance frequency with a frequency band, configured to produce output signal. The system further comprises an analysis unit adapted to monitor said output signal with the acoustic signal while the transducer emits the sequence of acoustic signals and detect deviations in the sensor output signal corresponding to one or more frequencies in the acoustic signal.

[0025] The transducer of acoustic signals may further be configured to select a period of the acoustic signal, the acoustic signal having a frequency band with one or more frequencies with a distance between them being larger than the resonance frequency band of the sensor, such that any frequency selected from the one or more frequencies falls outside the resonance frequency band of the sensor.

[0026] The transducer of acoustic signals may further be configured to select an amplitude of the periodic signal to be smaller than a threshold amplitude value.

[0027] The transducer may further be configured to produce a periodic acoustic signal, the periodic acoustic signal being composed of one or more harmonics each having a frequency and a phase, such that harmonics with frequencies in the vicinity of the resonance frequency band of the sensor are removed.

[0028] The transducer being further configured to produce a periodic acoustic signal, the periodic acoustic signal having a gap in its frequency spectrum which corresponds to the mechanical resonance frequency of the sensor.

[0029] The system for detecting interference may further comprise a processing module, arranged to notify the transducer if the sensor is active or not, for proceeding or ceasing, respectively, with creating a gap in its frequency spectrum. The processing module being further arranged to notify the transducer if requirements regarding accuracy of the sensor are met or not, for proceeding or ceasing, respectively, with creating a gap in its frequency spectrum.

[0030] The transducers may comprise a plurality of transducers configured to transmit the acoustic signal. Each transducer in the plurality of transducers may be configured to transmit frequency components of the acoustic signal. Each transducer in the plurality of transducers may be configured to transmit a different frequency component of the acoustic signal. Each transducer in the plurality of transducers may be configured to transmit a same frequency component of the acoustic signal.

[0031] This invention thus provides a method to reduce or eliminate interference in gyroscope readings caused by ultrasound signals. The method involves emitting ultrasound signals in such a way that their harmonics do not coincide with the gyroscopic sensor's frequency, thereby minimizing disturbances. The invention is not limited to ultrasound signals, and the same applies to acoustic signals in other frequency bands too, including audible and infrasound bands if they overlap with the operating frequency of the gyroscope. In the discussion below reference is made to a gyroscope, based on a practical use-case, but the sensor may be any sensor type being affected by vibrations or acoustic signals, such as: MEMS sensors, QCM sensors, SAW sensors, piezoelectric sensors, and resonant pressure sensors.

[0032] BRIEF DESCRIPTION OF DRAWINGS

[0033] Examples of the invention are disclosed with reference to the following drawings, wherein:

[0034] Figs. 1a-1 d shows different situations involving an interference as handled by the present invention.

[0035] Fig. 2 illustrates a transmitted signal and a detected interference caused by the signal.

[0036] Fig. 3 illustrates an exemplary chirp signal and an exemplary chirp signal with missing frequencies, in the time and frequency domain, and their autocorrelation function in each case. DETAILED DESCRIPTION

[0037] Example embodiments are described with reference to the drawings. The examples are illustrations only and are not limiting for the invention.

[0038] Figure 1a shows an interference 17 between a transducer 13 of acoustic signals 16 and a sensor 14. The transducer 13 is connected to an interface and processor controlling the transmitted acoustic signal 16, thus having known characteristics, especially in terms of frequency bands, for example bring used for communication purposes or for acoustic proximity measurements. The signal 16 from the transducer 13 also propagates 17 to the sensor 14 which also is adapted to communicate through a connection to the interface 12. This interface may be processor controlling the operation of the device, both involving the acoustic communication 16 and the sensor 14 output. As stated above this may be a gyroscope or any other sensor having a sensitivity to acoustic signals which may disturb the measurements. An example of such a system is discussed in WO2020 / 246897 where acoustic proximity measurements are used in combination with an accelerometer or gyroscope to monitor the use of a device

[0039] Since the transmitted signal has known characteristics, especially relating to transmission time periods, frequency range and amplitudes, the output from the sensor will correspond to the transmitted signals, and based on this the processor may analyze the signals to find the effect of the transmitted signals on the sensor output.

