Abstract: The process of detecting the presence of insects or insect larvae in a solid substrate, e.g. wood, in which the behavioral patterns of the insects to be detected are established. These behavioral patterns are compared to actual noise and vibration patterns detected in the substrate, after extraneous noise is filtered from the actually detected information and the data has been converted to analog form. The actual analysis is performed by a microcomputer. The microcomputer analysis yields an output indicative of damage or movement activity or lack of such activity.

Abstract: Detection of insect infestation in an agricultural commodity is provided by piezoelectric means for generating electricity in response to vibration only of a frequency above about 500 Hertz, in vibrational communication with the agricultural commodity. The present invention may be utilized to detect infestation by a variety of different insects such as rice weevil, lesser grain borer, angoumais moth, in numerous types of agricultural commodities including corn, wheat, rice nuts, cotton, etc.. Various embodiments are disclosed including use of the piezoelectric means, on a probe, with a sample cup, in a device for telemetry, and with various container means for containing an agricultural commodity including e.g. a truck, ship, railroad car and storage bin such as a silo or grain elevator.

Abstract: An acoustic emission transducer has an improved design and mounting arrangements for using it to monitor machine tool operating condition. The transducer has a hollow housing with external threads capable of making a threaded mounting connection through which acoustic emission energy generated by operation of a machine tool propagates and is then transmitted by the housing. Also, a wear plate is attached to one end of the externally-threaded housing and supports a piezoelectric detecting element in the housing. The plate is capable of transmitting acoustic emission energy and the detecting element is capable of detecting it and generating an electrical signal in response thereto. In a surface mounting arrangement of the transducer, an adapter is used in mounting the transducer to a surface of the machine tool support structure. In an integral mounting arrangement of the transducer, the housing of the transducer is threaded directly into an internally threaded cavity in the machine tool support structure.

Abstract: Method and apparatus for determining a point of inflection in a evaluating maximum prior stresses to which a sample has been subject is accomplished by acoustical emission response from the sample versus the applied stress to the sample. The method comprises applying a compressive force to the sample in a manner which gradually and uniformly increases stress on the sample. Stress as applied to the sample is measured and simultaneously, cumulatively acoustic emission pulses are counted in response to the gradually increasing applied stress to the sample. In an X-Y co-ordinate system, the measured stress is plotted along one co-ordinate and the cumulative acoustic emission count supplied along the other co-ordinate to develop a curve having a recognizable point of inflection to indicate maximum prior stresses to which the sample had been previously subjected.

Abstract: A tool monitoring system for detecting a tool failure of a tool employed in a tool machine, comprising artificial signal generating unit for generating a predetermined artificial tool failure signal simulating the acoustic emission signal obtained in an actual failure of the tool, acoustic emission transducing unit adapted to be mounted on the tool machine near the tool and driven by the artificial signal generating unit for applying the artificial tool failure signal to the tool machine, acoustic emission sensing unit mounted on the tool machine near the tool so as to receive, in a setting mode of the system where the transducing unit is mounted on the machine, the applied artificial tool failure signal from the acoustic emission transducing unit through the tool machine and, in a monitoring mode of the system where the tool is operated, an acoustic emission from the tool, and signal processing unit for analyzing an output signal generated from the acoustic emission sensing unit to detect the tool failure of

Abstract: A method and apparatus for monitoring the structural acoustic signature of a structural member in response to a transient load, corresponding to detected vibration frequencies transmitted by the structural member including the fundamental and harmonic frequencies of the structural member, to determine changes in structural integrity and to determine the nature and type of transient loads. The structural acoustic signature of the structural member in a first condition in response to a first transient load is compared to a structural acoustic signature from a second transient load whereby differences in the signatures correspond to the occurrence of changes in the elastic qualities or condition of the structural member. The signatures are preferably evaluated in the frequency domain. The nature and type of transient load can be determined by evaluating the waveform shape of a structural member in response to the unknown load against a history of waveform shapes corresponding to known laods.

Abstract: Wood and other article destroying insects, when feeding, induce vibrations in the article being destroyed which is monitored and amplified to an audible level. The vibratory sounds are then analyzed as by comparison with other records of known destructive insects to determine the probable species of insect and its location.

