Abstract: A method for ultrasonically inspecting a generator field tooth for the detection, characterization and/or sizing of cracks thereat is disclosed. An electromagnetic acoustic transducer (EMAT) productive of a test signal having a defined angle of refraction with respect to the tooth material is selected. The EMAT is positioned at an outer surface of the tooth absent a fluid couplant and oriented so as to direct the test signal to propagate through the tooth toward a load surface of the tooth where a butt joint of a set of wedges is disposed. The EMAT is activated so as to test the load surface proximate the butt joint for cracks thereat.

Abstract: A method for ultrasonically inspecting a generator field tooth for the detection, characterization and/or sizing of cracks thereat is disclosed. A monolithic piezoelectric transducer (MPT) productive of a test signal having a defined angle of refraction with respect to the tooth material is selected. The MPT is positioned at an outer surface of the tooth and oriented so as to direct the test signal to propagate through the tooth toward a load surface of the tooth where a butt joint of a set of wedges is disposed. The MPT is activated so as to test the load surface proximate the butt joint for cracks thereat.

Abstract: A transducer-based sensor system including a drive signal generator for generating a drive signal, a transducer coupled to the drive signal generator and configured to receive the drive signal, a mixer coupled to the transducer and configured to receive output from the transducer where such output results at least in part from physical movement of the transducer, and a diplexer operatively coupled with an output of the mixer and configured to present a substantially matched output impedance to the mixer over an operative range of output frequencies.

Abstract: A method and apparatus is provided to analyze a dual wall structure having at least one hollow core therein and having the same unknown material sound velocities in walls and in post as well. A transducer is located in at least two different positions with respect to the structure, whereby the transducer propagates an ultrasonic wave toward the dual wall structure. A portion of the ultrasonic wave is reflected back to the transducer. One wave traverses a portion of the dual wall structure that has a core filled with a medium having a known material acoustic property. A second wave traverses a portion of the post that has an unknown material sound velocity. From time of flight measurements of the above mentioned waves, the wall thickness and core shift, if any, can be determined.

Abstract: A method of testing a material sample for defects, comprising the steps of applying a test signal to the material sample, receiving a return signal from the material sample and analysing the return signal to determine whether the material sample is defective. In one aspect of the present invention the steps of receiving a return signal and analysing it include the step of selecting a frequency range to reduce the effect of potentially interfering signals. In another aspect of the present invention a reference signal obtained from a non-defective sample is subtracted from the return signal to give a difference result and the difference result is indicative of whether the material sample is defective. Apparatus for carrying out the above-defined methods are also provided.

Abstract: A method for inspection of tubular goods includes using ultrasonic detection means to obtain wall thickness measurement of discrete sections of a tubular good and recording each measurement in association with both the longitudinal and circumferential position at which each measurement was obtained. Accordingly each measurement of wall thickness represents a small portion of the wall thickness of said tubular in three dimensional space. A plurality of said measurements may thereby be displayed by computer means in virtual three dimensional formal. Differing wall thickness readings made he represented by different shading or color display, so that anomalies of interest may be readily detected. Alternatively the recorded information may be readily processed by computer means to calculate the effect of stressors on the wall of said tubular good.

Abstract: A tuning device (23) and an apparatus that incorporates the tuning device (23) for use in testing the integrity of a railway line (30) to obtain an improved test signal, the tuning device (23) including an elongate member (23) adapted to be attachable at one end of the railway line (30) being tested in situ or is attachable to an attachment member (21) coupled to the section (10) of railway line (30), and wherein a vibration signal measuring means (24) is adapted to be secured to the other end of the elongate member (23).

Abstract: A method for characterizing a suspension with particles floating therein, which method comprises the steps of generating an acoustic actuation signal and registering an acoustic reflected signal. Further, a first dataset is calculated on the basis of the reflected signal, the dataset containing information which represents an autocorrelation function as a function of time of the reflected signal. Thereupon, first datasets are combined into a second, cumulated dataset, which represents a sum of the autocorrelation functions which correspond with the first datasets. Finally, a representation of a particle size distribution is determined by solving this representation from an expression for the second, cumulated dataset in terms of the representation of a particle size distribution.

