NO348147B1

NO348147B1 - A device, system and method for acoustic impedance adaptation

Info

Publication number: NO348147B1
Application number: NO20230113A
Authority: NO
Inventors: Sanat Wagle; Kamal Raj Chapagain; Werner Bjerke; Jan Hjermstad
Original assignee: Elop Tech As
Priority date: 2023-02-06
Filing date: 2023-02-06
Publication date: 2024-09-02
Also published as: NO20230113A1; WO2024167415A1

Description

A device, system and method for acoustic impedance adaptation

Technical field

The present disclosure relates to a device for emission and reception of acoustic signal to and from a test material, a system for acoustic signal emission and reception of acoustic signal and a method for emitting and receiving of acoustic signal for enabling analysis of a test material. More specifically, the disclosure relates to a device for emission and reception of acoustic signal to and from a test material, a system for acoustic signal emission and reception of acoustic signal and a method for emitting and receiving of acoustic signal for enabling analysis of a test material as defined in the introductory parts of the independent claims.

Background art

A problem with the solutions of the prior art is that investigating constructions for material changes/deteriorations using ultrasound emission and reception is that the ultrasound signals weakens and reflects due to acoustic mismatch of various elements in the signal path. The signal to noise ratio, SNR, tends to be too low to be able to exploit the received signals to its fullest extent.

In US 2017 /0292936 Al it is shown a method, system, and device for ultrasonic signal emission and reception of reflected ultrasonic signal enabling nondestructive analysis of solid material such as in roads, bridges, and other constructions.

In US 2019/0162703 Al it is shown a device, system and method for emission and reception of ultrasonic signal to and from a test material, wherein the device comprising one or more wheel assemblies wherein each wheel assembly further comprising: one or more transducers arranged partially or completely embedded in a coupling medium/partial or complete inner ring.

There is thus a need for improved instruments to solve the problem and provide a signal path with an improved SNR ratio.

Summary

It is an object of the present disclosure to mitigate, alleviate or eliminate one or more of the aboveidentified deficiencies and disadvantages in the prior art and solve at least the above mentioned problem. According to a first aspect there is provided a device for emission and reception of acoustic signal to and from a test material, the device comprising one or more wheel assemblies wherein each wheel assembly comprising: one or more broad frequency range transducers, arranged with a backing and a propagating medium, the transducer being coupled in a static nonmoving position to an axle, the device further comprising one or more rotating tire sections, the tire section comprising an encircling tube section and an elastomer ring encircling the tube section, the tire section being arranged around the broad frequency range transducers and axle, and the elastomer ring including fillers for changing the acoustic impedance of the elastomer ring, the fillers being metal, and/or metal compounds, and/or chemical compounds, particles.

One of the main contributors to the challenging SNR is the great difference in the acoustic impedance levels of the various segments lying in the acoustic path from transmitter to receiver. The present discloser has investigated ways to reduce or eliminate these differences in acoustic impedance and thus reduce or solve the problem. Using metal, and/or metal compounds, and/or chemical compounds, particles as fillers in the elastomer ring provides a means to alter the acoustic impedance.

According to some embodiments, the frequency range of the broad frequency range transducers range is chosen to be in a subrange of between 20kHz to 1MHz.

Although the embodiments discussed is related to examination of concrete installations such as buildings, floors, bridges, and the like, the present disclosure also provides a way to investigate installations and materials such as constructions made of wood, such as in buildings, floors, and bridges, or even composite materials comprising but not limited to reinforced concrete and masonry, composite wood such as plywood, reinforced plastics, such as fibrereinforced polymer or fiberglass, ceramic matrix composites (composite ceramic and metal matrices), and metal matrix composites, for example used in shipping, industry, windmill industry and others.

According to some embodiments, when the test material is concrete, the frequency range of the broad frequency range transducers is chosen to be in a subrange of between 20kHz to 250kHz, or when the test material is wood, the frequency range of the broad frequency range transducers is chosen to be in a subrange of between 20kHz to 500kHz, or when the test material is a composite material, the frequency range of the broad frequency range transducers is chosen to be in a sub range of between 20kHz to 1MHz ;

According to some embodiments, the propagating medium of the one or more broad frequency range transducers is a lens/waveguide arranged at the distal end of the broad frequency range transducers, pointing towards the inward facing surface of the orbital outer ring.

The propagating medium may be of a fluid or solid material, or a combination of the two. In present disclosure the propagating medium is chosen or modified to represent a required acoustic impedance. Examples of solid material is a lens/waveguide of a material such as a polymer. Example of a fluid propagating medium is Glycerine, Glycol or similar.

According to some embodiments, the metal fillers included in the elastomer ring and/or the tube, and/or the propagating medium and/or the backing is one or more of:, Tungsten, Alumina, Titanium dioxide, steel, iron, copper, superalloy, Molybdenum, Silicon carbide, Hafnium Nitride, Iridium, beryllium, Ruthenium, Osmium, carbon, graphene, and diamond.

According to some embodiments, the metal fillers included in the elastomer ring and/or the tube, and/or the propagating medium and/or the backing is Tungsten.

Fillers used in the present disclosure fulfils multiple tasks. Using Tungsten provides a raised level of acoustic impedance with low relative portion when mixed with an elastomer.

According to some embodiments: the particles of the Tungsten is of a size less than 5 µm, for minimizing attenuation effects.

The smaller the size of the particles are, the higher frequency may be transmitted through the elastomer with low attenuation rate. It is a correlation between the attenuation rate of a wavelength of the acoustic signal and the size of the particles used to raise the impedance level of the elastomer.

According to some embodiments, the acoustic impedance of the elastomer ring and/or the tube, and/or the propagating medium and/or the backing is changed, by including a fraction of metal, and/or metal compounds, and/or chemical compounds, particles, to minimize differences in acoustic impedance compared to the acoustic impedance of the transducers.

According to some embodiments, the acoustic impedance of the elastomer ring and/or the tube, and/or the propagating medium and/or the backing is changed, by including a fraction of metal, and/or metal compounds, and/or chemical compounds, particles, to minimize differences in acoustic impedance compared to the acoustic impedance of the test material.

It is thus provided a solution to reduction of the acoustic impedance path by optimizing the various elements in the path to the transducers, or in some instances it may be advantageous to optimize the elements in the path to the test material.

According to some embodiments, the acoustic impedance of the elastomer ring, the tube, and the propagating medium is changed, by including fractions of metal, and/or metal compounds, and/or chemical compounds, particles, such that the acoustic impedance variation along an impedance path between transmitting broad frequency range transducer via the test material and receiving broad frequency range transducer is minimized by being provided to be closer to the impedance level of one or both of the broad frequency range transducer and the test material.

According to some embodiments, the acoustic impedance of the elastomer ring, the tube, and the propagating medium have a maximum variation of 50% of the impedance level of the broad frequency range transducers and/or the test material.

In some embodiments it is not possible to eliminate variations in the acoustic impedance level of the various portions of the acoustic impedance path, and therefore it is a task to minimize the differences of acoustic impedance of some or most portions of the path to reduce the attenuation level.

