A system and method for acoustic detection of a physical event

Abstract

The present disclosure relates to a system (100) for acoustic detection of a physical event, the system (100) comprising: at least one converting element (10) for converting the physical event to a characteristic sound; an acoustic sensor (40) configured to be mechanically connected to a structure (50) at a distance from the at least one converting element (10); and a processor (42, 62) coupled to the acoustic sensor (40), wherein the at least one converting element (10) is configured to react to the physical event by generating a characteristic sound and inducing the characteristic sound into the structure (50), wherein the acoustic sensor (40) is configured to register the characteristic sound generated by the at least one converting element (10) as structure-borne sound propagating through the structure (50), and wherein the processor (42, 62) is configured to detect the physical event based on the characteristic sound registered by the acoustic sensor (40).

Description

[0001] A system and method for acoustic detection of a physical event

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a system for acoustic detection of a physical event and a method for acoustic detection of a physical event. More specifically, the present disclosure relates to a system and method for acoustic detection of a physical event as defined in the introductory parts of the independent claims.

[0004] BACKGROUND ART

[0005] Physical events or phenomenon, such as changes in temperature, changes in moisture and / or humidity, pressure changes, radiation changes, changes in weight, displacement of an object or similar, can sometimes have devastating effects and may therefore need to be monitored. Different types of sensor devices, such as cameras, thermometers, pressure sensors, proximity sensors etc., can be used to detect different types of physical events. How these sensor devices are configured vary, but there are many sensor devices that are both complex and expensive.

[0006] Acoustic sensors have become more common lately and are used in various areas, for detecting for example sparks or fire, displacement of objects, water consumption etc. As an example, document CN112891790B discloses a lithium battery fire-fighting device with amongst others a sound sensor.

[0007] An acoustic sensor may, for example, be used to detect a physical event by registering the sound of a spark, the sound of water pouring or the sound of a moving object.

[0008] A problem with using acoustic sensors is that the environment around the acoustic sensor can affect the accuracy of the sensor, since background noise can disturb the registration of the relevant sound. Also, some sounds are difficult to register in an efficient way by means of a common acoustic sensor.

[0009] While the prior art addresses some of the problems associated with detecting physical events using acoustic sensors, they often fail to provide a compact and space-saving solution, which is simple and easy to assemble and use and which detects physical events in a reliable way. There is thus a need for an improved system for acoustic detection of physical events.

[0010] SUMMARY

[0011] It is an object of the present disclosure to mitigate, alleviate or eliminate one or more of the deficiencies and disadvantages in the prior art and solve at least one of the current problems.

[0012] It is a particular object of the present disclosure to provide a system for acoustic detection of a physical event, which is simple, compact and easy to assemble and use.

[0013] Another object of the present disclosure is to provide a system for acoustic detection of a physical event, which is cost-efficient and can be used in various applications.

[0014] According to a first aspect of the present disclosure, there is provided a system for acoustic detection of a physical event. The system comprises at least one converting element for converting the physical event to a characteristic sound; an acoustic sensor configured to be mechanically connected to a structure at a distance from the at least one converting element; and a processor coupled to the acoustic sensor, wherein the at least one converting element is configured to react to the physical event by generating a characteristic sound and inducing the characteristic sound into the structure, wherein the acoustic sensor is configured to register the characteristic sound generated by the converting element as structure-borne sound propagating through the structure and the processor is configured to detect the physical event based on the characteristic sound registered by the acoustic sensor.

[0015] By means of the system as disclosed herein, a physical event that normally does not emit a sound or is difficult to register a sound from, can be converted to a characteristic sound that can be registered by means of an acoustic sensor. Thus, the system according to the present disclosure can convert an inaudible physical event to audible sound by means of the converting element. The physical event may be a change in temperature (increase or decrease), a change in moisture caused by e.g. a leakage, a pressure change, a displacement of an object, degradation due to excessive irradiation or similar. The converting element is configured to react to the physical event and thereby generate a sound, which is induced into the structure. The converting element may be a mechanical construction. The converting element is suitably a simple mechanical construction comprising one or more materials or geometries that react to a certain physical event or phenomenon, such as changes in temperature, moisture, pressure, radiation, weight or similar. The converting element may be arranged in association with an object or in an environment where a physical event should be detected. The converting element will react to the physical event by generating a characteristic sound and inducing it into the structure. The converting element is thus configured to at least temporarily physically interact with the structure, such that the characteristic sound propagates through the structure and can be registered by the acoustic sensor. By means of the structure, the acoustic sensor and the converting element will, at least temporarily, be mechanically connected. The structure-borne sound induced into the structure can propagate a long way and the acoustic sensor may thereby be arranged far away from the converting element and the location of the physical event. Avoiding electrical components such as the acoustic sensor at the location of the physical event could be advantageous for safety reasons and it also allows the system to be used to detect physical events in environments where there is no electricity, as long as the sensor is mechanically connected (directly or indirectly) to a structure in said environment. Furthermore, the system allows multiple converting elements to be connected to the same structure and a single sensor and processor can thereby be used to detect the physical event at different locations on / along the same structure. By having an acoustic sensor that registers the characteristic sound of the converting element as structure-borne sound, surrounding sounds or noise will not interfere with the registered sound compared to when using a microphone for detecting airborne sound. The characteristic sound generated by the converting element will this way easily be registered and a reliable system for detecting a physical event is achieved.

[0016] The shape and configuration of the converting element gives the characterising sound generated by the converting element. This way, the processor will be able to determine that the registered sound origin from the converting element and thus that a physical event has occurred at the location of the converting element.

[0017] The converting element may comprise an actuating portion configured to be brought into movement by the physical event, the movement of the actuating portion causing the characteristic sound to be generated. The material and / or geometries of the actuating portion may cause the actuating portion to move or be displaced when the physical event occurs. The converting element may comprise a sound-generating portion connected to the actuating portion. The movement of the actuating portion may affect and move at least a part of the sound-generating portion and the characteristic sound may thus be generated by the sound-generating portion upon actuation of the sound-generating portion by the actuating portion. The sound-generating portion may be configured to induce the characteristic sound into the structure. The sound-generating portion may comprise at least one contact portion configured to be arranged in physical contact with the structure. This way, the characteristic sound generated by the converting element will be transferred into the structure via the contact portion.