Abstract: Provided are systems and methods for multi-channel non-destructive inspection which provide high data throughput, logarithmic amplification of large dynamic range, and simplicity of supporting electronics. More specifically, provided are systems and methods for inspecting a structure that may use an interface board, two pulser boards, each coupled to 16 transmit channels, and two receiver boards, each coupled to 16 receive channels, where the receiver boards are capable of processing data from the 32 receive channels by logarithmically amplifying at least 70 dB of dynamic range. A receiver board may include a serial connection of two layers of multiplexing switches to provide 70 dB isolation between channels, a logarithmic amplifier for logarithmically amplifying 70 dB of dynamic range, a linear amplifier, and an analog-to-digital converter.

Abstract: An imaging method for observing the propagation of a shear wave simultaneously at a multitude of points in a diffusing viscoelastic medium. The shear wave is caused to be generated by firing at least one focused ultrasound compression wave into the viscoelastic medium by means of an array of transducers, and then emitting at a fast rate and using the same array of transducers, unfocused ultrasound compression waves serving to obtain a succession of images of the medium, and processing the images obtained in this way in deferred time in order to determine the movements of the medium during the propagation of the shear wave.

Abstract: A surface wave chemical detector comprising at least one surface wave substrate, each of said substrates having a surface wave and at least one measurable surface wave parameter; means for exposing said surface wave substrate to an unknown sample of at least one chemical to be analyzed, said substrate adsorbing said at least one chemical to be sensed if present in said sample; a source of radiation for radiating said surface wave substrate with different wavelengths of said radiation, said surface wave parameter being changed by said adsorbing; and means for recording signals representative of said surface wave parameter of each of said surface wave substrates responsive to said radiation of said different wavelengths, measurable changes of said parameter due to adsorbing said chemical defining a unique signature of a detected chemical.

Abstract: The invention relates to a method for determining the size of a fracture (26) in a workpiece (20), in particular the depth of a fracture (26) in said workpiece (20), by means of the ultrasound pulse method, comprising the following method steps: a workpiece (20), with a front surface (22) and a back surface (24), having a fracture (26), extending from the back surface (24) and an angle test head (28) is applied to the front face (22), transmits ultrasound pulses at an angle alpha into the workpiece (20) and receives echoes from said pulse, the angle test head (28) is moved at least once over the fracture (26), such that the radiation beam (46) from the angle test head (28) completely covers the fracture (26), the received echo signals are digitized and stored in a memory (40) as variable pairs of echo signal versus runtime, the variable pairs form a value upwardly defined by an envelope (48) and the dimension of the fracture (26) is determined from the width of the envelope (48) at a given partial amplitude a

Abstract: A nano-indentation ultrasonic detecting system for detecting mechanical properties of a target material. An indentation device, disposed on a surface of the target material, generates an indentation on the surface, obtaining the relation between the Young's modulus and the Poisson's ratio of the target material. An ultrasonic generator is movably disposed on the surface of the target material, generating at least two different ultrasonic signals thereon. An ultrasonic receiver is disposed on the surface of the target material and separated from the ultrasonic generator, receiving the ultrasonic signals. The result of a nano-indentation experiment are applied in the ultrasonic theory and iterated by the ultrasonic experimental data and theory, obtaining the Young's modulus of the target material. The obtained Young's modulus of the target material is substituted back in the result of the nano-indentation experiment, obtaining the Poisson's ratio of the target material.

Abstract: Systems and methods for determining the velocity of ultrasonic surface skimming longitudinal waves on various materials are described herein. In embodiments, a surface skimming longitudinal wave is generated at a first location on a material, at least a portion of that wave is detected at a second location on the material, the time-of-flight of that wave between the first and second locations is determined, and then the velocity of that wave is determined. One or more crystallographic orientations of the material may then be determined based upon that velocity.

Abstract: A method and system for detecting weld signatures from an ultrasound scan data obtained from scanning a pipeline is provided. The method includes a step for mapping multiple amplitude responses from the ultrasound scan data, each amplitude response being representative of a respective sensor signal. Continuous amplitude responses are located from the amplitude responses and corresponding signatures are identified for the continuous amplitude responses. The method also includes a step for tagging the corresponding signatures as weld signatures.

Abstract: An apparatus for noninvasively monitoring the flow and/or the composition of a flowing liquid using ultrasound is described. The position of the resonance peaks for a fluid excited by a swept-frequency ultrasonic signal have been found to change frequency both in response to a change in composition and in response to a change in the flow velocity thereof. Additionally, the distance between successive resonance peaks does not change as a function of flow, but rather in response to a change in composition. Thus, a measurement of both parameters (resonance position and resonance spacing), once calibrated, permits the simultaneous determination of flow rate and composition using the apparatus and method of the present invention.

