Abstract: The apparatus and method for moving a sensor over a workpiece includes a sensor, and an actuating member. The sensor, such as a non-destructive test sensor, is carried by the actuating member, and the actuating member is at least partially disposed within a housing. The actuating member is adapted for automated movement in one direction, and the housing may be configured to be grasped by an operator and manually moved in another direction. As such, the sensor may automatically move in one direction with respect to the workpiece without manual intervention, and manually move in another direction, such that the sensor is moved by the combination of automated and manual movement. In addition, the actuating member may have at least two substantially parallel arms extending from near the sensor, which permits the sensor to slide along the workpiece while maintaining a substantially normal relationship to a surface of the workpiece.

Abstract: In one embodiment of the present invention, an apparatus for characterizing an acoustic impedance of an engineering component acoustically coupled to an acoustic waveguide includes: a pressure measurement apparatus adapted to be moved and to be disposed to measure pressure signals, the pressure signals being measured at respective ones of a plurality of predetermined locations along the acoustic waveguide; an exciter adapted to excite the acoustic waveguide with an excitation signal; a data collection module adapted to incorporate the pressure signals from the pressure measurement apparatus into a pressure signal set; a transform module adapted to transform the pressure signal set to a frequency domain set; a wave shape identifier adapted to identify a plurality of wave shape parameters from the frequency domain set; and a statistical computer adapted to compute from the frequency domain set a statistical measure for the wave shape parameters, the statistical measure being selected from the group consisting o

Abstract: A method of producing a bonded wire connection between an electronic component or a subassembly and a carrier by introducing energy from an ultrasound transducer into a wire that is to be bonded. According to this method, during the introduction of energy the impedance of the ultrasound transducer is measured as a function of time. The shape of the curve representing this time dependence is evaluated on the basis of a pre-specified comparison criteria, and the power input to the ultrasound transducer and/or a bond weight exerted on the wire is/are controlled in dependence on the result of this evaluation. A device usable for carrying out this method is also described.

Abstract: In one embodiment of the present invention, an apparatus for characterizing an acoustic impedance of an engineering component acoustically coupled to an acoustic waveguide comprises: a pressure measurement apparatus adapted to be moved and to be disposed to measure pressure signals, the pressure signals being measured at respective ones of a plurality of predetermined locations along the acoustic waveguide; an exciter adapted to excite the acoustic waveguide with an excitation signal; a data collection module adapted to incorporate the pressure signals from the pressure measurement apparatus into a pressure signal set; a transform module adapted to transform the pressure signal set to a frequency domain set; a wave shape identifier adapted to identify a plurality of wave shape parameters from the frequency domain set; and a statistical computer adapted to compute from the frequency domain set a statistical measure for the wave shape parameters, the statistical measure being selected from the group consisting

Abstract: In a device having a sound tube and a receiver, a test signal is generated to apply to the receiver. An electrical impedance of the receiver is measured, and a length of the sound tube is estimated by a shift in frequency of at least one of a maximum and a minimum in the electrical impedance.

Abstract: Method of producing a bonded wire connection between an electronic component or subassembly and a carrier by introducing energy from an ultrasound transducer into a wire that is to be bonded, wherein during the introduction of energy the impedance of the ultrasound transducer is measured as a function of time, the shape of the curve representing this time dependence is evaluated on the basis of prespecified comparison criteria, and the power input to the ultrasound transducer and/or a bond weight exerted on the wire is/are controlled in dependence on the result of this evaluation.

Abstract: Disclosed is a noise source visualizing system used in a wind tunnel test to measure generated sounds, the system comprising an acoustic mirror for converging sound waves of sounds generated on a surface of a vehicle during a wind tunnel test; a microphone measuring the converged sound waves; an image-photographing unit photographing locations on the vehicle at which the sounds are generated; a first display unit displaying the sounds measured by the microphone as colors that vary according to characteristics of the sounds; a movable traverse to which the acoustic mirror is connected for enabling the acoustic mirror to collect the sounds; a workstation for analyzing the converged sound waves measured by the microphone, the images photographed by the image-photographing unit, and the signals displayed through first display unit; and a second display unit overlapping then displaying image signals photographed by the image-photographing unit and the colors displayed on the first display unit.