According to some embodiments, the tire section has an outward surface of the shape of one of: circular, flat, superellipse, convex or concave parabola, narrow or wide grooves, or triangular.

According to some embodiments, the tire section has an outward surface of the shape of one of: circular, superellipse, convex, or triangular.

Some shapes of the elastomer used in the tire sections has been more advantageous to use, specifically in the task of increasing the contact between the elastomer of the encircling elastomer ring and the test material.

According to some embodiments, the outward surface shape of the tire section is selected from a table defining relation between two or more of: amplitude, SNR and signal integrity.

According to some embodiments, the amount of included metal particles in the elastomer ring is adapted to a predefined Shore hardness.

According to some embodiments, the predefined Shore hardness is defined by a Shore 00 scale value < 20.

The Shore hardness must be low enough to provide a good adaptability of the wheel to uneven elements of the test material to increase the contact area between the encircling elastomer ring and the test material.

According to some embodiments, the predefined Shore hardness is altered by adding a softener to lower the Shore value of the elastomer ring, thereby facilitating the elastomer ring to better maintain contact to an uneven surface of a test material.

The filler increasing the acoustic impedance also raises the Shore hardness of the material, and when used in the elastomer wheel it has been found that softeners may be used to compensate and bring the Shore hardness down to an acceptable level.

According to some embodiments, the resulting Shore hardness and/or shape of the elastomer ring and/or the pressure imposed on the wheels are adapted to provide a contact footprint between the elastomer ring and the test material that improves the beam spread in terms of uniformity and/or SNR (signal to noise ratio)/SIR (Signal to interference ratio), and/or signal utilization.

According to a second aspect there is provided a system for acoustic signal emission and reception of acoustic signal, comprising: one or more device/wheels assemblies according to the above described embodiments, a carriage to which the one or a plurality of devices/wheels assemblies are mounted, a control mechanism for steering the carriage along a path over the surface of a test material, and control logic for powering and controlling the broad frequency range transducers, storing data, and/or communication of data.

According to some embodiments, the system further comprises navigation means for providing absolute position of the carriage.

According to some embodiments, the system further comprises display means.

According to some embodiments, the system further comprises tracking means for providing relative position.

According to some embodiments, the system further comprises computer means for receiving acoustic signal data and for processing the acoustic signal data.

According to some embodiments, the computer means are remote computer means.

According to a third aspect there is provided a method for emitting and receiving of acoustic signal for enabling analysis of a test material, the method comprises the step of: providing one or a plurality of systems according to any of the above described system embodiments, emitting acoustic signals from a transducer; receiving reflections of the emitted acoustic signals from the test material with one or a plurality of broad frequency range transducers ; storing and/or transferring the received acoustic signal data to a computer means and analysing the received acoustic signals.

According to some embodiments, the method further comprises the step of: moving the carriage along a predefined path; emitting acoustic signals from individual broad frequency range transducers according to a predefined emission pattern; receiving the reflected acoustic signal from the test material with one or a plurality of broad frequency range transducers configured to be receiving the individual emitted acoustic signal.

According to some embodiments, the method further comprises to compare the result of the analysis of a section of a test material with a previous analysis of the same section of the test material, and to identify changes in the test material.

Effects and features of the second and third aspects are to a large extent analogous to those described above in connection with the first aspect. Embodiments mentioned in relation to the first aspect are largely compatible with the second and third aspects.

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 disclosure.

Hence, it is to be understood that the herein disclosed disclosure is not limited to the particular component parts of the device described or steps of the methods described since such device and method may vary. It is also 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 claim, 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 words "comprising", "including", "containing" and similar wordings does not exclude other elements or steps.

Terminology

When the term “transducer” is used it shall be understood to encompass transmitting and/or receiving acoustic transducers, and/or combined transmittingreceiving acoustic transducers of any type.

When the term “acoustic signal” is used it shall be understood to cover all type of acoustic and ultrasound signals.

The terms “propagating medium”, “lens”, “waveguide” is used in different embodiments, but it shall be understood that any of these may be used in any of the embodiments substituting the one mentioned.

Brief descriptions of the drawings

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.

Figure 1 shows a cross section of an embodiment of the present disclosure showing the wheel assembly transmitting an acoustic signal through a test material and being received by a receiving wheel assembly.

Figure 2 shows a diagram of the impedance path between the sending and receiving transducers with backing.

Figure 3 shows a diagram showing the relation between acoustic impedance, mass density, and velocity for Tungsten.

Figure 4 show various profiles of the encircling elastomer ring

Figure 5 show some detailed aspects/ratios of the profile.

Figure 6 shows the relation between pressure put on the encircling elastomer ring and the receiving signal amplitude.

Figure 7 shows a further diagram of the impedance path between the sending and receiving transducers with backing, wherein the propagating medium is a lens or waveguide.

Figure 8 illustrates a wheel assembly according to present disclosure.

Figure 9 is pictures and figures of an embodiment and wheel assembly of the present disclosure.

Figure 10 shows diagrams of the signal path either in a longitudinal to the moving direction signal path or a perpendicular to the moving direction signal path.

Figure 11 shows different footprints of the elastomer rings on test material.

Detailed description

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 to fully convey the scope of the disclosure to the skilled person.

Figure 1 shows a cross section of an embodiment of the present disclosure showing the wheel assembly transmitting an acoustic signal through a test material, the acoustic signal being reflected by the test material and received by a receiving wheel assembly. Figure 2 shows the corresponding acoustic impedance level in the acoustic signal path through the various elements between the sending and receiving transducers with backing.

The first aspect of this disclosure shows a device 100 for emission and reception of acoustic signal to and from a test material 15, the device 100 comprising one or more wheel assemblies 110 wherein each wheel assembly 110 comprising: one or more broad frequency range transducers 20,20’, arranged with a backing 97,97’ and a propagating medium 52, the transducer 20,20’ being coupled in a static nonmoving position to an axle 22, the device 100 further comprising one or more rotating tire sections 23, 23’, 26, 29, 29’, the tire section 23, 23’, 26, 29, 29’ comprising an encircling tube section 26 and an elastomer ring 23, 23’ encircling the tube section 26, the tire section 23, 23’, 26, 29, 29’ being arranged around the broad frequency range transducers 20,20’ and axle 22, and the elastomer ring 23 including fillers 23’ for changing the acoustic impedance of the elastomer ring 23, 23’, the fillers 23’ being metal, and/or metal compounds, and/or chemical compounds, particles.

When more than one tire sections are comprised in a wheel assembly 110, the transducers 20, 20’ may be arranged on one longer axle 22, and all or some of the multiple elastomer rings 23, 23’ may be arranged to encircle one longer tube section 26, the one longer tube section encircling all or some of the transducers 20, 20’.

The acoustic impedance of the transmitting transducer 20 and the receiving transducer 20’ may be different. In such an embodiment where the acoustic impedance of the transducers 20, 20’ are not the same, this may be mirrored in the fillers 23’ included in any of the backing 97,97’, the propagating medium 52, the tube section 26, and the encircling elastomer ring 23. The acoustic impedance path is then on each side of the test material optimized relative the corresponding side transducer.