Abstract: An apparatus for detecting a failure in a bearing has an acoustic emission sensor which detects acoustic emission from the bearing and outputs signals indicative of power of the acoustic emission, a bandpass filter which passes only signals in the range of from 100 kHz to 500 kHz out of the signals received from the aforementioned sensor, and a comparator which compares each of the signals in the range of from 100 kHz to 500 kHz extracted by the bandpass filter with a predetermined threshold value and outputs event signals each of which expresses that the signal from the bandpass filter exceeds the threshold value. This apparatus also has a computer which receives the event signals from the comparator, determines time intervals in which the event signals occur, totals the number of event signals for respective timer intervals, and determines whether or not the number of totaled events exceeds a predetermined threshold value to determine a failure in the bearing.

Abstract: Apparatus and methods are disclosed for acoustically detecting different conditions of boiling occurring within a liquid and developing useful control signals correlated to the detected boiling condition. Distinctions are made between no-boiling, sub-cooled boiling, and full or rolling boiling conditions.

Abstract: Method and apparatus for evaluating the density profile of a wood-derived specimen. A sample of the material is mounted on a lathe and rotated at high speed. An acoustic emission transducer is coupled to a cutting tool, brought into contact with the specimen to produce an AE signal, as the tool is moved across the thickness of the rotating sample. The acoustic emission signal is then transformed into an electrical signal and the resultant electrical signal is amplified and transmitted to a second amplifier for further amplification and analysis of the signal.

Abstract: A method and device for monitoring the operation of a component which is located in a sealed enclosure and is movable into a selected operating position in response to an activating signal uses the steps of: generating a short-duration acoustic signal in the enclosure in response to the movement of the component into the selected operating position; sensing the acoustic signal at the exterior of the sealed enclosure; and determining the time relationship between the activating signal and the acoustic signal. The acoustic signal is generated by an element which is carried by or moveable with the component and which generates the acoustic signal by striking an interior surface of the enclosure when the component moves into the selected operating position.

Abstract: Method and apparatus for determining vertical density profiles in wood composites. A fly cutter is rotated across the edge of a wood composite panel to produce acoustic emissions that themselves produce an RMS voltage. The changes is RMS voltage so produced are recorded and thereby the acoustic emission is recorded. The detected signal is transformed into electrical signals, amplified and transmitted to a suitable detecting transducer.

Abstract: In a functional evaluation device for use in evaluating functional degradation of an artificial device buried in a living body, frequency zones of acoustic emission are detected by the use of the fact that the functional degradation brings about variation of the frequency zones. The acoustic emission may be measured at two different positions adjacent to the artificial device so as to detect an arrival time difference of the acoustic emission and to thereby locate the functional degradation. The acoustic emission is therefore picked up by a pair of transducers placed at the two positions and is processed by a processing circuit for detecting whether or not the functional degradation takes place and by a determining circuit for locating the functional degradation.

Abstract: An apparatus and method for detecting insects detects insects by detecting ultrasonic signals which are generated by mechanical disturbances in material on which insects are feeding caused by the insects feeding on the material.

Abstract: Method and apparatus are disclosed for inducing dimensional stability in cured composite structures using acoustic emission analysis to identify the appropriate level and extent of coincident thermal conditioning. Temperature of the composite structure is lowered at a bounded rate to a minimum temperature typical of the intended operating environment. Passive stress wave acoustic emissions of the composite are analyzed to generate a signature of stress relaxation events over time. When the rate of stress relaxation events decreases below a predetermined percentage of the maximum rate, and remains below that level for a period of time sufficient to predict operational stability, thermal conditioning is terminated.

Abstract: A transducer is provided for measuring tangential dynamic displacement of a transient nature at a point location on the surface of a mechanical body. This broadband transducer is particularly useful for detection and measurement of acoustic emission signals. The essential components are a large, extended compound backing (1), a sensing piezoelectric element of low geometric symmetry (2) having the proper static polarization, an electrode system (3) and (4), an attachment process (3a), and a means of leveling the transducer (5). The element is characterized by two parallel plane faces of contact, the area of the rear face of attachment being much larger than the front face. The front face has a width dimension which is small in comparison to the wavelength of the highest frequency of interest.

