WO2021043414A1

WO2021043414A1 - Microphone blocking detection control

Info

Publication number: WO2021043414A1
Application number: PCT/EP2019/073777
Authority: WO
Inventors: Mari Partio; Anu Huttunen
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2019-09-05
Filing date: 2019-09-05
Publication date: 2021-03-11
Also published as: CN114303389A; EP4018681A1

Abstract

An improved microphone blocking detection method and system that utilizes control information from a control unit (4) capable of detecting wind noise or handling noise from microphone signals, optionally combined with signals from inner sensors (9) (such as a voice accelerometer, a voice pickup sensor or an inner microphone) to prevent erroneous blocking detection when the control unit (4) has identified wind noise, handling noise or other abnormalities. The method can further utilize detection of background noise and a user's own voice detection (OVD) information as additional controlling features to stop the blocking detection in a silent situation when there is no background noise or speech.

Description

MICROPHONE BLOCKING DETECTION CONTROL

TECHNICAL FIELD

The disclosure relates in general to digital audio signal processing techniques, and in particular to methods and systems for controlling automatic detection of microphone blocking in apparatuses (such as mobile devices with headsets) comprising multiple microphones.

BACKGROUND

Systems comprising an audio recording apparatus, such as a headset connected physically or via wireless connection to a mobile device, can make use of more than one microphone to pick-up and record audio from the surrounding environment, such as the voice of the user of the mobile device. Occasionally, the operation of one or more of these microphones may become blocked, partially blocked, broken or otherwise impaired in operation.

For example, small particles such as dust may become embedded in the microphone leading to a deterioration in the operation of the microphone, a microphone may become blocked or partially blocked by a finger or other body part, or by some item the user is wearing (such as a scarf or a hat). A microphone may also break or partially break due to a mechanical or other cause, and/or a microphone may become impaired due to sound distortion introduced by environmental factors such as wind. This may lead to a reduction in the quality of the recorded audio. In addition, any beamforming - usually used for noise reduction and better sound pick-up from desired direction - needs to be switched off during microphone blocking since it will lead to an erroneous output.

In a headset with multiple microphones, the system can switch from the blocked microphone to one that is not blocked. Usually microphone blocking is detected by comparing microphone power levels. However, blocking detection calculated in this way leads to erroneous result during wind noise or handling noise (handling noise emerges when user touches microphone or microphone hole). This is because during wind noise or handling noise microphone power levels usually vary fast in relation to one another. Also, in a silent situation (with no or very low background noise) the comparison of microphone power levels does not produce a reliable result. In US9467779B2 (Microphone partial occlusion detector, Apple Inc, Oct. 11 , 2016) a microphone partial occlusion detector determines a low frequency band separation of the first and second audio signals and a high frequency band separation of the first and second audio signals to generate a microphone partial occlusion function that indicates whether one of the microphones is partially occluded. Voice activity detection (VAD) is utilized for evaluating partial occlusion conditions.

In US9699550B2 (Reduced microphone power-up latency, Qualcomm Inc., Jul. 4, 2017) a first microphone is configured to wake-up other microphones. In case low noise level detector of first microphone fails to exceed selected threshold level, handover command is sent to second microphone.

In WO2014037766A1 (Detection of a microphone impairment, Mar. 13 2014) microphone impairment is detected by different methods by comparing microphone signals or powers calculated from them to selected threshold.

SUMMARY It is an object to provide an improved microphone blocking detection method and apparatus which overcomes or at least reduces the problems mentioned above, by preventing blocking detection during wind noise, handling noise or other abnormalities.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures. According to a first aspect, there is provided an apparatus comprising: at least one pair of microphones, each microphone configured to generate at least one microphone signal; a processor configured to monitor at least one pair of microphone signals, wherein each microphone signal is generated by a different one of a pair of microphones, determine at least one blocking signal by comparing the at least one pair of microphone signals, each blocking signal indicating if a microphone is blocked, and update a blocking status of at least one of the pair of microphones based on the blocking signal; and a control unit configured to monitor the presence of at least one of a wind noise or a handling noise based at least partly on the microphone signals, and generate a control signal indicating the presence; wherein the processor is further configured to prevent updating the blocking status if the control signal indicates presence of at least one of a wind noise or a handling noise.

Preventing blocking detection when the control unit has identified wind noise, handling noise or other abnormalities results in a microphone blocking detection method that can be used in an apparatus such as a headset which is more reliable and more accurate than previously known methods.