Typically two or more transducers 20, 20’ are mounted inside the wheel assembly 110, for example, and typically each transducer 20, 20’ send/receives the acoustic signal to/from the test material 15 through all the portions of the acoustic signal path as shown in figure 2, via the propagating medium 52, a portion of the tube 26, corresponding elastomer ring 23, 23’ of the sending portions of the path, and back through the same elements belonging to the receiving portions of the path. Such that when for example a wheel assembly 110 has 8 transducers there is 8 elastomer rings, one for each transducer. In some embodiments more or fewer (one elastomer ring covering the width of several transducers) elastomer rings may be provided for each transducer.

The transducer is typically arranged connected to a backing 97, 97’, the backing being advantageously selected or modified to have the same impedance level as the transducer. The task for the backing is to dampen and prevent reflections to/from areas and directions not in the desired acoustic signal path. The backing may for example be composed of epoxy with Tungsten filler to achieve the same impedance level as the transducer.

The transducers 20, 20’ may have different properties dependent on if it is a transmitting transducer 20 or a receiving transducer 20’.

The elastomer rings 23, 23’are mounted to the tube 26 and arranged on a tube section in a radial position in line with a corresponding transducer 20, 20’ as can be seen in figure 8A. The lower part of the figure shows one possible embodiment of the axle 22 and 10 transducers 20, 20’ arranged on the axle, the axle and the arranged transducers are comprised inside the wheel assembly 110 shown in the upper portion of the figure.

Additionally stopper rings 29 may be arranged around the tube 26. These stopper rings 29 may be arranged between some or all elastomer ring 23, 23’to facilitate for some expansion room for the contact area between the elastomer and the test material when pressure is applied to the wheel assembly under use. The stopper rings 29’ may be arranged on the outer side of each distal elastomer ring 23, 23’to keep the elastomer rings 23, 23’in place relative the transducers 20, 20’. A further embodiment have only stopper rings 29 arranged on the outer side of each distal elastomer ring 23.

In one embodiment of present disclosure there are provided for that one wheel assembly comprise transmitting transducers 20 only, and another wheel assembly comprising receiving transmitters 20’ only, such that when a carriage is assembled with two wheel assemblies there is one transmitting wheel 110 assembly and one receiving wheel assembly 110, such as illustrated in figure 9A to figure 9D, and figure 10A. Acoustic signals propagates in a longitudinal to the moving direction to be received by the receiving transducer.

In a further embodiment of present disclosure there are provided for that one wheel assembly comprise transmitting 20 and receiving transducers 20’ such that when a carriage is assembled with two wheel assemblies there is a variation of transmitting portions of the wheel assembly and receiving portions of the same wheel assembly 110, such as illustrated in figure 9A to figure 9D, and figure 10B. Acoustic signals propagates in a perpendicular to the moving direction to be received by the receiving transducer.

Also, when emitting acoustic signals the reflections may be received by some or all other receiving transducers, also diagonally between transducers in the wheel assemblies 110.

The frequency range of the broad frequency range transducers 20,20’ range may be found in the range between 20kHz to 1MHz, wherein when the test material 15 is concrete, the frequency range of the broad frequency range transducers 20,20’ range is between 20kHz to 250kHz, or when the test material 15 is wood, the frequency range of the broad frequency range transducers 20,20’ range is chosen to be in a subrange of between 20kHz to 500kHz, or when the test material 15 is a composite material, the frequency range of the broad frequency range transducers 20,20’ range is chosen to be in a subrange of between 20kHz to 1MHz;

The frequency range of the broad frequency range transducers 20,20’ range chosen to be in a subrange of between 20kHz to 250kHz is related to examination of concrete installations such as buildings, floors, and bridges. Concrete has a high impedance level, typical 10 MRayl.

The frequency range of the broad frequency range transducers 20,20’ range is chosen to be in a subrange of between 20kHz to 500kHz is related to investigating installations and materials such as constructions made of wood, such as buildings, floors, and bridges. Wood has a medium impedance level, typical 1,52,5 MRayl.

The frequency range of the broad frequency range transducers 20,20’ range being in a sub range between 20kHz to 1MHz is related to examination of composite materials comprising but not limited to reinforced concrete and masonry, composite wood such as plywood, reinforced plastics, such as fibrereinforced polymer or fiberglass, ceramic matrix composites (composite ceramic and metal matrices), and metal matrix composites.

The propagating medium 52 may be of a fluid or solid material, or a combination of the two. In present disclosure the propagating medium is chosen or modified to represent a required acoustic impedance. Examples of solid material is a lens/waveguide of a material such as a polymer. Example of a fluid propagating medium is Glycerine, Glycol or similar. If a solid material propagating medium is used, it may be additional be provided a thin layer/level of fluid with acoustic properties around the solid lens/waveguide to ensure proper contact between the lens/waveguide and the tube.

In a further embodiment of present disclosure the propagating medium 52 of the one or more broad frequency range transducers 20,20’ is a lens/waveguide arranged at the distal end of the broad frequency range transducers 20,20’, pointing towards the inward facing surface of the orbital outer ring. The lens/waveguide may comprise a surface 54 which will be brought in contact with the inside of the tube 26, the surface having a lubricating formula, or be of a low friction dry material having required acoustic properties. Such material may for example be ROBALON<®>, or any type of polymer or polytetrafluoroethylene (PTFE), graphite, hexagonal boron nitride, molybdenum disulfide, tungsten disulfide, metal alloys, PVDF or strongly hydrated brush polymers, or others.

In a further embodiment of present disclosure the metal fillers 23’ included in the elastomer ring 23, 23’and/or the tube 26, and/or the propagating medium 52 and/or the backing 97 is one or more of: Tungsten, Alumina, Titanium dioxide, steel, iron, copper, superalloy e.g. Inconel, Molybdenum, Silicon carbide, Hafnium Nitride, Iridium, beryllium, Ruthenium, Osmium, carbon, graphene, and diamond, or other.

In an advantageous embodiment the metal fillers 23’ included in the elastomer ring 23, 23’and/or the tube, and/or the propagating medium 52 and/or the backing, is Tungsten.

A material such as Tungsten is chosen as filler, in the portions of the wheel assembly 110 where the acoustic signal propagates between transducer and test material, because of its ability to raise the volume weight of a compound, and hence the impedance level, with less volume ratio Tungsten/mixing material. For the elastomer ring this is found to be of specific importance. The lower the volume ratio of filler is used for reaching the required volume weight, the better it will maintain the elasticity of the compound. This is a significant feature of the elastomer for improving/maintaining the contact between the elastomer and the surface of the test material.

Further it is found that the particles of the Tungsten may be of a size less than 5 µm, for minimizing attenuation effects on the acoustic signal path. The particle size in the acoustic signal path between transmitting and receiving transducer is chosen to be small compared to the wavelength of the acoustic signal in order to minimize signal scattering. This is in contrast with the case concerning the backing which advantageously will comprise fillers increasing the scattering effects, for example by comprising larger particle sizes.

