A modular acoustic sensor device associated method of use

Abstract

A modular device 10 for detecting sounds within a specimen comprises: a housing 20 defining an interior chamber 26 with an opening 27; an acoustic sensor 40 in the chamber with a sensing surface 40a f

Description

[0002] Red palm weevil (RPW), Rynchophorus ferruginues causes fatal damage to young coconut and oil palms accounting to about 10% of the loss of crop in the World. The weevil’s larvae develop within the tree stem and crown, damaging the vascular system and eventually cause the death of the tree. The top ten countries that grow coconuts are Indonesia (21 million metric tons (mMT)), Philippines (15 mMT), India (10 mMT), Sri Lanka (2 mMT), Brazil (1.9 mMT), Thailand (1.3 mMT), Vietnam (1.12 mMT), Mexico (1 mMT), Papua New Guinea (0.93 mMT), and United Republic of Tanzania (0.6 mMT). If Sri Lanka is taken as an example, the coconut industry accounts for 1.5% of the GDP (around £700 million). It has been estimated that 10% of young coconut palms in Sri Lanka are lost annually due to RPW attack. Accordingly, during the period of 2000-2005, nearly 200,000 young palms have been killed by RPW resulting in a financial loss of about US $ 1,800,000. The larvae feed on the soft tissues on the stem and bud region destroying internal tissues. Early detection of infested palms at the early stage by external symptoms is difficult because the RPW larvae develop internally within the tree, hidden from sight.

[0003] RPW larvae produce a characteristic crunching sound as they feed on the palm fibres because, due to their morphology, they chew rhythmically at a specific frequency. It is therefore known to detect the presence of RPW larvae in palms using detectors with audio sensors; in particular, piezoelectric sensors attached to a probe inserted into a specimen tree, whereby the larvae’s distinct sounds propagate through the fibrous palm tissue to the probe to be transmitted to the attached sensor. However, it has proven to be difficult to discriminate the sounds characteristic of the RPW larvae from other sounds picked up by the audio sensors. For example, honey bees, water being pumped naturally internally within the tree, and the tree bending and twisting in the wind all produce sounds within the tree that are similar to those characteristic of the RPW larvae. Further difficulties arise from unwanted background environmental noise external to the tree also, such as wind and vehicle noises. Attempts to mitigate these difficulties have included applying signal processing techniques to the signals output from the audio sensors to attempt to isolate the sounds of those of the RPW larvae from the unwanted sounds also picked up by the sensors, and to analyse the captured sound in real-time, supplying an audible tone or visible signal when the analysis detects a sound indicative of the presence of RPW larvae. One known signal processing technique is to apply an active band pass filter in the 800-2,500 Hz frequency band, which has been identified as the effective frequency range of the RPWs acoustic emissions. A trained operator determines whether the palm tree is infested, based on the number and frequency of the positive tones or visible signals. To date, this has required a physical signal processing unit to be supplied with the detector, which has meant relatively high cost units that are not well afforded by the typically rural farming communities for whom they would be of most benefit.

[0004] Recommended management methods, such as applying toxic chemical treatments (insecticides) are often not adequately practiced by the farmers due to shortage of labour and high cost of operations, as well as difficulties in obtaining the necessary treatments.

[0005] Hence a reliable, inexpensive and convenient early detection method is necessary to save the infested palms.

[0006] One prior device and technique is disclosed in WO2020099847, which discloses a wood boring insect detector that comprises a housing defining a hollow interior chamber and including an opening connecting the interior chamber to the exterior; a spacer member surrounding the opening and defining an internal cavity; and an acoustic sensor mounted within the interior chamber. A probe projects through the opening and the internal cavity of the spacer. An exposed tip portion of the probe is for insertion into a specimen. A base portion of the probe is connected to the acoustic sensor. The spacer member defines a separation between the housing and the specimen and a depth of insertion of the probe tip into the specimen. When the tip portion is inserted into a specimen, wood boring insect activity within the specimen is transmitted as vibrations along the probe to the acoustic sensor, which converts those vibrations to an output signal of a characteristic acoustic frequency indicative of the presence of wood boring insect activity within the specimen. The detector includes specially configured internal cavities / chambers, a mount and a resilient pad, and a resilient outer sheath, which are physical elements that filter out much of the background noise for particularly good acoustic properties.

[0007] Whilst the device of WO2020099847 overcomes some of the above-identified problems, the probe is formed integrally with the rest of the device. As such, if the probe becomes damaged, which is quite possible with repeated insertion and extraction from different specimens, and in transport and storage therebetween, particularly in the relatively harsh environment in which the specimens are typically located - e.g. palm plantations, the device will need to be replaced as a unit. Moreover, different specimens may require different probe lengths for best detection of insect activity, so where users want to sample in multiple different specimen types they need to hold a corresponding stock of different devices, each with appropriate probe lengths.