Abstract: A vibration sensor (1) for monitoring the state of rotating components or bearings, includes a housing (2), a sensor element (3), evaluation electronics (4), and at least one interface (5, 6). With the vibration sensor (1), reliable monitoring of the state of rotating components and bearings can be done easily and economically, and in addition the vibration sensor can be easily operated. The evaluation electronics (4) has an analog-to-digital converter (7), and a signal conditioning device (8) having a plurality of signals, which have been acquired by the sensor element (3), and which are converted into a state value using signal analysis and a diagnosis algorithm.

Abstract: The invention relates to a method for determining the threshold value of screens which enable an evaluation of a sound coupling during the ultrasound testing of a series of spot welding joints of a selected type. Initially, a geometrical minimal thickness dMin is established for the spot welding joints. At least one echo of the front surface (entrance echo) is received in addition to one echo of the first reflection on a rear wall of the spot welding joint (first rear wall echo) and at least one further (n-th) rear wall echo. The propagation time tMin of the ultra sound pulse is defined for the path to the front surface to the rear wall and back to the front surface at a minimal thickness dMin and a propagation time tT for the total thickness. A first screen (B1) is set for the signal of the rear wall echo, starting at a moment in time t1S=tE+tMin?tSA and ending at a moment in time t1T=tE+tT+tSE, whereby tSA and tSE are additional small security measures.

Abstract: A toroidal-type continuously variable transmission component, such as an input disk, an output disk, an inner ring of a power roller bearing, and an outer ring of the power roller bearing, which is functioned as a rolling member, has a layer a depth of which is 0.5 mm or less from the surface thereof. The layer does not include a non-metallic inclusion having a maximum diameter of up to 0.1 mm in the area thereof having a depth of 0.5 mm or less from the surface thereof.

Abstract: An inspection method can easily determine welding condition by just comparing an echo height returned from the weld zone of a real product with a master data. An master data is made based on the data from prepared test pieces corresponding to the real product.

Abstract: A gas concentration measurement instrument comprises: ultrasonic wave transmitting means for transmitting an ultrasonic wave according to an ultrasonic wave generation signal composed of a group of rectangular pulse waves; ultrasonic wave receiving means for converting the ultrasonic wave transmitted through the gas in the measurement region into an electric signal to use it as an ultrasonic wave reception signal; and gas concentration measuring means for measuring the signal output time when the ultrasonic wave generation signal is outputted, generating an envelope processing signal by subjecting the ultrasonic wave reception signal to an envelope extracting processing, measuring the threshold fall time when the envelope processing signal decreases below a predetermined threshold after exceeding the threshold, and measuring the difference between the threshold fall time and the signal output time as change in the gas concentration.

Abstract: System and method for resolving phase ambiguities of various transducer arrays, including non-coplanar interferometer antennas on an aircraft skin, in order to determine the direction of arrival of a signal received by the array and emitted by a source remote from the array.

Abstract: An ultrasonic transducer for measuring a part with a coating having at least one acoustic transducer, and a buffer delay line having an impedance matched to an impedance of the coating.

Abstract: An abnormality diagnosis system for diagnosing a presence or absence of an abnormality of a bearing unit for a railway vehicle axle, comprises a sensing/processing portion for outputting a signal generated from the bearing unit as an electric signal, a calculating/processing portion for making an abnormality diagnosis of the bearing unit based on an output of the sensing/processing portion, a result outputting portion for outputting a decision result of the calculating/processing portion, and a controlling/processing portion for feeding back a control signal to a control system of the railway vehicle based on the decision result.

Abstract: A system for inspecting a refractory furnace having an outer shell and an inner refractory brick lining includes a stress wave generator for generating stress waves that propagate through the outer shell and the refractory brick lining. A stress wave sensor senses reflected stress waves returning to the outer shell. A processing unit in communication with the stress wave sensor processes output generated by the stress wave sensor to generate data representing the condition of the refractory brick lining. In this manner, the location and geometry of anomalies within the refractory brick lining can be determined without requiring the refractory furnace to be shut down.

Abstract: The invention concerns a method for non-destructive ultrasonic control, combining time-of-flight diffraction (TOFD) and inclined longitudinal wave techniques, of weld joints assembling two abutted parts. The method consists of using the time-of-flight diffraction technique, displacing in the longitudinal or circumferential direction, along the weld joint to be controlled, at least one pair consisting of a first transducer and of a second transducer, one transmitting and the other receiving ultrasonic waves, these transducers being laterally positioned on either side of the joint to be controlled, these transducers comprising piezoelectric ceramics or crystals. Furthermore, it consists of displacing along the welded joint to be controlled, using the inclined longitudinal wave technique, at least a third transducer, so as to detect any defect of the joint located at a thickness ranging between 0.5 mm and 15 mm.

