Abstract: A sound level monitor device has a microphone. A sound level measurement circuit is coupled to the microphone. The sound level measurement circuit takes sound signals monitored by the microphone and converts the sound signals to digital signals. A display is coupled to the sound level measurement circuit. The display will show the different measurement signal values. A single control button is coupled to the sound level measurement circuit. Pressing the control button a first time activates the sound level measurement circuit so a current measurement signal value is shown on the display. Pressing the single control button a second time causes a highest recorded measurement signal value, since the sound level measuring device has been presently activated, to be shown on the display. The highest recorded measurement signal value remains on the display until a higher recorded measurement signal is monitored.

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: 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: The present invention relates to a method, system and device for monitoring noise received by individuals operating in noisy environments. The device comprises a substantially credit card size housing and can be worn as a “badge”. The device includes a monitoring means for monitoring sound, and a display for displaying various noise parameter values, including a percentage value of cumulative noise dose received by the device. The device includes an input key which enables a user to select one of a plurality types of hearing protection equipment, so the user can indicate to the device the hearing protection equipment they are wearing. This enables the device to monitor compliance. The device also includes an input key enabling the user to acknowledge when an unallowable noise dose level has been reached.

Abstract: An acoustic measurement installation including acoustic measurement instrumentation, in particular an acoustic measurement antenna fitted with at least one microphone; a positioning system for positioning the antenna by ultrasound and including at least one ultrasound emitter mounted on the antenna at a known distance relative to the microphone and an ultrasound receiver base for receiving the signals emitted by each emitter and adapted to determine the position of each emitter; and a control unit for controlling the positioning system for positioning the antenna and the acoustic measurement instrumentation. The control system is adapted during a first stage to cause each emitter to emit in succession in order to determine the position of the antenna, and during a second stage to cause the microphones to perform acquisition in order to implement acoustic measurement using the measurement instrumentation.

Abstract: Method and apparatus for simultaneous acoustic measurement at a point (M) in space of the three components of the sound intensity vector. A preferred omnidirectional vector probe (40) includes a central ring (42) with four small, microphones on tubes attached to the ring spaced from one another in a regular tetrahedral arrangement. The tubes are parallel to the axis of the ring, two on one side (58) and two on the reverse side (60) of the ring, with two of the microphones pointing in one direction and two in the opposite direction. The microphone signals are processed by an analog-to-digital converter feeding a digital signal processor (68) and employing a cross-spectral formulation to compute a sound intensity vector at the measurement point (M). Sound velocity and pressure can also be determined at this point. The resulting data may be outputted on a computer screen or other device (70). Additional related features and methods are disclosed.

Abstract: A method for measuring a film strength of a film on an object. An incident angle of pressure waves with respect to an object to be measured, the object including a base coated with a film, is set for applying the pressure waves to the object. The incident angle is varied over a range including a critical angle ?cr. The object generates surface waves, in response to the pressure waves, at and near the critical angle. In response to the surface waves, the object generates leaky waves, which are pressure waves caused by the surface waves. The intensity of pressure waves including reflected waves and leaky waves from the object are measured. A received intensity V0 at an incident angle where no leaky wave is generated, and the intensity difference VC between V0 and the received intensity at the critical angle ?cr when the film strength is high are measured.

Abstract: An ultrasonic power meter is provided for measuring ultrasonic power emitted by a device (18) under test. The meter includes a casing forming a chamber (16) within which an ultrasonic absorber (14) formed from polyurethane material is located. Overlying the absorber (14) is a membrane (12) of polyvinylidene fluoride which acts as a pyroelectric detector. The meter also includes a transfer medium (10), typically water, for allowing the transfer of ultrasonic energy emitted from a device (18) under test to the meter.

Abstract: A method of ultrasound inspection is provided. The method includes providing a composite first part, introducing ultrasound to the part, receiving reflections of the ultrasound introduced in the first part, and predicting a residual strength of the first part using an amplitude of the received reflections.

Abstract: A liquid measurement system including interface apparatus for sharing the excitation and signal processing of an ultrasonic transonic transducer and temperature measuring device remotely located at a liquid container is disclosed. The interface apparatus includes a common conduction path coupled to both of the ultrasonic transducer and the temperature device for conducting first excitation signals to the ultrasonic transducer and the corresponding echo signals therefrom, and for conducting second excitation signals to the temperature measuring device and the response signals therefrom, and an interface circuit for governing the conduction of the first and second excitation signals over the common conduction path from their generating sources and for providing a balanced interface for receiving both of the echo signals and response signals from the common conduction path.