[0008] The inventors have also determined that repeated insertion of a probe into a specimen, particularly a young specimen, can damage that specimen.

[0009] The present invention seeks to mitigate at least some of these difficulties. BRIEF SUMMARY OF THE DISCLOSURE

[0010] In accordance with a first aspect of the present invention, there is provided a modular acoustic sensor device for detecting sounds in a specimen, the device comprising: a housing defining a hollow interior chamber and including an opening connecting the interior chamber to the exterior; an acoustic sensor mounted within the interior chamber, whereby a sensing surface of the acoustic sensor faces the exterior through the opening; and a probe comprising a base portion and a tip portion. The probe is removably coupled to the acoustic sensor such that when coupled the base portion is in direct contact with the sensing surface and the tip portion projects through the opening for insertion into the specimen. When in use the tip portion is inserted into the specimen, sounds within the specimen are transmitted as vibrations along the probe to the acoustic sensor, which converts those vibrations to an output signal.

[0011] The modular nature of the device is advantageous because the probe can easily be removed to be replaced by another probe, for example in the case of the first probe being damaged, or in the case where a probe of a different length is required.

[0012] Where it is desirable to avoid the damage that insertion of a probe may cause, for example in the case of a young specimen, a blanking plate can be coupled to the sensing surface instead of a tipped probe. The blanking plate would be in direct contact with the exterior of the specimen through the opening, and sounds within the specimen would be transmitted as vibrations across the blanking plate to the acoustic sensor. The blanking plate can be considered as a probe without the tip portion; i.e. a tipless probe. Thus, in accordance with a second aspect of the invention, there is provided a modular acoustic sensor device for detecting sounds in a specimen, the device comprising: a housing defining a hollow interior chamber and including an opening connecting the interior chamber to the exterior; an acoustic sensor mounted within the interior chamber, whereby a sensing surface of the acoustic sensor faces the exterior through the opening; and a tipless probe comprising a base portion. The probe is removably coupled to the acoustic sensor such that when coupled the base portion is in direct contact with the sensing surface and a portion projects through the opening for attachment against the specimen. When in use the probe is attached to the specimen, sounds within the specimen are transmitted as vibrations across the probe to the acoustic sensor, which converts those vibrations to an output signal.

[0013] The probe (either tipped or tipless) may be removably coupled to the acoustic sensor via a magnetic coupling. The magnetic coupling may comprise at least one magnet mounted to the acoustic sensor on an opposed side to the sensing surface. At least the base portion of the probe may comprise ferromagnetic metal. According to a third aspect of the invention, there is thus provided a modular acoustic sensor device for detecting sounds in a specimen, the device comprising: a housing defining a hollow interior chamber and including an opening connecting the interior chamber to the exterior; an acoustic sensor mounted within the interior chamber, whereby a sensing surface of the acoustic sensor faces the exterior through the opening; and at least one magnet mounted to the acoustic sensor on an opposed side to the sensing surface for removably coupling a probe to the acoustic sensor. In use, when the probe is coupled to the acoustic sensor the base portion is in direct contact with the sensing surface a portion, which may be a tip portion, projects through the opening for attachment to or insertion into the specimen. Sounds within the specimen are transmitted as vibrations across or along the probe to the acoustic sensor, which converts those vibrations to an output signal.

[0014] Alternatively, rather than the magnets being located in the device, the magnets may be located in the base portion of the probe, with a ferromagnetic member being located on the opposed side of the acoustic sensor. However, by locating the magnet(s) on the opposed side to the sensor surface the removable coupling can be provided in a space-efficient manner because the or each magnet can be positioned within the interior chamber where not interfering with other components that may be located within, and the probe can be very of simple thus inexpensive construction.

[0015] A magnetic coupling is advantageous for ease of coupling and decoupling of the probe from the sensor, since it merely requires a user to pull the probe from the sensor to release the coupling, with the reattachment of the or another probe simply requiring the replacement probe to be brought into close proximity with the sensor in order to effect the coupling. Notably, probes are typically made from steel already, so are inherently ferromagnetic and suited for such use. The probe is typically metal; preferably steel and more preferably stainless steel. Even if a non-magnetic material were wanted to be used for the probe tip, all that is needed is to incorporate a ferromagnetic material in the base portion to provide that functionality.

[0016] The device of any of the first to third aspects may further comprise a resilient, isolating mount between the sensor and the housing. The resilient mount is typically made with silicone rubber having a Shore hardness in the range of 45 to 75, more preferably 50. The resilient mount helps to isolate the sensor from background vibrations transmitted to the housing, such as mechanical vibrations induced from touching and scratching of the exterior of the detector, thereby further filtering out unwanted background noise from the output signal. In other words, the resilient mount acts as a signal filter by restricting the vibrations of the acoustic sensor to substantially just those transmitted via the probe.

[0017] The sensor may be a piezoelectric sensor.