Abstract: Disclosed herein is a method for imaging anisotropic media comprising selecting multiple points within the anisotropic media, which is to be imaged; determining an acoustic path between each selected point in the anisotropic media and a receiver position on the surface of the anisotropic media; calculating an acoustic wave velocity at all necessary points; determining an acoustic path length based on each selected point in the anisotropic media and the receiver position; determining a time delay for each acoustic wave between each image point and the receiver position on the surface of the anisotropic media; calculating a sum for each point selected based on the appropriate acoustic wave velocities and the acoustic path lengths; and generating an image of the anisotropic media using the coherent sums generated for each said image point selected.

Abstract: An electronic signal relating to a sonic wave when an intended gas does not exist in air is synchronized and locked in a feedback circuit constituting a phase-locked loop (PLL). Then, an electronic signal relating to another sonic wave when the intended gas exist in the air is input into the feedback circuit to release the synchronization (lock) of the feedback circuit to measure as a given electronic signal the difference in phase of the sonic wave in the air between with and without the intended gas to be detected. The intended gas can be detected as the electronic signal due to the difference in phase of the sonic wave.

Abstract: Methods and systems for determining the resonance frequency of a resonator, using the Doppler effect. An interrogating sonic beam including a carrier frequency and one or more resonator exciting frequencies is directed at a resonator disposed in a measurement environment. Resonator vibrations are excited by the resonator exciting frequencies. The carrier frequency is modulated by the vibrating part(s) of the resonator. The returning signal is received and analyzed to determine the amplitude of the Doppler shifted sideband frequencies. The resulting data is processed to determine the resonator's resonance frequency. Using calibrated resonating sensors having a resonance frequency that varies as a function of a physical parameter in a measurement environment, the method and systems allow determining the value of the physical variable from the sensor's resonance frequency.

Abstract: Apparatus for non-destructively testing material to enable detection of any damage sites, comprising means for generating localized heating at any damage site in the material, and means for imaging the material to enable detection of any localized heating at the damage site.

Abstract: A method for determining vibration amplitude limits of a mechanical device. The method comprises identifying a mechanical device and a frequency range for a spectrum to be analyzed, retrieving vibration spectra comprising individual spectrum for the mechanical device and the frequency range, calculating frequency for the individual spectrum, and identifying the individual spectrum with the smallest number of frequency lines. In addition, the method comprises calculating noise bandwidths and a largest noise bandwidth, removing outlier data, calculating conditional kernel density, and calculating vibration amplitude limits to detect faults in the mechanical device.

Abstract: By measuring, for an ultra-low-expansion glass material, the frequency dependence of acoustic velocities and attenuation coefficients of bulk waves (longitudinal waves and shear waves), and the density, its fundamental acoustic properties are revealed, and a standard specimen for use in system calibration is prepared. By an absolute calibration method using the standard specimen, absolute values for both the LSAW and LSSCW velocities are obtained. Moreover, there are obtained relationships for the acoustic properties and the coefficient of thermal expansion to evaluate the coefficient of thermal expansion from the acoustic properties. In case there is a distribution of characteristics due to periodic striae, an accurate acoustic property distribution in the substrate can be ascertained and an evaluation performed, by selecting for the substrate a cutting angle with respect to the striae plane.

Abstract: A transducer-based sensor system, including a transducer array having a plurality of transducers, a selector coupled with the transducer array and an output processing subsystem. Defined between each transducer and the output processing subsystem is an output transmission path associated with the individual transducer. The selector is configured to apply control signals to the transducer array to cause the array to have at least one selected transducer and at least one unselected transducer. The system is configured so that, for a selected transducer, the output transmission path for that transducer is enabled, so as to permit output signals to be transmitted from the selected transducer to the output processing subsystem. The system is further configured to isolate any unselected transducers, by disabling the output transmission path for such transducers, to thereby prevent transmission of output signals to the output processing subsystem.