In a possible implementation form of the first aspect the processor is further configured to determine the at least one blocking signal by calculating a signal power ratio between the at least one pair of microphone signals over a predetermined frequency band; and comparing the signal power ratio to at least one predetermined threshold value. In a further possible implementation form of the first aspect the processor is further configured to determine a blocking signal for each of the at least one pair of microphones, wherein comparing the signal power ratio to a higher threshold value determines a blocking signal for one microphone and comparing the signal power ratio to a lower threshold value determines a blocking signal for the other microphone of the pair of microphones.

In a further possible implementation form of the first aspect, at least one of the control signals is a binary signal, the value of the control signal being 1 when any presence of a wind noise or a handling noise is detected and 0 otherwise; or the blocking signal is a binary signal, the value of the blocking signal being 1 if a microphone is blocked and 0 otherwise.

In a further possible implementation form of the first aspect the apparatus further comprises at least one inner sensor arranged in a housing; and the control unit is further configured to detect the presence of at least one of a wind noise or a handling noise based on at least one of said microphone signals and at least one inner sensor signal from the at least one inner sensor. In an embodiment, the inner sensor is at least one of a voice accelerometer, VACC, a voice pickup sensor, VPU, or an inner microphone. Utilizing an inner sensor (e.g. integrated in a headset) in addition to microphone signals helps determining the control signal in a more accurate way.

In a further possible implementation form of the first aspect the control unit is further configured to detect the presence of a user’s own voice based on at least one of the microphone signals and the at least one signal from the at least one inner sensor, and generate an own voice detection, OVD, signal; and the processor is further configured to only update the blocking status if the OVD signal indicates presence of a user’s own voice. This solution helps to limit the blocking detection to those time periods when a user’s own voice is detected, thereby improving the reliability of the microphone blocking detection especially in a silent situation.

In an embodiment, the OVD signal is a binary signal, the value of the OVD signal being 1 if a user’s own voice is detected and 0 otherwise. In a further possible implementation form of the first aspect the processor is further configured to detect a background noise value by analyzing at least one of the at least one microphone signal and the at least one signal from the at least one inner sensor; and only update the blocking status if at least one of the background noise value exceeds a predetermined background noise threshold value or the OVD signal indicates presence of a user’s own voice, otherwise prevent updating the blocking status. This helps further improving the reliability of the microphone blocking detection by stopping the blocking detection if the noise level is not high enough. According to a second aspect, there is provided a method for controlling microphone blocking detection in an apparatus comprising a processor, a control unit, and at least one pair of microphones, the method comprising: monitoring, by the processor, at least one pair of microphone signals, wherein each microphone signal is generated by a different one of a pair of microphones; determining, by the processor, at least one blocking signal by comparing the at least one pair of microphone signals, each blocking signal indicating if a microphone is blocked; updating, by the processor, a blocking status of at least one of the pair of microphones based on the blocking signal; monitoring, by the control unit, the presence of at least one of a wind noise or a handling noise based at least partly on the microphone signals, and generating a control signal indicating the presence; and configuring the processor to prevent updating the blocking status is if the control signal indicates presence of at least one of a wind noise or a handling noise. An apparatus configured in this way to prevent blocking detection when the control unit has identified wind noise, handling noise or other abnormalities results in more reliable and more accurate microphone blocking detection than known from existing devices, because it can help avoiding erroneous results and faulty detection of microphone blocking or impairment during wind or handling noise. In a possible implementation form of the second aspect determining the at least one blocking signal comprises: calculating a signal power ratio between the at least one pair of microphone signals over a predetermined frequency band; and comparing the signal power ratio to at least one predetermined threshold value.

In a further possible implementation form of the second aspect determining the at least one blocking signal comprises determining a blocking signal for each of the at least one pair of microphones, wherein comparing the signal power ratio to a higher threshold value determines a blocking signal for one microphone and comparing the signal power ratio to a lower threshold value determines a blocking signal for the other microphone of the pair of microphones.

In a further possible implementation form of the second aspect at least one of the control signal is a binary signal, the value of the control signal being 1 when any presence of a wind noise or a handling noise is detected and 0 otherwise; or the blocking signal is a binary signal, the value of the blocking signal being 1 if a microphone is blocked and 0 otherwise.

In a further possible implementation form of the second aspect the apparatus further comprises at least one inner sensor arranged in a housing; and the method further comprises detecting the presence of at least one of a wind noise or a handling noise by the control unit based on at least one of said microphone signals and at least one inner sensor signal from the at least one inner sensor. In an embodiment, the inner sensor is at least one of a voice accelerometer, VACC, a voice pickup sensor, VPU, or an inner microphone. Utilizing an inner sensor (e.g. integrated in a headset) in addition to microphone signals helps determining the control signal in a more accurate way.