[0018] The device may further comprise a resistor connected in parallel with the sensor, wherein the resistor has a resistance in the range: 1kQ to 60kQ; preferably 1kQ to 10kQ; more preferably 2.2kQ.

[0019] The housing may be cylindrical. This is a convenient shape to manufacture and is best suited for housing a typically substantially circular acoustic sensor.

[0020] The device may further comprise a resilient sheath covering at least a majority of the housing surface. The resilient sheath, typically formed of silicone, further helps to isolate the housing and more particularly the acoustic sensor within from external background noise.

[0021] The device may further comprise an electrical output connector to form an electrical connection with a mating electrical input connection (port) of a portable computing device for the transmittal of the output signal to the portable computing device. The portable computing device is typically a mobile phone or the like, and typically operates under the Android™ operating system. Other operating systems are of course available. The optional presence of the resistor connected in the sensor circuit modifies the output signal to be suitable for certain connected devices, such as those operated under the Android™ operating system, for which the 2.2kD resistor provides the optimum value for the sensor. The electrical output connector may comprise an audio jack, such as a 3.5mm audio jack. This is one convenient and common form of electrical connector for connecting the device to the associated portable computing device (e.g. mobile phone), e.g. via the device’s audio jack socket. It will be understood that other forms of connection can be made instead, such as a Lightning connector to connect to Apple™ devices, and USB connections.

[0022] The device may further comprise a microprocessor within the chamber for processing the output signal, for example to filter and / or amplify the signal prior to output.

[0023] The device may be for use in detecting wood boring insects, such as red palm weevil larvae. As such, the specimen may typically be a coconut palm tree, a natural habitat of the red palm weevil. This is a typical application for the device, and has evident economic benefits as set out above. Alternative applications of the technology are also envisaged however, as would be understood by the skilled reader. The insect to be detected may be different from the red palm weevil larva, so the specimen would be the habitats of those other insects. By way of example, the specimen could be a different type of palm plant, such as a date or Canary palm. Moreover, the specimen need not be living - for example it could be wood in the form of a piece of construction timber or furniture or a ship. One further example is that the device may also or instead be for use in diagnosing other specimen health-related issues through acoustic analysis, for example detecting transpiration in a plant or tree, which has become possible due to the greater sensitivity of the device than known detectors.

[0024] According to a fourth aspect of the invention, there is provided a detection kit comprising: the device of any of the first to third aspects, as described above; and a portable computing device configured to receive the output signal from the acoustic sensor in the device and to output an audio signal for listening by an operator.

[0025] The portable computing device (typically a mobile phone) may be configured to process the received output signal from the acoustic sensor and to output a modified audio signal for listening by an operator, for example through headphones connected to the portable computing device. Mobile phone ownership is typically high, so this can be exploited to advantage by carrying out the signal processing task associated with converting the acoustic sensor’s output signals to a useable audible signal for listening by the operator within the phone rather than in a separate microprocessor-based signal processing unit. This therefore eliminates the need for such a separate microprocessorbased signal processing unit and the device can therefore be kept simple and inexpensive. Appropriate signal-processing software (e.g. a smartphone app) may be provided with the device (e.g. in the form of a download link).

[0026] According to a fifth aspect of the invention, there is provided a method of detecting sounds within a specimen, comprising: providing a device according to the first aspect, as described above; inserting the probe into the specimen; forming a communication connection between the device and a portable computing device, whereby the portable computing device receives the output signal from the audio sensor; processing the output signal in the portable computing device; and analysing the processed signal to determine whether that signal is indicative of a characteristic sound to be detected.

[0027] According to a sixth aspect of the invention, there is provided a method of detecting sounds within a specimen, comprising: providing a device according to the second aspect, as described above; attaching the probe against the specimen; forming a communication connection between the device and a portable computing device, whereby the portable computing device receives the output signal from the audio sensor; processing the output signal in the portable computing device; and analysing the processed signal to determine whether that signal is indicative of a characteristic sound to be detected.

[0028] The processing in the portable computing device may comprise at least one of amplifying and filtering the received output signal.

[0029] Analysing the processed signal to determine whether that signal is indicative of a characteristic sound may comprise determining if frequencies in the output signal are indicative of the presence of wood boring insect activity within the specimen. Alternatively or as well, analysing the processed signal to determine whether that signal is indicative of a characteristic sound may comprise determining if frequencies in the output signal are indicative of transpiration within the specimen.

[0030] The method may further comprise: outputting an audio signal for listening by an operator, in which case analysing the processed signal may comprise the operator listening to the audio signal and deciding whether that signal includes a characteristic frequency. In some embodiments, the method may further comprise: within 5 minutes prior to the operator listening to the audio signal, first listening to a recorded audio signal known to have been recorded in the presence of wood boring insect activity. It has been recognised that the human auditory cortex has a working memory of approximately 5 minutes during which time recently heard sounds are retained. Thus, by providing for the operator to listen to an effective control signal containing a characteristic sound (e.g. of fibres being crunched at the characteristic frequency for a particular larva) within that time frame, it is easier for the operator to recognise that characteristic sound within the subsequently heard audio signal, thereby increasing the chances of correctly identifying the presence (or absence) of an insect within the specimen. Likewise, the operator may prime themselves for detecting transpiration by first listening to an appropriate recorded audio signal.

