Patent Description:
Electronic devices that are configured to register sound waves and provide electric signals that represent the registered sound waves are necessarily equipped with a microphone and associated analogue and digital circuitry configured to process and transmit these signals. For some types of such devices, it is imperative that the microphone is fully operational and that an operator or user of the device is able to ascertain himself or herself of the operational status. For example, one type of such a device is a device for surveillance. Such a device for surveillance may, e.g., be a surveillance camera. A surveillance camera is typically equipped with a microphone for obtaining audio information associated with video information registered by the surveillance camera as well as obtaining audio information that is not associated with any video information.

<CIT> shows a method for detecting a microphone condition, which involves comparing an electrical response to an expected response and determining the microphone condition based on the comparison.

According to a first aspect there is provided a method for determining a status of a microphone according to claim <NUM>.

Thus, by providing a predetermined impulse waveform to a piezoelectric component close to the microphone and in mechanical connection with the microphone, the microphone will receive a mechanical impulse from the piezoelectric component that will result in a relative movement between a membrane within the microphone and an encapsulating part of the microphone. Hence, by triggering the piezoelectric component to emit a mechanical impulse, i.e. to undergo a change in spatial extension according to the received impulse waveform, the microphone will register this as a relative movement between the membrane within the microphone and an encapsulating part of the microphone. As a consequence of this relative movement, the microphone will create a response signal in the same way as if the membrane was displaced relative the encapsulating part by a sound wave, but without any generation of sound that may be an audible disturbance from the point of hearing of an outside observer. Such a method enables an operator to obtain an operational status at any time and with any desired regularity without generating undesirable noise.

The determination whether a response signal waveform from the microphone corresponds to the predetermined impulse waveform may comprise determining that a timing difference between the response signal waveform and the predetermined impulse waveform is within a predetermined timing difference interval. Such a determination is simple. Further it allows for a more or less deteriorated response signal waveform to be used in the determination.

Alternatively, or in combination, the predetermined impulse waveform may comprise an encoded pattern. In such a case, the determination whether a response signal waveform from the microphone corresponds to the predetermined impulse waveform may comprise determining that the response signal waveform comprises the encoded pattern. By utilizing a waveform with an encoded pattern that is more or less complex, a more reliable determination is possible in that spurious signals that may be mistaken for a response from the microphone may be disregarded.

The encoded pattern may be a sequence of a predetermined number of impulses delimited by a respective predetermined time interval.

While registering an audio signal from the microphone and while providing the audio signal to an audio signal receiver, prior to transmitting the predetermined impulse waveform to the piezoelectric component, provision of a temporary replacement audio signal is initiated, and after the determination whether a response signal waveform from the microphone corresponds to the predetermined impulse waveform, the provision of the audio signal to the audio signal receiver is resumed.

In other words, by replacing the audio signal, during a time period when the piezoelectric component emits a mechanical impulse, with a replacement audio signal it is possible to prevent a response signal waveform corresponding to the mechanical impulse from reaching the audio signal receiver and thereby prevent the audio signal receiver from generating potentially undesired "clicking" noise. For example, the temporary replacement audio signal may be in the form of a computed extrapolation or interpolation of the audio signal provided to the audio signal receiver prior to the initiation of provision of the temporary replacement audio signal. In another example, the temporary replacement audio signal may be a difference audio signal computed by subtracting a predetermined response signal waveform from the response signal waveform from the microphone.

According to a second aspect, a non-transitory computer-readable storage medium is provided. The non-transitory computer-readable storage medium has stored thereon instructions for implementing the method according to the first aspect when executed on a device having processing capabilities.

According to a third aspect, a device is provided as in claim <NUM>.

The device may comprise a printed circuit board (PCB) and the microphone and the piezoelectric component may both be attached to the PCB in the vicinity of each other.

As for the method according to the first aspect, such a device is advantageous in that it, i. , enables an operator to obtain an operational status of the microphone at any time and with any desired regularity without generating undesirable noise.

Furthermore, the piezoelectric component may be any of a multi-layer ceramic capacitor, (MLCC), and a piezoelectric actuator made of lead zirconate titanate (PZT).