Abstract: A process for measuring the bond of a coating on a substrate. Ultrasound echoes through the substrate of a test piece are collected and their amplitudes are measured, their decay being a function of the bond of a coating deposited on the opposite face of the substrate. Preliminary tests on calibration test pieces give a correlation function so that it is unnecessary to carry out expensive and uncertain mechanical tests on the test pieces.

Abstract: An improved heat shield provides thermal insulation and reduced noise transmission of vehicular engine components, including exhaust manifolds. The structure has three layers; an outer structural metal layer, a center insulation layer to isolate heat and dampen noise, and an inner metal layer directly adjacent the shielded component for reflecting heat back to the shielded component. The heat shield is attached by bolts to the shielded component. In the described embodiment, the volume of the insulation layer is expanded by approximately 15 to 20 percent over conventional shields to produce a softer, thicker material having a lower density but unchanged mass. The invention provides a technique to achieve desired thickness and density in insulation layers via modal finite element analysis. The relatively thicker heat shield more effectively absorbs vibration and attenuates noise without increase in mass. In the described embodiment, the layer contains cellulose, diatomaceous earth, talc, and fiberglass.

Abstract: A sound field measuring apparatus has: an exponential pulse generator 11 which outputs a pulse signal to speakers 4a, 4b, . . . ; a microphone 6 which is disposed in an acoustic space 5 where the speakers 4a, 4b, . . . are disposed, and which detects a pulse signal output from each of the speakers 4a, 4b, . . . ; and a calculation section 15 which detects a time when the signal detected by the microphone 6 exceeds a predetermined threshold. The calculation section 15 calculates a time period from a time when the pulse signal is generated by the exponential pulse generator 11 to the time when the signal exceeds the predetermined threshold.

Abstract: A two-dimensional ultrasonic probe has a transmitting function of an ultrasonic signal without electric interconnection of a numerous number of microcomponents and without increase in crosstalk and electric impedance. This probe includes an optical fiber array having a plurality of optical fibers to which light generated from a light source is made incident, a plurality of ultrasonic detecting elements, formed at one ends of the respective optical fibers, for modulating incident light via the optical fibers on the basis of the ultrasonic signal to be applied, and an ultrasonic transmitting element using a piezoelectric element.

Abstract: A device for detecting or analyzing machinery damage is used preferably in the determination of defects in roller bearings. Pulse-like machinery or bearing noise acquired by a sensor is converted into special time signals. These time signals correspond to events which are basically periodic in occurrence. The time signals are sent to one, preferably several, classification units depending on the time differences. Before classification, combination of adjacent time signals or events is performed using their pulse heights. The combining is multiplicative or obeys some other bivalent relation. Classification forms a frequency distribution with an abscissa which is divided into time units. Specific characteristics of the frequency distribution provide information on incipient or manifest machinery damage.

Abstract: The invention provides a method and an apparatus for measuring the size, concentration and size distribution of particles in a fluid by determining the characteristics of an acoustic speckle signal of the particles and relating these characteristics to the size and concentration characteristics of the particles. The method and the apparatus are especially useful for the measurement of the size distribution of small particles in optically opaque liquids.

Abstract: Ultrasound echoes (L5, L8, etc.) through the substrate (2) of a test piece (1) are collected and their amplitudes are measured, their decay being a function of the bond of a coating (2) deposited on the opposite face of the substrate (2); preliminary tests on calibration test pieces give a correlation function so that it is no longer necessary to carry out expensive and uncertain mechanical tests on the test pieces (1).

Abstract: A method for quality control testing of a laser shock peening process of a production workpiece includes (a) ultrasonically scanning at least a portion of a laser shock peened surface on the workpiece wherein a region having deep compressive residual stresses imparted by the laser shock peening process extends into the workpiece from the laser shock peened surface, (b) digitizing a signal derived from the scanning and forming a digitized image of intensity values from the scanning, (c) calculating at least one statistical function value for a plurality of points of the digitized image of the workpiece based on the intensity values, and (d) comparing the statistical function value to a pass or fail criteria for quality assurance of the laser shock peening process or accepting or rejecting the workpiece.