Abstract: Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble.

Abstract: A method includes the steps of segment-wise detecting and bringing into coincidence signal waveforms for conversion into monotone and continuous trajectories for real-time pattern recognition, localization, and monitoring optical and acoustic signals. The method also determines transit-time differentials, wherein pre-programmed key signals are detected by signal sampling, data is correlated from the sampled signals, and pairs of signal combinations of given signal transit-time differentials from the coincidence of the detected signals are determined.

Abstract: A pipe 16 having a produced fluid 18 (liquid an/or gas) and at least two acoustic pressure sensors 20-24, is provided with a cylindrical sleeve 30 attached to the pipe 16 at two locations around a sensing region where the sensors 20-24 are located, the sleeve forming a closed cavity 32 filled with a fluid (or material) having an acoustic impedance (&rgr;c2) that is much less than the acoustic impedance (&rgr;c1) of the produced fluid 18 in the pipe 16 (i.e., &rgr;c2<<&rgr;c1), which causes the sleeve 20 to isolate the acoustic sensors 20,22,24 from being affected by acoustic properties of the cavity 32 and the acoustic properties outside the pipe 16. For most effective acoustic, the cavity 32 may be evacuated.

Abstract: The present invention provides fluidic devices and systems which have micromachined ultrasonic transducers integrated into microchannels. The ultrasonic transducers generate and receive ultrasonic waves. The transducers can be disposed and operated to measure fluid characteristics such as pressure, density, viscosity, flow rate and can also be used to mix and pump fluids.

Abstract: The method and apparatus according to the invention determines the acoustic spatial characteristics of an enclosure, particularly of a vehicle occupant compartment in a motor vehicle. A piece of equipment emits a useful sound together with a test sound. By analyzing a recorded analysis sound, the test sound is emitted in a psychoacoustic masking range of the useful sound. Advantageously, the covering range of the useful sound is determined in a useful-sound analysis block before the useful sound and the test sound are emitted.

Abstract: The invention concerns a method of detecting a reflex of the human stapedius muscle, in particular for a hearing test. According to the method, the reflex is triggered by means of an acoustic signal, and the impedance or the variation in impedance brought about by means of the reflex at the eardrum is measured by means of a further acoustic signal. The object of the invention is to further improve the stapedius reflex audiometry method so that it can be applied in practice. To that end, at least two chronologically successive or mutually overlapping substantially identical acoustic signals are used. The information concerning a possible impedance variation at the eardrums obtained by forming the difference between the acoustic characteristics produced and registered by the signals.

Abstract: Disclosed is a system and method for determining the thermodynamic properties and percentage of each component of a multi-component gas medium by using speed of sound in conjunction with other data. The present system comprises a computer system with means for obtaining the temperature, pressure, and speed of sound of a gas medium. The computer system operates according to operating logic stored in memory. According to the operating logic, measurements of the temperature, pressure, speed of sound and acoustic impedance are recorded in a gas pipe or other transport device to determine a convergent temperature range. Next a convergent series is extrapolated from the convergent temperature range and a convergent series calculation using isochoric convergence iterations is performed to obtain estimates of the thermo-physical properties of the gas medium.

Abstract: A method of determining the acoustic impedance of a fluid in a borehole, by gating a reflected acoustic signal into a plurality of time slots, and comparing received energies of the signal for the time slots to obtain a value indicative of the acoustic impedance of the fluid. The value may be normalized to yield the acoustic impedance of the fluid using the acoustic impedance of, e.g., water as a calibration point. The comparison is performed by comparing a ratio of an integration of a first ring down time slot and a second ring down time slot, to an integration of an internal reflection time slot. The acoustic pulse may be generated using a transducer immersed in an intermediate fluid contained within a chamber defined in part by a plate in contact with the borehole fluid and having a thickness such that a mechanical resonance frequency of the plate in a thickness mode is substantially equal to a resonance frequency of the transducer.

