Abstract: A grain tailings elevator for a combine harvester includes a an elevator housing having an interior containing a conveyor arrangement configured to transport grain tailings through the elevator housing to a discharge outlet. The elevator housing has a side wall with a window to the interior of the elevator housing. A camera having a camera housing containing an image sensor is mounted to the side wall of the elevator housing over the window with the image sensor in registration with the window. The image sensor is trained on the conveyor arrangement and configured to image the grain tailings transported by the conveyor arrangement through the elevator housing.

Abstract: A device and method are provided for determining whether a laminate is bonded or debonded from its substrate. The device and method provide simple, accurate, rapid, cost-effective, and reliable means for assessing the bonding state of a laminated substrate.

Abstract: A turbomachine airfoil element includes an airfoil having pressure and suction sides spaced apart from one another in a thickness direction and joined to one another at leading and trailing edges. The airfoil extends in a radial direction a span that is in a range of 0.83-0.93 inch (21.1-23.6 mm). A chord length extends in a chordwise direction from the leading edge to the trailing edge at 50% span and is in a range of 0.80-0.90 inch (20.4-22.9 mm). The airfoil element includes at least two of a first mode with a frequency is 3135±10% Hz, a second mode with a frequency is 6634±10% Hz, a third mode with a frequency is 13260±10% Hz, a fourth mode with a frequency is 16838±10% Hz and a fifth mode with a frequency is 17980±10% Hz.

Abstract: A detection system (100) and a method for identifying structural change (300) with a substrate (200) includes a sensor (101) configured to resonate at variable frequencies, the resonant frequency of the sensor changing in response to structural change in the substrate, a detector (102) located in proximity to the sensor for detecting the resonant frequency of the sensor, and a receiving device (103) in communication with the detector for receiving information output by the detector, an analyzing device (108) in communication with the receiving device for and interpreting information output by the receiving device. The sensor includes an engagement surface for engaging the substrate. The detector is located on the sensor and away from the engagement surface in such a way that the sensor and the detector are arranged to form a laminated structure.

Abstract: A method of monitoring a condition of a dynamic system includes installing a vibration signal acquisition device at a predetermined location of the dynamic system, acquiring vibration signals by the vibration signal acquisition device, analyzing the vibration signals in a frequency domain, and predicting a change in the condition of the dynamic system based on the vibration signals in the frequency domain. A system is also provided, and a condition of the dynamic system includes clogging.

Abstract: A voice-controlled electronic device that includes an axisymmetric device housing having a longitudinal axis bisecting opposing top and bottom surfaces and a side surface extending between the top and bottom surfaces. The device can further include a plurality of microphones disposed within the device housing and distributed radially around the longitudinal axis; a processor configured to execute computer instructions stored in a computer-readable memory for interacting with a user and processing voice commands received by the plurality of microphones and first and second transducers configured to generate sound waves within different frequency ranges.

Abstract: An active mechanical waveguide including an ultrasonically-transmissive material and a plurality of reflection points defined along a length of the waveguide may be driven at multiple resonant frequencies to sense environmental conditions, e.g., using tracking of a phase derivative. In addition, frequency-dependent reflectors may be incorporated into an active mechanical waveguide, and a drive frequency may be selected to render the frequency-dependent reflectors substantially transparent.

Abstract: The objective of the present invention is to provide a hardness meter which estimates hardness in a stable manner regardless of a compression strength. A hardness meter includes: a movable portion which is continuously pressed against an object to be measured; a sensor which outputs an output signal reflecting a reaction force at a part of the object to be measured; a motive force mechanism that causes the movable portion to perform a piston motion; a hardness estimating portion which estimates the hardness of the object on the basis of an alternating current component of the output signal, generated by the piston motion; a position estimating portion which estimates a measurement position information by shooting with a camera; and a hardness map display portion which maps and displays the hardness on a schematic diagram of the surface of a living body based on the measurement position information.

Abstract: The disclosure provides a method for identifying a modal frequency of a beam bridge by considering influence of environmental temperature. The method includes the following steps: installing a sensor on a newly-built beam bridge without damage, measuring a dynamic response of the beam bridge cinder ambient excitation, recording temperature data, processing by a modal parameter identification method to obtain a modal frequency value at the temperature, and starting from a modal frequency corresponding to the temperature, carrying out iterative calculation to obtain the modal frequency at any temperature. The modal frequency value at any temperature is obtained by arranging a small number of sensors and carrying out a small number of tests, so that the influence of the temperature on the modal frequency is quantified, furthermore, the part of environmental influence is eliminated in future damage evaluation of the beam bridge, which allows for a more accurate damage evaluation result.