Abstract: A device for measuring the height of a sheet pile by using a reflectively operating radiation detector, a sheet separating device and a device for conveying separated sheets to a printing machine being assigned to the pile, comprising a system for measuring the propagation time of a radiation pulse originating from a radiation source and reflected at a sheet surface, the amplitude of the pulse being within a predefined range and lower than the amplitude of the reflection of the same radiation pulse at the surface of the sheet located closest to the radiation source, the radiation detector being connected to the measuring system.

Abstract: In a method of screening bulk material, a gas is conducted in counterflow to a direction of movement of bulk material for separating the bulk material into a fraction of coarse particles and a fraction of fine particles. In order to limit the amount of coarse particles in the outgoing fraction of fine particles, the amount of coarse particles contained in the fraction of fine particles is measured and compared with a desired value. When encountering a deviation of the measured the amount of coarse particles contained in the fraction of fine particles form the desired value, the energy of gas is so controlled as to match the amount of coarse particles contained in the fraction of fine particles with the desired value.

Abstract: A method of determining the quality of insertion of an electrical terminal includes the steps of capturing the sound associated with insertion of the terminal. The terminal is typically inserted into a connector associated with a wire harness. By capturing the sound, the system is able to compare the captured sound to an expected sound. If the captured sound differs from the expected sound then a determination is made that the terminal is not properly inserted.

Abstract: A method and apparatus for measurement of wide dynamic range signals is provided. The method and apparatus is particularly suited to measurement of physical parameters over a wide dynamic range and utilizes a plurality of concurrently operating channels of moderate dynamic range, each of which incorporates a detector. The method has the steps of transducing the physical signal into an electrical signal; amplifying and filtering the electrical signal through a plurality of channels, each of which operating within a preselected range of levels; applying the filtered and amplified electrical signals to a plurality of detectors, one for each channel; averaging, using a first time constant, the electrical signals to create a plurality of outputs; sampling the outputs; determining which channel of the plurality of channels has a valid output; averaging, using a second time constant greater than the first time constant, the resultant series of valid output samples (i.e.

Abstract: Apparatus for automatically determining the total sound power emitted by a work machine. The noise testing system employs a processor and remote control to control the measurement of both exterior and interior sound generated by a work machine in either a dynamic or static operating mode.

Abstract: A motor vehicle having a remotely operable subsystem provided with an acoustic emitter has a system having a microphone on the vehicle, a signal processor connected to the microphone for determining an ambient sound level at the microphone, and a controller connected between the signal-processor and the acoustic emitter for controlling an output volume of the emitter in accordance with the determined ambient sound level at the microphone.

Abstract: An ultrasonic measurement method in an ultrasonic measurement system having an ultrasonic transducer includes emitting an ultrasonic pulse from the ultrasonic transducer. An ultrasonic pulse is received in accordance with a pulse travel time wherein the amplitude of the received ultrasonic pulse varies according to the pulse travel time. A first electrical signal is provided representative of the received ultrasonic pulse wherein the amplitude of the first electrical signal varies in accordance with the pulse travel time. A second electrical signal is provided in accordance with the first electrical signal wherein the amplitude of the second electrical signal is substantially independent of the pulse travel time. In order to determine the second electrical signal variable amplification is applied to the first electrical signal in accordance with the travel time.

Abstract: A process using ultrasonic inspection for testing the internal soundness of cathode sputtering targets, whose active part is made of aluminum with a very high degree of purity or a very pure aluminum alloy, consisting, after selection of an ultrasound sensor functioning at an operating frequency greater than 5 MHz, preferably between 10 and 50 MHz, and adjusting the appropriate measurement sequence, using a target immersed in a liquid and which has ceratin artificial defects simulating decohesions in the target, taking a count in terms of size and number of the internal decohesions per unit volume and selecting, for the applications requiring a very high degree of etching fineness, the targets with a decohesion density of .ltoreq.0.1 decohesion larger than 0.1 mm/cm.sup.3 of active metal of the target, and cathode sputtering targets selected according to the process having no more than 0.1 internal decohesion larger than 0.1 mm/cm.sup.3 of active metal of the target.

Abstract: An alternate formulation is derived for predicting acoustic radiation from a vibrating object in an unbounded fluid medium. The radiated acoustic pressure is shown to be expressible as a surface integral of the particle velocity, which is determinable by using a non-intrusive laser Doppler velocimeter. Solutions thus obtained are unique. Moreover, the efficiency of numerical computations is high because the surface integration can be readily implemented numerically by using the standard Gaussian quadratures. This alternate formulation can be desirable for analyzing the acoustic and vibration responses of a lightweight, a flexible or a structure with a hostile environment for which a non-intrusive laser measurement technique must be used.