[0018] According to an example of the present disclosure, the sound-generating portion comprises at least one vibrational element configured to be brought into vibration by the physical event, the configuration of the at least one vibrational element causing the characteristic sound to comprise at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies. The at least one vibrational element of the sound-generating portion may be configured to be brought into vibration by the movement of the actuating portion.

[0019] The movement of the actuating portion may itself generate a characteristic sound indicating that a physical event has occurred. However, the vibrational element being brought into vibration by the movement of the actuating portion will add at least one characteristic frequency to the characteristic sound and the converting element will this way have a unique identity. The movement of the actuating portion may cause a sound pulse of short duration and the vibrational element may cause a lingering note or reverberation giving the characterising sound its identity. In some embodiments, the system may be configured such that detection by the sensor of the sound pulse caused by the actuating portion triggers the processor to perform a frequency analysis of a lingering sound following the sound pulse. This way, computationally demanding frequency analysis can be performed only in response to movement of the actuating portion of a converting element, thereby ensuring energy-efficient monitoring of the physical event.

[0020] The at least one vibrational element may comprise an elongated leg with a free end and be connected at the other end to the actuating portion or the sound-generating portion. The sound-generating portion of the converting element may comprise a plurality of vibrational elements.

[0021] The at least one vibrational element may comprise a vibrational portion extending between a pivot point and the free end of the vibrational element, wherein the converting element may comprise means for manually adjusting the length of the vibrational portion in order to manually affect at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies. Thus, by manually adjusting the length of the vibrational portion a specific and unique identity can be given to the converting element. This way, the converting element can be manufactured with a generic configuration and the user can individualise each converter element to generate different characteristic sounds. This means that a user having a plurality of converting elements, can adjust the length of the vibrational portion of each vibrational element of each converting element and that way create unique identities of the converting elements. The means for adjusting the length of the vibrational portion of the at least one vibrational element may comprise markings, dentations, fold lines or perforations for bending or removing a part of the vibrational portion, and that way adjust the length of the vibrational portion. Alternatively, the means for adjusting the length of the vibrational portion of the at least one vibrational element may comprise a slider element movable along the length of the vibrational element. The slider element will connect the vibrational element with a fixed support structure and will thereby constitute the pivot point of the vibrational portion. The position of the slider element will thus determine the position of the pivot point of the vibrational element. By moving the slider element, the pivot point is moved and the length of the vibrational portion is adjusted.

[0022] The converting element may comprise an attachment portion for attaching the converting element on the structure or an object mechanically connected to the structure. The attachment portion may be configured as a clip, a snap-on mechanism or as a clamping mechanism. Alternatively, the attachment portion comprises adhesive for adhering the converting element to the structure or an object mechanically connected to the structure.

[0023] According to an example of the present disclosure, the actuating portion comprises a snapping mechanism configured to perform a snapping movement into a stable state of the snapping mechanism in response to the physical event. The snapping movement is a sudden movement caused by a quick release of energy that is either pre-stored as potential energy in the snapping mechanism or stored in the snapping mechanism in response to the physical event. The snapping movement may generate a characteristic sound and the sound-generating portion will induce the characteristic sound into the structure. When the actuating portion comprises a snapping mechanism configured to perform a snapping movement into a stable state of the snapping mechanism in response to the physical event, the at least one vibrational element may be configured to be brought into vibration by the snapping movement of the snapping mechanism. The sudden movement of the snapping mechanism will bring the vibrational element into vibration and cause the characteristic sound to comprise at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies.

[0024] The snapping mechanism may be a bi-stable mechanism configured with a snap-through instability, configured to perform the snapping movement between a first stable state and a second stable state of the bi-stable mechanism in response to the physical event. Such mechanism typically transitions rapidly between the two stable states and the rapid movement from one stable state into the other stable state will cause the characteristic sound to be generated. In embodiments employing at least one vibrational element, the rapid movement between the two stable states may bring the at least one vibrational element into vibration, causing the characteristic sound to comprise at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies.

[0025] The snapping mechanism of the actuating portion may comprise a dome-shaped part configured to snap-through in response to the physical event. The snapping mechanism is this way configured with a snap-through instability, configured to perform the snapping movement between a first stable state and a second stable state of the bi-stable mechanism in response to the physical event, whereby the dome-shape is inverted. When the dome-shaped actuating portion reacts to a physical event and the snapping movement occurs, the characteristic sound will be induced into the structure via the sound-generating portion, which is mechanically connected to the structure.

[0026] The snapping mechanism of the actuating portion may alternatively comprise at least one somewhat resilient part and at least one engagement element arranged to move in relation to each other in response to, for example, a change in temperature or moisture, such that the resilient part eventually disengage from the at least one engagement element and springs back, thereby causing the snapping movement. The at least one resilient part and the at least one engagement element may thus be engaged in a normal unaffected state of the converting element. When there is a physical event, the resilient part will build up energy as it flexes and / or bends against the at least one engagement element. As the resilient part and the at least one engagement element continue to move in relation to each other, the resilient part will eventually quickly release the energy and spring back at the other side of the at least one engagement element. The resilient part may thus have a stable state on each side of the at least one engagement element. In this way, the snapping mechanism may be said to function as a ratchet device or similar. The at least one engagement element may be a groove, recess or bulge. The resilient part may be a resilient protrusion, needle, spike, tooth or similar. The snapping mechanism may comprise a plurality of engagement elements, such as a plurality of grooves, recesses, bulges, or an undulating pattern. In the event that the snapping mechanism comprises two resilient parts, they may be arranged such that the order in which they engage / disengage with the at least one engagement element will affect the characteristic sound that is generated, whereby the processor can determine in which direction the resilient parts are moving based on the characteristic sound. This can be used in determining, for example, if the change in moisture is an increase or a decrease.