Abstract: A portable acoustic impedance data acquisition and processing system is provided for use with a test object. The system includes a dynamic signal analyzer, a test head, a removable microphone holder, a cylindrical endcap fitting, an amplifier, and one or more power supply sources. The test head includes a compression driver and a cylindrical waveguide tube. The waveguide tube has a first end connected to the compression driver and a second end that is open. The removable microphone holder is attachable to the waveguide tube near its second end and a number of microphones are insertable into the microphone holder. During use, the dynamic signal analyzer provides audio output test signals that are amplified by the amplifier and fed to the compression driver for use as the acoustic test signal. The microphones provide measured signals to the dynamic signal analyzer which analyzes them and makes the results available to the operator.

Abstract: A device for measuring the acoustic absorption properties of materials such as liners for jet engines has a first housing, an acoustic driver configured to provide acoustic energy to the first housing, a second housing attached to the first housing, and an acoustic driver configured to provide acoustic energy to the second housing. Acoustic sensors are used to measure the acoustic energy emitted from the two housings and to measure the absorption of each of the housings.

Abstract: A method of measuring in a material a time-of flight of a signal having a first signal burst and a second signal burst, the first signal burst having a first set of cycles and the second signal burst having a second set of cycles. The method includes identifying a cycle in the second signal burst corresponding to a cycle in the first signal burst, to measure the time-of-flight of the signal.

Abstract: In an ultrasonic probe, an acoustic matching layer, which is fixed on the front side of a transducer for transmitting an ultrasonic wave and receiving a reflected wave thereof and matches in acoustic impedance the transducer to a living tissue in an object to be examined, is formed in such a structure that the acoustic impedance thereof is varied continuously in the thickness direction from the transducer to the object to be examined.

Abstract: A system for ultrasound transmission in materials comprising a reference unit, an examination unit, at least a case equipped in at least the examination unit, and a signal processing unit. The reference unit consists of at least an input ultrasonic transducer T.sub.o and at least an output ultrasonic transducer R.sub.o. The examination unit consists of at least an input ultrasonic transducer T.sub.s and at least an output ultrasonic transducer R.sub.s. The case is placed between the ultrasonic transducers T.sub.s and R.sub.s. The signal processing unit is connected with output terminals of the ultrasonic transducers R.sub.o and R.sub.s. When electric signals are applied to the ultrasonic transducers T.sub.o and T.sub.s, ultrasounds are emitted in air from the ultrasonic transducers T.sub.o and T.sub.s, respectively, and then received by the ultrasonic transducers R.sub.o and R.sub.s, respectively.

Abstract: The presence of bubbles on such photographic material, as is well known, results in significant defects in the photographic materials produced so that it is important, in the manufacture of such photographic materials, to detect the presence of such bubbles in the liquid emulsion and to take appropriate remedial action. Described herein is a bubble detector comprising a conduit for liquid to be monitored, the conduit having opposing flattened, generally parallel walls, and a transducer engaged with one of the generally parallel walls and operable to apply alternating displacements to one of the generally parallel walls, at an ultrasonic frequency, in a direction generally normal to the generally parallel walls to transmit sonic or ultrasonic waves through liquid passing through the conduit.

Abstract: A portable two microphone acoustic impedance data acquisition and analysis system provided in a lightweight, fully portable, battery powered instrument with a dual capability of either on-site or remote-site analysis of measured data on the acoustic impedance of acoustically absorbing duct liners of aircraft jet engines. The fully portable instrument is capable of being operated by relatively unskilled personnel to provide acoustic impedance and non-linearity measurements on acoustic liners at airports and aircraft maintenance facilities. The measured data on the engine duct acoustic liner can be an input directly to the data analysis system at the data acquisition site for on-site analysis, or can be recorded for input to a data analysis system at a later time, or can be recorded and transmitted, such as by a telephone modem, to a data analysis system at a remote-site.