[0031] The method may further comprise: selecting a probe having a tip length suitable for the specimen under test; and coupling the selected probe to the acoustic sensor. Notably, the tip length of the probe may be zero in the case of a tipless probe or blanking plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 is an underside perspective view of a modular acoustic sensor device according to one embodiment; Figure 2 is a cross-sectional side view through the centre of the device of Figure 1; Figure 3 is another underside perspective view of the device of Figure 1, but showing only the housing - i.e. with the probe detached; Figure 4 is a side perspective cross-sectional view through the centre of the housing according to one embodiment; Figure 5 is a top side perspective view of the housing of the device of Figure 1, with the housing depicted as transparent to show the internal components; Figure 6 is a lower side perspective view of the device of Figure 1, with the housing depicted as transparent to show the internal components; Figure 7 is a top plan, cross-sectional view of the detector of Figure 1, taken on a plane central to an audio jack socket; Figure 9 is top, side perspective view of the housing of the device of Figure 1, showing an audio jack connector; Figure 9 is a schematic view of an exemplary device positioned on a specimen and electrically connected to a portable computing device and, in turn, to headphones; Figures 10A and 10B are graphs depicting data derived from acoustic recordings made using a device according to the invention, comparing results from a healthy tree with those from an unhealthy tree; Figures 11A and 11B correspond to Figures 10A and 10B, but zoomed in on a narrower time window to show greater detail; Figure 12 is a cross-sectional side view through the centre of another version of the device; Figure 13 is a top side perspective view of the housing of the device of Figure 12, with a back portion of the housing depicted as transparent to show the internal components; and Figure 14 is a lower side perspective view of the device of Figure 1, with a front portion of the housing depicted as transparent to show the internal components. DETAILED DESCRIPTION

[0033] In the following description, a device according to the invention will be described primarily in the context of its use for detecting sounds indicative of wood boring insect activity in a specimen, in particular but not exclusively for detecting such activities in palm trees. However, the teachings extend to the use of the device for detecting sounds more broadly indicative of the health of the specimen under test, such as transpiration levels.

[0034] One embodiment of a modular acoustic sensor device 10 for detecting sounds in a specimen 100 is described with reference to the accompanying drawings Figures 1 to 11B. The device 10 comprises a substantially cylindrical housing 20 typically formed in two parts: a back portion 22; and a front portion 24, which fit together to define a hollow interior chamber 26. As depicted, the front portion 24 comprises a cylindrical peripheral side wall 24a and an inwardly-projecting lip 24b. The back portion 22 comprises a discshaped cap that attaches to the rear of the front portion, closing off the rear of the interior chamber 26. The front portion 24 includes a central opening 27 connecting the interior chamber 26 axially to the exterior through a front surface 25 of the housing, which is defined by an inner edge of the lip 24b. It will be understood that the division between the back and front portions 22, 24 may be located more forwardly, in which case at least a portion of the peripheral side wall could be formed in the back portion 22. In other embodiments, rather than being split perpendicular to a longitudinal axis, the housing 20 may be formed of two side portions conjoined parallel to the longitudinal axis, e.g. a clamshell housing.

[0035] In one embodiment, the housing 20 is manufactured from a plastic material, typically ABS, and is typically moulded, although it will be appreciated that other materials and other manufacturing techniques may be used instead. In one example, the housing 20 has a wall thickness of 1.5-3 mm, a diameter of 26-30 mm and an interior chamber length (i.e. height of the interior chamber 26 between the top side of the back portion 22 and the underside of the front portion 24) of 8-15 mm.

[0036] In another embodiment, as depicted in the accompanying drawings Figures 12 to 14, a modular acoustic sensor device 210 is functionally similar to the device 10 described above, but has a modified housing form that is particularly suited to manufacture using additive manufacturing (3D printing) techniques. The length of the housing 220 of this embodiment may be 22.3 mm, and the outside diameter may be 34 mm. Unless differences are explicitly described, the components of the device 210 are similar to those of the device 10 and common components or elements that are substantially identical, except perhaps dimensionally, are denoted by common reference signs.

[0037] The housing 220 is substantially cylindrical and is typically formed in two parts: a back portion 222; and a front portion 224, which fit together to define a hollow interior chamber 26. As depicted, the front portion 224 comprises a cylindrical peripheral side wall 224a and an inwardly-projecting lip 224b at a front-most end. An annular lip 224c projects inwardly towards a rear end of the peripheral side wall 224a. The back portion 222 comprises a cup-shaped cap that attaches to the rear of the front portion, closing off the rear of the interior chamber 26. The cap comprises a disc-shaped rear surface 222a from which projects a cylindrical peripheral side wall 222b towards the front. The peripheral side wall 222b is diametrically smaller than and overlaps with the peripheral side wall 224a. The rear portion 222 connects with the front portion via a snap-fit engagement of the annular lip 224c into a corresponding annular recess 222c about the front end of the side wall 222b.