[0027] According to an example, the physical event is a change in temperature, wherein the actuating portion of the converting element comprises at least one material having a thermal expansion property, such that a change in temperature causes a movement of the actuating portion. That the at least one material has a thermal expansion property means that the material is configured to change size and / or shape in response to a change in temperature, which change in size and / or shape constitutes or causes the movement of the actuating portion. The movement of the actuating portion may bring at least one vibrational element into vibration. The change in temperature may be an increase or a decrease in temperature. In one example, the actuating portion comprises at least two materials having different thermal properties, such that a change in temperature causes a movement of the actuating portion. The different thermal expansion properties of the materials of the actuating portion will cause the materials to expand at different rates when heated or cooled, which will cause the actuating portion to bend or move in different directions depending on the temperature. In one example, the structure is a piping system or similar and the at least one converting element may be arranged somewhere along the piping system to identify a risk of freezing in the piping system by detecting a decrease in temperature. In another example, the structure is an electrical cabinet or similar, and the system is arranged to identify a fire risk inside the cabinet by detecting an increase in temperature. In this event, the converting element(s) may be arranged on an electrical component, mounting rails or an inside wall of the cabinet, and the acoustic sensor may, for example, be arranged on the outside of the cabinet.

[0028] According to another example, the physical event is a change in moisture, wherein the actuating portion comprises at least one material having a hygroscopic property, such that a change in moisture causes a movement of the actuating portion. The at least one material of the actuating portion may thus be a hygroscopic material capable of absorbing or adsorbing a fluid. That the material has a hygroscopic property means that the material is configured to change size and / or shape in response to a change in moisture, which change in size and / or shape constitutes or causes the movement of the actuating portion. The movement of the actuating portion may bring at least one vibrational element into vibration. It is to be understood that moisture is herein defined as water or other liquid diffused as vapour, within a solid, or condensed on a surface. Thus, a change in moisture will herein include everything from a change in humidity to a moisture increase caused by leakage of a liquid. The actuating portion may be configured to react to an increase and / or a decrease of moisture. In one example, the structure is a piping system or similar and the at least one converting element may be arranged somewhere along the piping system, typically in association with a pipefitting or pipe connection, to identify a leakage. The actuating portion may comprise two parts comprising materials with different hygroscopic properties. The at least two materials (or parts) having different hygroscopic properties typically involves a first material being prone to absorb or adsorb moisture and a second material less prone to absorb or adsorb moisture. When the first material adsorbs or absorbs moisture, the first material will swell or expand. The converting element is suitably configured, such that expansion of the first material will cause a movement of the second material, whereby a characteristic sound is generated. Similarly, a decrease in moisture may cause the first material to contract or shrink, which will cause a movement of the second material.

[0029] In another example, the physical event is a change in pressure, wherein the converting element is configured, such that a change in pressure causes a movement of the actuating portion. The converting element may be configured, such that a change of a surrounding pressure in relation to a pressure inside the converting element will cause a movement of the actuating portion. As an example, the converting element may be arranged inside a pressure tank, on the inside of a wall of the pressure tank. The acoustic sensor can this way be arranged on the outside of the pressure tank wall and will still be able to register the characteristic sound propagating through the tank wall and the system can thereby detect an increase in pressure at an early stage. The converting element may be hollow and thus comprise an inner chamber. The inner chamber may be delimited by the sound-generating portion and the actuating portion of the converting element. The converting element may be arranged inside the tank with the sound-generating portion abutting the inside of the tank wall, and the actuating portion facing in the opposite direction, towards the centre of the tank. When the pressure inside the pressure tank changes in relation to the pressure inside the converting element, the actuating portion will be affected and the pressure difference will eventually cause a movement of the actuating portion. When the pressure in the tank exceeds the pressure inside the converting element, the actuating portion may be moved inwards, into the inner chamber of the converting element. When the pressure in the tank becomes lower than the pressure inside the converting element, the actuating portion may be moved outwards, away from the inner chamber. The movement of the actuating portion will cause the characteristic sound to be generated. The actuating portion suitably comprises a dome-shaped snapping mechanism, and the pressure difference between the surroundings and the converting element will cause the snapping movement, which movement causes the characteristic sound to be generated. The characteristic sound is then induced into the tank wall by means of the sound-generating portion. The converting element may also comprise at least one vibrational element, which is brought into vibration by the movement of the actuating portion.

[0030] According to yet another example, the physical event is an increase in electromagnetic irradiance, wherein the actuating portion comprises a material that degrades by electromagnetic irradiance, the actuating portion being configured such that it breaks after having been subject to a certain amount of irradiance, which causes a movement of the actuating portion. The movement of the actuating portion may bring at least one vibrational element into vibration. The sound-generating portion may be biased and the actuating portion may be arranged to hold the sound-generating portion in a biased position, wherein when the actuating portion breaks and thus moves, the soundgenerating portion is no longer held in its biased position and generates the characteristic sound.

[0031] In one example, the physical event is a change in weight, wherein the converting element is configured, such that a change in weight causes a movement of the actuating portion and / or causes the at least one vibrational element of the sound-generating portion to be brought into vibration. As an example, the physical event is a displacement of an object, wherein the converting element is configured such that the displacement of the object causes the at least one vibrational element of the sound-generating portion to be brought into vibration.

[0032] The converting element may be configured such that the actuating portion is brought into movement both when a physical event occurs and when a state of the converting element returns to a normal state. For example, the converting element may be configured such that the actuating portion is brought into movement both when the temperature changes from a normal temperature, and when the temperature returns to normal. Likewise, the converting element may be configured such that the actuating portion is brought into movement both when a moisture level changes from normal and when it returns to normal. This way, the same converting element can be used multiple times. As an example, the converting element may be configured to react when the temperature falls below zero, indicating a risk of freezing. A snapping movement of the actuating portion may occur when the temperature falls below zero, whereby the acoustic sensor registers the characteristic sound and the processor detects the temperature change. The operator may then perform some sort of action to avoid problems, for example pour hot water through the pipes or activate a heater or similar. When the temperature in vicinity of the converter element increases to normal temperature, the converting element may react again and generate a characteristic sound registered by the sensor. The movement of the actuating portion when the temperature returns to normal may be in an opposite direction compared to the movement caused by the decrease in temperature. The characteristic sound generated when the temperature returns to normal may be different from the characteristic sound generated when the temperature decreases. The processor may then detect that the converting element has returned to its original state based on the registered characteristic sound and thus that the problem with too low temperature no longer exists. The same is applicable when the converting element is configured to react to an increase in temperature from a normal temperature, and to a subsequent decrease in temperature back to the normal temperature.

