Abstract: A device for detecting and recording violation of vehicle noise laws. The device includes one or more sound level sensors, cameras, microphones, microcontrollers, electronic data storage, user interfaces, and internal power sources. The device requires no operator, external power source, or information network connection and its design protects against weather, theft, and vandalism.

Abstract: A method of tracking record player stylus elapsed play time for quality and maintenance utilizes stylus playtime chronograph. The stylus playtime chronograph includes an internal memory that stores elapsed time of an associated stylus, wherein memory of the elapsed time will be maintained on the chronograph even if power supply is interrupted; a display that will display hour truncated elapsed time of an associated stylus; a start button to start and restart the recording of elapsed time of an associated stylus; a stop button to stop or pause the recording of elapsed time of an associated stylus; and a reset button to allow for resetting of the chronograph and allow the chronograph to be used for the another stylus.

Abstract: Disclosed embodiments may relate to systems and methods for monitoring and/or mapping noise data from a plurality of noise monitoring devices. In some embodiments, the plurality of noise monitoring devices may include hearing protection devices configured to detect noise, and typically may communicate such noise data (which may also include location) so that the noise data can be pooled. The pooled noise data from the plurality of noise monitoring devices may then be used to the benefit of one or more of such noise monitoring devices.

Abstract: Provided is a capacitive pressure sensor that prevents the position of an electrode face in the direction parallel to a diaphragm from deviating from the position of the diaphragm, and accurately measures pressure. The capacitive pressure sensor includes: the diaphragm that deforms under pressure; an electrode member having the electrode face opposed to the diaphragm with a gap between the diaphragm and the electrode face; a body having one end to which the diaphragm is joined, and accommodating at least a portion of the electrode member; an insulating positioning member that is provided in the body and positions at least the portion of the electrode member in the body; and a pressing mechanism that holds and presses the insulating positioning member or the electrode member in the direction parallel to the diaphragm.

Abstract: Provided is a measurement system for evaluating an electronic apparatus that, when a vibrator of the electronic apparatus is pressed against the human ear, delivers a sound generated by vibration of the vibrator. The measurement system includes: an ear-shaped unit composed of an ear model simulating the human ear and an artificial ear canal portion constituting an artificial ear canal extending from the ear model; an artificial mandible portion disposed next to the artificial ear canal portion in the ear-shaped unit in a planar view; and a vibration detection unit that is disposed on a plane of the artificial mandible opposite to the ear model and detects and outputs vibration delivered to the artificial mandible portion.

Abstract: A portable binaural recording and playback device includes headphones with embedded outside facing microphones attached to a dongle with embedded stereo microphone preamplifier or audio codec containing a microphone preamplifier, analog to digital converter/digital to analog converter (or digital signal processor), allowing for the recording and playback of high quality binaural audio by connecting the dongle digitally to a mobile phone or electronics device, or via an analog cable to a camera or device with an analog microphone input.

Abstract: A vibration monitoring and analysis system may include a transducer configured to convert sensed vibration into an alternating current. A processing module may analyze the alternating current and produce an output configured to convey information regarding characteristics of the alternating current. One or more analysis modules may be utilized to compare a waveform of the sensed vibration to known patterns, for example to identify known events and/or conditions.

Abstract: An audio capture device generates two microphone beam patterns with different directivity indices. The audio capture device may determine the position of a user relative to the audio capture device based on sounds detected by the separate microphone beam patterns. Accordingly, the audio capture device allows the determination of the position of the user without the complexity and cost of using a dedicated listening device and/or a camera. In particular, the audio capture device does not need to be immediately proximate to the user (e.g., held near the ear of the user) and may be used to immediately provide other services to the user (e.g., audio/video playback, telephony functions, etc.). The position of the user may include the measured distance between the audio capture device and the user, the proximity of the user relative to another device/object, and/or the orientation of the user relative to the audio capture device.