In a further possible implementation form of the second aspect the method further comprises detecting, by the control unit, the presence of a user’s own voice based on at least one of the microphone signals and the at least one signal from the at least one inner sensor, and generating an own voice detection, OVD, signal; and configuring the processor to only update the blocking status if the OVD signal indicates presence of a user’s own voice. This solution helps to limit the blocking detection to those time periods when a user’s own voice is detected, thereby improving the reliability of the microphone blocking detection method especially in a silent situation.

In an embodiment, the OVD signal is a binary signal, the value of the OVD signal being 1 if a user’s own voice is detected and 0 otherwise.

In a further possible implementation form of the second aspect the method further comprises: detecting, by the processor, a background noise value by analyzing at least one of the at least one microphone signal and the at least one signal from the at least one inner sensor; and configuring the processor to only update the blocking status if at least one of 1 ) the background noise value exceeds a predetermined background noise threshold value or 2) the OVD signal indicates presence of a user’s own voice, otherwise prevent updating the blocking status. This helps further improving the reliability of the microphone blocking detection by stopping the blocking detection if the noise level is not high enough.

According to a third aspect, there is provided a system for controlling microphone blocking comprising a processor, a control unit, at least one pair of microphones, and a storage device configured to store instructions that, when executed by the processor, cause the components of the system to perform a method according to any possible implementation form of the second aspect.

These and other aspects will be apparent from and the embodiment(s) described below. BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, the aspects, embodiments and implementations will be explained in more detail with reference to the example embodiments shown in the drawings, in which: Fig. 1 illustrates in a combined flow diagram an apparatus in accordance with an embodiment of the first aspect and a method in accordance with an embodiment of the second aspect;

Fig. 2 illustrates in a combined flow diagram an apparatus in accordance with another embodiment of the first aspect and a method in accordance with another embodiment of the second aspect;

Fig. 3 illustrates in a combined flow diagram an apparatus in accordance with another embodiment of the first aspect and a method in accordance with another embodiment of the second aspect;

Fig. 4 illustrates in a combined flow diagram an apparatus in accordance with another embodiment of the first aspect and a method in accordance with another embodiment of the second aspect;

Fig. 5 illustrates a system in accordance with an embodiment of the third aspect;

Figs. 6 to 9 illustrate algorithm performances in different situations as a result of using an apparatus in accordance with another embodiment of the first aspect, a method in accordance with another embodiment of the second aspect, or a system in accordance with another embodiment of the third aspect.

Fig. 10 illustrates in a flow diagram a method in accordance with another embodiment of the second aspect.

DETAILED DESCRIPTION Detection of microphone blocking in a headset based on comparing the microphone power levels does not work during wind or handling noise. If the blocking detection is updated during wind or handling noise, it might lead to an erroneous result. The solution described below in connection with the figures allows to stop the blocking detection during wind noise or handling noise utilizing control information from an additional control unit capable of detecting wind noise or handling noise from microphone signals optionally combined with signals from inner sensors.

Fig. 1 illustrates in a combined flow diagram an apparatus as well as method steps for controlling microphone blocking detection in an apparatus 1 according to the present disclosure. The apparatus comprises at least a processor 6, a control unit 4, and one pair of microphones 2, indicated separately as a first microphone 2A and a second microphone 2B. However, it should be noted that any number of microphones 2 could be used in the apparatus 1 as long as they are each capable of generating at least one microphone signal 3.

In a first step 101 , the processor 6 is configured to monitor a pair of incoming microphone signals 3A,3B, each microphone signal 3A,3B generated by a different microphone 2A,2B, and comparing the microphone signals 3A,3B to each other.

In a next step 102, processor 6 determines at least one blocking signal 7 for each of the microphones 2A,2B based on the comparison, the blocking signal 7 indicating if a microphone 2A,2B is detected as being blocked.

In a next step 103, processor 6 tries to update a blocking status 8 of at least one of the pair of microphones 2 based on the blocking signal 7.

In the meantime, the control unit 4 is continuously monitoring 104 the microphone signals 3 for detecting the presence of at least one of a wind noise or a handling noise, and generates in a next step 105 a control signal 5 indicating the presence.

If the control signal 5 indicates presence of at least one of a wind noise or a handling noise, the processor 6 is instructed, as a step before step 103, to prevent updating the blocking status 8.

In an embodiment, as also illustrated in Figs. 6 to 9, the control signal 5 is a binary signal, the value of the control signal 5 being 1 when any presence of a wind noise or a handling noise is detected and 0 otherwise. In an embodiment, the apparatus 1 also comprises at least one inner sensor 9 arranged in a housing 12, and the control unit 4 is configured to detect the presence of wind noise or handling noise using an additional inner sensor signal 10 from the inner sensor 9.

