Aspects of the subject technology provide for joint processing of signals from acoustic microphones and signals from vibration sensors that directly or remotely sense vibrations of the source of the sound itself. The vibration sensors may include remote vibration sensors such as a light-based microphone, which may be implemented as an optical microphone. Joint processing of the signals may include detecting a sound from the source in the signals from the acoustic microphone by selecting a portion of the signals from the acoustic microphone based on the signals from the vibration sensor.

A calibration apparatus for calibrating a laser Doppler vibrometer includes: a frequency shifter stage that: receives, from the laser Doppler vibrometer, primary laser light; produces frequency shifted light; communicates the frequency shifted light to a reflector; receives frequency shifted light reflected by the reflector; produces secondary light; and communicates the secondary light to the laser Doppler vibrometer, such that the laser Doppler vibrometer receives the secondary light from the frequency shifter stage and produces a synthetic velocity shift from the secondary light; and the reflector that receives and reflects the frequency shifted light back to the frequency shifter stage.

A portable facility failure diagnosis device using detection of radiation ultrasonic waves, comprising: an ultrasonic sensor array; a data acquisition board (DAQ board) in which an electronic circuit for acquiring ultrasonic signals at a sampling frequency of the ultrasonic signals sensed by the ultrasonic sensor array is mounted on a substrate of the data acquisition board (DAQ board); a main board in which an operation processing device that processes the ultrasonic signals received from the DAQ board is mounted on the substrate and the processed ultrasonic sound source information to a display device; a data storage medium storing data processed in the operation processing device of the main board; a display device visually displaying the data processed; and an optical camera picking up an image of a direction.

A method of recovering audio signals and corresponding apparatus according to an embodiment of the present invention using video or other sequence of images enables recovery of sound that causes vibrations of a surface. An embodiment method includes combining representations of local motions of a surface to produce a global motion signal of the surface. The local motions are captured in a series of images of features of the surface, and the global motion signal represents a sound within an environment in which the surface is located. Some embodiments compare representations of local motions of a surface to determine which motions are in-phase or out-of-phase with each other, enabling visualization of surface vibrational modes. Embodiments are passive, as compared to other forms of remote audio recovery that employ active sensing, such as laser microphone systems. Example applications for the embodiments include espionage and surveillance.

A method of determining a property of a sound field from a plurality of measured sound field parameters, the method comprising: receiving a plurality of measured sound field parameters each indicative of a sound field parameter measured by a sensor of an array of sensors, the sensor being positioned at a measurement position; providing a model of a sound field, the model comprising a set of elementary waves and having associated with it a set of model parameters; computing, from the model, computed values of the sound field parameter at each of the measurement positions and as a function of said model parameters; determining a set of parameter values of the model parameters so as to reduce an error measure by performing an iterative minimization process including a plurality of iterations, the error measure comprising an error term operable to compare the computed and the measured sound field parameters; computing the property of the sound field from the determined set of model parameters.

A part (120) may be subjected to both a resonance inspection and a surface vibration inspection. Various protocols (230; 240; 250; 280; 260) are disclosed as to how the results of one or more of these inspections may be used to evaluate the part (120).

Disclosed is a system and method for testing a structure mode of vibration based on digital image recognition, which comprises a camera, targets, a bridge, a vertical acceleration sensor and a lateral acceleration sensor; the camera is arranged near the bridge head of the bridge; the bridge is equipped with a plurality of targets equidistantly inside guardrails on both sides; and the vertical acceleration sensor and the lateral acceleration sensor are fixedly arranged on the camera. The present application avoids the arrangement of a large number of sensors and complicated wiring in the bridge vibration detection, saves time and reduces economic cost, is convenient to operate, has relatively high precision, and has broad application prospects.

A system for simultaneously detecting audio-characteristics within a body over multiple body surface locations comprising a coherent light source directing at least one coherent light beam toward the body surface locations, an imager acquiring a plurality of defocused images, each is of reflections of the coherent light beam from the body surface locations. Each image includes at least one speckle pattern, each corresponding to a respective coherent light beam and further associated with a time-tag. A processor, coupled with the imager, determines in-image displacements over time of each of a plurality of regional speckle patterns according to said acquired images. Each one of the regional speckle patterns is at least a portion of a respective speckle pattern. Each regional speckle pattern is associated with a respective different body surface location. The processor determines the audio-characteristics according to the in-image displacements over time of the regional speckle patterns.

A laboratory system has demonstrated the measurement of three degrees of vibrational freedom simultaneously using a single beam through heterodyne speckle imaging. The random interference pattern generated by the illumination of a rough surface with coherent light can be exploited to extract information about the surface motion. The optical speckle pattern is heterodyne mixed with a coherent reference. The recorded optical data is then processed to extract three dimensions of surface motion. Axial velocity is measured by demodulating the received time-varying intensity of high amplitude pixels. Tilt, a gradient of surface velocity, is calculated by measuring speckle translation following reconstruction of the speckle pattern from the mixed signal.

A method of measuring fluctuations in electric fields is disclosed, the method comprising the step of: placing a Liquid Crystal Device in communication with the electric field, the device having disparate orthogonal polarization sensitivity to an external electric field; utilizing an optical probe beam having a known polarization state to interrogate the liquid crystal of the liquid crystal device to produce a response beam; and analyzing the polarization state of the response beam to provide an indicator of the corresponding fluctuations in the electric field.