Abstract: According to one embodiment, reactor oscillation power ranges monitor includes: a receiving unit which receives LPRM signals; an exclusion processing unit which searches the LPRM signals allocated to the cell for an LPRM signal corresponding to an exceptional condition; an averaging unit which averages the allocated LPRM signals; a time averaging unit which calculates a time average of the average flux value; a normalized value calculation unit which divides the average flux value by the time averaged flux value; an initialization unit which outputs an initialization signal identifying the cell allocated to an LPRM signal which is changed to correspond or not correspond to the exceptional condition; and a determination unit which derives at least one of amplitude and cycle of a power oscillation from the normalized value.

Abstract: An exemplary uncomfortable sound pressure evaluation system consecutively presents sound stimulation groups to a user. Each sound stimulation group includes a sound stimulation, and the sound stimulation groups differ in frequency from one another. The system includes: an extraction section configured to extract, for each sound stimulation group, information concerning event-related potential relating to the sound stimulation; an estimation section configured to estimate an uncomfortable sound pressure (UCL) of the user from the information concerning event-related potential; and a correction section configured to determine whether the estimated UCL is higher than a predefined maximum UCL or not, and if a proportion of those determination results which indicate the UCL to be higher than the maximum UCL is smaller than predetermined, correcting each UCL determined as higher than the maximum UCL to a sound pressure equal to or less than the maximum UCL.

Abstract: An apparatus may include two or more electrical conductors, one or more signal devices, and an analyzer. The one or more signal devices may be adapted to apply one or more signals to the two or more electrical conductors and receive one or more signals from the two or more electrical conductors. The analyzer may be adapted to determine power level in the nuclear reactor using at least one of the applied signals and at least one of the received signals. A method of determining power level in a nuclear reactor may include: measuring impedance values of two or more electrical conductors disposed in the nuclear reactor and using the measured impedance values to determine the power level. A method of operating a nuclear reactor may include: measuring the impedance values and using the measured impedance values to determine parameters of the nuclear reactor.

Abstract: A test battery method and system for use in assessing auditory function (e.g., the screening or diagnosis of impairments, fitting of hearing aids, etc.) is provided which performs one or more auditory tests including, for example, an acoustic reflectance test. Such an acoustic reflectance test may be a reflectance tympanometry test that includes a feedback system to control static pressure in the ear canal. Such acoustic reflectance tests may be used alone or in combination with one or more other auditory tests. Further, for example, such a battery of tests may include middle-ear muscle reflex tests in combination with one or more other auditory or hearing tests.

Abstract: Methods and apparatus for determining an estimated physical location of a fault in a pipeline or electrical transmission line using localization devices coupled thereto. In an embodiment, a first and second localization device each generate time values representing times when the respective localization device detected the fault. The estimated fault location is calculated, by one of the localization devices or a separate computing device, based upon the reported time values. In some embodiments, the calculation is further based upon characteristics of the pipeline or electrical transmission line, or based upon characteristics of matter transported through the pipeline. In some embodiments, the localization devices transmit time or sequence values to the other device, and the values received by the devices just before the detection of the fault may additionally be utilized to calculate the estimated physical location of the fault.

Abstract: A method of determining pore size of a porous material. The method includes saturating the porous material with a conducting liquid. Measuring, with an electro-acoustic device, a phase of the seismo-electric or electro-seismic signal at a single frequency or multiple frequencies. Calculating an average pore size from the measured phase of the seismo-electric or electro-seismic signal at single frequency using a theory that takes into account the hydrodynamic relaxation of the conducting liquid inside of the pores of the porous material. Calculating pore size distribution from the similar measurement conducted at multiple frequencies using the same theory.

Abstract: An acoustic probe and an acoustic diagnostic system. The acoustic probe includes a housing; a transducer, which is arranged inside the housing, transmits an acoustic wave to a target object, and receives an acoustic echo signal from the target object; and a magnetic field generator, which is arranged inside the housing and generates a magnetic field to the target object.