An example of the acoustic impedance path is shown in figure 2, wherein the test material is concrete. The aim of the fillers is to change the impedance level of each portion of the acoustic signal path.

Acoustic impedance is given by product of speed of sound in the material and mass density of the material. The unit is Rayl. For example, speed of sound in water is 1500 m/s with mass density of 1000 kg/m<3 >which gives acoustic impedance of 1.5 MRayl. Acoustic impedance of concrete is about 10 MRayl and the transducer in this example is about 34 MRayl.

When acoustic impedance of the elements in the acoustic path (Backing 97, 97’, Transducer 20, 20’, Propagating medium 52, tube 26, elastomer 23) is provided to be in the same range improves the acoustic energy transfer with less ringing.

Typical material used in the various portions of the acoustic path is: for backing for example a mix of epoxy and Tungsten, for transducer for example a polymer such as PVDF, for propagating medium typically a polymer or a fluid with acoustic properties, the tube for example a polymer based hard material, and the coupling portion of the wheel for example an elastomer. All or some of the various parts may be impedance altered with fillers as discussed. Other material serving the same purposes may be used.

It is in one embodiment a goal to alter the acoustic impedance of the elastomer to be in the same range as that of the transducer of 34 MRayl. This can be seen in figure 2 as the shaded field, where one type of filler is added to the material of the propagating medium, one type of filler is added to the material of the tube, and one type of filler is added to the material of the coupling/elastomer to alter the acoustic impedance of propagating medium, tube and the elastomer to be closer to the transducer and the backing. The ideal scenario is that there are no jumps in the acoustic impedance path between transmitting and receiving transducer, or as few significant interfaces that change the acoustic impedance considerably.

The present disclosure provides for such a scenario wherein the acoustic impedance path is optimized towards least possible attenuation of the acoustic signal. The acoustic impedance of the elastomer ring 23, 23’and/or the tube 26, and/or the propagating medium 52 and/or the backing is changed, by including a fraction of metal, and/or metal compounds, and/or chemical compounds, particles, to minimize differences in acoustic impedance compared to the acoustic impedance of the transducer.

In one embodiment the focus of present disclosure is to use only single sided impedance matching to adapt the internal coupling materials (and elastomer) to the transducer to achieve improved signal path with less internal reflections from interfaces with acoustic mismatch. This way it is avoided to attempting any quarterwave matching to the test object (e.g. concrete) as it is not feasible to achieve this with deformable elastomers. Thus techniques of prior art arranged to utilize such quarterwave matching is not the focus of the technique of present disclosure.

In a different scenario wherein the test material is not concrete, but for example wood having a much lower acoustic impedance level than concrete. It may then be advantageous to change the acoustic impedance of the elastomer ring 23, 23’to the test material 15. It may also be advantageous in the same embodiment to change the acoustic impedance of the tube 26 to be more like the transducer 20, 20’. In such a way there will be a significant acoustic impedance interface between the tube 26 and the elastomer ring 23, 23’. In an even further embodiment one could match the impedance level of the elastomer ring 23, 23’, the tube 26, and the propagating medium 52 to the test material, and such provide the one significant impedance interface between the transducer 20, 20’ and the propagating medium 52 only. The acoustic impedance of the elastomer ring 23, 23’and/or the tube 26, and/or the propagating medium 52 and/or the backing is changed, by including a fraction of metal, and/or metal compounds, and/or chemical compounds, particles, to minimize differences in acoustic impedance compared to the acoustic impedance of the test material and/or the transducer.

The acoustic impedance of the elastomer ring 23, 23’, the tube 26, and the propagating medium 52 is provided, by including fractions of metal, and/or metal compounds, and/or chemical compounds, particles, such that the acoustic impedance variation along an impedance path between transmitting broad frequency range transducer 20 via the test material 15 and receiving broad frequency range transducer 20’ is minimized by being provided to be closer to the impedance level of one or both of the broad frequency range transducer 20,20’ and the test material.

Even if it is possible to increase the acoustic impedance of the elastomer ring 23, 23’ to a higher level, also the same as concrete, as seen in the table in figure 3 illustrating ratios with Tungsten filler, there is a practical limitation to how large portion of fillers may be used. This is related to that the elasticity and strength of the elastomer ring deteriorate when the volume ratio of filler becomes too high. When the Shore 00 value of the elastomer ring moves above 20 it starts to be harder and lose the ability to adapt to the surface of the test material 15, and then the propagating acoustic signal quality quickly deteriorate.

Thus there has been found that attenuation of the signal may be acceptable in a scenario wherein the acoustic impedance of the elastomer ring 23, the tube, and the propagating medium 52 have a maximum variation of 50% of the impedance level of the broad frequency range transducers 20,20’ and/or the test material.

There will be differences of the impedance level at each side of any interface, although, when matching the impedance path to the transducer, keeping the differences to a point where no element on each side of the test material is within 50% of the transducer is advantageous.

When matching the impedance path to the test material, keeping the differences to a point where elements close to each side of the test material is within 50% of the test material is advantageous.

It is also a strong correlation between the pressure applied to the elastomer ring 23, 23’and the received signal strength as shown in figure 6A. It can be seen that a pressure of 1,5 kg on a circular, parabolic, or triangular profile gives a good response amplitude when looking at the mVpp values. It is recognized that a softer elastomer ring, with lower Shore 00 value, will require less pressure to achieve satisfying amplitude reception.

This is related to both the manner in which the elastomer may be filling any groves or squeeze out air pockets between the elastomer ring and the test surface, as well as to what form the interface footprint between the elastomer and the test material becomes. An elongated elliptical form is not as good as a uniform circular form.

Thus there is provided for an elastomer ring profile having a better performance when pressure is applied to the wheel assembly/elastomer ring.

Figure 4A to figure 4G discuss various elastomer ring profiles and their capability to provide a less attenuating path for the acoustic signal. In figure 4A to Figure 4F only the right half side of the profile is shown. Figure 4G shows a full triangular elastomer profile.

The tire section has an outward surface of the shape of one of: circular, flat, superellipse, convex or concave parabola, narrow or wide grooves, or triangular as shown in figure 4A to figure 4G. More advantageously the tire section has an outward surface of the shape of one of: circular, superellipse, convex, or triangular as shown in figure 4A, 4C, 4F and 4G respectively.

A convex curved surface will adapt more easily to cavities/unevenness in the test surface when pressure is applied to wheel.

In figure 5 it is exemplified a parabola profile.

The outward surface shape of the tire section is selected to optimize the relation between two or more of: amplitude, SNR and signal to interference ratio (SIR).

The amount of included metal particles in the elastomer ring 23, 23’ is adapted to a predefined Shore hardness, and the preferred Shore hardness is selected by a Shore 00 scale value < 20.

The Shore hardness is altered by adding a softener to lower the Shore value of the elastomer ring 23, thereby facilitating the elastomer ring 23, 23’ to better provide contact to an uneven surface of a test material.

The Shore hardness is chosen to be low enough to provide an improved ability of the elastomer ring to “embrace” or fill uneven elements of the test material and thus maintain the contact area between the encircling elastomer ring and the test material also when the surface test material is not smooth.