[0038] The front portion 224 includes a central opening 27 connecting the interior chamber 26 axially to the exterior through a front surface 25 of the housing, which is defined by an inner edge of the lip 224b. It will be understood that the division between the back and front portions 222, 224 may be located more forwardly, in which case at least a portion of the peripheral side wall could be formed in the back portion 222. As with the embodiment of Figures 1 to 8, the housing 220 may be formed of two side portions conjoined parallel to the longitudinal axis, e.g. a clamshell housing.

[0039] For either the device 10 or the device 210, an acoustic sensor in the form of a substantially circular piezoelectric sensor 40 is mounted within the interior chamber 26 such that a sensing surface 40a of the acoustic sensor faces the exterior through the opening 27 towards the front side of the device. Electrical leads (not shown) extend from the sensor 40 to an electrical connector in the form of a 3.5 mm audio jack socket 44. A resistor (not shown) is typically connected in parallel between the leads. The resistor has a resistance in the range: 1kQ to 60kQ; preferably 1kQ to 10kQ; more preferably 2.2kQ, for reasons explained below. Rather than being located internally of the housing 20; 220, the resistor may be within the body of a jack 46 of a connector cable 47 connected to the socket 44, or in parallel between a pair of leads within such a connector cable 47, as shown in Fig. 8. A microprocessor 48 may be electrically connected between the sensor 40 and the electrical connector 44. Where provided, the microprocessor 48 may be located as shown in the internal cavity. In other embodiments, the microprocessor 48 may instead be externally of the housing, e.g. as a separate module

[0040] Although depicted as an audio connector in the form of a 3.5 mm audio jack socket 44 and associated audio connection jack 46 and cable 47, it will be understood that the electrical connector for transmitting the signals from the device 10; 210 may take alternative forms, such as a USB socket and associated cable.

[0041] The sensor 40 is mounted in the interior chamber 26 of the housing 20; 220 via an isolating member in the form of an annular sensor mount 50. As depicted, the sensor mount 50 comprises a pair of silicone rings 50a, 50b that each fit snugly within the front portion 24; 224, abutting the interior surface of the peripheral side wall 24a; 224a. The frontmost ring 50a sits on an inner surface of the lip 24b; 224b. In the embodiment depicted in Figures 1 to 8, a rigid outer rim 41 of the sensor is sandwiched between the rings 50a, 50b. The outer rim 41 is radially smaller than the surrounding housing 20; 220 such that there is a physical separation. Moreover, in the embodiment depicted in Figures 1 to 8, each of the rings 50a,50b includes an outer groove that together define an annular gap 53 around the outer rim 41. In the embodiment depicted in Figures 12 to 14, the sensor 40 is mounted to the sensor mount 50 via an intermediary member 275 in the form of a circular plate extending substantially centrally across the chamber 26. A rear side of the sensor 40 abuts a front surface of the plate 275, which is circumscribed by a rim 276 that is radially smaller than the surrounding housing 220. The rim 276 is securely retained between the rings 50a,50b. The sandwiched arrangement of the rim 276 between the rings 50a,50b is maintained by the engagement of the rear portion 222 with the front portion 224, whereby the front edge of the peripheral side wall 222b abuts the ring 50b, to prevent rearward movement thereof.

[0042] It will be appreciated that rather than comprising a pair of rings, the isolating member may take other forms instead, including being a single unitary member.

[0043] The sensor mount is typically made with silicone rubber having a Shore hardness in the range of 45 to 75; preferably about 50. The resilient nature of the mount helps to isolate the sensor 40 from background vibrations transmitted to the housing 20; 220; 220, as explained in greater detail below. Primarily, however, the sensor mount 50 functions to act as a signal filter by restricting the piezoelectric sensor vibrations.

[0044] A probe 30 projects through the opening 27 towards the front of the device and has an exposed tip portion 32 for insertion into a specimen 100, and a base portion 34 connected to the acoustic sensor 40. The free end of the tip portion 32 is sharp. As such, the probe 30 has a needle-like form. The probe 30 is removably coupled to the acoustic sensor 40 such that when coupled the base portion 34 is in direct contact with the sensing surface 40a and the tip portion 32 projects through the opening 27 for insertion into the specimen 100.