Abstract: A vehicle inspection apparatus includes: an exciter roller (3) configured to apply vibration to a vehicle (6); a control device 5 configured to control the exciter roller (3); and a vibration setting unit (the control device (5)) configured to set a vibration that is input to a wheel (7) of the vehicle (6) when abnormal noise generated in the vehicle (6) is detected. The control device (5) provides a range of vibrations including the vibration set by the vibration setting unit and applies the range of vibrations to the vehicle (6).

Abstract: An atomic force microscope is provided having a controller configured to store one or more positional parameters output by a sensor assembly when a light spot is located at a first preset position on the surface of the cantilever. The controller is further configured to operate an actuator assembly so as to induce movement of the spot away from the first preset position, to detect said movement of the first spot based on a change in the one or more positional parameters output by the sensor assembly, and to operate an optical assembly in response to the detected movement of the first spot to return the first spot to the first preset position.

Abstract: This application relates to an apparatus and method for detecting a microcrack using orthogonality analysis of a mode shape vector and a principal plane in a resonance point. The apparatus may include a measurement unit comprising multiple sensors and configured to measure whether a crack exists at a measurement target, and an analysis unit configured to determine whether a crack exists, on the basis of measurement values of the respective sensors. The measurement unit includes a fixing jig configured to fix the measurement target, an excitation means configured to apply a predetermined impact to the measurement target, and multiple acceleration sensors attached at predetermined locations on the measurement target. The analysis unit may further calculate frequency responses of the measurement target to the impact applied by the excitation means, and determine whether a crack exists by analyzing the number of resonance points and independence of the resonance points.

Abstract: There is provided a method for determining material properties in an active acoustic spectroscopy system, the method comprising: acquiring a multidimensional acoustic spectrum from a material in a container using acoustic spectroscopy; reducing the dimensionality of the acoustic spectrum using a mathematical dimensionality reduction method, thereby forming a reduced acoustic spectrum describing a material state; and determining if the material state belongs to a predetermined material state cluster. There is also provided a system for performing the described method.

Abstract: A haptic system is described. The haptic system includes a linear resonant actuator (LRA), a receiver, and a transmitter. The LRA has a characteristic frequency and provides a vibration in response to an input signal. The receiver is configured to sense received vibration from the LRA. The transmitter is configured to provide the input signal to the LRA. The receiver is coupled with the transmitter and provides vibrational feedback based on the received vibration. The input signal incorporates the vibrational feedback.

Abstract: A haptic system is described. The haptic system includes a linear resonant actuator (LRA), a receiver, and a transmitter. The LRA has a characteristic frequency and provides a vibration in response to an input signal. The receiver is configured to sense received vibration from the LRA. The transmitter is configured to provide the input signal to the LRA. The receiver is coupled with the transmitter and provides vibrational feedback based on the received vibration. The input signal incorporates the vibrational feedback.

Abstract: Described is a method for estimating a material property of an object by means of a laser ultrasonic (LUS) measurement equipment comprising a generation laser, a detection laser and a detector.

Abstract: A method for preventing damage in a bearing of a generator includes monitoring, via a controller, one or more electrical signals of the power conversion assembly. The method also includes converting the electricals signal(s) to a frequency domain. Further, the method includes extracting one or more spectral components in frequency bands of the frequency domain around one or more known characteristic frequencies of the bearing. Moreover, the method includes determining at least one characteristic of the spectral component(s) in the frequency bands. In addition, the method includes comparing the characteristic(s) of the spectral component(s) in the frequency bands to at least one baseline value. The method further includes generating a fault signal or a baseline signal for the bearing based on the comparison. In response to the fault signal being generated, the method includes implementing a control action.

Abstract: A laser projection device, including at least one reflector unit having at least one reflector element that is configured to deflect at least one laser beam to be projected, and having at least one drive unit that is configured to excite at least the reflector element into resonant vibration. The laser projection device includes at least one temperature compensation unit, which is configured to acquire a vibrational frequency of at least the reflector element and to ascertain the temperature of the reflector unit from it.