An MLCC is advantageous in more than one way. For example, an MLCC is an extremely simple construction and thereby very cheap; it is also very reliable over a long period of time and it is therefore a safe choice when implementing the present functionality in a microphone equipped device that is to be monitored over long time periods.

The figures should not be considered limiting; instead, they are used for explaining and understanding.

Reference will now be made to <FIG>, which schematically illustrates a device <NUM> and <FIG> and <FIG> that exemplify a respective impulse waveform <NUM> and a respective corresponding response signal <NUM>.

The device <NUM> comprises circuitry <NUM>, a microphone <NUM> and a piezoelectric component <NUM>. The piezoelectric component <NUM> and the microphone <NUM> are located in a vicinity of each other and arranged in mechanical connection with each other. The circuitry <NUM> is connected to the microphone <NUM>. The circuitry <NUM> is connected to the piezoelectric component <NUM>. Further electronic components <NUM> are indicated as being part of the device <NUM>. These further electronic components <NUM> may for example comprise circuits and other means, such as imaging circuitry and a lens system for realizing a surveillance camera.

Communication between the circuitry <NUM> of the device <NUM> and external entities is realized via input/output circuitry <NUM>. For example, communication may be realized between the circuitry <NUM> and a network <NUM> in which an audio signal receiver <NUM> and other communicating entities <NUM> are interconnected. For example, the device <NUM> may be a network surveillance camera connected to the internet, i.e. network <NUM>, operated by an operator or user computer system, i.e. entity <NUM>, and wherein the audio signal receiver <NUM> forms part of such an operator or user computer system.

The circuitry <NUM> of the device <NUM> is configured to carry out overall control of functions and operations of the device <NUM>. The circuitry <NUM> may include a processor, such as a central processing unit (CPU), microcontroller, or microprocessor. The processor is configured to execute program code stored in a memory <NUM> in order to carry out functions and operations of the device <NUM>.

The memory <NUM> may be one or more of a buffer, a flash memory, a hard drive, a removable medium, a volatile memory, a non-volatile memory, a random access memory (RAM), or another suitable device. In a typical arrangement, the memory <NUM> may include a non-volatile memory for long term data storage and a volatile memory that functions as system memory for the circuitry <NUM>. The memory <NUM> may exchange data with the circuitry <NUM> over a data bus. Accompanying control lines and an address bus between the memory <NUM> and the circuitry <NUM> also may be present.

Functions and operations of the device <NUM> may be embodied in the form of executable logic routines (e.g., lines of code, software programs, etc.) that are stored on a non-transitory computer readable medium (e.g., the memory <NUM>) of the device <NUM> and are executed by the circuitry <NUM> (e.g., using the processor). Furthermore, the functions and operations of the device <NUM> may be a stand-alone software application or form a part of a software application that carries out additional tasks related to the device <NUM>. The described functions and operations may be considered a method that the corresponding part of the device is configured to carry out. Also, while the described functions and operations may be implemented in software, such functionality may as well be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and/or software.

The circuitry <NUM> is configured to execute a transmitting function <NUM>. The transmitting function <NUM> is configured to transmit a predetermined impulse waveform <NUM> to the piezoelectric component <NUM> to induce a mechanical impulse in the piezoelectric component <NUM>. Hence, the impulse inducing function <NUM> is configured to induce the piezoelectric component <NUM> to undergo a change in spatial extension or vibrate according to the received impulse waveform. The change in spatial extension or vibration may have characteristics that may vary based on the mechanical properties of the context wherein the piezoelectric component <NUM> and the microphone <NUM> are arranged.

<FIG> illustrates an example where the predetermined impulse waveform <NUM> is in the form of a square wave having a leading edge at time t<NUM> and a trailing edge at time t<NUM>. The piezoelectric component <NUM> reacts to the predetermined impulse waveform <NUM> in that it undergoes a change in spatial extension as a reaction to the leading edge and as a reaction to the trailing edge of the predetermined impulse waveform <NUM>. The microphone <NUM> responds by creating the response signal waveform <NUM> that is schematically illustrated by a respective waveform peak at time t<NUM> and at time t<NUM>. The points in time t<NUM> and t<NUM> are shifted in relation to the points in time t<NUM> and t<NUM> as a consequence of the mechanical and electronic characteristics of the components involved.