[0045] The probe 30 is typically formed of a metallic material. Preferred and particularly suited materials include steel and alloys thereof, in particular stainless steel. In one embodiment, the probe 30 is made of stainless steel. A steel-based or otherwise ferromagnetic probe is advantageous as providing a convenient mechanism for the removable attachment of the probe 30 to the sensor 40 through use of one or more magnets 60 in the vicinity of the sensor 40. In one embodiment, as illustrated, three permanent magnets 60 are evenly spaced on a rear side of the acoustic sensor 40, on the opposed side to the sensing surface 40a. The or each magnet 60 is selected to provide a magnetic field sufficient to securely hold the probe 30 to the acoustic sensor 40 yet which allows a user to remove the probe by pulling the probe 30 away from the housing 20; 220. In the embodiment illustrates in Figures 1 to 8, the magnets 60 may be disposed directly on the rear surface of the acoustic sensor 40. In the embodiment illustrated in Figures 12 to 14, the magnets 60 may be disposed within corresponding associated holes 277 in the intermediary member 275. The holes may be blind holes 277.

[0046] By having the probe 30 removably coupled to the acoustic sensor 40, different probes may be provided for different purposes. In one example probes 30 having different length tip portions 32 may be used to give corresponding different depths of insertion into a specimen. This may be advantageous to allow a single device (or at least the housing part 20; 220 thereof and all of its internal components) to be used with a number of different specimens, for example of different ages or different species, to ensure that the probe tip 32 punches an optimum distance into the specimen for a reliable reading.

[0047] By way of example, a probe 30 for use with coconut palm specimens may have a probe tip portion 32 with a thickness (diameter) in the range of 1-3 mm and a length in the range of 15-30 mm, whereas a probe 30 for use with other palm tree specimens may have a probe tip portion 32 with a length in the range of 30-100 mm. In either case, the base portion 34 typically has a diameter in the range of 15 to 18 mm, which provides a sufficient surface area for secure and reliable contact with the acoustic sensor 40.

[0048] In use, when the tip 32 is inserted into a specimen 100, sounds within the specimen 100 are transmitted to the probe 30 and will excite the piezoelectric sensor 40, converting kinetic energy of the vibrations to electrical energy in the form of output signals to be transmitted from the device 10; 210 as is known.

[0049] Thus, if wood boring insects such as RPW larvae are active in the specimen 100, then that activity is transmitted as vibrations along the probe 30 to the acoustic sensor 40, which converts those vibrations to an output signal that will include a characteristic acoustic frequency indicative of that activity within the specimen. Because the piezoelectric sensor 40 is mounted on the mount 50, the vibrations sensed by the sensor 40 are restricted to substantially just those transmitted through the probe 30; background mechanical vibrations such as induced through touching or scratching, which might otherwise be transmitted to the sensor 40 as a result of handling the device 10; 210, are filtered out. The arrangement is sensitive enough not only to effectively detect wood boring insect activity directly, but also to determine other metrics indicative of the general health of the specimen. For example, and as illustrated by reference to Figures 10A to 11B, which represent a continuous wavelet transform (CWT) applied to the data using a Daubechies 10 (DB10) mother wavelet, the sensed vibrations can be analysed to detect rates of transpiration of the specimen, which may be an indicator of whether the specimen can be classified as healthy or unhealthy. In the specific illustrated example, the inventors have utilised the DB10 wavelet on downsampled data reduced by a factor of 100 to handle the original data's excessive length. Upon closer examination of the prevailing bursts, it becomes evident that the healthier tree exhibits a greater abundance of high-frequency components in contrast to the unhealthier one.

[0050] Another advantage of the removable probe 30 is that if it were to become damaged, for example during insertion into or retraction from a specimen 100, or in transit between different specimens or test sites, only the relatively inexpensive probe 30 would need to be replaced rather than the entire device 10; 210. Moreover, the removable probe 30 can be left in position within a specimen 100. A user could attach the acoustic sensor surface 40a of a housing 20; 220 to the base portion 34 of the probe by bringing the housing 20; 220 into close proximity against the specimen to form the magnetic coupling. Once a test has been carried out, the acoustic sensor 40 can be separated from the probe by pulling on the housing 20; 220, and that sensor 40 can be used for another test on another specimen 100. By leaving the probe 30 in position in a specimen, consistent repeatable tests can be carried out to provide proper comparison over time.

[0051] Especially for young specimens with easily damaged trunks, a blanking plate (not shown) can be coupled to the sensing surface 40a instead of a tipped probe. The blanking plate would be in direct contact with the exterior of the specimen (e.g. directly bearing against the outer surface of the trunk) through the opening 27, and sounds within the specimen would be transmitted as vibrations across the blanking plate to the acoustic sensor. The blanking plate can be considered as a probe 30 without the tip portion; i.e. just the base portion 34.

[0052] A cover in the form of a resilient sheath (not shown) covers a majority of the housing surface. More particularly, the sheath has a circular base and a cylindrical sidewall extending therefrom that respectively extend across the back and side surfaces of the housing 20; 220. A lip portion extends inwardly at the front end of the sidewall and partially covers the front surface 25 of the housing 20; 220. The resilient sheath, typically formed of silicone, which can be stretched over the housing 20; 220 to form a snug cover, further helps to isolate the housing 20; 220 and more particularly the acoustic sensor 40 within from external background noise, by absorbing incident vibrations.