Abstract: A measurement point determination method for determining the number or an arrangement of measurement points for a measurement apparatus that performs measurement processing of a measurement item at a plurality of measurement points, the method comprises the steps of acquiring a minimum value and a maximum value of the number of measurement points, acquiring a target value of uncertainty for the measurement item of the measurement apparatus, estimating uncertainties when the measurement item is measured by the measurement apparatus using two or more of the numbers of measurement points between the minimum value and the maximum value of the number of measurement points, and determining the number of measurement points of the measurement apparatus on the basis of the target value and the estimated uncertainties.

Abstract: A MEMS photoacoustic gas sensor includes a first membrane and a second membrane opposing the first membrane and spaced apart from the first membrane by a sensing volume. The MEMS photoacoustic gas sensor includes an electromagnetic source and communication with the sensing volume to deflect the first membrane and the second membrane.

Abstract: The invention is generally directed to phacoemulsification systems and methods, and more particularly to systems and methods for providing transverse phacoemulsification. In accordance with one embodiment, a phacoemulsification system is provided having a handpiece with a needle, wherein the phacoemulsification system is configured to vibrate the distal end of the needle in both an effective transverse direction and an effective longitudinal direction when power, having a single effective operating frequency is applied to the handpiece.

Abstract: The invention provides a signal redundancy control system. The system includes multiple first signal collecting devices, second signal collecting devices and a controller, wherein the multiple first signal collecting devices are configured to collect the dynamic information of default devices where the first signal collecting devices are located in real time; one second signal collecting device corresponding to each of the first signal collecting devices is disposed on each default device, and is configured to collect the dynamic information of the default device where the second signal collecting device is located in real time; the controller is configured to determine whether the first signal collecting devices include fault information or not, and positions each default device according to the dynamic information acquired by the first signal collecting devices or the second signal collecting devices.

Abstract: A computer-implemented method analyzes periodic information in digital vibration data associated with a machine. The method involves generating a spectral periodic information plot (PIP) based on the digital vibration data, and locating amplitude peaks in the PIP at frequencies associated with fundamental frequencies of interest. Peaks occurring at fundamental fault frequencies and at related harmonic frequencies are removed from the PIP, while retaining energy values associated with the removed peaks. Remaining peaks in the PIP are classified as synchronous periodic peaks and non-synchronous periodic peaks. The remaining peaks in the PIP are graphically plotted along with the fault frequencies and related harmonic frequencies in different colors or different line styles on a display device to identify different groups of frequencies of interest.

Abstract: A method of evaluating quality of a wind turbine blade which has a hollow structure where an interior space of the wind turbine blade is surrounded by an outer skin which includes a laminated body includes: setting a scanning line on at least a part of an inner wall surface or an outer wall surface of the outer skin; and moving an ultrasound probe along the scanning line; generating a cross-sectional image corresponding to the scanning line, on the basis of a position of the ultrasound probe or a reflection echo to detect an indication whose echo level is greater than a first threshold; obtaining an inclination of the indication with respect to a reference line as a first parameter; and evaluating the lifetime or the breakage risk of the wind turbine blade on the basis of the first parameter.

Abstract: The embodiments disclosed herein relate to the examination of gemstones including diamonds, both cut/polished and rough, using the technology of Resonant Ultrasound Spectroscopy. The resonant frequencies are obtained by mechanically causing the stone to vibrate using a swept sine oscillator, sensing the resonance vibrations, and displaying the spectrum to yield a pattern describing the stone. The resonance fingerprints can be used to both track an individual stone to verify its integrity or to grade a rough stone to establish potential value.

Abstract: Embodiments of the disclosure provide systems and methods for detecting a resonant frequency of an optical beam-steering device. The method may include driving the optical beam-steering device with a driving signal oscillating at a plurality of frequencies. The method may also include detecting, by an acoustic detector, an acoustic signal caused by a movement of the optical beam-steering device. The method may further include analyzing a spectrum, by a controller, of the acoustic signal. The method may additionally include determining, by the controller, the resonant frequency of the optical beam-steering device based on the spectrum.