In an embodiment the inner sensor 9 is a voice accelerometer (VACC), a voice pickup sensor (VPU), or an inner microphone.

As indicated by the dashed line in Fig. 1 , the control unit 4 can be a part of the processor 6, e.g. as part of the algorithm package of the processor 6. However, in some embodiments processing of the control signal 5 and determination of the blocking signal 7 can happen in a connected device comprising a separate processor, such as a mobile device 14 shown in Fig. 5.

In an embodiment shown in Fig. 2, the step of determining 102 the at least one blocking signal 7 comprises the step 1021 of calculating a signal power ratio (Rp) between the power of the pair of microphone signals 3A and 3B from the pair of microphones 2A and 2B respectively and, in a next step 1022, comparing the signal power ratio (Rp) to at least one predetermined threshold value T (see below in more detail).

In an embodiment only certain frequencies between predetermined frequency bands are used for comparing the pair of microphone signals 3A and 3B and calculating the signal power ratio (Rp). In an embodiment, the frequency band between 2kHz and 2.5kHz is used for the comparison.

In an embodiment, a blocking signal 7 is determined in a step 1023 for each of the pair of microphones 2A and 2B. In an embodiment, as indicated in Fig. 2, this blocking signal 7 is a binary signal, the value of the blocking signal 7 being 1 if a microphone 2A,2B is blocked and 0 otherwise.

As shown in Fig. 3, initially the blocking signal 7 is set as zero (not blocked) for each microphone. Then, in a next step 1024, a blocking signal 7 for each of the pair of microphones is determined by comparing the signal power ratio (Rp) to a predetermined lower threshold value (Tl) to determine a blocking signal 7 for the first microphone 2A (change to 1 if Rp < Tl), and if the signal power ratio (Rp) is equal or higher than the predetermined lower threshold value (Tl), comparing the signal power ratio (Rp) to a predetermined higher threshold value (Tl) to determine a blocking signal 7 for the second microphone 2B (change to 1 if Rp > Th, leave unchanged if Rp £ Th). Thus, the blocking signal 7 stays zero (not blocked) if the condition Tl < Rp < Th is fulfilled. The blocking signal 7 is then used for updating the (temporary) blocking status 8 of any or each of the microphones 2A,2B.

Fig. 4 illustrates in a combined flow diagram a further possible embodiment of the apparatus as well as the respective method steps according to the present disclosure. In these implementations, features that are the same or similar to corresponding features previously described or shown herein are denoted by the same reference numeral as previously used for simplicity.

In this embodiment, as explained above in connection with Fig. 1 , the control unit 4 is a part of the algorithm package of the processor 6. The processor 6 can be integrated in a headset and thus provide a standalone apparatus 1 for controlling microphone blocking detection.

In addition to the steps describe before, in a possible embodiment the control unit 4 is further configured to detect, in a further step 107, the presence of a user’s own voice based on at least one of a microphone signal 3 from the pair of microphones 2 and an inner sensor signal 10 from an inner sensor 9 and generate an own voice detection (OVD) signal 11 accordingly, indicating the presence of a user’s own voice.

In an embodiment, the processor 6 is configured to only update the blocking status 8 in a further step 108 if the OVD signal 11 indicates presence of a user’s own voice.

In an embodiment, as illustrated in Figs. 6 to 9, this OVD signal 11 is a binary signal, the value of the OVD signal 11 being 1 if a user’s own voice is detected and 0 otherwise. Alternatively, a continuous OVD signal 11 , for example, is also conceivable. In a further possible embodiment the processor 6, or the control unit 4 can also be configured to, in a step 109 before the optional own voice detection step 107, detect a background noise value (noise level) N by analyzing at least one of a microphone signal 3, an OVD signal 11 , and an inner sensor signal 10, and determine whether this background noise value N exceeds a predetermined background noise threshold value Nt. In an embodiment, the processor 6 is configured to only update the blocking status 8 if N > Nt, otherwise either check in an optional own voice detection step 107, as described above, the presence of a user’s own voice, or directly prevent updating the blocking status 8.

In an embodiment combining the optional steps above, the processor 6 is configured to check 110 and only update the blocking status 8 if at least one of the background noise value N exceeds a predetermined background noise threshold value Nt or the OVD signal 11 indicates presence of a user’s own voice, otherwise prevent updating the blocking status 8. This solution allows to stop the blocking detection if the noise level is not high enough and limit the blocking detection to those time periods when OVD (user’s own voice) is detected. In other words, microphone blocking detection can be prevented in a silent situation when there is no background noise or speech, thereby avoiding false block detection.