[0053] When connected to a suitable portable computing device such as a smartphone 80 programmed to receive the output signal from the acoustic sensor 40 in the device 10; 210 and to output an audio signal for listening by an operator, the device 10; 210 forms a detection kit, for example for detecting wood boring insect activity or transpiration rates of a specimen. The portable computing device 80 may be configured to process the received output signal from the acoustic sensor 40 and to output a modified audio signal for listening by an operator, for example through headphones 90 connected to the portable computing device 80 via a lead 92. Appropriate signal-processing software (e.g. a smartphone app) may be provided with the device (e.g. in the form of a download link). The processing in the portable computing device 80 may comprise at least one of amplifying and filtering the received output signal to produce the audio signal.

[0054] In one embodiment, the connection between the device 10; 210 and the portable computing device 80 is made by connecting an audio cable 47 between the audio jack socket 44 on the device 10 and a compatible audio jack socket 82 on the portable computing device 80 in a known manner. In the case of a smartphone 80 operating under the Android™ operating system, the inclusion of a 2.2kQ resistor 46 provides the optimum signals for processing by the smartphone 80.

[0055] The audio jack connection is one convenient and common form of electrical connector for connecting the device 10; 210 to the associated portable computing device 80 (e.g. mobile phone), but it will be appreciated that there are numerous other ways in which the electrical connection could be made, including other forms of physical connectors, or wireless signal transmission. Likewise, the connection between the portable computing device 80 and the associated headphones 90 may be made via a standard audio jack connection (and a splitter may be used so that both the headphone lead 92 and the connector 47 can be connected to a single audio port 82 on the device 80), or could be made by other known means, including wireless transmission. Moreover, a speaker could be used rather than headphones for listening to the output audio signal. However, headphones can be advantageous in passively (or actively) blocking out background sounds.

[0056] In use, an operator connects the device 10; 210 to an associated portable computing device 80 and, in turn, to headphones 90. The device 10; 210 is placed on a specimen 100 to be tested, by inserting the probe 30 into the specimen. Optionally, a strap (not shown) may be secured around the specimen 100 and the device 10; 210 to hold the device 10; 210 in place. This is particularly suited to embodiments where a tipless probe is used. The sensor 40 in the device 10; 210 is able to passively convert vibrations in the specimen to output signals for onward transmission to the portable computing device 80 over the connection. The portable computing device 80 thus receives the output signal from the audio sensor 40, processes that output signal and outputs an audio signal over the connection to the headphones 90 to be listened to by an operator. The operator listens to the audio signal and decides, based on experience, whether that audio signal includes a characteristic sound (frequency) indicative of the presence of, for example, wood boring insect activity within the specimen. If so, the operator can mark the specimen 100 as infested.

[0057] Because it has been recognised that the human auditory cortex has a working memory of approximately 5 minutes during which time recently heard sounds are retained, the inventors have determined that by providing for the operator to listen to a sound recording containing a characteristic sound (e.g. of fibres being crunched at the characteristic frequency for a particular larva) within that time frame, the operator is effectively ‘primed’ to recognise that characteristic sound within the subsequently heard audio signal, thereby increasing the chances of correctly identifying the presence (or absence) of an insect within the specimen. Thus, the operator can listen to a ‘pure’ sound recording of the insect activity to be identified immediately prior to listening to the output signal from the device 10; 210. The ‘pure’ sound recording may have been made under controlled conditions, such as in a laboratory setting, to ensure that it is substantially free from unwanted background noise. It may also have been subject to signal processing for the same purpose. Such ’pure’ recordings therefore have a minimal amount of noise (as opposed to useful signal) and are typically stored in the device 80 (e.g. in a non-volatile memory), and can be accessed for playback for example through user-selection within an app. The output signals from the device 10; 210 may also be stored to memory in the device 80 for subsequent recall and analysis. It will be understood that the sound recordings (both the ‘pure’ recording and recordings made in the field by the detector) may alternatively be stored remotely.

[0058] Whereas described by reference to use in the field, the output signal from the device 10; 210 may also or instead be stored for off-site analysis. This may be particularly beneficial in the case of analysis of the signals for transpiration rates indicative of specimen health, which may not be immediately discernible to a human operative’s ear.

[0059] Overall, the configuration of the housing 20; 220 and the resilient mount 50, as well as the optional outer sheath, provide for particularly good acoustic properties; providing physical elements that filter out much of the background noise so that substantially only noises emanating from within the specimen 100 (i.e. the characteristic crunching sound produced by the insects chewing on fibres in the specimen) are picked up by the acoustic sensor 40 and therefore, output to be heard by an operator of the device 10; 210.

