A method for microphone selection, applied in a mobile device having at least two microphones, the method includes: transmitting, by using an ultrasonic transmitter of the mobile device, first ultrasonic waves within a testing box, wherein the first ultrasonic waves are transmitted with a predefined transmission strength and at different frequencies selected from a predefined frequency range; acquiring, by using each of the at least two microphones to receive second ultrasonic waves reflected from the first ultrasonic waves within the testing box, frequency response values of the second ultrasonic waves received by each of the at least two microphones; and determining one of the at least two microphones which has a highest frequency response value, as a microphone for receiving ultrasonic waves for the mobile device.

This disclosure presents methods and systems to reduce measurement jitter of a resonating element. A time control is utilized to analyze the phase of a received frequency from the resonating element. Using that analysis, the time control can determine a next time point to direct the re-excitation of the resonating element. Through controlling when the resonating element is electrically excited, the measurement analyzer can determine a pressure or temperature at the location of the resonating element while accounting for remaining resonating energy from previous electrical excitations. The method and system can allow for measurements to be taken at a significantly faster rate while reducing uncertainty, e.g., jitter, in the collected measurements.

A high-frequency dynamic pressure transducer calibration system and method is provided. The method directs a source onto a diaphragm of a dynamic pressure transducer. An oscillating voltage at a target frequency (or range of frequencies) is generated. The oscillating voltage is coupled to an electrical connector of the dynamic pressure transducer. A deflection pattern of the diaphragm is recorded. The dynamic pressure transducer is calibrated by correlating magnitude of the deflection pattern with the oscillating voltage as a function of the target frequency (or range of frequencies).

A vibration rectification error correction circuit includes a first correction circuit that obtains a digital value based on a signal to be measured output from a sensor element configured to measure a physical quantity and corrects a vibration rectification error of the digital value by a correction function based on a product of values obtained by biasing the digital value.

The present invention is a pressure coupling chamber (1) developed for comparison calibrations of acoustic pressure-sensitive hydrophone (2) in the frequency range from Hz to 1 kHz. A hydrophone (2), reference receiver unit (3) and acoustic source (6) under test are acoustically coupled in the chamber through the air-filled medium inside the pressure coupling chamber (1). Acoustic sources (6) that are going to create acoustic pressure in the pressure coupling chamber (1), placed on the side walls of the chamber (1) to surround the pressure-sensitive active surface of hydrophone (2), are driven to create a hydrostatic pressure effect in the related frequency range in the chamber. Calibration of tested hydrophone (2) with comparison method is carried out by measuring the output voltages of tested hydrophone (2) and the reference receiver unit (3).

An infrasound detector comprises an infrasound transducer, signal feedback path, and feedback force transducer. The infrasound transducer is configured to transduce an infrasound signal to an electrical signal. The signal feedback path is arranged to feed a feedback signal from the infrasound transducer to a feedback force transducer. The feedback force transducer is configured to transduce a feedback electrical signal to a feedback force signal and arranged to provide the feedback force signal as input to the infrasound transducer.

The invention relates to a monitoring process of the state of health of at least two vibration sensors of a twin turbomachine comprising a low-pressure body and a high-pressure body, a vibration sensor being located at the front of the turbomachine, a vibration sensor being located at the rear of the turbomachine, each of the sensors being configured to measure vibrations of the low-pressure and high-pressure bodies at the front and at the rear of the turbomachine, the process being executed in a processing unit (20) of the turbomachine communicating with each of the sensors and comprising the following steps: reception of the low-pressure (NBP) and high-pressure (NHP) speeds of the turbomachine and when said speeds are simultaneously in predetermined ranges, reception of the front and rear vibratory levels of the low- and high-pressure bodies registered by each sensor; determination of the average of the values of the vibratory levels of the low- and high-pressure bodies received over a predetermined reception period; determination of the state of health of said at least first and second vibration sensors from comparison of the average values of the vibratory levels of the low- and high-pressure bodies determined at predetermined thresholds.

A measurement terminal includes: a storage that stores, for each of one or more inspection objects, setting information including a parameter related to a feature of an inspection and an abnormality; a processor; and a memory having instructions that, when executed by the processor, cause the processor to perform operations. The operations include: acquiring audio data of sound from an inspection object; deriving, based on the setting information of a corresponding one of the one or more inspection objects, a required time for acquiring the audio data of sound from the inspection object to be used for determining a presence or absence of the abnormality in the inspection object; and determining the presence or absence of the abnormality in the inspection object based on the audio data of sound from the inspection object for the derived required time.

This disclosure presents methods and systems to reduce measurement jitter of a resonating element. A time control is utilized to analyze the phase of a received frequency from the resonating element. Using that analysis, the time control can determine a next time point to direct the re-excitation of the resonating element. Through controlling when the resonating element is electrically excited, the measurement analyzer can determine a pressure or temperature at the location of the resonating element while accounting for remaining resonating energy from previous electrical excitations. The method and system can allow for measurements to be taken at a significantly faster rate while reducing uncertainty, e.g., jitter, in the collected measurements.

An acoustic testing apparatus may include connections for multiple devices under test (DUTs) to support simultaneous testing of two or more miniature electroacoustic devices. The acoustic testing apparatus may allow the testing of multiple DUTs with a ratio of less than one reference microphone per DUT. Thus, the speed of testing DUTs may be increased without adding significant cost through additional reference microphones. For example, a single reference microphone may be used to test two or four DUTs coupled together through an acoustic test cavity.