Abstract: A mobile device for testing an axle-mounted roller bearing of a railcar to determine possible defects in the bearing. A movable base plate has an electric motor, a drive roller, a driven roller, and a plurality of leveling jacks mounted thereon. The motor actuates the driver roller and the leveling jacks raise the base plate to move the drive roller and driven roller into contacting engagement with the outer race of the roller bearing. The outer race of the bearing is rotated by the drive roller at a predetermined rate. Shock pulses of energy also known as an acoustic emission, are emitted by defects in the bearing. A probe which senses such emissions is connected by a cable to a monitoring instrument. The probe is placed on a test point having direct metallic contact with the bearing, whereby the monitoring instrument will measure the type and magnitude of shock pulses, if any, emanating from the bearing. These readings are used to determine the type and extent of possible defects present in the bearing.

Abstract: In acoustic emission non-destructive testing, broadband frequency noise is distinguished from narrow band acoustic emission signals, wherein the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events.

Abstract: A method for the rapid acoustic emission testing of pressure vessels wherein the flow rate of the pressurizing fluid is increased while maintaining the velocity of the pressurizing fluid, as it enters the pressure vessel, below the velocity which would cause the generation of flow noise.

Abstract: A method and apparatus for monitoring cracks of a rotatable body by detecting cracks by measuring accoustic emission signals and evaluating the depth of cracks from the result of the comparison of assumed vibrations of the rotatable body and its measured vibrations. By this method and apparatus not only the beginning of cracking of the rotatable body, but also the progress of cracking on an online basis can be detected and monitored.

Abstract: The present invention provides a method which avoids the expense and danger of previous methods used to discover gas contained in geological formations to be mined. Specifically, it has been found that increasing gas contents of evaporite samples emit increasing levels of sound when dissolved in water. By recording the sounds given off by small grab samples taken from within the mine and from the specific formation to be mined, the volume of gas in the sample can be ascertained and gas liberation during mining operations may be predicted. The method comprises the steps of: obtaining a sample; placing it into water and placing the water and sample into a sound-proof chamber; recording the acoustic emissions given off as the sample dissolves; using the recorded acoustic emissions to determine the presence and volume of gas in the sample; and predicting the volume of gas in the evaporite formation to be mined.

Abstract: The sound created by moving and chewing of insect larvae infested inside an agricultural commodity is acoustically detected and amplified, and thereafter transduced into an electrical signal which is electrically amplified for observation.

Abstract: A transducer for sensing transient elastic waves in metallic components particularly in steel weldments below water on offshore structures comprises a piezoelectric sensing element (1) for coupling to the metallic component and shielded from noise arriving in directions other than the component by an elastomeric encapsulation (22) such as of aerated polyurethane.

Abstract: An apparatus for discriminating a machining state from a non-machining state in a machine tool wherein a workpiece is machined with a cutting tool or grinder, comprising plural vibration sensors including at least one acoustic-emission sensor, which detect vibrations of different frequency bands, respectively, which are produced during machining of the workpiece by the tool. A discriminating device judges that the workpiece is being machined by the tool when levels of output signals generated from at least two of the vibration sensors are higher than respective predetermined threshold levels, and judges that the workpiece is not being machined by the tool when the level of an output signal generated from less than two of the vibration sensors is higher than a predetermined threshold level. Also disclosed is a method for discrimination between the machining and non-machining states.

Abstract: Method and apparatus for estimating the location of an unknown sound source in a structure to be monitored, wherein sounds from at least three known sound sources are detected by a plurality of detectors. At least one of peak value data and signal arrival time data derived from the outputs of the detectors are classified for each of the known sound sources and stored in a storage. Pattern differences from each of the known sound sources to a number of predetermined positions respectively, are calculated to prepare for each of the known sound sources a correspondence table indicating relationships between the calculated pattern difference and the real distances from the known sound source positions to the predetermined positions, the correspondence table being stored in a storage. The pattern differences for each of the known sound source positions are calculated on the basis of the sound signal data derived through detection of a sound from an unknown sound source and the data stored in the storage.