Abstract: A noise dosimeter with capability to rapidly predict noise exposure over an extended time period based on a measurement of short duration. Either an acoustic or an electrical earphone adapter provides a convenient means to connect the noise dosimeter to an external sound source. A direct input jack operable to receive at least one audio signal provides a signal to an RMS detector, which provides a DC signal to a two-stage amplifier circuit. The outputs of the amplifiers are provided to a processor having multiple A/D channels. The processor calculates accumulated noise doses and drives a display, which in one embodiment includes a panel of light-emitting diodes. In one embodiment, the dosimeter includes functionality for control of external devices such as sound boards.

Abstract: Propagation of ultrasound through a porous body saturated with liquid generates electric response. This electro-acoustic effect is called “seismoelectric current”, whereas reverse version, when electric field is driving force, is “electroseismic current”. It is possible to measure seismoelectric current with existing electro-acoustic devices, which had been designed for characterizing liquid dispersions. Such versatility allows calibration of said devise using dispersion and then applying it for characterizing porous body. In general, magnitude of seismoelectric current depends on porosity, pore size, zeta potential of pore surfaces and elastic properties of matrix. It is possible to adjust conductivity of liquid for simplifying these dependences. For instance, liquid with high ionic strength causes double layers become thin comparing to the pore size, which eliminates dependence of said currents on pore size. We suggest using such case for characterizing porosity.

Abstract: A test battery method and system (10, 100, 200, 225) for use in assessing auditory function (e.g., the screening or diagnosis of impairments, fitting of hearing aids, etc.) is provided which performs one or more auditory tests including, for example, an acoustic reflectance test. Such an acoustic reflectance test may be a reflectance tympanometry test that includes a feedback system to control (426) static pressure in the ear canal. Such acoustic reflectance tests may be used alone or in combination with one or more other auditory tests. Further, for example, such a battery of tests may include middle-ear muscle reflex tests in combination with one or more other auditory or hearing tests.

Abstract: The present disclosure relates to a system and method for characterizing an impact in a fabric. The system may include a sensing element woven in the fabric wherein a parameter of the sensing element depends on a strain in the sensing element; a transducer coupled to the sensing element wherein the transducer is configured to generate an output based on the parameter of the sensing element; and a controller coupled to the transducer, the controller configured to receive the output of the transducer, to determine a strain in the sensing element based, at least in part, on a change in the output of the transducer, and to characterize the impact in the fabric based on the strain in the sensing element.

Abstract: A sensor system responsive to acoustic or seismic signals. One system includes a frame and a piezo-electric sensor element. The sensor element, responsive to a wavefield of seismic or acoustic energy, is positioned about the frame. Coupling between the sensor element and the frame is so limited as to render direct coupling of the sensor element with the wavefield the predominant means for stimulating the sensor element with seismic energy. Another system includes a frame and a cable element, responsive to a seismic or acoustic wavefield, extending about the frame. Coupling between the cable element and frame is so limited as to render direct coupling of the sensor element with the wavefield the predominant means for stimulating the sensor element with acoustic or seismic energy. The element may be coaxial cable or have piezo-electric properties to generate a charge differential measurable as a voltage between conductors.

Abstract: Propagation of ultrasound through a porous body saturated with liquid generates electric response. This electro-acoustic effect is called “seismoelectric current”, whereas reverse version, when electric field is driving force, is “electroseismic current”. It is possible to measure seismoelectric current with existing electro-acoustic devices, which had been designed for characterizing liquid dispersions. Such versatility allows calibration of said devise using dispersion and then applying it for characterizing porous body. In general, magnitude of seismoelectric current depends on porosity, pore size, zeta potential of pore surfaces and elastic properties of matrix. It is possible to adjust conductivity of liquid for simplifying these dependences. For instance, liquid with high ionic strength causes double layers become thin comparing to the pore size, which eliminates dependence of said currents on pore size. We suggest using such case for characterizing porosity.