From Fig. 4 it can also be seen that using an OVD signal 11 for blocking detection is optional, it can be used in all cases or for example only in silent cases, or it can be left out of the algorithm completely. In a similar fashion, using the determined background noise value N for blocking detection is also optional, it can be used in all cases, in some cases, or it can be left out of the algorithm completely.

Fig. 5 illustrates a system according to the present disclosure, comprising a processor 6, a control unit 4, at least one pair of microphones 2A and 2B, and a storage device 13 configured to store instructions that, when executed by the processor 6, cause the components of the system to perform a method according to any one of the possible embodiments described above. In these implementations, features that are the same or similar to corresponding features previously described or shown herein are denoted by the same reference numeral as previously used for simplicity.

In this embodiment, similarly to the embodiment described above in connection with Fig. 4, the control unit 4 is a part of the algorithm package of the processor 6. The processor 6 and the storage device 13 can both be integrated in a headset and thus provide a standalone apparatus 1 for controlling microphone blocking detection.

The apparatus 1 can further include at least one inner sensor 9 arranged in a housing 12, the inner sensor 9 preferably being at least one of a voice accelerometer, VACC, a voice pickup sensor, VPU, or an inner microphone. In this case, as described above, the control unit 4 is configured to detect the presence of at least one of a wind noise or a handling noise based on at least one inner sensor signal 10 from the at least one inner sensor 9. Also, as described above, the control unit 4 can be further configured to detect the presence of a user’s own voice and generate an own voice detection (OVD) signal 11 , as well as to detect a background noise value (noise level) N.

The microphones 2A and 2B can be included in a headset as shown in Fig. 5. The headset can be a set of earphones or headphones that are either cordless or connect to a mobile device 14 via a wired connection. In a preferred embodiment as shown on Fig. 5, both microphones 2A and 2B are integrated in or near the housing 12 of a pair of earphones/headphones that connect to a mobile device in a cordless manner (such as via Bluetooth, Bluetooth LE, or Wireless signals). As shown in the figure, both microphones 2A and 2B can be integrated in the housing 12 of the same earpiece. Flowever, in an alternative embodiment, each microphone 2A and 2B can be integrated in a different earpiece. In case of a wired connection the microphones 2 can be integrated into the wires, either both a first microphone 2A and a second microphone 2B integrated into the side of the wire leading to the same side of the earphones/headphones, or the first microphone 2A and a second microphone 2B can be integrated into different (left and right) sides of the wires. The mobile device 14 may for example be a mobile communications handset device such as a smartphone or a multi-function cellular phone, or a mobile terminal or user equipment of a wireless communication system. In some embodiments the apparatus can be an audio recorder, such as an MP3 player, a media recorder/player (also known as an MP4 player), or any suitable portable apparatus suitable for recording audio or audio/video camcorder/memory audio or video recorder.

In some embodiments any or each of the microphones 2A,2B can be a solid state microphone, in other words capable of capturing audio signals and outputting a suitable digital format signal, in some other embodiments the microphones 2 can comprise any suitable microphone or audio capture means, for example a condenser microphone, capacitor microphone, electrostatic microphone, Electret condenser microphone, dynamic microphone, ribbon microphone, carbon microphone, piezoelectric microphone, or micro electrical- mechanical system (MEMS) microphone. In some embodiments the microphone 2 is a digital microphone array, in other words configured to generate a digital signal output (and thus not requiring an analogue-to-digital converter). The microphone 2 or array of microphones can in some embodiments output the audio captured signal to an analogue-to-digital converter (ADC). In some embodiments the apparatus can further comprise an analogue-to-digital converter (ADC) configured to receive the analogue captured audio signal from the microphones 2A,2B and outputting the audio captured signal in a suitable digital form. The analogue-to-digital converter can be any suitable analogue-to-digital conversion or processing means. In some embodiments the microphones are 'integrated' microphones containing both audio signal generating and analogue-to- digital conversion capability. In some embodiments the apparatus 1 comprises audio subsystems with a digital-to- analogue converter for converting digital audio signals from a processor to a suitable analogue format. The digital-to-analogue converter (DAC) or signal processing means can in some embodiments be any suitable DAC technology. Furthermore, the mobile device 14 can comprise in some embodiments a speaker. The speaker can in some embodiments receive the output from the digital-to-analogue converter and present the analogue audio signal to the user. In some embodiments the speaker can be representative of multi-speaker arrangement, a headset, for example a set of headphones, or cordless headphones. Although the apparatus 1 is shown having both audio capture and audio presentation components (in the form of a headset comprising both speakers and microphones), it would be understood that in some embodiments the apparatus 1 can comprise only the audio capture part of the audio subsystem such that in some embodiments of the apparatus the microphones (for audio capture) are present. In some embodiments, the processor 6 can be configured to execute various program codes. The implemented program codes can comprise for example audio recording and microphone defect detection routines. In some embodiments the apparatus 1 further comprises a memory. In some embodiments the processor 6 is coupled to memory. The memory can be any suitable storage means 13. In some embodiments the memory comprises a program code section for storing program codes implementable upon the processor 6. Furthermore, in some embodiments the memory can further comprise a stored data section for storing data, for example data that has been recorded or analysed in accordance with the application. The implemented program code stored within the program code section, and the data stored within the stored data section can be retrieved by the processor 6 whenever needed via the memory-processor coupling.

