Showing papers on "Microphone published in 1992"

Use of Audio Signals for Chatter Detection and Control

Abstract: This paper compares various sensors and shows that a microphone is an excellent sensor to be used for chatter detection and control. Comparisons are made between the microphone and some other common sensors (dynamometers, displacement probes, and accelerometers) regarding sensing of unstable milling. It is shown that the signal from the microphone provides a competitive, and in many instances a superior, signal tht can be utilized to identify chatter. Using time domain milling simulations of low-radial-immersion, low-feed, finishing operations it is shown that for these cuts (especially at relatively high speeds) chatter is not adequately reflected in the force signal because of the short contact time, but that it is clearly seen in the displacement signal. Using the dynamics of existing production milling machines it is shown how the microphone is more suitable to chatter detection than other remotely placed displacement sensors, especially in cases that involve flexible tooling and workpieces. Aspects important for practical implementation of a microphone in an industrial setting are discussed. Limitations of the microphone are addressed, such as directional considerations, frequency response, and environmental sensitivity (i.e., workspace enclosure, room size, etc). To compensate for expected unwanted noises, commonly known directionalization techniques such as isolation, collection, and intensity methods are suggested to improve the ability of the microphone to identify chatter by reducing or eliminating background and extraneous noises. Using frequency domain processing and the deterministic frequency domain chatter theory, a microphone is shown to provide a proper and consistent signal for reliable chatter detection and control. Cutting test records for an operating, chatter recognition and control system, using a microphone, are presented; and numerous examples of chatter control are listed which include full and partial immersion, face-and end-milling cuts.

Remote monitoring unit

Abstract: A remote monitoring apparatus includes a camera for producing a video signal from a picture of a remote site location being monitored, an image processor for outputting an image signal through an image processing process for the video signal, a microphone for producing a sound signal from a sound at the location, a temperature sensor for outputting a detection signal when a temperature change higher than a predetermined level is detected at the location, a gas sensor for outputting a detection signal when a concentration of oxygen gas smaller than a predetermined first level or a concentration of hydrogen gas greater than a predetermined second level is detected in the location, a converter for outputting digital signals by converting the image signal, the sound signal and the detection signals, and a radio transmitter for transmitting the digital signals of the converter to a radio receiver of a control equipment via radio transmission. In this apparatus, the camera, the image processor, the microphone, the temperature sensor, the gas sensor, the converter, and the radio transmitter are built in an enclosure case and the security of the remote site location is monitored from a central control equipment by using the remote monitoring unit placed at the remote site location.

Device for picking up bone-conducted sound in external auditory meatus and communication device using the same

Abstract: A device for picking up bone-conducted sound in the external auditory meatus includes a fitting portion for accommodation in a navicular cavity formed between a tragus cartilage portion and an entrance portion of an external auditory meatus, and a bone conduction microphone unit for insertion into the external auditory meatus in such a manner as to be brought into contact with a wall of the external auditory meatus. The bone conduction microphone unit is held by the fitting portion via a resilient member in such a manner that at least a portion of the bone conduction microphone unit contacting the external auditory meatus is resiliently brought into contact with the wall of the external auditory meatus substantially orthogonally. Also disclosed is a communication device in which an earphone unit for transmitting sound from the outside is accommodated in the fitting portion of the device for picking up bone-conducted sound in the external auditory meatus, and a sound conductive tube of the earphone unit is open at a portion of the fitting portion facing the external auditory meatus.

Hearing aid device

Abstract: A device is designed to provide persons with a mild, moderate, severe or profound hearing loss the ability to hear sound that would be inaudible, as well as the ability to hear ambient environmental noise. The device is fabricated as: (1) a receiver assembly having a pliable flexible strip worn in the outer ear with a small transducer which extends into the auditory canal, and (2) a transmitter assembly having a microphone located remotely on the person whereby information is transmitted to the receiver assembly via modulated carrier waves. The need for a battery in the receiver assembly is eliminated as the power supply is driven by magnetic induction from the transmitter assembly positioned a few inches away, as in a neck pendant.

Bone conductive ear microphone and method.