Abstract: Provided is apparatus suitable for continuous long-term monitoring of acoustic emissions, particularly from large structures such as pipelines. The apparatus comprises a plurality of detector-analyzer units coupled to a central control unit via a communications link. Each detector-analyzer unit comprises an acoustic detector, signal processing means, and a microprocessor. Preferably, the signal processing means comprises at least one signal conditioner, and at least one measuring circuit which provides digital output signals representing a set of emission parameters. The microprocessor preferably periodically receives and compares the digital output signal representing each of the emission parameters with the base values thereof, and provides a warning signal if a problem situation is perceived as a result of such comparison.

Abstract: A method and apparatus for diagnosing pathologies of the ear, particularly pathologies such as otitis media, directs into the ear canal a sequence of acoustic waves covering a range of frequencies from a few hundred Hz to several kHz and determines the presence or absence of resonance when the incident and reflected waves are combined. The measurements are made without pressurizing the ear canal and it is not required that the contact between the instrument and the ear be air-tight. Accordingly, essentially no discomforture of the patient results from use of the instrument. The requisite measurements are made quickly (of the order of tens of milliseconds) and thus the distorting effects of patient movement are effectively eliminated. An improved version of the instrument is completely self-contained and hand-held and has the form of a "tee" in which the resonant frequency and amplitude are visually indicated by means of horizontally-and-vertically disposed arrays of light-emitting diodes.

Abstract: A small non-colinear transducer array for omnidirectional acoustic emission monitoring is disclosed. The small transducer array consists of four piezoelectric sensor elements of sufficiently small diameter as to function as essentially point receivers and of sufficient frequency response as to be sensitive to the signals to be detected. The sensor elements of the transducer array are close together and are non-colinear so that the signals received by them can be used for determining the group velocity of acoustic waves on solid plates and on plate-like structures such as shells and pipes, and to permit determination of both the source direction and distance.

Abstract: Pressure vessels are tested for structural integrity by recording acoustic events generated in the vessel's walls while it is immersed in water and subjected to internal pressure above the vessel's working pressure. Acoustic events are recorded by sensors fixed either to the wall of the vessel or to the walls of the water container in which the test is conducted. In preferred form, the vessel is water filled throughout the test and its volumetric increase with pressure is measured in an initial over-pressurization.

Abstract: An apparatus for detecting damage to the cutting tool fitted in a machine tool controlled by automatic machining control circuit means such as a microprocessor, which acts to sense the level of acoustic emission generated by the machine tool during machining, compares that level with one of a plurality of different predetermined data values which are stored in a memory circuit, and generates a warning signal if the noise level exceeds the predetermined level. The different data values stored in the memory circuit are respectively utilized for different machining conditions, i.e. different combinations of cutting tool, machining material, feed rate, etc.

Abstract: A system for monitoring the vibration of a power driven cutting tool during machining first produces a signal proportional to the vibration spectrum of the tool over a preselected band width. This is passed through a digitally controlled attenuator which is adjusted to provide an output signal at a preselected level. The degree of attenuation is stored, as is a reference value which is generated as a function of the attenuated signal. Then, during subsequent machining operations under the same machining conditions the attenuator is controlled to provide the same degree of attenuation and the reference value, which is in the form of a digital signal, is compared with the rectified and digitized output of the attenuator. When the latter exceeds the reference value a control signal is generated which either provides an audible or visual warning that the cutting tool is worn and therefore due for replacement or initiates an automatic tool changing operation.

Abstract: A ceramic product is exposed to a light from a tungsten lamp, so that a specified region of the product is heated. In this heating process, acoustic emissions from the ceramic product are detected by an AE sensor which is acoustically coupled to the ceramic product by means of a waveguide passage. A temperature gradient directed from the surface toward the inner part of the ceramic product is formed by heating, and thermal stress is applied to the product so that tensile stress is produced in the inner part of the product. In practical use, a crack constituting the core of fracture is caused to grow by the thermal stress, and an acoustic emission is released. The existence of a defect can be evaluated by detecting the acoustic emission. Also, the location of the defect in the product can be detected by heating part of the product. The equivalent crack dimension a.sub.