In some further embodiments the apparatus 1 can comprise a user interface. The user interface can be coupled in some embodiments to the processor 6. In some embodiments the processor can control the operation of the user interface and receive inputs from the user interface. In some embodiments the user interface can enable a user to input commands to the electronic device or apparatus, for example via a keypad, and/or to obtain information from the apparatus 1 , for example via a display which is part of the user interface. The user interface can in some embodiments comprise a touch screen or touch interface capable of both enabling information to be entered to the apparatus 1 and further displaying information to the user of the apparatus 1.

In some embodiments the apparatus further comprises a transceiver, the transceiver in such embodiments can be coupled to the processor 6 and configured to enable a communication with a cordless headset, other apparatus or electronic devices, for example via a wireless communications network. The transceiver or any suitable transceiver or transmitter and/or receiver means can in some embodiments be configured to communicate with other electronic devices or apparatus via a wire or wired coupling. The coupling can be any suitable known communications protocol, for example in some embodiments the transceiver or transceiver means can use a suitable universal mobile telecommunications system (UMTS) protocol, a wireless local area network (WLAN) protocol such as for example IEEE 802.X, a suitable short-range radio frequency communication protocol such as Bluetooth, or infrared data communication pathway (IRDA). It is to be understood again that the structure of the electronic device could be supplemented and varied in many ways.

In some embodiments where one of the microphones 2 is determined to be impaired, blocked, or non-functional, the signals can be downmixed which is can be represented on the display. It would be understood that in some embodiments the number of microphones used as an input can be more than two and the number of input channels can be more than two and the number of downmixed channels output can be more than or fewer than two (where the number of downmixed channels is less than the number of input channels). In some embodiments where the apparatus 1 is configured to receive microphone signals 3 from four or more microphones 2 then an impaired or non-functional microphone 2A can be replaced by a functional microphone 2B such that the apparatus 1 can continue to record or capture a multichannel signal. In some embodiments the indicator can be configured to modify the user's habits, such as the way the user is holding the apparatus. For example, a user may hold the apparatus 1 and one or more of microphones may be blocked by the user's fingers. In the case where audio is being recorded with the first microphone 2A and the second microphone 2B being active, some embodiments may determine or detect that the active microphone has been blocked and switch the functionality of that active microphone with one of the passive microphones. Furthermore, in some embodiments, on determining that a third microphone is also blocked then a fourth microphone can be selected. In some embodiments the indicator can further be used to determine or select microphone or audio signal processing parameters. These can in some embodiments be equalisation or signal processing parameters to acoustically tune the input audio signals. However, in some embodiments these parameters can be associated with the location or distribution of the microphones selected. For example in some embodiments where a distance and relative direction between the microphone inputs is required, for example in directional analysis of the input audio signals, then the indicator can be used not only to select the functional microphone but generate, determine or select the microphone related distance and relative direction parameters used in processing the audio signals.

Figs. 6 to 9 illustrate algorithm performances in different situations as a result of using an apparatus according to the present disclosure. In these exemplary illustrations microphones 2A and 2B are represented as microphone 1 and microphone 2.

In Fig. 6 microphone 2 is correctly detected as blocked in a situation where there is background noise, based on the signal power ratio (Rp) between microphone 1 and microphone 2. Here, the ratio Rp is greater than the higher threshold (Th), thus the second microphone is detected as blocked. In Fig. 7 microphone 2 is correctly detected as blocked in a silent situation (i.e. when there is no background noise). In this figure it can be seen that during silent time periods the signal power ratio (Rp) value is between the higher and lower threshold, and thus blocking detection cannot be correctly detected. However, in such a silent situation the OVD signal helps to find the time periods where blocking can be reliably detected and thus blocking detection results remain correct throughout the test signal.

As can be seen in Fig. 8, the control information WIND can prevent updating blocking detection result when there is wind noise. Otherwise the blocking status would be updated erroneously, since sometimes the microphone signal power ratio is lower than the lower threshold, which would indicate that microphone 1 is blocked.