Abstract: An ear piece device (10) configured for being supported in the ear and providing a microphone (17) which is sensitive only to sounds conducted within the skull of the user is contained within a housing (11) which is configured at one end to fit snugly at the ear canal of the user, but not to extend within the ear canal A microphone element is coupled within the housing This microphone element includes an inertial platform (30) which has sufficient inertial mass to substantially resist movement associated with the housing by reason of audio vibration and includes signal means for generating a signal representing vibrations transferred into the housing in the form of audio vibrations from the user This signal is supplied to an audio circuit (68) for processing and reproduction of the user's voice A speaker element (13) may be included within the ear device and can be decoupled acoustically so as to avoid feedback

Unidirectional ear microphone and method

Abstract: An ear piece device (10) configured for being supported in the ear and providing a microphone (17) which primarily detects only sounds originated by the user is contained within a housing (11) which is configured at one end to fit snugly at the ear canal of the user, but not to extend within the ear canal A microphone element (18) is coupled within the housing in a position such that the microphone element is separated from contact with the skull of the user by the housing This microphone element (18) is contained within a casement (25) which is mechanically and acoustically isolated from vibrations occurring within the housing

Fabrication of silicon condenser microphones using single wafer technology

Abstract: A condenser microphone design that can be fabricated using the sacrificial layer technique is proposed and tested. The microphone backplate is a 1- mu m plasma-enhanced chemical-vapor-deposited (PECVD) silicon nitride film with a high density of acoustic holes (120-525 holes/mm/sup 2/), covered with a thin Ti/Au electrode. Microphones with a flat frequency response between 100 Hz and 14 kHz and a sensitivity of typically 1-2 mV/Pa have been fabricated in a reproducible way. These sensitivities can be achieved using a relatively low bias voltage of 6-16 V. The measured sensitivities and bandwidths are comparable to those of other silicon microphones with highly perforated backplates. The major advantage of the new microphone design is that it can be fabricated on a single wafer so that no bonding techniques are required. >

Acoustic transfer function simulating method and simulator using the same

Abstract: A plurality of acoustic transfer functions for a plurality of sets of different positions of a loudspeaker and a microphone in an acoustic system are measured by an acoustic transfer function measuring part. The plurality of measured acoustic transfer functions are used to estimate poles of the acoustic system by a pole estimation part, and a fixed AR filter is provided with the estimated poles as fixed values. A variable MA filter is connected in series to the fixed AR filter and the acoustic transfer function of the acoustic system is simulated by the two filters. The filter coefficients of the variable MA filter are modified with a change in the acoustic transfer function of the acoustic system.

Method and apparatus for estimating the level of acoustic feedback between a loudspeaker and microphone

Abstract: An improved echo cancelling device for reducing the effects of acoustic feedback between a loudspeaker and microphone in a communication system. The device includes an adjustable filter for receiving a loudspeaker signal and generating in response thereto an echo estimation signal. The device subtracts the echo estimation signal from the microphone signal to produce an echo corrected microphone signal. During periods of time when the microphone signal is substantially derived from acoustic feedback between the loudspeaker and the microphone, the device adjusts transfer characteristics of the filter to reduce the echo corrected microphone signal. The improvement includes estimating from the adjusted transfer characteristics an energy transfer ratio representative of the ratio of the energy of the microphone signal to the energy of the loudspeaker signal. The device compares the microphone signal to the energy transfer ratio multiplied by the loudspeaker signal to identify periods of time when the microphone signal is substantially derived from acoustic feedback between the loudspeaker and the microphone.

Noise reducing microphone apparatus

Abstract: A noise reducing microphone apparatus having an adaptive noise canceller which has a primary input and a reference input and in which the reference input signal is subtracted from the primary input through an adaptive filter and the adaptive filter is adaptively controlled by an output signal resulted from the subtraction, comprises: a pair of microphone units disposed in close locations; and subtracting means for performing subtraction of outputs from the pair of microphone units. An output from one of the microphone units is supplied as the primary input signal of the adaptive noise canceller. A differential output from the pair of microphone units is supplied as the reference input signal of the adaptive noise canceller.