Abstract: A method for simulating an ultrasonic response of a metal part is carried out by an electronic simulating device. The method includes computing a first distribution of ultrasonic waves for the part without defect, in response to an ultrasonic excitation toward said part computing a second distribution of ultrasonic waves for a predefined zone (S3k) of the part, including a defect (20), in response to an ultrasonic excitation toward said zone (S3k), with the computation of elementary distributions, each corresponding to an ultrasonic response received by a receiver located at a border (F) of said zone; and determining a resultant distribution of ultrasonic waves for the part with defect, from the first and second computed distributions, the resultant distribution forming a simulation of an ultrasonic response received from the part including the defect (20), in response to an ultrasonic excitation toward said part.

Abstract: A method is provided for increasing accuracy in measuring complex Young's modulus and complex shear modulus of a material using a processing system. The material is tested to obtain an experimental frequency response transfer function of normal displacement to input force. A model panel is developed in the processing system as a modeled frequency response transfer function. The modeled transfer function is used at a range of fixed frequencies to calculate displacements of the model panel divided by the input force while varying material parameters. The modeled frequency response transfer function is compared with the experimental frequency response transfer function to compute error function values. These values indicate the most accurate material property values as those minimizing the computed error function values.

Abstract: A system may include a device. The device may be configured to receive machine vibration data identifying a measure of vibration of a machine. The vibration, of the machine, may be caused by a combination of first vibration caused by a motion of components of an undercarriage of the machine and second vibration that is unrelated to the first vibration. The device may be configured to identify a segment, of the machine vibration data, corresponding to the first vibration; transform the segment, using a Fast Fourier Transform (FFT), into a signal in a frequency domain; and analyze the signal to identify a signature spectrum associated with the motion of components. The device may be configured to predict, based on the signature spectrum, an amount of wear of the components. The device may be configured to cause an action to be performed based on the amount of wear of the components.

Abstract: Active auscultation may be used to determine organ (e.g., lung or heart) characteristics of users. An acoustic or piezo-electric signal (e.g., a pulse, a tone, and/or a broadband pulse) may be projected into an animal (typically human) body or thorax. The signal interacts with the body, or lungs, and in some cases may induce resonance within the body/lungs. A resultant signal may be emitted from the body which may be analyzed to determine, for example, a lung's resonant frequency or frequencies and/or how the sound is otherwise absorbed, reflected, or modified by the body. This information may be indicative of lung characteristics such as lung capacity, a volume of air trapped in the lungs, and/or the presence of COPD.

Abstract: A rotating electrical machine of the present invention evaluates a relative displacement of members and improves reliability further even when two or more members operate or move. A rotating electrical machine of the present invention comprises a stator and a rotor disposed on an inner side of the stator with a predetermined gap. The stator includes vibration measuring devices, each of the vibration measuring devices placed on each of at least two members included in the stator, the members having different displacements or phases with each other. The rotating electrical machine includes a device that acquires a relative displacement of one of the members included in the stator by evaluating a difference between displacements or phases measured by the vibration measuring devices and that evaluates a lifetime of the one of the members included in the stator based on the relative displacement.

Abstract: A system (1) for infectious disease screening. The system is for use with an assay device (2) which incorporates an ultrasonic transducer for generating ultrasonic waves to lyse cells in a biological sample. The system (1) comprises a frequency control module which is configured to control the ultrasonic transducer (49) to oscillate at an optimum frequency for cell lysis, a PCR arrangement (16) which is configured to receive and amplify the DNA from the sample; and a detection arrangement (70) which is configured to detect the presence of an infectious disease in the amplified DNA and to provide an output which is indicative of whether or not the detection arrangement (70) detects the presence of an infectious disease in the amplified DNA.

Abstract: A machining environment measurement device, which enables automatic identification of a vibration source which may cause defects in a machined surface based on pieces of vibration data without performing an actual machining process, includes a reference machining data storage unit that stores reference machining data computed based on time-series data of vibration measured in advance in an ideal machining environment; a data acquisition unit that acquires time-series data of vibration of at least a holder attached to a spindle of the machine tool detected by a holder measurement sensor; an analysis unit that analyzes the time-series data and computes feature data indicating a feature of the time-series data; a comparative determination unit that compares the feature data with the reference machining data and determines a machining environment of the machine tool; and a display unit that displays the determination result of the comparative determination unit.

Abstract: Methods and downhole tools for operation within in a wellbore that extends into a subterranean formation. The operation includes simultaneously causing a change in a first parameter of fluid drawn into the downhole tool from the formation and determining a change in a second parameter of the fluid relative to the change in the first parameter. A third parameter of the fluid is determined based on the first and second parameter changes.