Abstract: Various applications for structured CNT-engineered materials are disclosed herein. In one application, systems are disclosed, wherein a structured CNT-engineered material forms at least part of an object capable of providing its own structural feedback. In another application, systems are disclosed, wherein a structured CNT-engineered material forms at least part of an object capable of generating heat. In yet another application, systems are disclosed, wherein a structured CNT-engineered material forms at least part of an object capable of functioning as an antenna, for example, for receiving, transmitting, absorbing and/or dissipating a signal. In still another application, systems are disclosed, wherein a structured CNT-engineered material forms at least part of an object capable of serving as a conduit for thermal or electrical energy.

Abstract: Certain embodiments of the present invention provide a system and method for predicting long-term exposure to a hazardous environment based on a user-controllable measurement interval of short duration. In an embodiment, the system includes an electronic circuit for receiving one or more signals representative of the level of a hazard in an environment using one or more of a hazard level sensor and a direct input jack. The system further includes a processor within the electronic circuit for determining an accumulated dose over a user-controllable measurement interval. In addition, the processor predicts hazardous exposure for a user-settable extended period greater than the user-controllable measurement interval and based on the accumulated dose. The dosimeter also includes a user-operable switch within the electronic circuit and in communication with the processor for controlling the user-controllable measurement interval to be less than a nominal measurement interval.

Abstract: Certain embodiments of the invention may be found in an ultra low power dosimeter assembly. The ultra low power dosimeter assembly may comprise a low power voltage source and a table circuit. The table circuit may be adapted to convert an input voltage to a second voltage level. The second voltage level may correspond to noise dose. The ultra low power dosimeter assembly may also comprise a switch adapted to trigger a control circuit. The control circuit may provide progressive attenuation of an output signal as the second voltage level increases. In certain embodiments, the control circuit may also be adapted to send one or more warning signals to a user of the ultra low power dosimeter. The one or more warning signals may be sent when the control circuit determines the second voltage level has reached one or more pre-determined threshold voltage levels.

Abstract: A personal noise dosimeter having functionality for increasing the dynamic range of the device. A microphone provides a signal to an RMS detector, which provides a DC signal to a two-stage amplifier circuit. The outputs of the amplifiers are provided to a processor having multiple A/D channels. The processor calculates accumulated noise doses and drives a display, which in one embodiment includes a panel of light-emitting diodes. A current source injects current into the output of the RMS detector to reduce performance degradation. Functionality detects and accounts for voltage offsets in the dosimeter. The microphone is turned off during offset determination. In one embodiment, the dosimeter includes functionality for control of external devices such as sound boards.

Abstract: Certain embodiments of the invention may be found in an ultra low power dosimeter assembly. The ultra low power dosimeter assembly may include a low power voltage source and a table circuit. The table circuit may be adapted to convert an input voltage to a second voltage level. The second voltage level may correspond to noise dose. The ultra low power dosimeter assembly may also include a switch adapted to trigger a control circuit. The control circuit may provide progressive attenuation of an output signal as the second voltage level increases. In certain embodiments, the control circuit may also be adapted to send one or more warning signals to a user of the ultra low power dosimeter. The one or more warning signals may be sent when the control circuit determines the second voltage level has reached one or more pre-determined threshold voltage levels.

Abstract: A noise dosimeter with capability to rapidly predict noise exposure over an extended time period based on a measurement of short duration. Either an acoustic or an electrical earphone adapter provides a convenient means to connect the noise dosimeter to an external sound source. A direct input jack operable to receive at least one audio signal provides a signal to an RMS detector, which provides a DC signal to a two-stage amplifier circuit. The outputs of the amplifiers are provided to a processor having multiple A/D channels. The processor calculates accumulated noise doses and drives a display, which in one embodiment includes a panel of light-emitting diodes. In one embodiment, the dosimeter includes functionality for control of external devices such as sound boards.

Abstract: An ultrasonic sensor is provided with a substrate unit where a thin-walled portion is arranged and a piezoelectric oscillator which is formed at the substrate unit. The piezoelectric oscillator includes two electrodes and a piezoelectric film positioned between the two electrodes. The thin-walled portion and the piezoelectric oscillator construct a membrane structure which will resonate at a predetermined frequency.