[0040] The transducer of acoustic signals may be a plurality of transducers configured to transmit the acoustic signal. Each transducer in the plurality of transducers may be configured to transmit frequency components of the acoustic signal.

[0041] Each transducer in the plurality of transducers may be configured to transmit a different frequency component of the acoustic signal. Alternatively, the plurality of transducers may be configured to transmit a same frequency component of the acoustic signal. Hence, the frequency components of the acoustic signal may be transmitted by the plurality of transducers. Alternatively, the frequency components are split between the plurality of transducers.

[0042] The transducer of acoustic signals may be configured to select an amplitude of the periodic signal to be smaller than a threshold amplitude value.

[0043] The transducer of acoustic signals 13 and the sensor 14 may be comprised in the same device. As illustrated in Figure 1b, a device 11 , for example as described in WO2020 / 246897, comprises an interface 12 which is connected to a transducer of acoustic signals 13 and a sensor 14. The device also includes a microphone or similar connected to the interface 12 for proximity measurements. In this example the transducer is a speaker and the sensor 14 is a gyroscope. The interface 12 can instruct the speaker to emit acoustic signals 16 which propagate through space. The emitted acoustic signals 16 may propagate through space, but an additional interference 17 may occur between the speaker 13 and the gyroscope 14 through the device material. That interference may be mechanical, caused by a coupling between the frequency of the emitted acoustic signals and the resonance frequency of the gyroscope 14.

[0044] The transducer of acoustic signals 13 and the sensor 14 may be comprised in different electronic devices. Figures 1c and 1d show a first device 18 comprising a transducer 13 of acoustic signals 16, and a second device 19 comprising a sensor 14. In the drawings the second device also includes a microphone 15, e.g. for receiving acoustic communication from the first device for presence detection such as in W02023 / 079014. In practice both devices 18,19 may be similar, for example two mobile phones, or different devices as discussed in WO2024 / 107059 where both devices include the similar transducers 13,15 being configured to communicate to each other acoustic and electromagnetic signals, as well as with Wi-Fi or similar electromagnetic signals.

[0045] The two devices 18,19 may communicate to exchange information through a backchannel. The first device comprises an interface 12a and the second device an interface 12b. Each interface may be used to create direct connections using Wi-Fi or Bluetooth Low Energy (BLE), as illustrated in Fig. 1c.

[0046] The backchannel may be a cloud-based service accessible to the first device and the second device enabling communication between the first device and the second device, as illustrated in Fig. 1d.

[0047] The first device may sweep through the supported frequency range in a controlled manner, playing each frequency for a period. When the second device detects an abnormal gyroscope reading, it may send a message to the first device. This message could be sent via a back channel, an acoustic message, a haptic message, or another communication method to indicate the detection of an abnormal sensory event. The duplex communication between the first device and the second device may also be forwarded by a shared cloud service that knows the network address of both devices and can communicate with both entities. Once the first device gets the information that the resonance frequency was detected for a particular sensor, the first device can restart the frequency sweep with a smaller frequency range to get more accurate detection of the resonance frequency. This process can continue iteratively with shorter and shorter frequency ranges around the resonance frequency until the accuracy is acceptable to both device and are within configurable thresholds.

[0048] One method to assess the impact on the gyroscope 14 is to output an acoustic signal (e.g. frequency sweep, ultrasound signal from an actual use-case, etc) on the device’s speaker 13 while simultaneously observing the gyroscope readings when the device is at a state where the gyroscope readings are relatively low because of minimal movement of the device. That may be for example when trying to record video, watch video, or when the device is at complete rest.

[0049] The method for detecting interference between a transducer of acoustic signals and a sensor having a mechanical resonance frequency with a frequency band, comprises transmitting an acoustic signal within a known range of frequencies, in a sequence during a predetermined time window. The method further comprises monitoring the output signal from the sensor within said time window. The method further comprises comparing the transmitted signal with the sensor output signal and detecting deviations in the sensor output signal corresponding to frequencies in the acoustic signal. The method comprises determining the acoustic frequencies interfering with the sensor signal.