The filler increasing the acoustic impedance also increase the Shore hardness of the material, and when used in the elastomer ring 23, 23’ it has been found that softeners may be added to the elastomer compound for bringing the Shore hardness down to an acceptable level but at the same time keeping the intended impedance level.

A test surface of concrete will typically have many uneven spots, protrusions and grooves, and the test surfaces may also not be clean. It is therefore important that the provided Shore hardness satisfy requirements to adaptation to rough surfaces and displacement of air, robustness (abrasion/tear strength), and prevention of stickiness to prevent dust and dirt.

The resulting Shore hardness and/or shape of the elastomer ring 23, 23’ and/or the pressure imposed on the wheels are adapted to provide a contact footprint between the elastomer ring 23, 23’ and the test material that improves the beam spread in terms of uniformity that is characterized by the circularity of the footprint and/or SNR/SIR, and/or signal utilization that is characterized by the size of footprint. The stopper rings 29 play an additional role in this task to space the elastomer rings 23, 23’ apart providing some space for the footprint of the elastomer ring towards the test material to change form from elliptical to circular when pressure is applied to the wheel assemblies. Figure 11A shows a wheel assembly 110 footprints between elastomer ring 23, 23’ on test material when no pressure is applied to the wheel assembly 110 showing more oval footprints, and figure 11B shows a wheel assembly 110 footprints between elastomer ring 23, 23’ on test material when pressure is applied to the wheel assembly 110 showing more uniform circular footprints.

The second aspect of this disclosure shows a system for acoustic signal emission and reception of acoustic signal, the system comprising: one or more device 100/wheels assemblies 110 according to the first aspect, a carriage to which the one or a plurality of device 100/wheels assemblies 110 are mounted, a control mechanism for steering the carriage along a path over the surface of a test material, and control logic for powering and controlling the broad frequency range transducers 20,20’, storing data, and/or communication of data.

The device in Figure 9E, or any variations of a device of the present disclosure, may have on board or attachable, via cable, induction or wireless communication access to: energy source, data storage, control logic, input and output control ports, display and audio.

Indication lights may be comprised in this system as well as in all versions of embodiments of the device 100 of the present disclosure.

The carriage may comprise means for driving the carriage, e.g. an electromotor (not shown), remote controller features, and further comprise energy source or sources, handles 205 for manually pushing and/or steering the carriage and means for wireless communication with an external control unit (not shown).

The control unit may be preprogrammed to guide the carriage to cover all segments of the test material as illustrated in figure 9F. Here a real life representation show the carriage position 200, the direction of movement 211, and the areas that have 212, 213, 214/ have not yet 215 been inspected. It may even be possible to distinguish between previous track of inspection 212, current track of inspection 213, and the overlap 214 of current track 213 of inspection relative to the previous 212 track of inspection.

By comparing the received data and the analysis result of this with the corresponding previously performed inspection, it is possible to detect changes in the underground of the test material. For example it may be possible to follow the deterioration of the reinforcement bar in a concrete bridge, and initiate corrective actions at an early stage of deterioration.

The laser unit may be used for measurement of distance in order to define the carriage position on the test material.

A wide variety of survey tasks ranging from shallow inspection to more deep surveys reaching longer into the construction material to be tested may be provided. Often there is a need to test/survey a broader depth range than possible with traditional instruments. The present disclosure provides for a solution to this in that the design of the wheel assemblies can be very flexibly arranged in modules of single wheel assembly to a multiple wheel assemblies arranged in an array mounted on an axle or on individual adapted frame connection arrangements. Such an embodiment is indicated in figure 9A 9B, 9C, 9D, 9E and 9F, where wheel assemblies of the type discussed in figure 8A to figure 8D is individually arranged on corresponding ball bearing connectors 72 to a frame 70, 71, and depending on transducer configuration enabling a survey that can span several depth ranges simultaneously.

The transducer design will also contribute to the total characteristic of the wheel assemblies. The higher the frequency and diameter of the transducers the narrower the beam angle is, and the more directional can the sound beam be controlled. In the opposite range, for wide beam requirements surveying the near surface area, it is desirable to operate with larger spread, hence lower diameter and lower frequency will achieve this.

Figure 9AD illustrates how two wheel assemblies constituting two wheel assemblies 110 arranged on two axles 22, 22’ coupled to a frame element 71.

The wheel assemblies mounted on a carrier is illustrated in figure 9AB and 9E may be operated to send acoustic signals, receive and store received acoustic signals together with positional information calculated out from a predefined starting point by registering the movement over the test material by the rolling motion of the wheels of the device 100 of the present disclosure or other mechanisms such as for example a computer mouse device and/or rotational encoder combined with a laser (not show) or infrared measuring means or the like (not shown).

The carrier may have on board or attachable, via cable, induction or wireless communication access to: energy source, memory, control logic, input and output control ports, display 400 and audio.

Indication lights may be arranged on the frame for purposes such as indicating contact status between the device 100 and the test material, alarm status if preset signal pattern is received, or if received signal in a specific position is not valid.

Indication lights may be colorcoded, such as for example red light if no contact or green light when contact is detected between the device 100 and test material. Other colors and switching pattern may be use for different purposes. One such purpose may be as a selftest indicator to be run prior to each job. It is also possible to use lights in a calibration routine where for example the device 100 may be rolled over a known test material with a known surface with a known expected test result when transducers emit signals in line with a preset test pattern and frequencies. If expected received signal is verified the device 100 is cleared for operation.

A connected computer 500 may also be used for purposes of storing, calibration, test and evaluation of test results. Computer 500 may be connected by cable, wireless communication or by transfer of data via a storage memory device. A storage memory device may be detachably mounted to the electronic circuits in the device 100, or may be connectable via an interface at the time of a data transfer operation.

The array of transducers may be used in different modes. Two different modes are shown in figure 10A and 10B. Other modes can be utilized.

In figure 10A, it is shown a mode for alongtrack inspection. One array of transducers, e.g. comprised in the trailing wheel assembly 110, are used for emitting signals into the underground of the test material, and one array of transducers, e.g. comprised in the leading wheel assembly 110 of the present disclosure is used as receiving means for receiving the emitted signals that has traveled into and through the test material and reflected from this.

In figure 10B, it is shown a mode for crosstrack inspection. This is achieved by allocating a number of transducers in one wheel assembly 110 for emitting the acoustic signal, and a number of transducers of the same wheel assembly 110 to receive the signal when reflected from the test material. One transducer may both emit and receive. In one scenario a transducer in the peripheral section of the wheel assembly 110 is emitting signals into the underground of the test material and one or more transducers in the midsection of the wheel assembly 110 receives the reflected signals.

It is possible to use more than one wheel assembly 110 for receiving. A transducer in the trailing wheel assembly 110 may emit, whilst the two leading wheel assemblies 110 receive, or all wheel assemblies 110 may be set up to be receiving transducers were one or more wheel assemblies 110 also emit.

One likely configuration in a system comprising 3 wheel assemblies 110 and the transducers in the middle wheel assembly 110 are used for emission of acoustic signals, and the two outer arrays of transducers/ wheel assemblies 110 for receiving the reflected signal from the test material.