In Fig. 6 and Fig. 9 it can be seen that during background noise, using OVD is not necessary for blocking detection. In the case where microphone 2 is blocked (Fig. 6), the microphone signal power ratio remains constantly higher than the higher threshold (Th). In the case where no microphone is blocked (Fig. 9) the microphone signal power ratio remains between the thresholds indicating that no microphone is blocked.

Fig. 10 illustrates a further embodiment of the method according to the present disclosure. The steps and components illustrated in this figure correspond to that of Fig. 3 and 4, but the right side of the figure further illustrates an aspect wherein the processor is configured prevent occasional fast changes in the blocking status of any of the microphones. In the figure it can be seen that, similarly as in the embodiments shown in Figs. 3 and 4, using the OVD signal for blocking detection is optional - it can be used in all cases or for example only in silent cases, or then it can be left out completely. Blockl and block2 denote temporary blocking status for microphones 2A and 2B, respectively. In order to prevent some occasional fast changes in blocking status, counters for setting blocking detection status to ON (1) and OFF (0) are utilized for both of the microphones. Block_off_counter_1 and block_off_counter_2 are compared to a threshold block_off_thd and blocking detection status of the corresponding microphone is set to 0 only after block_off_counter for that microphone is above the threshold. Similarly, block_on_counter_1 and block_on_counter_2 are compared to block_on_thr and blocking detection status of the corresponding microphone is set to 1 after block_on_counter for that microphone is above the threshold. According to further possible embodiments, microphone signal power ratios at selected frequency bands can be utilized as features together with control features obtained from the control unit 4 and optional further OVD signals, possibly in combination of other features, as input data for a machine learning algorithm for blocking detection. Such machine learning algorithm could be for example classification or regression trees, K-nearest neighbors, random forest, or a neural network.

According to even further possible embodiments, a control signal 5 indicating presence of wind or handling noise obtained from a control unit 4 in accordance with the present disclosure, optionally using inner sensor signals 10 from an inner sensor 9 such as a voice accelerometer (VACC), a voice pickup sensor (VPU), or an inner microphone, can be used as input for an algorithm to control microphone calibration gain estimation. This way calibration gain estimation can be prevented during those time periods that contain wind noise or handling noise.

The various aspects and implementations has been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject-matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

The reference signs used in the claims shall not be construed as limiting the scope.

Claims

1. An apparatus (1 ) comprising: at least one pair of microphones (2), each microphone (2A,2B) configured to generate at least one microphone signal; a processor (6) configured to monitor at least one pair of microphone signals (3), wherein each microphone signal (3A,3B) is generated by a different one of a pair of microphones (2), determine at least one blocking signal (7) by comparing said at least one pair of microphone signals (3), each blocking signal (7) indicating if a microphone (2A,2B) is blocked, and update a blocking status (8) of at least one of said pair of microphones (2) based on said blocking signal (7); and a control unit (4) configured to monitor the presence of at least one of a wind noise or a handling noise based at least partly on said microphone signals (3), and generate a control signal (5) indicating said presence; wherein said processor (6) is further configured to prevent updating said blocking status (8) if said control signal (5) indicates presence of at least one of a wind noise or a handling noise.

2. The apparatus according to claim 1 , wherein said processor (6) is further configured to determine said at least one blocking signal (7) by calculating a signal power ratio (Rp) between said at least one pair of microphone signals (3) over a predetermined frequency band; and comparing said signal power ratio (Rp) to at least one predetermined threshold value (T).

3. The apparatus according to claim 2, wherein said processor (6) is further configured to determine a blocking signal (7) for each of said at least one pair of microphones (2), wherein comparing said signal power ratio (Rp) to a higher threshold value (Th) determines a blocking signal (7) for one microphone (2A) and comparing said signal power ratio (Rp) to a lower threshold value (Tl) determines a blocking signal (7) for the other microphone (2B) of said pair of microphones (2).

4. The apparatus according to any one of claims 1 to 3, wherein at least one of said control signal (5) is a binary signal, the value of said control signal (5) being 1 when any presence of a wind noise or a handling noise is detected and 0 otherwise; or said blocking signal (7) is a binary signal, the value of said blocking signal (7) being 1 if a microphone (2A,2B) is blocked and 0 otherwise.

5. The apparatus according to any one of claims 1 to 4, wherein said apparatus further comprises at least one inner sensor (9) arranged in a housing (12), said inner sensor (9) preferably being at least one of a voice accelerometer, VACC, a voice pickup sensor, VPU, or an inner microphone; and wherein said control unit (4) is further configured to detect the presence of at least one of a wind noise or a handling noise based on at least one of said microphone signals (3) and at least one inner sensor signal (10) from said at least one inner sensor (9).