Abstract: An abnormal noise detector for detecting abnormal noises resulting from a marred tooth surface in a gear of a gear unit is disclosed. A first embodiment of a detector comprises a microphone placed in the vicinity of a gear unit to be tested, a bandpass filter for filtering the output of the microphone so as to pass only an integral multiple of the fundamental frequency of noise due to meshing of the gears of the gear unit, a rectifier for rectifying the filtered output from the bandpass filter, a differentiator for differentiating with respect to time the DC output from the rectifier, a waveform shaper for shaping the output from the differentiator into pulses suitable for counting, and a pulse counter for quantifying the pulses in the output from the waveform shaper. A second embodiment comprises a microphone, a digital frequency analyzer, and a data monitoring computer responsive to the digital frequency analyzer for monitoring the output thereof.

Abstract: An abnormal noise detector for detecting abnormal noises produced by a gear unit with an eccentrically mounted gear is disclosed. A first embodiment comprises a microphone placed in the vicinity of a gear unit to be tested, a bandpass filter connected to the microphone which passes only a band of frequencies centered around an integral multiple of the normal fundamental frequency of the noise produced by the meshing of the gears of the gear unit, an amplitude detector which detects the amplitude of the signal from the bandpass filter, a frequency deviation detector which detects the frequency deviation of the signal from the bandpass filter, and recorders for recording the values of the signals from the amplitude detector and the frequency deviation detector as a function of time. A second embodiment comprises a microphone, a digital frequency analyzer and a central processing unit for determining whether abnormalities exist in the data produced by the digital frequency analyzer.

Abstract: The present invention relates to a method for acoustic testing of multiple segment complex structures for detecting changes in the integrity of such structures to anticipate failure. The method of the present invention in its simplest form requires providing each segment of a complex multiple segment structure with at least one acoustic sensor, recording the intensity and frequency distribution of the acoustic waves sensed by such acoustic sensor; and finally comparing the acoustic waves that are sensed either against a standard, over time, and/or from one segment of the complex multiple segment structure to another segment of the complex multiple segment structure.

Abstract: A method of detecting the presence of flaws in wire as it passes through a wire drawing die involves monitoring the output in the megacycle range of an acoustic sensor attached to the drawing die.

Abstract: The invention is a method of determining whether an adhesively bonded joint between two structural elements meets established strength requirements. The method comprises the following steps: (1) Determining by test the levels of acoustic energy to be directed and/or focused by a transducer 12 on a minute area of the adhesively bonded joint 14 and further the application times thereof.

Abstract: An acoustic emission monitoring system used for monitoring fatigue crack growth in metal or other materials such as occur, for example, in highway bridges during normal traffic loading. The transducers are placed on the plates to be tested to allow detection of acoustic emission from a particular site. By applying specific recognition methods to the acoustic emission AE, detection of flaws can be detected from a random noise background. The pattern recognition technique first subjects the received AE energy to an energy window test and if the energy is within the window, it is subjected to a rate test and if the energy exceeds predetermined rates, it is passed to a location test so as to locate the position of flaws.

Abstract: An acoustic crack detection method and device in which an impact is produced between an actually tested metal piece and an anvil. This impact generates an acoustic wave formed of a plurality of components, one of these wave components being produced by vibrations of the metal piece and having a frequency indicating a cracked or uncracked state of this piece. A microphone senses the acoustic wave generated by the impact and a measuring circuit receives the signal from the microphone for measuring the energy, within a predetermined time gate and within a predetermined frequency bandwidth, of the wave component of interest. The measured energy is compared with a reference level in order to determine if the actually tested metal piece is cracked or not.

Abstract: Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

Abstract: The apparatus comprises one or more acoustical transducers associated with a particular interchangeable rotor blade for monitoring acoustic emissions emitted by the rotor blade under operating stress. The output of the transducers is connected to a computer associated with the particular aircraft. The transducer output signals are processed by the computer and filtered to allow real time stress return level readings so as to accumulate a count of critical acoustic emissions which are indicative of progressive irreversible structural fatigue or damage to the interchangeable rotor blade.