[0050] Figure 2 shows a graph depicting a chirp signal 21 and the impact on the gyro traces in graph 22. The frequency of the signal is ramped up in the region 23. Until the point 24a, and between the point 24b and 25a, the gyro traces in 22 are stable, with limited noise. The same happens also when the acoustic signal is not transmitted. Within the regions defined by the dashed lines 24a-24b and 25a-25b, the gyro traces demonstrate an increase in their intensity, which is caused by the transmitted signal. The regions 24a-24b and 25a-25b are therefore the regions where resonance is observed. This shows that when the sound frequency is far from the gyroscope’s resonance frequency or the acoustic signal is not transmitted, the readings from the gyroscope are almost constant with limited noise. When the sound frequency approaches the resonance frequency, gyroscope’s readings begin to gradually deviate from their mean values with the maximum deviation at the point where the acoustic signal’s frequency matches the gyroscope’s resonance. It is also shown that for sensor with more than one resonance frequency within the frequency range this is also detected and may be handled in a similar way.

[0051] The acoustic signal could be a periodic always-on signal or pulsed signal. It could be a sinusoid or include numerous different frequency components such as a chirp signal. With a periodic acoustic signal, the spectrum will be discrete. The spectrum will of course depend on the frequency components of the acoustic signal which may vary from use-case to use-case. Regardless, only certain frequencies will be within the signal’s frequency band. The positions of these frequencies and the distance between them are determined by the period of the signal. If the distance between these frequencies is greater than the band in which they disturb the gyroscope, it is possible to choose the signal period in such a way that none of the ultrasonic frequencies fall into the band where they would interfere with the gyroscope.

[0052] Usually, it is sufficient to create two of such ultrasound signals with two different periods of repetition. If the periods are chosen appropriately, it is possible that if one signal produces interference, the other signal will not affect the gyroscope.

[0053] The dependency of the deviation of gyroscope readings on the ultrasonic signal amplitude can be measured. Acoustic signals with low amplitudes produce negligible amount of interference, if at all. However, beyond a specific amplitude, the deviation of the gyroscope readings rises to its maximum level and becomes independent of further increase in the ultrasonic signal amplitude. It might be therefore an option to combine the frequency avoidance scheme with amplitude reduction albeit as long as the SNR of the acoustic signal is above a given threshold enabling acceptable use-case performance.

[0054] One solution for an ultrasound signal transmitting a chirp signal encompassing the gyroscope’s resonant frequency, is to remove frequency components from the chirp signal close to the resonance frequency of the gyroscope. This is illustrated in Figure 3, where the signal is shown in the time domain 31a, 31 b, the frequency domain 32a, 32b and their autocorrelation functions 33a, 33b. The chirp signal containing all the frequencies is illustrated in the time domain 31a, in the frequency domain 32a, and its autocorrelation function in 33a. The chirp signal with the missing frequencies is illustrated in the time domain 31 b, in the frequency domain 32b, and its autocorrelation function 33b. In the frequency domain 32a, the original chirp signal shown in the time domain 31a has all the harmonics and the autocorrelation function 33a demonstrates a specific periodicity. In the frequency domain 32b, the chirp signal shown in the time domain 31 b, has some of the harmonics either removed completely (i.e. zeroed) or only scaled down in amplitude 34. As illustrated in the time domain 31 b, the chirp signal is still continuous and the periodicity of the autocorrelation function 33b changes. Harmonics with frequencies in the vicinity of the resonance frequency band of the sensor may be removed in this way.

[0055] Since the resonance frequency varies between gyroscope components due to manufacturing process, the frequency component removal may be done specifically for each device based on the resonant frequency of each individual gyroscope. If the ultrasound signal is periodic, it can be synthetized by summing up harmonics of different frequencies having specified phases. It is then a simple matter of excluding the harmonics closer than a defined threshold to the gyroscope’s resonant frequency. The threshold can be parametrized and adapted to a specific acoustic signal or use-case. The threshold, that is, the number of harmonics that needs to be lowered or even zeroed out for a given gyroscope can be found through measurements on the impact of the gyroscope data while the ultrasound signal is transmitted while the use-case is enabled.