Abstract: A system and method of measuring the linear and nonlinear response of an unknown acoustic termination uses a small probe assembly containing a sound source and microphone to determine the reflection function of the unknown acoustic termination. The probe assembly is used with a calibration tube to calculate an electrical signal that will provide a desired acoustic stimulus signal to the acoustic termination. The calibration tube is also used to characterize the signal processing properties of the sound source and microphone, as well as other associated signal processing circuits such as amplifiers, filters, and the like. The calibrated system is subsequently coupled to the unknown acoustic termination to deliver the acoustic stimulus signal. The reflection function is indicative of the power transferred to the unknown acoustic termination. The measurement of the linear transfer characteristic is applicable to any unknown acoustic termination such as a musical instrument or the auditory system.

Abstract: There is provided a method for measuring a sound absorption power of a theater chair with a human being seated thereon. The method includes steps of disposing a theater chair which is an object of measurement in a measuring environment; disposing a dummy sound absorber in the theater chair, the dummy sound absorber having a shape in which it is in contact with the theater chair, a sound absorption power and a chair pressing force in such a manner that the dummy sound absorber simulates a human being seated on the theater chair; causing changes in the theater chair which changes are substantially equivalent to a change in the state of the theater chair caused when a human being gets seated on the chair and a change in the sound absorption power of the theater chair caused by seating of the human being thereon; and measuring the sound absorption power of the theater chair. There is also provided a dummy sound absorber used for carrying out this method.

Abstract: A device for permitting evaluation of the acoustic impedance of liner designs used to attenuate noise in engine aircraft inlet and exhaust ducts, and in particular multiple degree of freedom designs of the type which include a porous facesheet followed by a backing depth followed by successive facesheet/backing depth combinations, includes a plurality of spacers of different thicknesses for varying the backing depths, and a movable plunger with a threaded adjustment mechanism for establishing the final backing depth. Gaskets and seals are installed at various interfaces to eliminate noise leakage paths. Two attachment bolts are used to hold the plunger assembly, face sheets, and spacers together, and an alignment disc positioned on the first facesheet is used to properly align an impedance tube waveguide on facesheet.

Abstract: The system uses a tunable inductor in series with the piezoelectric crystal excitation transducer in the probe which has a flux modulation coil. The bias current through this flux modulation coil is controlled by the system. It is controlled such that the inductance of the tunable inductor cancels out the capacitive reactance of the load impedance presented by the probe when the probe is being driven by a driving signal which matches the mechanical resonance frequency of the probe. The resulting overall load impedance is substantially purely resistive. The system measures the phase angle and monitors the power level. The system uses this information to adjust the bias current flowing through the flux modulation coil to maintain the substantially purely resistive load impedance for changing power levels. This information is also used to adjust the frequency of the driving signal to track changing mechanical resonance conditions for the probe at different power levels.

Abstract: An electrical circuit system for measuring the acoustic admittance of the ear cavity, for use in single and multiple tone tympanometry and acoustic reflex response testing, in which the probe tone applied to the ear cavity can be varied over a wide frequency range and a wide range of admittance variation can be measured. The signal output of the system, derived from the output signal of a microphone located in the ear cavity, is a DC voltage accurately proportional to the logarithm of the measured admittance of the ear cavity. An RMS to DC converter, an error integrator and an exponential element provide a closed control loop system for a variable gain amplifier so as to maintain the microphone output signal level constant regardless of admittance variations in the ear cavity. The level of the signal applied to the probe tone driver to accomplish this is a measure of the cavity admittance.