Abstract: A waveguide is provided, particularly for use in acoustic emission applications involving a hostile environment, comprised of a member selected from the group consisting of aluminum oxide and beryllium oxide. The waveguide is solid in form, and varies in length depending upon the specific application or use of the waveguide and the frequency of the signal. Size varies inversely to frequency levels. The cross sectional dimension will vary depending upon application, and will generally conform to the size of the crystal sensor element being utilized in a particular application.

Abstract: An acoustic emission is detected by a pickup, and its output is converted by a A/D converter into a digital signal, which is provided to a fast Fourier transform processor. The fast Fourier transform processor comprises a cascade connection of a plurality of operation stages, each composed of first and second input memories, a third memory having stored therein a rotation vector and an arithmetic unit for performing a Butterfly operation through using the pipelined architecture. In each stage one of the first and second input memories and the third memory are read out and the Butterfly operation is carried out on the pipelined basis. The operation result is written into that one of the first and second input memories of the next operation stage which has not been read out; thus all the operation stages perform a pipelined operation as a whole. The power of a spectrum obtained as the operation result of the last operation stage is calculated, obtaining a signal corresponding to the acoustic emission.

Abstract: Acoustic emission monitoring is a non-destructive testing technique that ects ultra-high frequency sound that stressed metal emits. In straightening a gun tube the workpiece is at first under no stress, is elastically deformed (with total springback when pressure is released), is plastically deformed (with some springback upon release of pressure), or it cracks under too great a pressure. Each of these stages produces a distinctly different type of acoustic emission. By listening to the workpiece during the pressing operation the operator can be alerted as to the stage the workpiece is in and he can adjust his operation accordingly.

Abstract: Methods and apparatus are disclosed for monitoring and controlling potential residual stress relief mechanisms in composite epoxy resin materials. Passive and injected, or active, acoustic signals originating in or propagated through a specimen material during the formation process produce signatures identifiable with known residual stress relief mechanisms. Real-time control of material temperature and external pressure during formation in response to acoustic signals measured or observed in relation to desired acoustic signature minimizes formation of undesired material properties.

Abstract: Apparatus for detecting acoustic emissions from metal matrix wire allows on-line measurement of the transverse strength of the wire as it is moving through its manufacturing process. A series of end and middle rollers guide the wire and form a bend in it. The location of the bend in the wire is maintained in contact with a liquid bath which, in turn, is contacted by the sensing surface of an acoustic transducer. Acoustic emissions from breaking of the fiber-matrix interface of the wire are transmitted by the bath and detected by the transducer.

Abstract: A process for monitoring the presence of cracks, formation of cracks and growth of cracks in constructions, for example off-shore oil and gas platforms, by recording and analysis of acoustic emissions from the construction, the sensors being mounted in the medium which surrounds the construction instead of on or in the construction itself.

Abstract: The invention relates to a method of measuring the dimensions of tools and/or workpieces of metal. The measuring is characterized in that an electro-erosive material-machining discharge in a dielectric is used as transmitter of pressure waves, the time of which through the tool or workpiece to the arrival in at least three well-defined positions is scanned and gives rise to time-responsive current pulses for a digital measuring system.

Abstract: The present invention allows the position of a defect to be located when it emits acoustic waves into a closed structure. The waves travel around closed routes in a section of the structure.To this end, it comprises at least three acoustic sensors (22-24), uniformly distributed on the surface of the section of the structure monitored, connected to logic (26, 27) for encoding the order of arrival of the signals detected. Control means (16, 20, 35) for controlling display means and means (19) for controlling the writing means of the latter, which is preferably a conventional dual-trace oscilloscope are described. The image of the section monitored is traced by two beams rotating in opposite directions, only one of which is illuminated for a brief instant at the moment of detection of the acoustic emission, as it passes the image point identifying the defect.

Abstract: Integrity of acetylene cylinder filler material is accurately and easily determined by monitoring acoustic emission counts as a function of load and establishing the distinctive signature of faulty filler material.