Abstract: An apparatus for measuring loss of sound traveled in a muffler of an automobile comprises: a first and second pipe between which the muffler, to be tested, is inserted; a sound source connected to one end of the first pipe opposite to the muffler to create a sound into the first and second pipes; the first microphones mounted at the first pipe to measure the level of sound before the muffler; the second microphones mounted at the second pipe to measure the level of sound after the muffler; and a non-reflect means connected to the second pipe for the sound passing through the first and second pipes so as not to reflect into them.

Abstract: An ultrasonic measurement method in an ultrasonic measurement system having an ultrasonic transducer includes emitting an ultrasonic pulse from the ultrasonic transducer. An ultrasonic pulse is received in accordance with a pulse travel time wherein the amplitude of the received ultrasonic pulse varies according to the pulse travel time. A first electrical signal is provided representative of the received ultrasonic pulse wherein the amplitude of the first electrical signal varies in accordance with the pulse travel time. A second electrical signal is provided in accordance with the first electrical signal wherein the amplitude of the second electrical signal is substantially independent of the pulse travel time. In order to determine the second electrical signal variable amplification is applied to the first electrical signal in accordance with the travel time.

Abstract: A method for reconstructing the acoustic field on the surface of a vibrating object based on measurements of the radiated acoustic pressure includes solving the Helmholtz equation directly using the expansion of a set of independent functions that are generated by the Gram-Schmidt orthonormalization with respect to the particular solutions to the Helmholtz equation. The coefficients associated with these independent functions are determined by requiring the assumed form of solution to satisfy the pressure boundary condition at the measurement points. The errors involved in these coefficients are minimized by the least squares method. Once these coefficients are specified, the acoustic pressure at any point, including the source surface, is completely determined.

Abstract: An elastic wave is applied to an object under the ground, so that an elastic wave which varies in accordance with the material and shape of the object under the ground is detected and the detected elastic wave is collated with characteristic data such as elastic wave data, or the like, of various objects registered in advance to thereby identify/discriminate the object under the ground. A vibration generating probe and a vibration receiving probe, or, alternatively, a vibration generating and receiving probe is put into the ground so as to come in contact with an object under the ground. Then, the vibration generating probe or vibration generating and receiving probe is hammered to generate an elastic wave. At least one of one longitudinal wave and two transverse waves of the elastic wave which has propagated to the object under the ground is received by the vibration receiving probe or vibration generating and receiving probe.

Abstract: A system and method for homogeneous bioassay uses acoustic energy emissions. A measurement cell is designed for binding reactions of mobile biorecognition molecules. The binding reaction contained in the measurement cell is for example a ligand/receptor binding reaction or a complementary nucleic acid binding reaction. A passive acoustic energy transducer is coupled to the measurement cell for detecting acoustic energy generated by the binding reaction of mobile biorecognition molecules. The passive acoustic energy transducer generates a corresponding analog electrical signal. A signal conditioner coupled to the passive acoustic energy transducer filters and amplifies the electrical signal. A signal analyzer determines spectra of the conditioned electrical signal corresponding to characteristic acoustic energy emissions of the binding reaction of mobile biorecognition molecules.

Abstract: Acoustic near field measurement method uniquely featuring mechanical econ, in terms of placement and motion of one or more acoustic measurement devices, which is accorded by the geometric character of a structure having indicia of symmetry. One or more devices are arranged, and/or caused to move with up to three degrees of freedom, so as to manifest conformance with respect to the surface of the structure. If desired, virtually complete acoustic near field mapping of the structure can be effectuated. Examples of the various embodiments of this invention include: circumferentially conformal arrayal of devices in combination with longitudinal movement of the arrayal; longitudinally conformal arrayal of devices in combination with circumferential movement of the arrayal; movement of one or more devices in a path or paths which are circumferentially conformal; movement of one or more devices in a path or paths which are longitudinally conformal; movement of one or more devices in a path or paths which are radial.