Abstract: An ultrasonic diagnostic apparatus for transmitting ultrasonic signals toward a subject, receiving signals reflected from the subject in response to the transmitted ultrasonic signals, and producing a tomographic image of the subject based on the received signals, includes: transmitting/receiving device having a plurality of channels for transmitting/receiving ultrasonic signals via the channels; and a linear or convex probe in which transducers in a number larger than the number of channels are arranged in one direction, in which probe, the transducers are connected to the channels inconsecutively in the arrangement direction, and the number of transducers in an aperture area from one end to the other of transducers that are connected to the channels is set to be larger than the number of channels.

Abstract: A system and method for determining whether leaks exist in a pressure vessel comprises measuring a mechanical response of the pressure vessel using any of an acoustic sensor and a vibration sensor; processing the mechanical response using a digital signal processor system; categorizing the processed mechanical response into events of interest and events not of interest; and determining if any of a ballistic impact and penetration of the pressure vessel has occurred based on the processed mechanical response, wherein the mechanical response comprises any of an acoustic response and a vibration response, wherein the events of interest comprise any of environmental events and ballistic events, wherein the categorizing comprises differentiating the environmental events from the ballistic events, and wherein the events not of interest comprise noise.

Abstract: A method, used in connection with a pulse-echo type sensor for determining the speed of sound in a gas, for improving the accuracy of speed of sound measurements. The sensor operates on the principle that speed of sound can be derived from the difference between the two-way travel time of signals reflected from two different target faces of the sensor. This time difference is derived by computing the cross correlation between the two reflections. The cross correlation function may be fitted to a parabola whose vertex represents the optimum time coordinate of the coherence peak, thereby providing an accurate measure of the two-way time diffference.

Abstract: The invention concerns a method for focusing acoustic waves useful for obtaining an image of a field to be observed in a dissipative heterogeneous medium (2, 3) around which acoustic transducers (T1–Tn, T?1–T?m) forming an imaging network and a target network. The method consists in following a training step during which pulse responses from the medium are measured between each transducer (Ti) of the imaging network (5) and several transducers (Tj) of the target network (6); deducing therefrom reference signals to be emitted by the transducers of the imaging network to produce a focused acoustic pulse in each transducer of the target network, then cumulatively, in determining reference signals to be emitted to focus an acoustic pulse on predetermined points in the medium. Said reference signals are stored and used subsequently to generate an acoustic image of the medium.

Abstract: In order to make it possible in ultrasonic flaw detection to generate ultrasonic waves containing a main beam only by use of an array probe and clearly identify a defect in a specimen by use of images, an element pitch P (the distance between centers of adjacent ultrasonic transducer elements in the array probe) is set longer than ¼ of the wavelength of longitudinal waves generated by the ultrasonic transducer elements and shorter than ½ of the wavelength and reception signals up to time corresponding to the sum of wall thickness round-trip propagation time for longitudinal waves and wall thickness round-trip propagation time for shear waves in the specimen are displayed.

Abstract: A remote mass is excited with one or more beams, and the surface vibrations of the excited mass are detected with one or more laser vibrometers. Each vibrometer generates a signal indicative of the surface vibrations which is stored, reversed in time, and applied to modulate an exciter beam that is then impinged onto the mass.

Abstract: An arrangement for tracking resonant frequency of electrically resonant structures through a single channel includes a variable frequency oscillator associated with each resonant structure which provides an excitation signal of a variable frequency encompassing a possible resonant frequency of the associated resonant structure. Coupling device(s) are provided which connect each variable frequency oscillator to said resonant structure(s). An I-mixer is provided for each oscillator which forms a synchronous detector, a first input of each I-mixer being connected to its associated oscillator and a second input being connected to the coupling device, each I-mixer mixing the excitation signal from the associated variable frequency oscillator with a response signal generated by the resonant structure(s) in response to each excitation signal.

Abstract: A method and system for determining the fiber volume fraction of a composite structure. The system includes a unit for ultrasonically determining the porosity volume fraction in the article, and a unit for calculating the volume fraction of the fibrous reinforcement material in the article based on the porosity volume fraction in the article and the mass densities of the article and the fiber and matrix materials within the article. The method entails determining the mass density of the article, obtaining the mass densities of the fiber material and the matrix material, ultrasonically determining the porosity volume fraction in the article, and then calculating the volume fraction of the fibrous reinforcement material in the article based on the porosity volume fraction in the article, the mass density of the article, the mass density of the matrix material, and the mass density of the fiber material.