[0056] If the ultrasound signal is one or more sinusoids with frequencies too close to the resonance frequency of the gyroscope, the options are either reducing the amplitude of the output signals or moving the problematic frequencies to higher or lower frequencies, based on frequency band availability, where the gyroscope data is not affected more than a specific threshold.

[0057] In one embodiment, the ultrasound signal may dynamically reduce the frequency range of the chirp signal by moving the start frequency or end frequency to avoid the frequency band where the gyroscope is impacted. Alternatively, the ultrasound signal needs to change whenever a gyroscope use-case sensitive to the noise of the gyroscope readings is running. With a narrower frequency band, the chirp SNR is lowered. The SNR drop will in most cases impact use-case performance. If the SNR drops below a specific threshold, supporting the use-case may become difficult if the gyroscope is used concurrently by use-cases sensitive to gyroscope performance and noise. In another embodiment, the ultrasound signal may dynamically create a gap in the frequency spectrum of the ultrasound signal based on whether the gyroscope or sensor with an overlapping frequency is active or not. If it is not active, the ultrasound signal can be transmitted as is while it creates the necessary gap when the sensor is active to prevent interference between the sensors. This process can be dynamic if the ultrasound use-case or another system process on its behalf monitors usage of the gyroscope. If the requested sampling rate of the gyroscope exceeds a configurable threshold where the data impact is too high, the ultrasound use-case can dynamically turn the gap feature on or off to prevent deterioration of the gyroscope data. To enable this feature, the processing module creating the ultrasound signal needs to be notified when the other sensor (e.g. gyroscope) is active. This scheme allows use-cases with different ultrasonic output signals in the same or different, overlapping frequency bands to adapt their output signal to the gyroscope resonance frequency in a use-case specific way, e.g. smaller gap due to lower amplitude.

[0058] In another embodiment, the sensor (e.g. gyroscope) may be usable with interference and the ultrasound signal can be transmitted without creating a gap in its frequency spectrum based on requirements to accuracy etc. To enable this feature, the processing module creating the ultrasound signal needs to be notified when the other sensor (e.g. gyroscope) is active and the necessary requirements to the sensor regarding accuracy etc.

[0059] If the electronic device has stored information about the resonance frequency of the actual gyroscope inside the device, the resonance frequency can be read by a software entity in the system or from the transmitting electronic device and made available (e.g. IO control, message, configuration parameter, RPC, etc) to the transmit module in the ultrasound use-case. The resonance frequency can either be supplied by the gyroscope vendor based on their data or be measured during device or component manufacturing or dynamically by the ultrasound use-case once the product is be used by an end-user. The transmit module can use the device information (i.e. resonance frequency) of the gyroscope to limit the size of the gap in the ultrasound signal to limit the performance impact of a specific usecase.

[0060] Having described example embodiments of the invention it will be apparent to those skilled in the art that other embodiments incorporating the concepts may be used. These and other non-limiting examples illustrated above are intended by way of example only and the actual scope of the invention is to be determined from the following claims.

Claims

P A T E N T C L A I M S1 . A method for detecting interference between a transducer of acoustic signals and a sensor having a mechanical resonance frequency with a frequency band, the method comprising the following steps: transmitting an acoustic signal within a known range of frequencies, in a sequence during a predetermined time window, monitoring the output signal from the sensor within said time window comparing the transmitted signal with the sensor output signal and detecting deviations in the sensor output signal corresponding to frequencies in the acoustic signal, and determining the acoustic frequencies interfering with the sensor signal.

2. The method of claim 1 , wherein the transducer of acoustic signals and the sensor are comprised in an electronic device.

3. The method of claim 1 , wherein the transducer of acoustic signals is comprised in a first electronic device, and the sensor is comprised in a second electronic device.

4. The method of any one of claims 1 - 3, wherein the acoustic signal is transmitted from a plurality of transducers.

5. The method of claim 4, wherein frequency components of the acoustic signal are transmitted by the plurality of transducers.