[0033] The converting element may hence be configured such that the characteristics of the sound generated by the converting element depends on the direction of movement of the actuating portion. In some embodiments, in order for the converting element to generate different sounds for the different directions of movement of the actuating portion, the converting element may be configured to generate at least two different sounds sequentially when the actuating portion is brought into movement, wherein the sequence of the two different sounds will help determine if the movement of the actuating portion is caused by the physical event or if it is caused by the converting element returning to its normal state. For example, the converting element may be configured such that a movement of the actuating portion causes vibration of both a first vibrational element having a first characteristic frequency and a second vibrational element having a second characteristic frequency, wherein the order in which the first and second vibrational elements start to vibrate depends on the direction of movement of the actuating portion. This way, the direction of movement of the actuating portion can be determined by the processor based on the order of the frequencies registered by the acoustic sensor.

[0034] It is to be understood that depending on the physical event to be detected, the structure through which the characteristic sound propagates from the converting element to the acoustic sensor may be different things. The structure may be a part of a piping system, a tube / hose, a cable or bundle with multiple cables, a wall, a floor, a container wall or any physical structure configured to enable propagation of sound through the structure.

[0035] According to another aspect of the present disclosure, a method for acoustic detection of a physical event is provided. The method comprises providing at least one converting element for converting the physical event to a characteristic sound, wherein the at least one converting element is configured to react to the physical event by generating a characteristic sound and inducing the characteristic sound into a structure; registering the characteristic sound generated by the converting element as structure-borne sound propagating through the structure by means of an acoustic sensor mechanically connected to the structure at a distance from the at least one converting element; and detecting the physical event based on the characteristic sound registered by the acoustic sensor by means of a processor coupled to the acoustic sensor. The processor may receive signals from the acoustic sensor corresponding to the registered characteristic sound and the processor may detect a physical event based on the received signals.

[0036] It is to be understood that all features and advantages with regard to the system as disclosed herein is also applicable on the method for acoustic detection of a physical event by means of this system.

[0037] The converting element may comprise a sound-generating portion with at least one vibrational element configured to be brought into vibration by the physical event, thereby causing the characteristic sound to comprise at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies, wherein the physical event is detected based on the at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies.

[0038] The converting element may comprise an actuating portion that comprises at least one material having a thermal expansion property, such that a change in temperature causes a movement of the actuating portion, which movement causes the characteristic sound to be generated, wherein detecting the physical event involves detecting the change in temperature based on the characteristic sound.

[0039] The converting element may comprise an actuating portion that comprises at least one material having a hygroscopic property, such that a change in moisture causes a movement of the actuating portion, which movement causes the characteristic sound to be generated, wherein detecting the physical event involves detecting the change in moisture based on the characteristic sound.

[0040] The converting element may comprise an actuating portion configured to be brought into movement by a change in pressure, which movement causes the characteristic sound to be generated, wherein detecting the physical event involves detecting a change in pressure based on the characteristic sound.

[0041] The converting element may comprise an actuating portion configured to be brought into movement by a change in electromagnetic irradiance, which movement causes the characteristic sound to be generated, wherein detecting the physical event involves detecting the change in electromagnetic irradiance based on the characteristic sound.

[0042] The at least one vibrational element may be configured to be brought into vibration by a displacement of an object, wherein detecting the physical event involves detecting the displacement of the object. The vibrational element may comprise a vibrational portion extending between a pivot point and a free end of the vibrational element and the method may further comprise adjusting the length of the vibrational portion in order to manually affect at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies.

[0043] The method may comprise the step of providing a plurality of converting elements, wherein the characteristic sound created by each converting element is associated with a unique identity and / or position of the converting element, wherein detecting the physical event further comprises determining a location of the physical event based on the unique identity and / or position of the converting element having created the registered characteristic sound.

[0044] According to another aspect of the present disclosure there is provided a computer program comprising computer-readable instructions which, when executed by a processor of a system for acoustic detection of a physical event as disclosed herein, causes the processor to perform the step of detecting the physical event based on a characteristic sound generated by a converting element and registered by an acoustic sensor of the system. The computer program may further comprise instructions for causing the processor of the system to perform any of, or any combination of, the method steps of the above-described method related to the processor.

[0045] The computer program or parts of the computer program may reside in a data storage medium of the acoustic sensor. In some embodiments, the computer program may be a distributed application comprising several computer program components configured to perform different steps of the above-described method. For instance, the computer program may comprise a first program component or application residing in the acoustic sensor, a second program component or application residing in the network server, and a third program component or application in form of a client application for presentation of data and interaction with a user, residing in a client device. In another example, the computer program may comprise a web application accessible via a web browser of the client device.

[0046] According to another aspect of the present disclosure there is provided a computer program product comprising at least one computer-readable medium, such as a non- transitory memory hardware device, storing the above-mentioned computer program.

[0047] The present disclosure will become apparent from the detailed description given below. The detailed description and specific examples disclose preferred embodiments of the disclosure by way of illustration only. Those skilled in the art understand from guidance in the detailed description that changes and modifications may be made within the scope of the appended claims.

[0048] BRIEF DESCRIPTIONS OF THE DRAWINGS

[0049] The above objects, as well as additional objects, features and advantages of the present disclosure will be more fully appreciated by reference to the following illustrative and nonlimiting detailed description of example embodiments of the present disclosure, when taken in conjunction with the accompanying drawings, of which:

[0050] Figure 1 illustrates a system for acoustic detection of a physical event according to an example of the present disclosure;

[0051] Figures 2a-c schematically illustrates a converting element according to an example of the present disclosure;

[0052] Figure 3 illustrates a system for acoustic detection of a physical event according to an example of the present disclosure; Figure 4 illustrates a system for acoustic detection of a physical event according to an example of the present disclosure;

[0053] Figure 5a-b schematically illustrate a converting element according to an example of the present disclosure;

[0054] Figure 6 illustrates a system for acoustic detection of a physical event according to an example of the present disclosure;

[0055] Figure 7a-b illustrate a system for acoustic detection of a physical event and a converting element according to an example of the present disclosure;

[0056] Figure 8a-b illustrate a system for acoustic detection of a physical event according to an example of the present disclosure; and

[0057] Figure 9 shows a flow diagram for a method for acoustic detection of a physical event according to an example of the present disclosure.

[0058] DETAILED DESCRIPTION

[0059] The present disclosure will now be described with reference to the accompanying drawings, in which preferred example embodiments of the disclosure are shown. The disclosure may, however, be embodied in other forms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided merely to fully convey the scope of the disclosure to the skilled person.