[0060] Whereas the exemplary removable coupling of the probe 30 and the acoustic detector 40 has been described in terms of a magnetic coupling, and in particular one in which one or more magnets are located in the housing 20; 220, it will be understood that alternative arrangements are conceivable. By way of example, the one or more magnets could instead be incorporated into the base portion 34 of the probe, with a suitable ferromagnetic member located in the housing 20; 220 to form the coupling. The ferromagnetic member could be incorporated into the acoustic sensor 40 itself. In other embodiments, non-magnetic removable coupling could be employed, for example via a suitable mechanical interface between the base portion 34 of the probe and the acoustic sensor 40. However, the described magnetic coupling is both inexpensive and robust and allows the probes 30 to take a very simple form.

[0061] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0062] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0063] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

1. A modular acoustic sensor device for detecting sounds in a specimen, the device comprising:a housing defining a hollow interior chamber and including an opening connecting the interior chamber to the exterior;an acoustic sensor mounted within the interior chamber, whereby a sensing surface of the acoustic sensor faces the exterior through the opening; anda probe comprising a base portion and a tip portion;wherein the probe is removably coupled to the acoustic sensor such that when coupled the base portion is in direct contact with the sensing surface and the tip portion projects through the opening for insertion into the specimen; and.wherein when in use the tip portion is inserted into the specimen, sounds within the specimen are transmitted as vibrations along the probe to the acoustic sensor, which converts those vibrations to an output signal.

2. A modular acoustic sensor device for detecting sounds in a specimen, the device comprising:a housing defining a hollow interior chamber and including an opening connecting the interior chamber to the exterior;an acoustic sensor mounted within the interior chamber, whereby a sensing surface of the acoustic sensor faces the exterior through the opening; anda tipless probe comprising a base portion;wherein the probe is removably coupled to the acoustic sensor such that when coupled the base portion is in direct contact with the sensing surface and a portion projects through the opening for attachment against the specimen; and.wherein when in use the probe is attached to the specimen, sounds within the specimen are transmitted as vibrations across the probe to the acoustic sensor, which converts those vibrations to an output signal.

3. The device of claim 1 or claim 2, wherein the probe is removably coupled to the acoustic sensor via a magnetic coupling.

4. The device of claim 3, wherein the magnetic coupling comprises at least one magnet mounted to the acoustic sensor on an opposed side to the sensing surface.

5. The device of claim 4, wherein at least the base portion of the probe comprises ferromagnetic metal.

6. The device of any preceding claim, further comprising a resilient, isolating mount between the sensor and the housing.

7. The device of any preceding claim, wherein the sensor is a piezoelectric sensor.

8. The device of any preceding claim, further comprising a resistor connected inparallel with the sensor, wherein the resistor has a resistance in the range: 1kQ to 60kQ; preferably 1kD to 10kQ; more preferably 2.2kQ.

9. The device of any preceding claim, wherein the housing is cylindrical.

10. The device of any preceding claim, further comprising a resilient sheath covering atleast a majority of the housing surface.

11. The device of any preceding claim, further comprising an electrical output connector to form an electrical connection with a mating electrical input connection of a portable computing device for the transmittal of the output signal to the portable computing device.

12. The device of claim 11, wherein the electrical output connector comprises an audio jack.

13. The device of any preceding claim, further comprising a microprocessor within the chamber for processing the output signal.

14. The device of any preceding claim, for use in detecting wood boring insects, and wherein the specimen comprises a palm tree.

15. The device of any preceding claim, for use in detecting transpiration, and wherein the specimen comprises a palm tree.

16. A detection kit comprising:the device of any preceding claim; anda portable computing device configured to receive the output signal from the acoustic sensor in the device and to output an audio signal for listening by an operator.

17. A method of detecting sounds within a specimen, comprising:providing a device according to any of claims 1 to 15;inserting the probe into or attaching the probe against the specimen;forming a communication connection between the device and a portable computing device, whereby the portable computing device receives the output signal from the audio sensor;processing the output signal in the portable computing device; andanalysing the processed signal to determine whether that signal is indicative of a characteristic sound to be detected.

18. The method of claim 17, wherein the processing in the portable computing device comprises at least one of amplifying and filtering the received output signal.

19. The method of claim 17 or claim 18, wherein analysing the processed signal to determine whether that signal is indicative of a characteristic sound comprises determining if frequencies in the output signal are indicative of the presence of wood boring insect activity within the specimen.

20. The method of any of claims 17 to 19, wherein analysing the processed signal to determine whether that signal is indicative of a characteristic sound comprises determining if frequencies in the output signal are indicative of transpiration within the specimen.

21. The method of any of claims 17 to 20, further comprising:outputting an audio signal for listening by an operator; andwherein analysing the processed signal comprises the operator listening to the audio signal and deciding whether that signal includes a characteristic frequency.

22. The method of any of claims 17 to 21, further comprising:selecting a probe having a tip length suitable for the specimen under test; andcoupling the selected probe to the acoustic sensor.

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