Earplug and hearing devices formed in-situ

Abstract: A custom-molded earplug (18) for swimming protection, hearing protection, and the like, is fabricated in situ by depositing a foaming material (14 or 24) within a person's ear (10 or 42) and allowing the foaming material to form foam (16 or 44). Acoustic and electronic equipment such as a Helmholtz resonator or other tuned device capable of modifying sound waves, a communications transmitter, a communications receiver, a communications transceiver, a hearing aid, an ear microphone, a personal earphone, and a hearing test transducer or probe tube can be fabricated in the ear in a similar fashion. Temperature sensing elements may also be incorporated within or positioned by the foaming material to provide an in the ear thermometer.

Speech dialogue system for realizing improved communication between user and system

Abstract: In the system, a speech input uttered by a human is received by a microphone which outputs microphone output signals. The speech input received by the microphone is then recognized by a speech recognition unit, and a synthetic speech response appropriate for the speech input recognized by the speech recognition unit is generated and outputted from a loudspeaker to the human. In recognizing the speech input, the speech recognition unit receives input signals in which the synthetic speech response, outputted from the loudspeaker and then received by the microphone, is cancelled from the microphone output signals.

A silicon subminiature microphone based on piezoresistive polysilicon strain gauges

Abstract: A silicon subminiature microphone, based on the piezoresistive effect in polysilicon using only one chip, is proposed. The acoustic sensor is fabricated by a technique that is compatible with a slightly modified CMOS process also using a standard micromechanical fabrication technology. The main production steps will be described, including the design and the fabrication of the sensor. Experimental results of the piezoresistive coupling factors and the temperature dependence of the polysilicon resistors are given. Measured results of the airborne sound sensitivity are about −92 dB/Pa. The frequency response is nearly flat with deviations of about ± 3 dB from 100 Hz to 5 kHz and with a resonance at 10 kHz.

Communication device having a speaker and microphone

Abstract: A radio or speaker-microphone unit (10) includes a housing having first (11) and second (12) portions. A speaker (22) is disposed in one of the portions and a microphone (23) in the other of the portions. The portions are movable between first and second relative positions, with one or the positions providing a handset configuration and the other providing a speaker-microphone configuration. A switch senses the relative position of the housing portions and adjusts the gain of an audio amplifier.

A silicon condenser microphone with structured back plate and silicon nitride membrane

Abstract: The fabrication process of a silicon condenser microphone and experimental results of the acoustic measurements are described. The microphone consists of two chips. One chip carries the 150 nm thick silicon nitride membrane, which has an area of 0.8 mm × 0.8 mm. The second chip contains the back electrode, the spacer and the contact pads of the microphone. In order to reduce the streaming resistances in the air gap, the back-electrode area is either structured with grooves by a plasma etching technique or with holes by an anisotropic etching technique. A frequency-independent sensitivity of 10 mV/Pa (open circuit, 1.8 mV/Pa measured) up to 30 kHz is obtained as a result of this structuring of the back-electrode area. Since the air-gap height is only 2 μm, the capacitance of the transducers ranges from 1 to 1.3 pF. The total size of the silicon microphone is 1.6 mm × 2 mm × 0.56 mm.

Microphone and microphone system

Abstract: An infrared-ray cordless microphone including a modulator for modulating an acoustic-to-electric converted sound signal through a predetermined process; and an infrared-ray transmitter for transmitting an output infrared signal obtained by converting the modulated sound signal from the modulator; wherein the infrared-ray transmitter is disposed at a lower end of the microphone body. There is also provided an infrared-ray cordless microphone system comprising such a microphone and a sound output means which includes an infrared-ray receiver for receiving the infrared signal from the microphone, a demodulator for demodulating the received infrared signal, and an electric-to-acoustic converter for converting the demodulated signal into a sound signal.

A ground-based narrow-band passive acoustic technique for estimating the altitude and speed of a propeller-driven aircraft

Abstract: The Doppler effect is the change in the observed frequency of an acoustic or electromagnetic wave due to the relative motion of source and observer. The acoustical Doppler effect is utilized here to estimate the altitude and speed of a propeller‐driven aircraft. The acoustic energy emitted by the aircraft is received by a microphone located just above ground level. The acoustic spectrum of the aircraft is dominated by a spectral line corresponding to the propeller blade rate which is equal to the product of the propeller shaft rotation rate and the number of blades on the propeller. For the present experiment, the aircraft is flown at a constant altitude and speed over the microphone. A frequency estimation technique is applied to the acoustic data from the microphone so that the Doppler shift in the propeller blade rate can be observed at short time intervals during the aircraft’s transit overhead. Using the altitude and speed of the acoustic source as the variable parameters, a simple model is fitted to the observed variation of the blade rate with time; estimates of the aircraft’s altitude and speed correspond to a least‐mean‐squares curve fit of the model to the observations. These estimates are then compared with the actual altitude and speed recorded by the aircraft itself as it flew over the microphone at each of the nominated altitudes: 250, 500, 750, 1000, 1250, and 1500 ft, and at each of the nominated speeds: 150, 200, and 250 kn.