[0060] It is to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It should be noted that, as used in the specification and the appended claims, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context explicitly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the terms "comprising", "including", "containing" and similar wordings are intended to be open-ended transitional terms that do preclude the possibility of additional elements or steps.

[0061] Figure 1 schematically illustrates a system 100 for acoustic detection of physical event according to an example of the disclosure. The system 100 comprises at least one converting element 10 for converting a physical event to a characteristic sound; an acoustic sensor 40 mechanically connected to a structure 50 at a distance from the at least one converting element 10; and at least one processor 42, 62 coupled to the acoustic sensor 40. The at least one converting element 10 is configured to react to the physical event by generating a characteristic sound and inducing the characteristic sound into the structure 50. The acoustic sensor 40 is configured to register the characteristic sound generated by the converting element 10 as structure-borne sound propagating through the structure 50 and the at least one processor 42, 62 is configured to detect the physical event based on the characteristic sound registered by the acoustic sensor 40.

[0062] In response to detection of the physical event, the system 100 may be configured to notify a user of the physical event, e.g., by generating a local alarm or by informing the user of the detection of the physical event via a mobile electronic device 70 to which the acoustic sensor 40 is communicatively connectable. Thus, when the at least one processor 42, 62 has detected a physical event, this can be presented on a mobile electronic device of the user, such that the user is informed and can take action if something needs to be done to handle the detected physical event.

[0063] The acoustic sensor 40 comprises a housing 45, such as plastic housing, which is securely attached to the structure 50 to ensure tight mechanical coupling between the sensor housing 45 and the structure 50. The acoustic sensor 40 further comprises an acoustic sensor element 41 configured to register acoustic signals in form of structure-borne sound or vibrations propagating through the structure 50. The acoustic sensor element 41 may, e.g., be a piezoelectric acoustic sensor element or a contact microphone for registering structure-borne sound in the structure 50. The acoustic sensor 40 further comprises a processor 42 and a data storage medium 43. The data storage medium 43 stores a computer program component which, alone or in collaboration with computer program components residing in one or more other devices to which the acoustic sensor 40 is connectable, constitutes a computer program for detection of a physical event.

[0064] In the illustrated example, the system 100 is a cloud-based system comprising a network server 60. The acoustic sensor 40 comprises a communication module 44 configured to communicate with a communication module 64 of the network server 60 using any known communication protocol. In some embodiments, the network server 60 is a web server connected to the Internet. The network server 60 further comprises a processor 62 and a data storage medium 63 storing a server-side component of the above-mentioned computer program. The logic required for processing the registered acoustic signals and for determining whether a physical event has occurred based on the processed acoustic signals may reside in any of the acoustic sensor 40 or the network server 60. The network server 60 is configured to communicate information relating to the detection of the physical event to a client device 70, such as a stationary computer, a laptop, a tablet computer or a mobile phone. In some embodiments, the client device 70 may store a client application communicating with the server-side component of the computer program. This way, alerts and / or other information relating to detection of the physical event may be communicated from the network sever 60 to the client device 70 in the form of push notifications.

[0065] The converting element 10 is configured to react to the physical event and thereby generate a sound, which is induced into the structure 50. The converting element 10 is suitably a simple mechanical construction comprising materials and / or geometries, which will react to a certain physical event or phenomenon. The converting element 10 suitably does not include any electronic components or intelligence. The shape and configuration of the converting element 10 gives the characterising sound generated by the converting element 10. This way, the at least one processor 42, 62 of the system 100 will be able to determine that the registered sound origin from the converting element 10 and thus that a physical event has occurred.

[0066] One example of how the converting element 10 can be configured is described with regard to Figure 2 below.

[0067] In this figure, the physical event is illustrated by means of arrows pointing towards the converting element 10. It is to be understood that the physical event could be a change in temperature (increase or decrease), a change in moisture, a pressure change, a displacement of an object, degradation due to excessive sunlight or similar.

[0068] Figures 2a-c show a converting element 10 and details of such a converting element 10 according to an example of the present disclosure. The converting element 10 may form part of a system 100 as disclosed in Figure 1.

[0069] Figure 2a show the converting element 10 comprising an actuating portion 30 configured to be brought into movement by the physical event. The converting element 10 also comprises a sound-generating portion 20 connected to the actuating portion 30. The sound-generating portion 20 is configured to be arranged in physical contact with the structure 50. The sound-generating portion 20 is configured to induce the characteristic sound into the structure 50. In this example, the sound-generating portion 20 extends on both sides of the actuating portion 30.

[0070] In this example, the sound-generating portion 20 also comprises at least one vibrational element 22 configured to be brought into vibration by the physical event. The configuration of the at least one vibrational element 22 causes the characteristic sound to comprise at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies. Thus, when the actuating portion 30 is brought into movement by the physical event, the movement of the actuating portion 30 causes the at least one vibrational element 22 to vibrate.

[0071] The movement of the actuating portion 30 itself typically causes a characteristic sound to be generated by the sound-generating portion 20 indicating that a physical event has occurred. However, the at least one vibrational element 22 being brought into vibration by the movement of the actuating portion 30 will add at least one characteristic frequency to the characteristic sound and the converting element 10 will this way have a unique identity.

[0072] In the illustrated example, the at least one vibrational element 22 comprises an elongated leg with a free end 26 and connected at the other end to the actuating portion 30. In this case, the connection point to the actuating portion 30 is also referred to as a pivot point P. The vibrational element 22 comprises a vibrational portion 24 extending between the pivot point P and the free end 26 of the vibrational element 22.

[0073] The actuating portion 30 may comprise a snapping mechanism 32 configured to perform a snapping movement into a stable state of the snapping mechanism 32 in response to the physical event. The snapping movement may cause the sound-generating portion 20 to generate the characteristic sound. The snapping mechanism 32 may be a bi-stable mechanism configured with a snap-through instability, configured to perform the snapping movement between a first stable state and a second stable state of the bi-stable mechanism in response to the physical event. Such mechanism typically transitions rapidly between the two stable states and the rapid movement from one stable state into the other stable state will bring the vibrational element 22 into vibration and / or cause the sound-generating portion 20 to induce the generated characteristic sound into the structure 50.