Abstract: Certain embodiments of the present invention provide a system and method for predicting long-term exposure to a hazardous environment based on a user-controllable measurement interval of short duration. In an embodiment, the system includes an electronic circuit for receiving one or more signals representative of the level of a hazard in an environment using one or more of a hazard level sensor and a direct input jack. The system further includes a processor within the electronic circuit for determining an accumulated dose over a user-controllable measurement interval. In addition, the processor predicts hazardous exposure for a user-settable extended period greater than the user-controllable measurement interval and based on the accumulated dose. The dosimeter also includes a user-operable switch within the electronic circuit and in communication with the processor for controlling the user-controllable measurement interval to be less than a nominal measurement interval.

Abstract: A three-dimensional array (10) of microphones (M) is used to determine the three-dimensional sound field above a surface element (?S) of a sound emitting surface (S), and the air-particle velocity (un) at the surface element (?S) is determined using Near-Field Acoustical Holography (NAH). A volume velocity sound source (11) is used to emit a volume velocity (Qv) in a listening position, and the array (10) of microphones (M) is used to determine the resulting three-dimensional sound field above the surface element (?S), and using NAH the resulting sound pressure at the surface element (?S) is determined. The acoustic transfer function (H) between the surface element (?S) and the listening position is assumed to be reciprocal and is determined as the ratio of the resulting sound pressure at the surface element (?S) to the volume velocity (Qv). The sound pressure in the listening position resulting from the surface element (?S) is determined as ?p=H.(un. ?S).

Abstract: An accurate measure of normally operating noise is required for a useful noise measurement system. A device is needed to make a representative measure of the boat's acoustic power using measured boat sound level with integrated corrections for sensed distance to the boat and measured ambient sound level. This device needs to make this measurement process invisible, automatic, and accurate from a law enforcement point of view.

Abstract: A system for detecting a sound level of vehicles comprising sensor units for detecting vehicles on a road and for measuring a sound level of a detected vehicle. A data processing unit is connected to the sensor units and has an identification recorder for operating the system by recording an identification of the vehicle detected if the sound level is above a given value.

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: The invention relates to a sensor for measuring acceleration and sound pressure, the sensor comprising a first pressure sensitive film (2) for measuring pressure (P) and second pressure sensitive film (5) having a mass (6) disposed thereon for measuring acceleration (A). The films are arranged concentrically in the same plane, so that pressure and acceleration are measured at the same point, thereby avoiding a phase difference between the two measurements.

Abstract: This invention relates to a method and a microprocessor-based apparatus for directly measuring the noise using a nuisance index (L.sub.DI) bound to two physical parameters of the noise: the average energy level (L.sub.E) and the fluctuation level of the noise.The apparatus is comprised of a microphone (M) connected to a pre-amplifier (1) and a detecting unit (2) controlling an analogical-to-digital converter (3) associated to a time (4) feeding a signal to a digital filter (5) and at the same time to one input of a comparator (6). The filter (5) feeds the filtered signal to an integrator (7) supplying the parameter (L.sub.E) and simultaneously to the second input of comparator (6) which supplies the parameter (L.sub..phi.) through counter (8) associated to a trimmer (10). Parameters (L.sub.E) and (L.sub..phi.) are indicated in block (9) of the display.

Abstract: User selection of meter ballistics is accomplished by separating the meter display from the meter drive circuitry. An input signal is input in parallel into appropriate level determining circuits, with the outputs being selected for processing by a microprocessor. The microprocessor processes the selected outputs according to a ballistic standard selected by an operator to generate a display signal. For LED displays the display signal has a bar component that illuminates all the LEDs up to the maximum level of the displayed output and a dot signal that illuminates only one or a very few LEDs around the maximum level of the displayed output.