It is also possible to use a single wheel assembly 110 utilizing the crosstrack geometry described above to achieve good test result.

Transducers may be used for emission or reception only, or for both emission and reception. A transducer serving as both emitting and receiving transducer for the same acoustic signal, i.e. the transducer emit an acoustic signal and then wait for the reflections of the signal and then receive the reflected signal, will only receive and detect reflections from objects or the like or material in the path of the emitted signal. If the object is a small vertical crack below the transducer, the reflected signal may be very weak and difficult to detect. In the present disclosure a set of transducers will, where each transducer either emit or receive an acoustic signal, not only measure reflected signals, but also measure the signal transmitted through the test material, and thus be able to measure the lack of reflection, or for example the timeofflight diffraction. These types of measurements will provide for better S/N ratio in the measurement data. Such configuration will be able to detect the omission of a reflected signal. For example if the signal is obstructed by an air pocket in the test material, and thus the signal propagation is severely obstructed, the receiving transducer will detect that the signal is not received as expected, and a conclusion may then indicate that there is a blocking medium between the emitting and receiving transducer, such as a crack, hole, nonrelaying medium or other.

The above additional ability to detect omission of a reflection may be utilized by a single wheel assembly 110 setup of the present disclosure as explained for figure 10B above. Enhancing the analyzing effect further may be achieved with the device 100 of present disclosure by combining the feature explained in Figure 10B with the features of using more than one wheel assemblies 110 as one example of which is explained for the transducer setup in Figure 10A above. In relation to cracks, obstructions and air pockets, the different transducer setups may be optimized further to detect along track oriented cracks, air pockets, obstructions, with the cross track inspection feature as explained for figure 10B above, or across track oriented cracks, air pockets, obstructions, with the along track inspection feature as explained for figure 10A.

In one embodiment the device may be used to find delamination/air pockets in sandwich structures, such as used in ships or wings (planes, wind turbines). Such sandwich structures may be constructed of multiple layers of different materials. All with potentially different response features relative acoustic signals of specific frequencies. The device 100 of present disclosure may be controlled in a manner to optimize the response at the specific depth of the test material where a specific sandwich layer interface is located. One could for example examine the interface between the innermost glass fiber layer and the core material in a 3 layer construction comprising an inner glass fiber layer, an outer glass fiber layer and a core polystyrene layer. Other materials and other number of layers may be used.

Another example of embodiment is to use the device to detect detachments/air pockets under building tiles, such as in a bathroom floor, where the outer layer is ceramic, and the inner layer is of concrete or wood, possibly with a water tight membrane structure in between.

It is also possible to maximize detection capability by executing a regime of emission of acoustic signals and reception of reflected signal where a more complex pattern of shifting the feature of each individual transducer dynamically as the acoustic data collection is performed. One pattern would be to let each transducer in turn act as the sole emitting source of an acoustic signal, and let all transducer of all wheels (if more than one) be receiving the reflected signal. This way it is possible to map the underground in many directions from perpendicular the motion direction to both sides of the emitting transducer. One example outlining one emitting transducer and 7 receiving transducers.

One possible regime of pattern is to let all transducers in turn be the emitting transducer, and let all transducers act as receivers for reflections of an emitted signal. This way it is possible to map all test material from all angles, sideways, forwards, backwards, angled in all directions and directly below. Using the motion of the device of the present disclosure as another parameter it is possible to make several such measurements when moving over the test material. For example an air pocket in the concrete would then be thoroughly exploited from many directions several times, and no “hidden” weaknesses will be omitted.

A different regime is to allocate one or more wheel assemblies 110 as transmitting transducers, and other wheel assemblies 110 as receiving transducers, and then activate several transmitting transducers simultaneously, and receive all reflected signals with the remaining transducers operating in receiving mode.

There are no limits to the size of the arrays of transducers or the wheel assemblies 110 used.

The transducers may be selected for being used with multiple and variable frequencies.

Examples of execution regimes may include, but is not limited to, different beamforming techniques. One example of an execution regime may be SAFT (Synthetic Aperture Focusing Technique).

The more detection data that is collected, the better S/N ratio will be possible to achieve in the analysis process when data is analyzed.

Analysis of the signal data received from the test material may provide for the compilation of detailed 2D and/or 3D images of the test material at various depths below the surface of the test material, typically 0 – 15 cm below the surface of the test material.

A carriage comprising one or more wheel assemblies 110 may comprise means for driving the carriage, e.g. an electromotor (not shown), remote controller features, and further comprise energy source or sources, handles for manually pushing and/or steering the carriage and means for wireless communication with an external control unit (not shown).

The control unit may be preprogrammed to guide the carriage to cover all segments of the test material.

By comparing the received data and the analysis result of this with the corresponding previously performed inspection, it is possible to detect changes in the underground of the test material. For example it may be possible to follow the deterioration of the reinforcement bar in a concrete floor, and initiate corrective actions at an early stage of deterioration.

Although the examples given above is directed towards instruments used above ground, it shall be understood that the device 100 of the present disclosure can be adapted to be used in subsea environments, wherein the instruments are mounted on for example an ROV to inspect subsea installations, pipelines, and the like.

The system may further comprises navigation means for providing absolute position of the carriage. Thus, tracking and positioning can be planned according to a test scheme for one time examination of larger constructions, but also for recurring test regimes ascertain that the new test follows the same path as previously performed.

The system may further comprises display means, for operational interface and for displaying test results.

The system may further comprises tracking means for providing relative position.

The system further comprises computer means for receiving acoustic signal data and for processing the acoustic signal data.

The third aspect of this disclosure shows a method for emitting and receiving of acoustic signal for enabling analysis of a test material, the method comprises the step of: providing one or a plurality of systems according to any of the second aspect, emitting acoustic signals from a transducer; receiving reflections of the emitted acoustic signals from the test material with one or a plurality of broad frequency range transducers 20,20’; storing and/or transferring the received acoustic signal data to a computer means and analysing the received signal data.

The method typically starts with the tester deciding what surface and construction material is to be examined/tested. Then select a suitable polymer ring material with desired impedance level. Then initiating the instrument comprising one or more wheel assemblies 110 of a type described above.

The instrument is lead over the test material 15 where also the tester apply sufficient pressure on the instrument in order for the elastomer rings to be sufficiently pressed/compressed towards the surface of the test material 15. A pressure indicator may be comprised to identify when correct pressure is applied. The pressure ensures that the elastomer ring will get a correct contact footprint with the test material, and that air pockets under the elastomer ring is pressed out on the sides of the interface between the elastomer ring and the surface of the test material. A fluid having acoustic properties may be used as a contact fluid to enhance the signal transmission, for example a glycerine, Glycol or similar liquid layer.

The received acoustic signals are analysed and presented to the tester, either via a computer attached to the carriage, and/or via a remote computer resource.

The method further comprises the step of: moving the carriage along a predefined path ; emitting acoustic signals from individual broad frequency range transducers 20,20’ according to a predefined emission pattern; receiving the reflected acoustic signal from the test material with one or a plurality of broad frequency range transducers 20,20’ configured to be receiving broad frequency range transducers 20,20’ for the individual emitted acoustic signal.