Abstract: A method for performing diagnostics of a structure subject to loads, in particular an aircraft structure, is described, said method being implemented by means of an arrangement of sensors located at relevant points of the structure and corresponding neural networks, and comprising: training the neural network in order to establish an associative relationship between the local displacement of the structure in a subset of relevant points and the local displacement of the structure in at least one residual relevant point; detecting the local displacement of the structure in a plurality of relevant points under operating conditions; estimating the local displacement of the structure in at least one residual relevant point by means of the associated neural network on the basis of the pre-established associated relationship; and comparing the local displacement of the estimated structure with the detected local displacement at the residual relevant point.

Abstract: A sensor device is coupled to a mechanical machine. The sensor device detects vibrations of the mechanical machine and transmits the vibration data to a remote processing device. The vibration data may be compressed prior to transmission. The remote processing device receives the data and generates a reconstructed version of the vibration data. The remote processing device includes a machine learning model trained to examine vibration data and to identify a motion pattern associated with an error condition. The machine learning model is applied to the reconstructed vibration data and detects an occurrence of an error condition in the mechanical machine. An alert indicating that an error condition has been detected is transmitted to a human operator. The human operator verifies the status of the mechanical machine and confirms that an error condition has occurred.

Abstract: A system with at least one control unit and a bearing arrangement that includes at least one sensor unit for measuring a quantity. The system is configured to find out with the help of the at least one sensor unit first values of the quantity in a first time span for a first set of instants of time. The system is further configured to infer second values of the quantity for a second set of instants of time from third values measured via the at least one sensor unit in a second time span. The first set of instants of time is different from the second set of instants of time.

Abstract: Methods and systems of monitoring and controlling a longwall mining system. One system includes a shearer including a cutter drum and a sensor mounted to the shearer. The system also includes an electronic controller including a processor and a memory, the electronic controller communicatively coupled to the sensor. The electronic controller is configured to receive vibration data from the sensor and determine a current vibration level associated with the shearer based on the vibration data. The electronic controller is also configured to compare the current vibration level to a vibration threshold. The electronic controller is also configured to, in response to the current vibration level exceeding the vibration threshold, adjust a cutting parameter for the cutter drum of the shearer. The electronic controller is also configured to control the cutter drum with the adjusted cutting parameter.

Abstract: In the system, two ultrasonic transducers, which form a pair and each have a piezoelectric ceramic plate-shaped element with a rectangular geometry, can be fastened to a surface of a component. The two ultrasonic transducers are arranged at a distance from one another such that there is no direct mechanical contact and they are arranged beside one another with a parallel orientation of their central longitudinal axes. The two elements have a different polarization along their width and are connected with the same polarity to an electrical voltage source. The two plate-shaped elements can also have an identical polarization along their width and can be connected in this case with opposite polarity to an electrical voltage source. At least one ultrasonic transducer and/or at least one further ultrasonic transducer is/are designed to detect ultrasonic waves reflected by defects and/or shear waves simultaneously emitted by the two ultrasonic transducers.

Abstract: The present invention relates to a method for detecting an analyte, which is based on the detection of a signal caused by a change of the mechanical properties of a permeable freestanding nanoparticle composite. The present invention also relates to a method for determining the concentration of and/or recognizing an analyte.

Abstract: According to one embodiment, an inspection apparatus determines an object to be in a first state when an intensity at a first frequency of a frequency characteristic is not less than a first threshold, and determines the object to be in a second state when the intensity at the first frequency is less than the first threshold. The frequency characteristic is generated based on a vibration of the object when the object is struck. The second state is different from the first state.

Abstract: A surface roughness analysis system and methods of analyzing surface roughness of a workpiece are presented. The surface roughness analysis system comprises a number of wave generators; a number of wave sensors; and an ultrasonic analysis system configured to receive material mechanical parameters for a workpiece, determine incident surface wave signal parameters for a source signal to be sent by the number of wave generators, and determine a cut-off wavelength using the material mechanical parameters, wherein the cut-off wavelength is a ratio of surface wavelength over incident wavelength.

Abstract: Systems and methods for testing a component, such as a battery, of a host device include transmitting one or more input acoustic signals into at least a portion of the host device, through input transducers coupled to the host device. One or more response signals generated in response to the one or more input acoustic signals are detected through recording transducers coupled to the host device. The one or more response signals are stored and compared with reference signals or datasets. One or more physical characteristics of the component or battery are analyzed based on the comparison.