6. The apparatus according to claim 5, wherein said control unit (4) is further configured to detect the presence of a user’s own voice based on at least one of said microphone signals (3A,3B) and said at least one signal from said at least one inner sensor (9), and generate an own voice detection, OVD, signal (11), said OVD signal (11 ) preferably being a binary signal, the value of said OVD signal (11) being 1 if a user’s own voice is detected and 0 otherwise; and wherein said processor (6) is further configured to only update said blocking status (8) if said OVD signal (11 ) indicates presence of a user’s own voice.

7. The apparatus according to claim 6, wherein said processor (6) is further configured to detect a background noise value (N) by analyzing at least one of said at least one microphone signal (3) and said at least one signal from said at least one inner sensor (9); and only update said blocking status (8) if at least one of 1) said background noise value (N) exceeds a predetermined background noise threshold value (Nt) or 2) said OVD signal (11) indicates presence of a user’s own voice, otherwise prevent updating said blocking status (8).

8. A method for controlling microphone blocking detection in an apparatus comprising a processor (6), a control unit (4), and at least one pair of microphones (2), the method comprising: monitoring (101), by said processor (6), at least one pair of microphone signals (3), wherein each microphone signal (3A,3B) is generated by a different one of a pair of microphones (2); determining (102), by said processor (6), at least one blocking signal (7) by comparing said at least one pair of microphone signals (3), each blocking signal (7) indicating if a microphone (2A,2B) is blocked; updating (103), by said processor (6), a blocking status (8) of at least one of said pair of microphones (2) based on said blocking signal (7); monitoring (104), by said control unit (4), the presence of at least one of a wind noise or a handling noise based at least partly on said microphone signals (3), and generating (105) a control signal (5) indicating said presence; and configuring (106) said processor (6) to prevent updating said blocking status (8) is if said control signal (5) indicates presence of at least one of a wind noise or a handling noise.

9. The method according to claim 8, wherein determining (102) said at least one blocking signal (7) comprises: calculating (1021) a signal power ratio (Rp) between said at least one pair of microphone signals (3) over a predetermined frequency band; and comparing (1022) said signal power ratio (Rp) to at least one predetermined threshold value (T).

10. The method according to claim 9, wherein determining said at least one blocking signal (7) comprises determining (1023) a blocking signal (7) for each of said at least one pair of microphones (2), wherein comparing (1024) said signal power ratio (Rp) to a higher threshold value (Th) determines a blocking signal (7) for one microphone (2A) and comparing said signal power ratio (Rp) to a lower threshold value (Tl) determines a blocking signal (7) for the other microphone (2B) of said pair of microphones (2).

11 . The method according to any one of claims 8 to 10, wherein at least one of said control signal (5) is a binary signal, the value of said control signal (5) being 1 when any presence of a wind noise or a handling noise is detected and 0 otherwise; or said blocking signal (7) is a binary signal, the value of said blocking signal

(7) being 1 if a microphone (2A,2B) is blocked and 0 otherwise.

12. The method according to any one of claims 8 to 11 , wherein said apparatus further comprises at least one inner sensor (9) arranged in a housing (12), said inner sensor (9) preferably being at least one of a voice accelerometer, VACC, a voice pickup sensor, VPU, or an inner microphone; and wherein the method further comprises: detecting (1041) the presence of at least one of a wind noise or a handling noise by said control unit (4) based on at least one of said microphone signals (3) and at least one inner sensor signal (10) from said at least one inner sensor (9).

13. The method according to claim 12, further comprising: detecting (107), by said control unit (4), the presence of a user’s own voice based on at least one of said microphone signals (3A,3B) and said at least one signal from said at least one inner sensor (9), and generating an own voice detection, OVD, signal (11 ), said OVD signal (11 ) preferably being a binary signal, the value of said OVD signal (11) being 1 if a user’s own voice is detected and 0 otherwise; and configuring (108) said processor (6) to only update said blocking status (8) if said OVD signal (11 ) indicates presence of a user’s own voice.

14. The method according to claim 13, further comprising: detecting (109), by said processor (6), a background noise value (N) by analyzing at least one of said at least one microphone signal (3) and said at least one signal from said at least one inner sensor (9); and configuring (110) said processor (6) to only update said blocking status (8) if at least one of 1 ) said background noise value (N) exceeds a predetermined background noise threshold value (Nt) or 2) said OVD signal (11) indicates presence of a user’s own voice, otherwise prevent updating said blocking status (8).

15. A system for controlling microphone blocking comprising: a processor (6), a control unit (4), at least one pair of microphones (2), and a storage device (13) configured to store instructions that, when executed by said processor (6), cause the components of the system to perform a method according to any one of claims 8 to 14.