[0074] Figures 2b and 2c show examples of the at least one vibrational element 22 of the soundgenerating portion 20, wherein the converting element 10 further comprises means 14 for manually adjusting the length of the vibrational portion 24 in order to manually affect at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies generated by the converting element 10. In Figure 2b, the means 14 for adjusting the length of the vibrational portion 24 of the at least one vibrational element 22 comprises markings, dentations, fold lines or perforations for bending or removing a part of the vibrational portion 24, and that way adjust the length of the vibrational portion 24. Thus, by removing a part of the vibrational element 22 at the free end 26 of the vibrational element 22, the vibrational portion 24 will be shorter and the characteristic frequency of the vibrational element 22 is changed. The figure shows a dotted section, which originally includes the free end 26 of the vibrational element 22. When this section is removed from the vibrational element 22, the free end 26 will instead be at the remaining part of the vibrational element 22.

[0075] In Figure 2c, the means 14 for adjusting the length of the vibrational portion 24 of the at least one vibrational element 22 comprises a slider element 14 movable along the length of the vibrational element 22. The slider element 14 will prevent or restrict movement of the vibrational element 22 and the position of the slider element will thereby determine the position of the pivot point P. By moving the slider element, the pivot point P is moved and the length of the vibrational portion 24 can be adjusted.

[0076] Figure 3 illustrates a system 100 for acoustic detection of a physical event according to an example of the present disclosure. The system 100 may be configured as disclosed in Figure 1. In this example, the physical event is a change in moisture and the system 100 is arranged in association with a pipe system. The structure 50 is thus a pipe system.

[0077] The system 100 comprises a plurality of converting elements 10 arranged in vicinity of a pipe connection of the pipe system, and the acoustic sensor 40 is arranged on a pipe of the pipe system at a distance from the converting elements 10. Each converting element 10 comprises an actuating portion 30 and a sound-generating portion 20, which in this example also comprises a vibrational element 22. The actuating portion 30 comprises at least one material having a hygroscopic property, such that a change in moisture causes a movement of the actuating portion 30, which movement causes a characteristic sound to be generated. The actuating portion 30 may be configured to react to an increase and / or a decrease of moisture.

[0078] The characteristic sound created by each converting element 10 in the system 100 is associated with a unique identity and / or position of the converting element 10. The at least one processor 42, 62 (see fig. 1) of the system 100 is configured to determine a location of the physical event based on the unique identity and / or position of the converting element 10 having created the registered characteristic sound. Depending on the location of the converting element 10, the characteristic sound from the converting element 10 propagating through the pipe system will be different. Additionally or alternatively, each converting element 10 may have differently configured vibrational elements 22, such that each converting element 10 is associated with a unique identity. Thus, when the moisture level increases at some end of the pipe connection, the corresponding converting element 10 will generate a characteristic sound and the at least one processor 42, 62 will not only detect that an increase in moisture has occurred, but can also, based on the unique identity of the converting element 10, determine where the leakage is in the pipe system.

[0079] Figure 4 illustrates a system 100 for acoustic detection of a physical event according to an example of the present disclosure. The system 100 may be configured as disclosed in Figure 1. In this example, the physical event is a change in temperature and the system 100 is arranged in association with an electrical cabinet. The structure 50 is thus an electrical cabinet. The change in temperature may be an increase or a decrease in temperature.

[0080] The system 100 comprises a plurality of converting elements 10 and the acoustic sensor 40 is arranged on the outside of the electrical cabinet, at a distance from the converting elements 10. In this example, one converting element 10 is arranged in the inside of the cabinet cover, one is arranged on an electrical component inside the cabinet and one converting element 10 is arranged on an electrical cable connected to the cabinet. Since the cabinet cover, the electrical component and the electrical cable are all mechanically connected to the cabinet in some way, the acoustic sensor 40 will be able to register the structure-borne sound generated by any of the converting elements 10.

[0081] The converting elements 10 may be configured as in Figure 2a. Each converting element 10 comprises an actuating portion 30 and a sound-generating portion 20. The soundgenerating portion 20 may comprise a vibrational element 22. In this example, the actuating portion 30 of each converting element 10 comprises at least one material having a thermal expansion property, such that a change in temperature causes a movement of the actuating portion 30. The actuating portion 30 may comprise a bi-metal.

[0082] Figures 5a-b illustrate how the actuating portion 30 of a converting element 10 reacts when there is a change in temperature. The converting element 10 may be configured as disclosed in Figure 4. In this example, the actuating portion 30 comprises at least two materials having different thermal expansion properties. The actuating portion 30 comprises a snapping mechanism 32 which is essentially dome shaped. In its normal state, the snapping mechanism 32 is essentially concave and the sound-generating portion 20 is connected to the structure 50. When the temperature changes above a predetermined temperature, the different thermal expansion properties of the materials of the actuating portion 30 will cause the dome-shaped snapping mechanism 32 to snap and invert its shape. Thus, the snapping mechanism 32 will become convex. This movement of the actuating portion 30 causes a characteristic sound to be generated by the soundgenerating portion 20, and causes the sound-generating portion 20 to induce the characteristic sound into the structure 50.

[0083] Figure 6 illustrates a system 100 for acoustic detection of a physical event according to an example of the present disclosure. The system 100 may be configured as disclosed in Figure 1. In this example, the physical event is a displacement of an object 300. The system 100 comprises a plurality of converting elements 10 formed on a common plate, upon which the objects 300 are arranged. The acoustic sensor 40 is removably arranged on the same plate as the objects 300. The plate thus constitutes the structure 50.

[0084] Each converting element 10 comprises an actuating portion 30 and a sound-generating portion 20 with a vibrational element 22. An object 300 is arranged on top of a converting element 10 and thus applies a force on the converting element 10. When an object 300 is removed from the plate, the force / weight on the converting element 10 is removed and that together with the geometry of the actuating portion 30 causes a movement of the actuating portion 30, such that the vibrational element 22 is brought into vibration and the characterising sound will propagate through the plate to the acoustic sensor 40. The converting elements 10 typically have differently configured vibrational elements 22. This way, the characterising sound generated by a converting element 10 will have a unique identity and the at least one processor 42, 62 (See Figure 1) will be able to determine not only that an object has been displaced, but also which product. The system 100 can this way be used as an inventory system.