Abstract: An acoustic energy-based, non-contact or contact testing approach provides low cost, highly accurate, and reliable information to (a) identify flaws and anomalies and (b) assess the integrity of a particular material. This approach is not hindered by surface conditions or impediments, and indeed, looks beneath the surface of the material by propagating an acoustic wave through the material using two differential transducers. A dynamic differential measurement is made of the material under a load condition and an unloaded condition that allows identification and assessment of various characteristics of the material. Multiple “windows” of information may be generated that permit (a) direct detection of flaws, defects, and anomalies using a scattering technique, (b) detection of crack closure and opening used to assess the stability of the material, (c) determination of strain on the material which relates to its performance, and (d) determination of defect dynamics linked to the defect size and stability.

Abstract: A method and apparatus for monitoring a condition having a known relation to, or influence on, the transit time of a cyclically-repeating energy wave moving through a transmission channel, by: (a) transmitting a cyclically-repeating energy wave through the transmission channel from a transmitter at one end to a receiver at the opposite end; (b) continuously changing the frequency of the transmitter according to changes in the monitored condition while maintaining the number of waves in the transmission channel as a whole integer; and (c) utilizing the changes in frequency of the transmitter to provide a continuous indication of the monitored condition. Operation (b) is preferably performed by detecting a predetermined fiducial point in each cyclically-repeating energy wave received by the receiver, but may also be performed by the use of a phase-locked loop circuit, to maintain the number of energy waves in the loop of the transmission channel as a whole integer.

Abstract: An approved method and apparatus for detecting partial discharge events within a transformer comprises asserting a MEMS acoustical probe through the wall of the transformer to optically measure partial discharge events. In an enhanced embodiment, temperature compensation is also possible, and detection may be confirmed via an independent electromagnetic or other sensor.

Abstract: A profiling system for obtaining a characterization of a medium under a surface. The profiling system comprising a plurality of system components exchanging messages through a communication interface. The system components comprise an energy impulse generator, a sensing assembly, and a user-computing interface. The generator, for transferring an energy pulse to the surface, comprises generator communication means for exchanging the messages with other system components. The sensing assembly includes sensors. Each one of the sensors comprises an accelerometer for detecting an acceleration on the surface resulting from the energy pulse and producing a signal representative of the acceleration. Each one of the sensors also comprises an interface communication means for transmitting the signal representative of the acceleration and exchanging messages with other system components through the communication interface.

Abstract: Generally described, a bending stiffness predicting system 20 includes a density measurement sub-system 24 and a sound wave velocity measurement sub-system 28. From the measurements of both density and speed of sound through the wood product received from the sub-systems 24 and 28, respectively, the bending stiffness (Y) may be predicted by calculating the bending stiffness (Y) according to the bending stiffness (MOE) equation: Y=k?V2/g; wherein k is the calibration constant, ? is the density or specific gravity of the member, V is the velocity of a sound through the member and g is the acceleration due to gravity. The calculation of wood product bending stiffness may be carried out manually, or may be calculated using a calculating sub-system 32 from the two measured values, density and velocity, according to Equation 1 above.

Abstract: A method and apparatus of determining the thickness of a lubricant film disposed between two bodies by measuring and performing a frequency spectrum analysis on a reflected or transmitted part of an ultrasound wave propagated towards said film is disclosed.

Abstract: A method of monitoring the condition of a thermal barrier coating on a turbine blade or vane during operation of the turbine is provided. The method includes providing a means for receiving acoustic output of the blade or vane during operation of the turbine and monitoring the acoustic output over time, to determine the condition of the thermal barrier coating on the blade or vane. The acoustic output arises from a force on the blade or vane, such as that due to impact of particles, a pulse of gas pressure or constant gas flow. An apparatus employing the above method for monitoring the condition of the thermal barrier coating during operation of the turbine, is also provided.

Abstract: Determining whether a device is defective by analyzing the sound signals generated by the device. Digital samples are generated to represent the sound signals. Digital samples are transformed from the time domain to the frequency domain to generate a frequency spectrum. By comparing the levels of intensity at a corresponding frequency to the threshold levels of intensity, defective devices can be determined.

Abstract: Method and apparatus for testing a directional acoustic device such as a directional hearing aid having level-dependent non-linear circuitry, in which two or more speakers are placed at desired positions relative to the hearing aid, e.g. in front and behind the hearing aid. The speakers are excited simultaneously with broadband excitation signals formed from components which are orthogonal to each other, e.g. sinusoids, where the bin frequencies of the Direct Fourier Transform (“DFT”) of one excitation signal are different from the bin frequencies of the other excitation signal. Thus, the response to each excitation signal can easily be extracted without filtering, allowing the directional characteristics of the hearing aid to be evaluated.