The method further comprises to compare the result of the analysis of a section of a test material with a previous analysis of the same section of the test material, and to identify changes 150 in the test material.

The person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims.

Claims

1. A device (100) for emission and reception of acoustic signal to and from a test material (15), the device (100) comprising one or more wheel assemblies (110) wherein each wheel assembly (110) comprising: one or more broad frequency range transducers (20, 20'), arranged with a backing (97, 97') and a propagating medium (52), the transducers (20, 20') being coupled in a static non‐moving position to an axle ( 22),

the device (100) being c h a r a c t e r i z e d b y : further comprising one or more rotating tire sections (23, 23', 26, 29, 29'), the tire section (23, 23', 26, 29, 29') comprising an encircling tube section (26) and an elastomer ring (23, 23') encircling the tube section (26), the tire section (23, 23', 26, 29, 29') being arranged around the broad frequency range transducers (20, 20 ') and axle (22), and the elastomer ring (23) including fillers (23') for changing the acoustic impedance of the elastomer ring (23, 23'), the fillers (23') being metal, and/or metal compounds, and/or chemical compounds, particles.

2. The device (100) according to claim 1, wherein; the frequency range of the broad frequency range transducers (20, 20') range is chosen to be in a sub‐range of between 20kHz to 1MHz.

3. The device (100) according to claim 1 or 2, wherein; when the test material (15) is concrete, the frequency range of the broad frequency range transducers (20, 20') is chosen to be in a sub‐range of between 20kHz to 250kHz, or when the test material (15) is wood , the frequency range of the broad frequency range transducers (20, 20') is chosen to be in a sub‐range of between 20kHz to 500kHz, or when the test material (15) is a composite material, the frequency range of the broad frequency range transducers (20, 20') chosen to be in a sub‐range of between 20kHz to 1MHz;

4. The device (100) according to any of the previous claims, wherein: the propagating medium (52) of the one or more broad frequency range transducers (20, 20') is a lens/waveguide arranged at the distal end of the broad frequency range transducers (20, 20'), pointing towards the inward facing surface of the orbital outer ring.

5. The device (100) according to any of the previous claims, wherein: the metal fillers (23') included in the elastomer ring (23) and/or the tube, and/or the propagating medium (52) and/or the backing is one or more of: Tungsten, Alumina, Titanium dioxide, steel, iron, copper, superalloy (e.g. Inconel), Molybdenum, Silicon carbide, Hafnium Nitride, Iridium, Beryllium, Ruthenium, Osmium, carbon, graphene, and diamond.

6. The device (100) according to any of the previous claims 1 to 4, wherein: the metal fillers (23') included in the elastomer ring (23, 23') and/or the tube, and/or the propagating medium (52) and/or the backing is Tungsten.

7. The device (100) according to claim 6, wherein: the particles of the Tungsten are of a size less than 5 µm, for minimizing attenuation effects.

8. The device (100) according to any of the previous claims, wherein: the acoustic impedance of the elastomer ring (23, 23') and/or the tube, and/or the propagating medium (52) and/or the backing is changed, by including a fraction of metal, and/or metal compounds, and/or chemical compounds, particles, to minimize differences in acoustic impedance compared to the acoustic impedance of the transducers (20, 20').

9. The device (100) according to any of the previous claims 1 to 7, wherein: the acoustic impedance of the elastomer ring (23, 23') and/or the tube, and/or the propagating medium (52) and/ or the backing is changed, by including a fraction of metal, and/or metal compounds, and/or chemical compounds, particles, to minimize differences in acoustic impedance compared to the acoustic impedance of the test material and/or the transducers (20, 20').

10. The device (100) according to any of the previous claims 1 to 6, wherein: the acoustic impedance of the elastomer ring (23, 23'), the tube, and the propagating medium (52) is changed, by including fractions of metal, and/or metal compounds, and/or chemical compounds, particles, such that the acoustic impedance variation along an impedance path between transmitting broad frequency range transducer (20) via the test material and receiving broad frequency range transducer (20') is minimized by being provided to be closer to the impedance level of one or both of the broad frequency range transducer (20, 20') and the test material.

11. The device (100) according to claim 9, wherein: the acoustic impedance of the elastomer ring (23, 23'), the tube, and the propagating medium (52) have a maximum variation of 50% of the impedance level of the broad frequency range transducers (20, 20') and/or the test material.

12. The device (100) according to any of the previous claims, wherein: the tire assembly (23, 23', 26, 29, 29') has an outward surface of the shape of one of: circular, flat, super‐ ellipse, convex or concave parabola, narrow or wide grooves, or triangular.

13. The device (100) according to any of the previous claims, wherein: the outward surface shape of the tire assembly (23, 23', 26, 29, 29') is selected from a table defining relation between two or more of : amplitude, SNR and signal integrity.

14. The device (100) according to any of the previous claims, wherein: the amount of included metal particles in the elastomer ring (23, 23') is adapted to a predefined Shore hardness.

15. The device (100) according to claim 14, wherein: the predefined Shore hardness is defined by a Shore 00 scale value < 20.

16. The device (100) according to claim 14 or 15, wherein: the predefined Shore hardness is altered by adding a softener to lower the Shore value of the elastomer ring (23, 23'), thereby facilitating the elastomer ring (23, 23') to better maintain contact to an uneven surface of a test material.

17. The device (100) according to any of the previous claims 14 to 16, wherein: the resulting Shore hardness and/or shape of the elastomer ring (23, 23') and/or the pressure imposed on the wheels (110) are adapted to provide a contact footprint between the elastomer ring (23, 23') and the test material that improves the beam spread in terms of uniformity and/or SNR/SIR, and/or signal utilization.

18. A system for acoustic signal emission and reception of acoustic signal, the system comprising: one or more device (100)/wheel assemblies (110) according to claim 1 to 17, a carriage to which the one or a plurality of device ( 100)/wheel assemblies (110) are mounted, a control mechanism for steering the carriage along a path over the surface of a test material, and control logic for powering and controlling the broad frequency range transducers (20, 20'), storing data , and/or communication of data.

19. The system according to claim 18, the system further comprises one or more of: navigation means for providing absolute position of the carriage.

display means,

tracking means for providing relative position, computer means for receiving ultrasonic signal data and for processing the acoustic signal data, and

the computer means are remote computer means.

20. A method for emitting and receiving of acoustic signal for enabling analysis of a test material, the method comprises the step of: providing one or a plurality of systems according to any of claim 19 to 20, emitting acoustic signals from a transducer; receiving reflections of the emitted acoustic signals from the test material with one or a plurality of broad frequency range transducers (20, 20'); and storing and/or transferring the received acoustic signal data to a computer means and analyzing the received acoustic signals.

21. The method according to claim 20, the method further comprising the step of: moving the carriage along a predefined path; emitting acoustic signals from individual broad frequency range transducers (20, 20') according to a predefined emission pattern; receiving the reflected acoustic signal from the test material with one or a plurality of broad frequency range transducers (20, 20') configured to be receiving broad frequency range transducers (20, 20') for the individual emitted acoustic signal.