[0085] Figure 7a-b illustrate a system 100 for acoustic detection of a physical event according to an example of the present disclosure. The system 100 may be configured as disclosed in Figure 1. In this example, the physical event to be detected by the system 100 is a change in pressure. The system 100 is arranged in association with a pressure tank 80 and at least one converting element 10 is arranged inside the tank, on an inside of the tank wall. The tank wall thus constitutes the structure 50. The acoustic sensor 40 is arranged on the outside of the tank. The converting element 10 is configured, such that a change in pressure causes a movement of the actuating portion 30, which causes the soundgenerating portion 20 to induce the characteristic sound into the tank wall.

[0086] Figure 7b shows the converting element 10 arranged on the inside of the tank wall. The converting element 10 may be hollow with an inner chamber 16. The actuating portion 30 of the converting element 10 also comprises an essentially dome-shaped snapping mechanism 32. The sound-generating portion 20 is abutting the tank wall. In a normal state of the converting element 10, shown to the left, the snapping mechanism 32 is convex and thus protrudes away from the tank wall. When the pressure inside the tank increases and exceeds the pressure inside the inner chamber 16 of the converting element, the snapping mechanism 32 will be subject to a force acting inwards, in direction of the tank wall. The dome-shaped snapping mechanism 32 will eventually snap, and become concave. This snapping movement will cause a characteristic sound to be generated and the characteristic sound will be induced into the tank wall by means of the sound-generating portion 20.

[0087] Figure 8a-b illustrate a system 100 for acoustic detection of a physical event according to an example of the present disclosure. The system 100 may be configured as disclosed in Figure 1. In this example, the physical event to be detected by the system 100 is a change in electromagnetic irradiance. In this example, the actuating portion 30 comprises a material, which degrades by electromagnetic irradiance. The actuating portion 30 will this way break after having been subject to a certain amount of electromagnetic irradiance. When the actuating portion 30 breaks a movement of the actuating portion 30 occurs, which causes a characteristic sound to be generated. Specifically, the movement of the actuating portion 30 will bring the at least one vibrational element 22 into vibration.

[0088] The converting element 10 may be arranged on a wall or similar, constituting the structure 50. The sound-generating portion 20 is abutting the structure 50, and may be adhered to it. The sound-generating portion 20 comprises two vibrational elements 22. In the normal state of the converting element 10, the sound-generating portion 20 is in a biased and folded position and the degradable actuating portion 30 is arranged to at least partly cover the vibrational element 22 and hold the sound-generating portion 20 in this biased position. When the actuating portion 30 breaks, the sound-generating portion 20 will unfold and the vibrational elements 22 will be brought into vibration. The acoustic sensor 40 can be arranged on the other side of the wall, and thus not be subject to electromagnetic radiation. The acoustic sensor 40 is mechanically connected to the structure 50 and registers the characteristic sound generated by the converting element 10. Thereby, the at least one processor 42, 62 of the system 100 detects the increase in electromagnetic irradiance.

[0089] Figure 9 illustrates a method for acoustic detection of a physical event according to the present disclosure. The method relates to a system 100 for acoustic detection of a physical event. The system 100 may be configured as disclosed in any of figure l-8b.

[0090] The method comprises providing slOl at least one converting element 10 for converting the physical event to a characteristic sound, wherein the at least one converting element 10 is configured to react to the physical event by generating a characteristic sound and inducing the characteristic sound into a structure 50; registering sl02 the characteristic sound generated by the converting element 10 as structure-borne sound propagating through the structure 50 by means of an acoustic sensor 40 mechanically connected to the structure 50 at a distance from the at least one converting element 10; and detecting sl03 the physical event based on the characteristic sound registered by the acoustic sensor 40 by means of at least one processor 42, 62 coupled to the acoustic sensor 40.

[0091] The converting element 10 may comprise a sound-generating portion 20 with at least one vibrational element 22 configured to be brought into vibration by the physical event, thereby causing the characteristic sound to comprise at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies, wherein the physical event is detected sl03 based on the at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies.

[0092] The converting element 10 may comprise an actuating portion 30 comprising at least one material having a thermal expansion property, such that a change in temperature causes a movement of the actuating portion 30, which movement causes the characteristic sound to be generated, wherein detecting sl03 the physical event involves detecting the change in temperature based on the characteristic sound. The movement of the actuating portion 30 may bring the at least one vibrational element 22 into vibration.

[0093] The converting element 10 may comprise an actuating portion 30 that comprises at least one material having a hygroscopic property, such that a change in moisture causes a movement of the actuating portion 30, which movement causes the characteristic sound to be generated, wherein detecting sl03 the physical event involves detecting the change in moisture based on the characteristic sound. The movement of the actuating portion 30 may bring the at least one vibrational element 22 into vibration.

[0094] The converting element 10 may comprise an actuating portion 30 configured to be brought into movement by a change in pressure, which movement causes the characterizing sound to be generated, wherein detecting sl03 the physical event involves detecting a change in pressure based on the characteristic sound.

[0095] The converting element 10 may comprise an actuating portion 30 comprising a material, which degrades by electromagnetic irradiance, the actuating portion 30 being configured such that it breaks after having been subject to a certain amount of irradiance, which causes a movement of the actuating portion 30, which movement causes the characteristic sound to be generated, wherein detecting sl03 the physical event involves detecting an increase of electromagnetic irradiance based on the characteristic sound. The movement of the actuating portion 30 may bring the at least one vibrational element 22 into vibration.

[0096] The at least one vibrational element 22 may be configured to be brought into vibration by a displacement of an object, wherein detecting sl03 the physical event involves detecting the displacement of the object.

[0097] The at least one vibrational element 22 may comprise a vibrational portion 24 extending between a pivot point P and a free end 26 of the vibrational element 22 and the method may further comprise adjusting sl04 the length of the vibrational portion 24 in order to manually affect at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies.

[0098] The method may comprise the step of providing slOl a plurality of converting elements 10, wherein the characteristic sound created by each converting element 10 is associated with a unique identity and / or position of the converting element 10, wherein detecting sl03 the physical event further comprises determining a location of the physical event based on the unique identity and / or position of the converting element 10 having generated the registered characteristic sound.

[0099] The person skilled in the art realizes that the present disclosure is not limited to the embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims.