The circuitry <NUM> is further configured to execute a response determining function <NUM>. The response determining function <NUM> is configured to determine whether the response signal waveform <NUM> from the microphone <NUM> corresponds to the predetermined impulse waveform <NUM>. Upon the response signal waveform <NUM> from the microphone <NUM> corresponding to the predetermined impulse waveform <NUM>, the response determining function <NUM> is configured to determine that the status of the microphone <NUM> is operational. For example, referring to <FIG>, a positive correspondence may be determined in a case where a time difference t<NUM>-t<NUM> is, within a reasonable error of margin, equal to a time difference t<NUM>-t<NUM>.

As exemplified in <FIG>, the device may comprise a PCB <NUM> to which the microphone <NUM> and the piezoelectric component <NUM> are attached. It is noted that the microphone <NUM> and the piezoelectric component <NUM> are located in vicinity to each other. Preferably, the microphone <NUM> and the piezoelectric component <NUM> are both arranged on the PCB <NUM> such that they are in direct mechanical contact with each other. This enables efficient transfer of the induced mechanical impulse in the piezoelectric component <NUM> to the microphone <NUM>. The microphone <NUM> comprises a housing, attached to the PCB <NUM>, and a membrane arranged within the housing. The attachment between the microphone housing and the PCB <NUM> may for example be in the form of solder, glue or by means of appropriate mechanical attachment means. Transfer of the induced mechanical impulse takes place from the piezoelectric component <NUM>, which has performed a spatial expansion followed by a spatial contraction as a response to the predetermined impulse waveform <NUM> from the transmitting function <NUM>, via the PCB <NUM> to the housing of the microphone <NUM>. A relative movement is thereby created between the membrane of the microphone <NUM> and the housing of the microphone <NUM>, resulting in the response signal <NUM> from the microphone <NUM> being determined by the response determining function <NUM>.

The piezoelectric component <NUM> may be a multi-layer ceramic capacitor (MLCC). However, other types of piezoelectric arrangements may be used. For example, a piezoelectric actuator made of, e.g., lead zirconate titanate (PZT).

Turning now to <FIG>, and with continued reference to <FIG>, <FIG> and <FIG>, a method for determining a status of a microphone <NUM> will be described. Some or all the steps of the method may be performed by the device <NUM> described above. However, it is equally realized that some or all of the steps of the method may be performed by one or more other devices having similar functionality. The method is typically executed by the circuitry <NUM>. However, it is to be appreciated that interaction may take place during execution with the operator or user computer system in the network <NUM> connected to the device <NUM> via the input/output circuitry <NUM>. The method comprises the following steps. The steps may be performed in any suitable order.

A transmitting step S202 comprises transmitting a predetermined impulse waveform <NUM> to a piezoelectric component <NUM>, the piezoelectric component <NUM> being located in a vicinity of the microphone <NUM> and arranged in mechanical connection with the microphone <NUM>, to induce a mechanical impulse in the piezoelectric component <NUM>.

A determining step S204 comprises determining whether a response signal waveform <NUM> from the microphone <NUM> corresponds to the predetermined impulse waveform <NUM>, and upon the response signal waveform <NUM> from the microphone <NUM> corresponding to the predetermined impulse waveform <NUM>, determining that the status of the microphone <NUM> is operational.

In the determining step S204, the determining whether a response signal waveform <NUM> from the microphone <NUM> corresponds to the predetermined impulse waveform <NUM> may comprise, in a determining step <NUM>, determining that a timing difference between the response signal waveform <NUM> and the predetermined impulse waveform <NUM> is within a predetermined timing difference interval.

As <FIG> illustrates, and as discussed above in connection with <FIG>, the predetermined impulse waveform <NUM> may be in the form of a square wave having a leading edge at time t<NUM> and a trailing edge at time t<NUM> and the response signal waveform <NUM> may comprise a respective waveform peak at time t<NUM> and at time t<NUM>. As exemplified in connection with <FIG>, a positive correspondence may be determined in a case where a time difference t<NUM>-t<NUM> is, within a reasonable error of margin, equal to a time difference t<NUM>-t<NUM>. A positive correspondence may alternatively be determined in a case where a time difference t<NUM>-t<NUM> and/or a time difference t<NUM>-t<NUM> is within a reasonable error of margin.