Abstract: A method and apparatus for obtaining information relating to the eating quality of meat. The meat under test may include a hot or cold meat carcass, raw or cooked meat or live animal. The method includes the steps of injecting an acoustic signal into the meat, monitoring the effect of the meat on at least one characteristic of the acoustic signal propagated into the meat, and applying the monitored effects to a predetermined algorithm relating eating quality to monitored acoustic effects to indicate the eating quality of the meat under test. The acoustic probe assembly of the apparatus includes a pair of arms adapted for insertion into a meat carcass. The arms carry respective means for coupling acoustic signals into and receiving signals from the carcass. Further, the arms include means for coupling the acoustic signals to the surface of a carcass and monitoring scattering of the acoustic signals to predict the eating quality of meat.

Abstract: An acousto-optic damage detector and locator uses acoustic energy propagated through a structure to modulate light transmitted through an optical fiber whereby the character of acoustic signals detected by the fiber varies according to the physical condition of the portion of the structure through which the pulses propagate to determine the existence, location and extent of faults within the structure.

Abstract: A method of continuously measuring the resistance of a track to transverse displacement comprises the steps of continuously advancing a dynamic stabilizer along the track, applying a power to the dynamic stabilizer to impart oscillations to the track extending transversely to the track in a horizontal plane, and recording a datum corresponding to the applied power as a correlated measurement value of the transverse track displacement resistance (QVW).

Abstract: A method is disclosed for identifying the presence or concentration of a target species in a sample by transmitting a wave of ultrasonic vibration through the sample and calculating, from measured values for time of flight of the wave through the sample and its attenuation during that time, an identification parameter dependent on the type or concentration of the target species in the sample and independent of the distance travelled by the wave through the sample. The method is more convenient to use than existing identification techniques because of the removal of distance from the measurements and calculations necessary. The method is of particular use in identifying polymers, for example, in reclamation and recycling processes. An apparatus for performing the method is also disclosed.

Abstract: An ultrasonic measurement method for distinguishing between unflawed and flawed parts comprises the steps of detecting at least two prominent resonant response frequencies, measuring the frequency difference between the two frequencies, determining the ratio of the frequency difference to one of said frequencies, and comparing the ratio to a predetermined part criterion. Resonant response frequencies dependant upon physical characteristics such as dimensions and weight are compared to other resonances which are at frequencies dependant upon stiffness of the part.

Abstract: The present invention is a maternal sound level device that functions to protect fetal hearing by alerting the mother whenever her fetus is exposed to sound pressure levels (SPL) which exceed predetermined levels. The device is comprised of a microphone (14) for SPL detection, preamplifier (2), weighting network (4), level detector (6), and alarm mechanism (8). This device is battery operated and can be easily clipped on a belt so as to be worn by pregnant women at the abdominal level to monitor SPL at the abdomen. SPLs are measured in the range of greater than 80 dB and less than 100 dB over a frequency range of greater than 30 Hz and less than 10,000 Hz. The mother is alerted to SPLs that are exceeding a predetermined level to protect the hearing of the mother's developing fetus by a visual and/or a mechanical alarm.

Abstract: A method and apparatus are provided for warning when the amplitude of conversations exceeds certain values. The apparatus includes a microphone and related circuitry which continuously produce a signal related to the amplitude of the conversation while the apparatus is operational. A comparator continuously compares the signal to a pre-set first value and produces an output as long as the signal indicates that the conversation exceeds a certain amplitude. There is a discriminator responsive to the comparator output which provides a discriminator output when the duration of the comparator output exceeds a pre-determined value. The discriminator is connected to an alarm which produces a warning signal when the discriminator provides the discriminator output. There may also be a second comparator which produces a visual signal when the amplitude of the conversation is above an amplitude which may be below the amplitude which activates the alarm.

Abstract: A method and system for mapping the acoustic near field of a stationary al symmetric structure are provided. The structure is subjected to a rotating excitation energy profile from a plurality of stationary excitation sites located radially around the structure. The acoustic near field of the structure due to the rotating excitation energy profile is measured along at least one line that conforms to a longitudinal surface of the structure. Mapping of the acoustic near field is complete when one rotation of the rotating excitation energy profile is complete.

Abstract: A portable hearing protection device evaluation apparatus which can be taken into the field to measure noise attenuation of a muff type hearing protection device under actual working conditions is provided. The apparatus includes two miniature microphones, one positioned inside a muff near the ear, the other positioned outside the muff to detect the noise in the environment. These two microphones simultaneously receive input signals which are provided to circuitry which determines and displays a single number output representing the noise attenuation.