Abstract: Apparatus and method for determining the steady state flow resistance of face sheets on fully assembled acoustic duct liners. Resistance is measured by subjecting the liner to a sinusoidal acoustic pressure field at the face sheet surface. The pressure field is applied through a cylindrical waveguide and is measured by a pressure transducer flush mounted on the inside of the waveguide near the liner face. A second pressure measurement, obtained by a similar transducer positioned further from the face, is combined with the first measurement to calculate the acoustic resistance for the excitation frequency. If the excitation frequency coincides with the resonant frequency of the liner configuration, then no significant pressure exists on the back surface of the liner face sheet. For this condition the root mean square (rms) pressure measured at the face sheet is equated to the static pressure drop used to obtain the steady state flow resistance.

Abstract: An automatic underwater acoustic impedance measuring apparatus is instrumented with transducers whose outputs are led to a computer for the automatic measurement of acoustic impedance. One hydrophone is positioned so that it senses the incident and reflected signals to compute reflection factor. A second hydrophone is positioned at the face of the sample material so that it senses the incident and reflected waves from which it is possible to compute the phase angle. Acoustic impedance is obtained from the phase angle and reflection factor, computed and printed out in real time and automatically swept through a frequency range of interest.

Abstract: A flexible U-shaped channel is abutted against a surface to be measured, thereby forming an acoustic duct, with the surface forming one wall of the duct. An acoustic source injects sound waves into the duct traveling parallel with the surface in order to establish a standing acoustic wave. Measurements of acoustic pressure at several points allows one to compute k.sub.y, the acoustic wave number normal to the surface, and from k.sub.y to compute the acoustic impedance of the surface.

Abstract: A portable acoustic impedance measuring device 10 is provided for measuring the impedance properties of a panel 12. The device 10 includes a horn section 14 having a flexible plate 18. The plate 18 can assume the curvature of the duct panel 12. The horn section 14 is supported adjacent the panel's surface by a spindle shaft 28 which spans or bridges the inside diameter of the duct 12. The curvature of the plate 18 may be locked to hold the curvature of any of a variety of different panels having various sizes and shapes.

Abstract: An automatic underwater acoustic impedance measuring apparatus is instrumented with transducers whose outputs are led to a computer for the automatic measurement of acoustic impedance. One hydrophone is positioned so that is senses the incident and reflected signals to compute reflection factor. A second hydrophone is positioned at the face of the sample material so that is senses the incident and reflected waves from which it is possible to compute the phase angle. Acoustic impedance is obtained from the phase angle and reflection factor, computed and printed out in real time and automatically swept through a frequency range of interest.

Abstract: The invention is an apparatus which allows selective testing of aircraft or other vehicular components without requiring disassembly of the vehicle or components. The invention consists of a broad-band noise source 11, a guide 12 to direct the acoustic energy, soft sealing insulation 17 to seal the guide to the noise source and to the vehicle component, and noise measurement microphones 13, 14, both outside the vehicle at the acoustic guide output and inside the vehicle to receive attenuated sound. By directing acoustic energy only to selected components of a vehicle via the acoustic guide, it is possible to test a specific component, such as a door or window, without picking up extraneous noise which may be transmitted to the vehicle interior through other components or structure. This effect is achieved because no acoustic energy strikes the vehicle exterior except at the selected component.

Abstract: Ultrasonic process and apparatus for monitoring and measuring the evolution with time of physico-chemical and biological phenomena. There is plunged into the medium or media (4) to be monitored a bar (3) into which ultrasound (2) is injected in order to collect secondary echoes (F2, F3) due to numerous reflections from the lateral surface of the bar (3) brought into contact with the medium (4), one of the secondary echoes (F2) is selected and the evolution with time of the amplitude of this echo is recorded, this representing the evolution of the medium being monitored, in particular the setting of concrete or the polymerization of a resin.

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: The invention provides an ultrasonic device for continuously and noninvasively monitoring instantaneous fluctuations in viscoelastic-related properties of tissue comprising a pair of substantially parallel spaced-apart piezoelectric transducers having a gap therebetween and adapted to bracket and come in direct contact with living tissue inserted in the gap between the transducers, at least one of the transducers being adjustable with respect to the other transducer whereby the distance between the transducers is adjustable to enable insertion and clamping of a segment of living tissue therein. The invention also provides a method for continuously and noninvasively monitoring instantaneous fluctuations in viscoelastic-related properties of a tissue with high resolution utilizing such a device.