Abstract: An ultrasonic frequency generator sets a plurality of parameters for a transducer to enable an ultrasonic operation to meet a plurality of criteria. The generator produces sets of power trains, each formed of a sequence of power bursts of an ultrasound signal having a variable amplitude and a variable frequency. The power bursts are provided with controllable durations and are separated from one another by controllable quiet times. A cavitation density function generator controls the amplitude of the power bursts. The power trains are provided with controlled durations, and variable degas time durations are included between sequences of bursts of the ultrasonic signals. A further function generator is used to control the frequency of the signal, thus providing a swept frequency burst. A controller is provided for setting the center frequency of the swept signal. The generator thus provides a waveform with seven controllable parameters which may be set to conform to any operational criteria.

Abstract: In order to compensate reproduction errors in electroacoustic transducers (W), for example electrodynamic loud-speakers, microphones and pickup systems, computer circuits are used. In a digital computer circuit, the electrical input signals (U.sub.1 ) are converted into altered output signals (U.sub.2) according to the inherent properties of the transducer (W), stored in a memory (PROM), with the aid of a programme, which is likewise stored. When analogue computer circuits are used, the complex inherent response of the converter (W) in respect of the amplitude/frequency response and phase/frequency response is approximated mathematically in a closed, inverse form, and the resulting function is simulated with the aid of integrators (B), summing elements (S), inverters (I) and adjusting members (P).

Abstract: A portable acoustic intensity measuring device comprising a pair of electroacoustic transducers at a positioned predetermined distance from one another. The measuring device utilizes analog summing, subtraction, integration and multiplier means for measuring an acoustic intensity vector midway between the two electroacoustic transducers. The acoustic intensity measuring device further comprises error correction means connected in circuit with a preamplifier means and a meter means. The error correction means includes switching means comprising a first switch connected in circuit with the preamplifier and summing means and subtraction means and a second switch connected in circuit with the multiplier and the meter for simultaneously switching the first and second preamplified analog signals at the summing input and subtraction input and for simultaneously switching the polarity of the acoustic intensity signal at the meter.

Abstract: An audio dosimeter for use by an individual for measuring exposure to sound which contains the following components:(a) an electronic microphonic sound sensor means,(b) an amplifier and weighting circuit,(c) an x-squared detector circuit,(d) a temperature compensation circuit;(e) analog to digital time converter,(f) a microcomputer which controls functions of the temperature compensator circuit and analog to digital time converter and has unique logarithmic mathematics for converting the signal from the converter into sound measurement values such as percent of dose, average and maximum decibel levels and instantaneous sound level.

Abstract: A device for selecting the proper sensitivity and acceptable background noise level for sound discrimination switches used for detection of selected sounds where the detection device includes peak signal detectors to receive audio voltage generated by the selected sounds and activate an alarm.

Abstract: The disclosure is related to a sound level meter including unique features for measuring, storing and displaying a maximum sound level generated by a passing motor vehicle or the like. The meter operates as an ordinary sound level meter until a predetermined threshold noise level is reached, at which time a novel circuit continuously detects the incoming sound level and electrically stores the maximum value detected. A comparison means compares the incoming sound level with the maximum stored level. When the incoming sound level decreases by a predetermined amount below the maximum stored value, a circuit is energized to lock the maximum value detected in a memory device. Additional means are provided to visually display the stored value.

Abstract: An apparatus for obtaining the farfield directional pressure intensity of a sonorous source placed in a fluid medium from pressure measurements taken in the nearfield of the source is disclosed. An acoustic antenna is placed in the nearfield of the source to map the acoustic pressure nearfield. The antenna consists of either a single receptor, or of two separate receptors, one fixed in position to define the direction and the other variable in position over the acoustic antenna. Each receptor is comprised of two oppositely facing parallel planar arrays of acoustic detectors separated by a predetermined distance. The detectors are arranged in each array in a predetermined matrix. The detector signals from both arrays are processed by either of two different methods, an additive or a multiplicative method, to obtain the farfield directional pressure intensity of the source.

Abstract: A sound level indicator apparatus includes a signal processing element which detects and processes sound pressure waves into quantifiable electrical signals. The indicator also includes an adjustment member which adjusts the quantifiable signals to compensate for intrinsic electrical variations in the processing element. Further included is a monitoring member which detects when the received sound is below a predetermined level. The indicator still further includes an indicator element which displays the quantified quantifiable signals and the low level monitor detection signal. The sound level indicator is operatively combined with a digital watch integrated circuit for containment in a case which is wearable on one's wrist.