Abstract: Apparatus and method for determining the condition of the floor to be cleaned by a cleaning robot. The apparatus comprises an ultrasonic wave signal transmitting circuit for transmitting an ultrasonic wave signal to an ultrasonic wave signal transmitter under the control of a microcomputer, a receiving amplifying unit for amplifying the ultrasonic wave signal transmitted from the ultrasonic wave signal transmitter and received in a ultrasonic wave signal receiver, a receiving demodulating unit for smoothing the output signal from the receiving amplifying unit to demodulate it and then apply it to the microcomputer. According to the control of the microcomputer, the ultrasonic wave signal is transmitted for a predetermined period. The period from the time when the ultrasonic wave signal is transmitted to the time when the ultrasonic wave signal is received in the ultrasonic wave signal receiver is measured.

Abstract: A test object having a plurality of protrusions is inspected for a defect and/or different-hardness by applying vibration to the test object. Spectral data of the vibration of the test object is analyzed based on signals indicative of the vibration of the protrusions. Spectral energy peaks are then detected in different spectral frequency regions corresponding respectively to the protrusions based on the signals. It is then determined whether there are two separate spectral energy peaks in the spectral region corresponding to each of the protrusions, thereby to determining whether there is a defect and/or different-hardness portion in each of the protrusions.

Abstract: A test object such as an engine cylinder is inspected for any defect such as a crack, a blowhole, a cavity, or the like by applying vibration to the test object at two different positions on a side thereof. While the test object is vibrating, signals indicative of the vibration of the test object are detected. From the detected signals, there are produced a signal indicative of a natural vibration of the test object and a signal indicative of a defect-induced vibration of the test object. The signal indicative of a natural vibration and the signal indicative of a defect-induced vibration are compared to determine whether there is a defect in the test object.

Abstract: The detection of sound emitted from a source in a dynamic environment of ambient background noise employs a sufficiently distributed array of sound intensity probes enclosing a sound source is adapted to collect measurements over the same time interval in a non-specific acoustic environment. Each probe in the array is comprised of a pair of mutually spaced microphones generally unmatched in their gain and phase response. A multi-channel fourier spectrum analyzer is used to provide a direct signal processing determination of sound intensity at each probe from pressure measurements taken at each microphone. Their computation is corrected to compensate for gain and phase mismatch between each microphone pair using independently derived probe calibration factors. These correction factors are linearly applied to the sound intensity determination at each probe of the array.

Abstract: A defect detecting method for detecting whether or not an object to be measured has a defect comprises the steps of vibrating the object to be measured, picking up the vibration, and detecting that a spectrum of the characteristic vibration of the object to be measured is separated into two portions. Also, a defect detecting apparatus comprises a vibrator vibrating an object to be measured, a detector for picking up an vibration of the object to be measured and for converting the vibration into an electric signal, and a signal processor for receiving the electric signal from the detector, for analyzing a spectrum of a characteristic vibration of the object to be measured, and for determining whether the defect is present or absent depending on whether a spectrum of a defect of the object to be measured is present or absent.

Abstract: The presence of pipeline connections can be checked by the transmitting of acoustic signals from a transmitter to an acoustic sensor within the pipe. This method is used in particular in the manufacture of cigarettes.

Abstract: An apparatus for processing acoustic emissions or stress waves in order to recognize features indicative of variations in the process producing the acoustic emissions. The apparatus comprises a transducer acoustically coupled to a machine or industrial process and arranged to detect the acoustic emissions and produce an electrical signal. The electrical signal is amplified by an amplifier and the mean level of the electrical signal is measured by a mean level detector and the minimum level of the electrical signal is measured by a minimum level detector. A ratio measurer measures the ratio of the mean level of the electrical signal to the minimum level of the electrical signal. This method is self compensating for variations in the operating conditions of the machine or industrial process, is not significantly affected by electromagnetic switching transients, and can cope with very high numbers of transient excursions.

Abstract: A system of three or more hydrophone arrays are utilized to measure underwater areal sound intensity. The hydrophone arrays bound at least one plane through which an areal sound intensity measurement is desired. Each hydrophone array comprises three orthogonal pairs of hydrophones with coincident acoustic centers. The output of each hydrophone in the system is simultaneously sampled and the outputs processed to obtain a vectorial sound intensity representation at each of the hydrophone arrays from which a representation of the areal sound intensity across the noted plane may be derived.