Abstract: An open-ended acoustic impedance tube is abutted against a material having a known acoustic impedance and a standing wave pattern is established in the tube. A first apparent impedance of the material is derived based on the standing wave pattern. A correction factor is computed based on the known impedance and the first apparent impedance. The open-ended impedance tube is then abutted against a sample material and a second apparent impedance is derived. The actual impedance of the sample is inferred from the second apparent impedance and the correction factor.

Abstract: In the injection of fluids into subsurface geological formations, such as for the purpose of recovering a mineral in that formation, it is important that the flow progress of that fluid is known at all points in the subsurface. This information is provided by injecting a selected fluid into the formation. This fluid may be a gas, or a liquid, or a mixture of gas and liquid. When this fluid is in the subsurface formation there will be a mixture of gas and liquid in selected proportion in the formation. This mixture in a geologic formation overlain by a shale, for example, will have a much higher reflection coefficient. A source of seismic waves is operated at the surface, and the received reflections are compared between spaced positions on the surface.

Abstract: Method and apparatus for measuring the acoustic impedance of a surface in which the surface is used to enclose one end of the chamber of a Helmholz resonator. Acoustic waves are generated in the neck of the resonator by a piston driven by a variable speed motor through a cam assembly. The acoustic waves are measured in the chamber and the frequency of the generated acoustic waves is measured by an optical device. These measurements are used to compute the compliance and conductance of the chamber and surface combined. The same procedure is followed with a calibration plate having infinite acoustic impedance enclosing the chamber of the resonator to compute the compliance and conductance of the chamber alone. Then by subtracting, the compliance and conductance for the surface is obtained.

Abstract: Measurement of the relative and actual value of acoustic characteristic impedances of an unknown substance, location of the interfaces of vertically-layered materials, and the determination of the concentration of a first material mixed in a second material. A highly damped ultrasonic pulse is transmitted into one side of a reference plate, such as a tank wall, where the other side of the reference plate is in physical contact with the medium to be measured. The amplitude of a return signal, which is the reflection of the transmitted pulse from the interface between the other side of the reference plate and the medium, is measured. The amplitude value indicates the acoustic characteristic impedance of the substance relative to that of the reference plate or relative to that of other tested materials. Discontinuities in amplitude with repeated measurements for various heights indicate the location of interfaces in vertically-layered materials.

Abstract: Acoustical transmission loss of sheet materials in the low frequency range is measured by utilizing a cylindrical test chamber containing a speaker directed towards the upper end to which the sheet material is mounted. Pressure gradient microphones are mounted on either side of the sheet material and are connected to electronic circuitry for responsively indicating the transmission loss measurement across said sheet material.

Abstract: An acoustic polarimeter for measuring the anisotropy of a sample comprises an electroacoustic transducer which transmits a high-frequency transverse acoustic wave and is fixed on a birefringent measuring plate. The acoustic wave is received by a second transducer and this latter is sensitive to the component of the wave which is parallel to the transmitted wave. Transmission devices are provided for delivering electrical signals which are frequency-modulated about a tunable mean frequency. The electrical signals applied to the second transducer are received on a zero indicator, thus permitting determination of the directions of the slow axis and fast axis of the sample as well as the angle of phase shift introduced by the sample.

Abstract: Ultrasonic apparatus and method measures the characteristics of materials by sensing changes in the impedance to applied drive excitation of an ultrasonic probe using a crystal sensor that is integral with the ultrasonic transducer.