Abstract: A method of and apparatus for accurately adjusting a hearing aid. First a wide-band reference signal of relatively low sound level, e.g. 40 to 50 dB, is reproduced via a loudspeaker. The gain of the hearing aid is adjusted so that the person wearing it can just hear this reference signal. Then, in addition to the reference signal, a periodically recurring narrow-band signal having a duration of approximately 150 msecs is reproduced and the range of the optimum sound-level of speech is determined for different central frequencies of this narrow-band signal. The range thus determined is compared with the range of optimum sound-level of speech for persons with normal hearing and subsequently the setting of the hearing aid is corrected so that the sound level experienced as a pleasing sound level of speech by the user of the hearing aid falls within the sound-level range which is pleasing to persons with normal hearing.

Abstract: A sound pressure level meter adapted for use in monitoring noise levels, particularly for use by law enforcement agencies wherein the device includes means for providing a logarithmic indication of the root mean square value of ambient sound pressure levels and wherein means are provided for holding and displaying a maximum sound pressure level detected over a given period of time and for providing an alarm when a detected level exceeds a predetermined threshold level.

Abstract: Apparatus for measuring pressure fluctuations in air or other gases in an area of elevated temperature. A condenser microphone is located in the area of elevated temperature and electronics for processing changes in the microphone capacitance is located outside the area and connected to the microphone by means of a high-temperature cable assembly. The microphone includes apparatus for decreasing the undesirable change in microphone sensitivity at high temperatures. The high-temperature cable assembly operates as a half-wavelength transmission line in an AM carrier system and maintains a large temperature gradient between the two ends of the cable assembly. The processing electronics utilizes a voltage controlled oscillator for automatic tuning thereby increasing the sensitivity of the measuring apparatus.

Abstract: A system and technique for determining the total radiated ultrasonic power output from a diagnostic ultrasound device having an output transducer includes a water chamber having a parabolic reflector. The transducer is mounted on the chamber at a location so that acoustic power from the transducer is focussed by the parabolic reflector to a first thermistor chip mounted in the chamber on a sound-absorbing rubber plate. The rise in temperature of the thermistor chip due to sound absorption changes its resistance. The thermistor chip is connected in one leg of a Wheatstone bridge. A reference thermistor chip is mounted on the rubber plate away from the ultrasonic beam and is connected in an opposite leg of the bridge. Starting from a null setting of the bridge, the output of the bridge after a suitable "response time" is in accordance with the acoustic energy delivered by the transducer.

Abstract: A method and apparatus for determining the directivity index (DI) and directivity factor (Q) of a loudspeaker is described. A microphone is placed in the throat of a horn-type loudspeaker to measure the acoustical pressure at this point. A second microphone is placed along an extension of a central axis of a loudspeaker at a predetermined distance from the mouth of the loudspeaker to measure the acoustical pressure at this point. The output of each of the microphones is rectified and converted to decibel form. The decibel signal representing acoustical pressure at the throat is subtracted from the signal representing the measured pressure at the predetermined distance. A signal (in decibel form) representing the distance of the second microphone from the mouth of the horn is added to the difference signal and a signal (in decibel form) in accordance with the diameter of the loudspeaker throat is subtracted from the difference signal to provide a signal in accordance with directivity index.

Abstract: In a sound level meter the output voltage of the microphone is fed to a voltage-frequency converter by way of an exponentially operating circuit, such as a squarer, and the output of the converter operates a binary counter having an indicator unit associated therewith. A gate circuit is controlled by a timing generator and is interposed between the voltage-frequency converter and the binary counter. The indicator unit includes a plurality of indicating elements which are connected at the outputs of the successive counter stages and each of the indicator elements is associated with a particular indicia carried on a dB scale. With a squarer as the exponential circuit the dB scale has a 3 dB incrementation for the respective indicator elements.