Hands-free voice communication in an automobile with a microphone array

Abstract: The authors present the result of their research on developing a hands-free voice communication system with a microphone array for use in an automobile environment. The goal of this research is to develop a speech acquisition and enhancement system so that a speech recognizer can reliably be used inside a noise automobile environment, for digital cellular phone application. Speech data have been collected using a microphone array and a digital audio tape (DAT) recorder inside a real car for several idling and driving conditions, and processed using delay-and-sum and adaptive beamforming algorithms. Performance criteria including signal-to-noise ratio and speech recognition error rate have been evaluated for the processed data. Detailed performance results presented show that the microphone array is superior to a single microphone. >

Adaptive heart-noise reduction of lung sounds recorded by a single microphone

Abstract: When analyzing lung sounds, heart sounds are an unavoidable and sometimes severely disturbing source of noise. An attractive noise-reduction scheme which is able to preserve the entire spectrum of the desired signal is adaptive filtering. However, such a scheme usually requires a second 'noise-only' reference-signal. A new noise-reduction method which needs only a single microphone signal is presented. This algorithm uses adaptive filtering and therefore still preserves the entire spectrum. Results from experiments with healthy subjects indicate that heart-noise reductions by 24 to 49% can be achieved using this method.

The virtual acoustic room

Abstract: A room may be used for a wide variety of performances and presentations. Each use places different acoustical requirements on the room. We desire a method of electronically controlling the acoustical properties of a room so that one physical space can accommodate various uses. A virtual acoustic room is a room equipped with speakers, microphones and signal processors that functions as an interactive room simulator. Sounds created in the room are detected by the microphones, processed to simulate a desired acoustical space, and returned to the room via the speakers. In order to ensure stable operation and enable simulation of arbitrary spaces, acoustic feedback from the speakers to the microphones must be canceled. The resulting system is a combination of acoustic feedback cancellation technology and multichannel room reverberation technology. This thesis investigates methods applicable to constructing a virtual acoustic room. Acoustic feedback cancellation using static, finite impulse response (FIR) filters is investigated. This technique involves measuring the speaker to microphone response using pseudo-random noise, and creating an FIR cancellation filter from the resulting room response. Multichannel room reverberation rendering is accomplished by using the source image method to determine the early echo response of the virtual room and simulating the diffuse reverberant response using digital reverberators based on nested and cascaded allpass filters. A single channel realtime acoustic feedback cancellation system and a four channel realtime room simulator were constructed. Thesis Supervisor: Barry Lloyd Vercoe, D.M.A. Title: Professor of Media Arts and Sciences This work was supported in part by the Television of Tomorrow Consortium and Pioneer, Incorporated.

Micromachined subminiature condenser microphones in silicon

Abstract: Silicon subminiature microphones can be manufactured with the methods of micromachining technology. Several condenser-type microphones have been designed and fabricated at our institute. Capacitive microphones are described, which have a structured back electrode and a membrane of silicon nitride. A smooth frequency response up to 30 kHz with a maximum open-circuit sensitivity of 10 mV/Pa is obtained. A special design of a capacitive sensor has been realized with the FET microphone. The drain current of a field-effect transistor with a suspended gate is modulated by the vibrations of the membrane. This design represents the first suspended-gate sensor, the drain current of which is deflection controlled. Design, construction and experimental results of sensitivity and frequency response are given.