In the determining step S204 and wherein the predetermined impulse waveform <NUM> comprises an encoded pattern <NUM>, the determining whether a response signal waveform <NUM> from the microphone <NUM> corresponds to the predetermined impulse waveform <NUM> may comprise determining S221 that the response signal waveform <NUM> comprises the encoded pattern <NUM>. For example, the encoded pattern <NUM> may be a sequence of a predetermined number of impulses delimited by a respective predetermined time interval <NUM>.

Such an example is schematically illustrated in <FIG>. The predetermined impulse waveform <NUM> in <FIG> comprises three square waves having leading and trailing edges at times t<NUM>, t<NUM>, t<NUM>, t<NUM>, t<NUM> and t<NUM>. The response signal waveform <NUM> is characterized by waveform peaks at times t<NUM>, t<NUM>, t<NUM>, t<NUM>, t<NUM> and t<NUM>. An encoded pattern may then be defined by predetermined time intervals between the times of the leading edges at t<NUM>, t<NUM> and t<NUM>. A positive determination that the response signal waveform <NUM> corresponds to the predetermined impulse waveform <NUM> may, e.g., then be when the time difference t<NUM>-t<NUM> corresponds to t<NUM>-t<NUM> and time difference t<NUM>-t<NUM> corresponds to t<NUM>-t<NUM>.

As exemplified in <FIG> and <FIG>, the predetermined impulse waveform <NUM> may comprise a square waveform. However, other waveforms may be used, for example a more complex waveform may be used in order to optimize the electric/mechanical interaction within the piezoelectric component <NUM>. In such examples, the response signal waveform <NUM> will also be more complex than the schematically exemplified waveform <NUM>.

In some embodiments, the method comprises a registering step <NUM> during which registering of an audio signal from the microphone <NUM> takes place and the audio signal is provided to an audio signal receiver <NUM>. In such embodiments, the method may comprise, prior to the step S202 of transmitting the predetermined impulse waveform <NUM> to the piezoelectric component <NUM>, a step S201 of initiating provision of a temporary replacement audio signal. In these embodiments, the method also comprises, after the determining step S204 of determining whether a response signal waveform <NUM> from the microphone <NUM> corresponds to the predetermined impulse waveform <NUM>, a resumption step S205 of resuming the provision of the audio signal to the audio signal receiver <NUM>.

The temporary replacement audio signal may be a computed extrapolation or interpolation of the audio signal provided to the audio signal receiver <NUM> prior to the initiation of provision of the temporary replacement audio signal. Alternatively, the temporary replacement audio signal may be a difference audio signal computed by subtracting a predetermined response signal waveform from the response signal waveform <NUM> from the microphone <NUM>.

In other words, the provision of the audio signal to the audio signal receiver <NUM> during the procedure of inducing the mechanical impulse in the piezoelectric component <NUM> is changed in that a replacement audio signal is provided instead. This means that the audio signal receiver <NUM>, being an automated system or a human operator, is alleviated of any discomfort of hearing a noise that is characteristic of the reaction by the microphone <NUM> to the predetermined impulse waveform <NUM>.

Claim 1:
A method for determining a status of a microphone (<NUM>), the method comprising:
- registering (<NUM>) an audio signal from the microphone (<NUM>) and providing the audio signal to an audio signal receiver (<NUM>);
- providing (S201), while registering (<NUM>) the audio signal from the microphone (<NUM>) and while providing the audio signal to an audio signal receiver (<NUM>), a temporary replacement audio signal to the audio signal receiver (<NUM>);
- transmitting (S202) a predetermined impulse waveform (<NUM>) to a piezoelectric component (<NUM>), the piezoelectric component (<NUM>) being located in a vicinity of the microphone (<NUM>) and arranged in mechanical connection with the microphone (<NUM>), to induce a mechanical impulse in the piezoelectric component (<NUM>);
- determining (S204) whether a response signal waveform (<NUM>) from the microphone (<NUM>) corresponds to the predetermined impulse waveform (<NUM>);
- resuming (S205) the provision of the audio signal to the audio signal receiver (<NUM>), and
- upon the response signal waveform (<NUM>) from the microphone (<NUM>) corresponding to the predetermined impulse waveform (<NUM>), determining that the status of the microphone (<NUM>) is operational.