22. The method according to claim 20 or 21, the method further comprises to compare the result of the analysis of a section of a test material with a previous analysis of the same section of the test material, and to identify changes (150) in the test material.

1. Device (100) for sending and receiving an acoustic signal to and from a test material (15), the device (100) comprises one or more wheel assemblies (110), in which each wheel unit (110) comprises: one or more transducers with a wide frequency range (20, 20'), provided with a rear part (97, 97') and a propagation medium (52), the transducers (20, 20') are connected in a static non-moving position to a shaft (22),

the device (100) is characterized by further comprising: one or more rotating cover sections (23, 23', 26, 29, 29'), the cover section (23, 23', 26, 29, 29') comprises an enclosing pipe section (26) and an elastomer ring (23, 23') surrounding the tube section (26), the tire section (23, 23', 26, 29, 29') is arranged around the wide frequency range transducers (20, 20') and the shaft (22), and the elastomer ring (23) includes fillers (23') to change the acoustic impedance of the elastomer ring (23, 23'), the fillers (23') being particles of metal, and/or metal compounds, and/or chemical compounds.

2. The device (100) according to claim 1, wherein; the frequency range of the wide frequency range transducers (20, 20') is chosen to be in a sub-range of between 20kHz to 1MHz.

3. The device (100) according to claim 1 or 2, wherein; when the test material (15) is concrete, the frequency range of the wide frequency range transducers (20, 20') is selected to be in a sub-range of between 20kHz to 250kHz, or when the test material (15) is wood, the frequency range of the wide frequency range transducers is selected ( 20, 20') to be in a subrange between 20kHz to 500kHz, or when the test material (15) is a composite material, the frequency range of the wide frequency range transducers (20, 20') is selected to be in a subrange of between 20kHz to 1MHz ;

4. The device (100) according to any one of the preceding claims, wherein: the propagation medium (52) of one or more wide frequency range transducers (20, 20') is a lens/waveguide arranged at the distal end of the wide frequency range transducer (20, 20'), which points to the inward facing surface of the orbital outer ring.

5. The device (100) according to any one of the preceding claims, in which: the metal fillers (23') included in the elastomer ring (23) and/or the tube, and/or the propagation medium (52) and/or the back part are one or more of: Tungsten, Aluminum, titanium dioxide, steel, iron, copper, superalloy (e.g. Inconel), Molybdenum, Silicon carbide, Hafnium nitride, Iridium, Beryllium, Ruthenium, Osmium, Carbon, graphene and diamond.

6. The device (100) according to any one of the preceding claims 1 to 4, wherein: the metal fillers (23') included in the elastomer ring (23, 23') and/or the tube, and/or the propagation medium (52) and/or the back part is tungsten.

7. The device (100) according to claim 6, wherein: particles of Tungsten have a size smaller than 5 µm, in order to minimize damping effects.

8. The device (100) according to any one of the preceding claims, wherein: the acoustic impedance of the elastomer ring (23, 23') and/or the tube, and/or the propagation medium (52) and/or the backing is changed by including a fraction with particles of metal and/or metal compounds, and/or chemical compounds, to minimize differences in acoustic impedance compared to the acoustic impedance of the transducers (20, 20').

9. The device (100) according to any one of the preceding claims 1 to 7, wherein: the acoustic impedance of the elastomer ring (23, 23') and/or the tube, and/or the propagation medium (52) and/or the rear part is changed by include a fraction with particles of metal and/or metal compounds, and/or chemical compounds, to minimize differences in acoustic impedance compared to the acoustic impedance of the test material and/or transducers (20, 20').

10. The device (100) according to any one of the preceding claims 1 to 6, wherein: the acoustic impedance of the elastomer ring (23, 23'), the tube and the propagation medium (52) is changed by including fractions with particles of metal and/or metal compounds, and/or chemical compounds, so that acoustic impedance variation along an impedance path between the wide frequency range transducer (20) via the test material and the receiving wide frequency range transducer (20') is minimized by being provided to be closer to the impedance level of one or both of the transducers with a wide frequency range (20, 20') and the test material.

11. The device (100) according to claim 9, wherein: the acoustic impedance of the elastomer ring (23, 23'), the tube and the propagation medium (52) has a maximum variation of 50% of the impedance level of the wide frequency range transducers (20, 20') and/or the test material.

The device (100) according to any one of the preceding claims, wherein: the cover section (23, 23', 26, 29, 29') has an outer surface shape which is one of: circular, flat, superellipse, convex or concave parabola , narrow or wide grooves, or triangular.

The device (100) according to any one of the preceding claims, wherein: the outer surface shape of the cover section (23, 23', 26, 29, 29') is selected from a table defining the relationship between two or more of: amplitude , SNR and signal integrity.

14. The device (100) according to any one of the preceding claims, wherein: the amount of included metal particles in the elastomer ring (23, 23') is adapted to a predefined Shore hardness.

16. The device (100) according to claim 14 or 15, wherein: the predefined Shore hardness is changed by adding a plasticizer to lower the Shore value of the elastomer ring (23, 23'), thereby making it easier for the elastomer ring (23, 23') to maintain contact with an uneven surface of a test material.

17. The device (100) according to any one of the preceding claims 14 to 16, wherein: the resulting Shore hardness and/or shape of the elastomer ring (23, 23') and/or the pressure applied to the wheels (110) are adapted for providing a contact footprint between the elastomer ring (23, 23') and the test material which improves beam spread in terms of uniformity and/or SNR/SIR, and/or signal utilization.

18. System for acoustic signal transmission and acoustic signal reception, the system comprising: one or more devices (100)/wheel assemblies (110) according to claims 1 to 17, a carriage to which the one or more devices (100)/wheel assemblies (110) is mounted, a control mechanism to steer the carriage along a path over the surface of a test material, and control logic to drive and control the transducers with a wide frequency range (20, 20'), storage of data and/or communication of data.

19. The system according to claim 18, the system further comprises one or more of: navigation means to provide the carriage's absolute position.

display means,

the computer resources are external computer resources.

20. Five-way method of transmitting and receiving an acoustic signal to enable analysis of a test material,

the method comprises the steps of: providing one or more systems according to any one of claims 18 to 19, emitting acoustic signals from a transducer; receiving reflections of the emitted acoustic signals from the test material with one or more wide frequency range transducers (20, 20'); and storing and/or transmitting the received acoustic signal data to a computer device and analyzing the received acoustic signals.

21. The method according to claim 20, wherein the method further comprises the step: moving the cart along a predefined path; emitting acoustic signals from individual wide frequency range transducers (20, 20') according to a predefined transmission pattern; receiving the reflected acoustic signal from the test material with one or more wide frequency range transducers (20, 20') configured to be receiving wide frequency range transducers (20, 20') for the individual emitted acoustic signal.

22. The method according to claim 20 or 21, the method further comprises comparing the result of the analysis of a part of a test material with a previous analysis of the same part of the test material, and identifying changes (150) in the test material.