A new condenser microphone with a p+ silicon membrane

Abstract: This paper presents the results of investigations which have led to the batch fabrication of a new condenser microphone and the subsequent measurement of its characteristics. With an overall size of 3 × 4 × 0.8 mm 3 including an hybrid JFET, the microphone has an integrated back-chamber and is achieved with a very simple IC-compatible process comprising only five photolithography steps. The diaphragm has a thickness of 1 μm. It is fabricated with the classical EDP boron etch-stop technique. Frequency responses of the microphone with a bias voltage of 20 V show sensitivities of 3.5 and 0.4 mV/Pa, depending on the fabrication parameters; the corresponding bandwidths are 2.5 and 20 kHz, respectively. Two methods of measurement have been set up in order to determine the built-in tension of heavily boron-doped silicon and have led to the same value of 70 MPa.

Round window electromagnetic implantable hearing aid

Abstract: An implantable hearing aid device including a vibrational element which is mounted to the round window of the cochlea and a transmitter which can be mounted externally of the ear or within the mastoid bone of the skull. The transmitter includes a microphone for picking up sound waves and converting the sound waves into electromagnetic signals which are imparted to the vibrational element fixed to the round window of the cochlea. The placement of the vibrational element on the round window provides significant advantages over conventional implantable hearing aids which transmit vibrational impulses to the oval window of the cochlea through a pathway which interferes with normal hearing. With the implantable hearing device of the present invention, the normal pathway used for receiving acoustically input sound waves is left unobstructed. With such an arrangement, two separate pathways are available for inputting vibrations to the cochlea, which allows constructive and destructive interference patterns to be set up between the acoustic wave vibrations and the magnetically induced vibrations. This allows the amplification of the signal components and canceling of the noise components.

Head diffraction compensated stereo system with loud speaker array

Abstract: A stereo audio processing system for a stereo audio signal processing reproduction that provides improved source imaging and simulation of desired listening environment acoustics while retaining relative independence of listener movement. The system first utilizes a synthetic or artificial head microphone pickup and utilizes the results as inputs to a cross-talk cancellation and naturalization compensation circuit utilizing minimum phase filter circuits to adapt the head diffraction compensated signals for use as loudspeaker signals. The system provides for head diffraction compensation including cross-coupling while permitting listener movement by limiting the cross-talk cancellation and diffraction compensation to frequencies substantially below approximately ten kilohertz.

An adaptive controller for the active absorption of sound

Abstract: An adaptive system is presented that allows a secondary acoustic source to become an active absorber of sound at the end of a closed duct. The system can also be generalized in order to achieve other termination impedances. The system consists of a loudspeaker, two microphones, and signal processing hardware including a digital signal microprocessor. The signals from the microphones are processed to obtain an error signal that represents the difference between the actual and the desired acoustic impedance of the termination. An absorbing termination requires, for example, that the microphone pair acts as a unidirectional probe picking up the sound reflected from the active termination only. This signal is used as the error signal that the digital controller is required to minimize. A simple analysis shows that this can be done adaptively using the ‘‘filtered‐X’’ LMS algorithm. A simple experimental setup is used to obtain an absorbing termination which is shown to work with periodic, random, and transient input signals.

Probe Microphone Measurements: Hearing Aid Selection and Assessment

Abstract: Explores the usage of of probe microphone measurements in hearing instrument fitting. Comprehensive and totally up-to-date, featuring a range of practical information, this text completely covers probe microphone measurements with 300 references.

Sound storage and sound retrieval system having peripheral with hand operable switches

Abstract: A sound compression/decompression peripheral which operates with a host computer or other remote sound data storage device. The peripheral comprises a plurality of hand operable switches which may be dedicated to functions to which users of tape recorders are accustomed such as "RECORD" "PLAY" "STOP" "REWIND" "FAST FORWARD" and "PAUSE". The switches may also perform other functions. One possible embodiment of the peripheral comprises: a microphone; a speaker; a μLaw codec which converts the analog signals from the microphone into digital pulse code modulated signals, and which converts digital pulse code modulated signals into corresponding analog signals for driving the speaker; a digital signal processor which compresses sound information carried in the pulse code modulated signals, which outputs compressed sound data to a microcontroller, which receives compressed sound data from the microcontroller, which decompresses the compressed sound data into pulse code modulated signals, and which outputs pulse code modulated signals to the encoder/decoder; a microcontroller which buffers compressed sound data between a personal computer and the digital signal processor, which monitors the status of a plurality of hand operable switches, and which relays switch status to the personal computer; and a plurality of hand operable switches.