Abstract: A turbomachine airfoil element includes an airfoil that has pressure and suction sides spaced apart from one another in a thickness direction and joined to one another at leading and trailing edges. The airfoil extends in a radial direction a span that is in a range of 4.47-4.77 inch (113.5-121.2 mm). A chord length extends in a chordwise direction from the leading edge to the trailing edge at 50% span and is in a range of 2.57-2.87 inch (65.3-72.9 mm). The airfoil element includes at least two of a first mode with a frequency of 297±10% Hz, a second mode with a frequency of 1035±10% Hz, a third mode with a frequency of 1488±10% Hz, a fourth mode with a frequency of 1524±10% Hz, a fifth mode with a frequency of 2855±10% Hz and a sixth mode with a frequency of 4462±10% Hz.

Abstract: A system and method for monitoring a dry gas seal positionable between a stationary housing and a rotatable shaft. A plurality of sense elements may rotate in response to the rotation of the rotatable shaft and a speed sensor may sense the speed of the rotatable shaft at speeds below one thousand rotations per minute based on sensing the plurality of sense elements. A processor may receive output signals from the speed sensor and may establish a position of the dry gas seal or an operating condition of the dry gas seal based on the signal from the speed sensor.

Abstract: Provided is an additive manufacturing system capable of performing in-process, layer-by-layer non-destructive testing, the additive manufacturing system including: a plate for producing a part thereon; a transducer attached to the plate and configured to induce vibrations in the part; and a laser vibrometer configured to detect a vibrational response of the part to determine whether defect and/or anisotropy exists within the part.

Abstract: Non-limiting examples of the present disclosure relate to devices, systems and methods for conducting non-destructive evaluation (NDE) of a wooden specimen, where structural integrity of the wooden specimen is assessed without being compromised. A non-limiting example of a wooden specimen is a wooden utility pole. One or more NDE devices, attached to the wooden specimen, are configured to transmit and/or receive ultrasonic signals to execute NDE of the wooden specimen. An exemplary NDE device may be controlled by another computing device via a data transmission connection. Examples described herein pertain to a variety of coverages that comprise but are not limited to: coverage for a single NDE device; coverage for a system of two or more NDE devices that are utilized to conduct NDE of the wooden specimen; and coverage where one or more NDE devices interface with one or more computing devices to conduct NDE of the wooden specimen.

Abstract: Methods and systems of monitoring and controlling a longwall mining system. One system includes a shearer including a cutter drum and a sensor mounted to the shearer. The system also includes an electronic controller including a processor and a memory, the electronic controller communicatively coupled to the sensor. The electronic controller is configured to receive vibration data from the sensor and determine a current vibration level experienced by a cutter drum of the shearer based on the vibration data. The electronic controller is also configured to compare the current vibration level to a vibration threshold. The electronic controller is also configured to detect an impact event associated with the cutter drum of the shearer based on the comparison and generate an impact event indication associated with the impact event.

Abstract: Methods and systems of monitoring and controlling a longwall mining system. One system includes a shearer including a cutter drum and a sensor mounted to the shearer. The system also includes an electronic controller including a processor and a memory. The electronic controller is configured to receive an impact event indication associated with an impact event of the cutter drum, the impact event indication based on vibration data collected by the sensor. The electronic controller is also configured to retrieve additional data associated with the impact event indication and link the additional data with the vibration data of the impact event indication. The electronic controller is also configured to create and store an impact event record including the vibration data and the additional data. The electronic controller is configured to, in response to receiving a maintenance request, export the impact event record for display.

Abstract: The present disclosure relates to evaluating an ovaling mode in a cylindrical object and determining a quality of the cylindrical object by analysis of the ovaling mode. In an embodiment, the present disclosure relates to a method for determining a structural quality of a cylindrical element, comprising measuring, as a result of a single applied force, surface vibrations of the cylindrical element via four or more surface transducers arranged on the cylindrical element along a circumference of the cylindrical element, the four or more surface transducers being equally spaced along the circumference, processing digital signals corresponding to each of the four or more surface transducers in order to generate a composite digital signal, transforming the composite digital signal to a frequency domain, comparing the transformed composite digital signal to a reference composite digital signal, and determining, based on the comparing, the structural quality of the cylindrical element.