Claims

CLAIMS1. A system (100) for acoustic detection of a physical event, the system (100) comprising: at least one converting element (10) for converting the physical event to a characteristic sound; an acoustic sensor (40) configured to be mechanically connected to a structure (50) at a distance from the at least one converting element (10); and a processor (42, 62) coupled to the acoustic sensor (40), wherein the at least one converting element (10) is configured to react to the physical event by generating a characteristic sound and inducing the characteristic sound into the structure (50), wherein the acoustic sensor (40) is configured to register the characteristic sound generated by the at least one converting element (10) as structure-borne sound propagating through the structure (50), and wherein the processor (42, 62) is configured to detect the physical event based on the characteristic sound registered by the acoustic sensor (40).

2. The system (100) according to claim 1, wherein the converting element (10) comprises an actuating portion (30) configured to be brought into movement by the physical event, the movement of the actuating portion (30) causing the characteristic sound to be generated.

3. The system (100) according to claim 2, wherein the at least one converting element (10) comprises a sound-generating portion (20) including at least one vibrational element (22) configured to be brought into vibration by the movement of the actuating portion (30), the configuration of the at least one vibrational element (22) causing the characteristic sound to comprise at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies.

4. The system (100) according to claim 3, wherein the at least one vibrational element (22) comprises a vibrational portion (24) extending between a pivot point (P) and a free end (26) of the vibrational element (22), wherein the converting element (10)comprises means (14) for manually adjusting the length of the vibrational portion (24) in order to manually affect at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies.

5. The system (100) according to claim 2, wherein the actuating portion (30) comprises a snapping mechanism (32) configured to perform a snapping movement into a stable state of the snapping mechanism (32) in response to the physical event.

6. The system (100) according to claim 5, wherein the snapping mechanism (32) is a bistable mechanism with snap-through instability, configured to perform the snapping movement between a first stable state and a second stable state of the bi-stable mechanism, in response to the physical event.

7. The system (100) according to any of the claims 2-6, wherein the physical event is a change in temperature, wherein the actuating portion (30) comprises at least one material having a thermal expansion property, such that a change in temperature causes a movement of the actuating portion (30).

8. The system (100) according to any of the claims 2-6, wherein the physical event is a change in moisture, wherein the actuating portion (30) comprises at least one material having a hygroscopic property, such that a change in moisture causes a movement of the actuating portion (30).

9. The system (100) according to any of the claims 2-6, wherein the physical event is a change in pressure, wherein the actuating portion (30) is configured such that a change in pressure causes a movement of the actuating portion (30).

10. The system (100) according to any of the claims 2-6, wherein the physical event is an increase in electromagnetic irradiance, wherein the actuating portion (30) comprises a material that degrades by electromagnetic irradiance, the actuating portion (30) being configured such that it breaks after having been subject to a certain amount of irradiance, which causes a movement of the actuating portion (30).

11. The system (100) according to claim 3 or 4, wherein the physical event is a displacement of an object (300), wherein the converting element (10) is configured such that the displacement of the object (300) causes the at least one vibrational element (22) of the soundgenerating portion (20) to be brought into vibration.

12. The system (100) according to any one of the preceding claims, wherein the system (100) comprises a plurality of converting elements (10), wherein the characteristic sound created by each converting element (10) is associated with a unique identity and / or position of the converting element (10), the processor (42, 62) being configured to determine the location of the physical event based on the unique identity and / or position of the converting element (10) having created the registered characteristic sound.

13. A method for acoustic detection of a physical event, the method comprising: providing (slOl) at least one converting element (10) for converting the physical event to a characteristic sound, wherein the at least one converting element (10) is configured to react to the physical event by generating a characteristic sound and inducing the characteristic sound into a structure (50); registering (sl02) the characteristic sound generated by the converting element (10) as structure-borne sound propagating through the structure (50) by means of an acoustic sensor (40) mechanically connected to the structure (50) at a distance from the at least one converting element (10); anddetecting (sl03) the physical event based on the characteristic sound registered by the acoustic sensor (40) by means of a processor (42, 62) coupled to the acoustic sensor (40).

14. The method according to claim 13, wherein the converting element (10) comprises a sound-generating portion (20) including at least one vibrational element (22) configured to be brought into vibration by the physical event, thereby causing the characteristic sound to comprise at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies, wherein the physical event is detected (sl03) based on the at least one characteristic frequency and / or the plurality of frequencies forming the characteristic sequence of frequencies.

15. The method according to claim 13 or 14, wherein the converting element (10) comprises an actuating portion (30) that comprises at least one material having a thermal expansion property, such that a change in temperature causes a movement of the actuating portion (30), which movement causes the characteristic sound to be generated, wherein detecting (sl03) the physical event involves detecting a change in temperature based on the characteristic sound.

16. The method according to claim 13 or 14, wherein the converting element (10) comprises an actuating portion (30) that comprises at least one material having a hygroscopic property, such that a change in moisture causes a movement of the actuating portion (30), which movement causes the characteristic sound to be generated, wherein detecting (sl03) the physical event involves detecting a change in humidity based on the characteristic sound.

17. The method according to claim 13 or 14, wherein the converting element (10) comprises an actuating portion (30) configured to be brought into movement by a change in pressure, which movement causes the characteristic sound to begenerated, wherein detecting (sl03) the physical event involves detecting a change in pressure based on the characteristic sound.

18. The method according to claim 13 or 14, wherein the converting element (10) comprises a material, which degrades by electromagnetic irradiance, the actuating portion (30) being configured such that it breaks after having been subject to a certain amount of irradiance, which causes a movement of the actuating portion (30) which movement causes the characteristic sound to be generated, wherein detecting (sl03) the physical event involves detecting an increase of electromagnetic irradiance based on the characteristic sound.

19. The method according to claim 14, wherein the at least one vibrational element (22) is configured to be brought into vibration by a displacement of an object (300), wherein detecting (sl03) the physical event involves detecting the displacement of the object (300).

20. The method according to claim 14, wherein the vibrational element (22) comprises a vibrational portion (24) extending between a pivot point (P) and a free end (26) of the vibrational element (22), the method further comprising: adjusting (sl04) the length of the vibrational portion (24) in order to manually affect at least one characteristic frequency and / or a plurality of frequencies forming a characteristic sequence of frequencies.

21. The method according to any one of claims 14-20, comprising the step of providing (slOl) a plurality of converting elements (10), wherein the characteristic sound created by each converting element (10) is associated with a unique identity and / or position of the converting element (10), wherein detecting (sl03) the physical event further includes determining a location of the physical event based on the unique identity and / or position of the converting element (10) having created the registered characteristic sound.

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