6. The method of claim 4, wherein frequency components are split between the plurality of transducers.

7. The method for detecting interference according to anyone of claims 1 - 6, further comprising the steps of:reducing interference by producing a periodic signal using the transducer, and selecting a period of the periodic acoustic signal, the acoustic signal having a frequency band with one or more frequencies with a distance between them being larger than the resonance frequency band of the sensor, such that any frequency selected from the one or more frequencies falls outside the resonance frequency band of the sensor.

8. The method for detecting interference according to anyone of claims 1 - 7, further comprising the step of: reducing interference by selecting an amplitude of the periodic acoustic signal to be smaller than a threshold amplitude value.

9. The method for detecting interference according to anyone of claims 1 - 6, further comprising the step of: reducing interference by producing a periodic acoustic signal using the transducer, the periodic acoustic signal being composed of one or more harmonics each having a frequency and a phase, such that harmonics with frequencies in the vicinity of the resonance frequency band of the sensor are removed.

10. The method for detecting interference according to anyone of claims 1 - 6, further comprising the step of: reducing interference by producing a periodic acoustic signal using the transducer, the periodic acoustic signal having a gap in its frequency spectrum which corresponds to the mechanical resonance frequency of the sensor.11 . The method for detecting interference according to claim 10, further comprising the step of: notifying the transducer if the sensor is active or not, for proceeding or ceasing, respectively, with creating a gap in its frequency spectrum.

12. The method for detecting interference according to claim 10 or claim 11 , further comprising the step of: notifying the transducer if requirements regarding accuracy of the sensor are met or not, for proceeding or ceasing, respectively, with creating a gap in its frequency spectrum.

13. A system for detecting interference between a transducer of acoustic signals and a sensor having a mechanical resonance frequency with a frequency band, comprising: a transducer of acoustic signals, configured to emit a sequence of acoustic signals; and a sensor having a mechanical resonance frequency with a frequency band, configured to produce an output signal, an analysis unit adapted to monitor said output signal with the acoustic signal while the transducer emits the sequence of acoustic signals and detect deviations in the sensor output signal corresponding to one or more frequencies in the acoustic signal.

14. The system for detecting interference according to claim 13, wherein the transducer of acoustic signals is further configured to select a period of the acoustic signal, the acoustic signal having a frequency band with one or more frequencies with a distance between them being larger than the resonance frequency band of the sensor, such that any frequency selected from the one or more frequencies falls outside the resonance frequency band of the sensor.

15. The system for detecting interference according to claim 13 or claim 14, wherein the transducer of acoustic signals is further configured to select an amplitude of the periodic signal to be smaller than a threshold amplitude value.

16. The system for detecting interference according to claim 13, the transducer being further configured to produce a periodic acoustic signal, the periodic acoustic signal being composed of one or more harmonics each having afrequency and a phase, such that harmonics with frequencies in the vicinity of the resonance frequency band of the sensor are removed.

17. The system for detecting interference according to claim 13, the transducer being further configured to produce a periodic acoustic signal, the periodic acoustic signal having a gap in its frequency spectrum which corresponds to the mechanical resonance frequency of the sensor.

18. The system for detecting interference according to claim 17, further comprising a processing module, arranged to notify the transducer if the sensor is active or not, for proceeding or ceasing, respectively, with creating a gap in its frequency spectrum.

19. The system for detecting interference according to claim 18, the processing module being further arranged to notify the transducer if requirements regarding accuracy of the sensor are met or not, for proceeding or ceasing, respectively, with creating a gap in its frequency spectrum.

20. The system according to any one of claims 13 - 19, wherein the transducers comprise a plurality of transducers configured to transmit the acoustic signal.21 . The system according to claim 19, wherein each transducer in the plurality of transducers is configured to transmit frequency components of the acoustic signal.

22. The system according to claim 19, wherein each transducer in the plurality of transducers is configured to transmit a different frequency component of the acoustic signal.

23. The system according to claim 19, wherein each transducer in the plurality of transducers is configured to transmit a same frequency component of the acoustic signal.

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