Abstract: An ultrasonic system that measures either the impedance of a fluid or liquid level utilizes moderately directional, bulk SV mode sound waves generated by a transducer and propagated in a homogeneous, flaw-free solid member. The SV wave propagates in the solid along a zigzag path that reflects at a solid-fluid interface in at least two areas and at an angle of incidence that exceeds the first critical angle by at least five degrees and is less than the second critical angle by at least ten degrees. The attenuated amplitude of the wave due to acoustic coupling between the solid and the fluid measures the impedance or an impedance related parameter of the fluid. The system preferably includes a second acoustic path that serves as a reference to compensate for changes in parameters such as temperature, the nature of the fluid, the transducer, the transducer coupling, and residues or corrosion at the solid-fluid interface.

Abstract: The apparatus consists of a circular, flexible disc held at a constant distance from a curved absorbing surface by pins or flexible ribs. Sound from a loudspeaker is fed to the center of the disc and allowed to propagate radially in the space between disc and absorber. Radial arrays of microphones on the disc surface sense sound pressure amplitude and phase, from which impedance is calculated.

Abstract: In order to determine the acoustic impedance of a human ear at various static pressures, a probe tightly fitted to the pinna of the ear transmits a short acoustic pulse with a wide frequency spectrum (such as white noise) from an electroacoustic transducer to the ear canal and receives back an acoustic response signal which a microphone converts into an electrical wave. The latter is digitized and transformed into terms of a Fourier series fed to a processor which, on the basis of similar terms stored in a memory and previously obtained with the same probe fitted to two different cylindrical calibrating cavities, derives therefrom the acoustic ear impedance at a particular air pressure. The processor also triggers an electric pulse generator, working into the electroacoustic transducer, and may progressively adjust a generator of static air pressure connected to the probe.

Abstract: Techniques for a broad band high frequency acoustic investigation of a subsurface formation around a borehole are described utilizing a range of acoustic frequencies selected to produce detectable acoustic backscatter from grains within the subsurface formation. The acoustic backscatter is detected and a spectrum thereof is produced and averaged over adjacent subsurface formation regions. A subsurface formation parameter such as the frequency dependency of the attenuation of the backscatter is determined from an analysis of the spectrum to provide an indication of the granularity property of the subsurface formation. Use of a broad range of frequencies enables a determination of the subsurface formation parameter over a large range of grain sizes. In another technique the spectrum of the detected backscatter is modified to remove the effect of the frequency response of the system with which the investigation is made.

Abstract: The shear absorption of a viscoelastic material is determined by directing acoustical energy at the viscoelastic material and sampling the backscattered signals that result when compressional waves propagate through the material and are scattered by either a fluid-filled or evacuated cavity contained therein. The backscattered signals are converted to a resonance amplitude versus frequency domain and the shear absorption of the viscoelastic material is determined from the frequency and the half-width of the resonance peaks.

Abstract: An apparatus and method for determining the material properties characterizing a fluid contained in a cavity inside a solid comprises analyzing the resonances in the amplitude of elastic waves scattered by the cavity. Specifically, the resonance positions and their widths are used to determine the sound speed and the density of the cavity filler. The sound speed is found from the spacing between two consecutive overtones of any mode, which asymptotically becomes uniform for the higher-index overtones. The density is obtained from the width of any high order resonance and accordingly, all the information about the material composition of the filler is contained, and can be extracted, from the high-frequency asymptotic region.

Abstract: A device for measuring acoustic properties and their changes in a sample of liquid, gas, plasma or solid. A variable frequency source is applied to the sample by means of a transducer to produce sound waves within the sample. The application of the variable frequency source to the sample is periodically interrupted for a short duration. Means are connected to the transducer for receiving the resulting acoustic signals during the interruptions for producing a control signal indicative of a difference in the frequency of the output of the variable frequency source and the frequency of a mechanical resonant peak in the sample. The control signal is applied to the variable frequency source to maintain its output frequency at the frequency of the mechanical resonant peak. The change in frequency of the variable frequency source is indicative of the shift in frequency of the mechanical resonant peak and the amplitude of the acoustic signals is indicative of the attenuation of the acoustic signals in the sample.