A method for measuring a speed of a fluid, comprising measurement phases and detection phases each carried out between two measurement phases, each detection phase comprising the steps of; measuring a spurious ultrasonic signal level; comparing the spurious ultrasonic signal level with a detection threshold capable of assuming a plurality of predefined values; if the measured spurious ultrasonic signal level is less than the detection threshold, reducing the detection threshold, and repeating the measurement step and the comparison step; when the measured spurious ultrasonic signal level becomes greater than or equal to the detection threshold, detecting a disturbance and, depending on the value of the detection threshold, determining if the disturbance originates from an anomaly or from attempted fraudulent activity.

A method is provided to measure a distribution of axial velocities and a flowrate in a pipe or a vessel. The method comprises selecting a single cross-section at a stable-flow segment in a pipe or a vessel, installing a plurality of acoustic wave sensors along a peripheral wall of the pipe or the vessel to form a plurality of effective sound wave paths; measuring sound wave travelling time on each sound wave path; substituting the measured sound wave travelling time data into the model formulas based on a sound path refraction principle for reconstruction calculation to obtain a distribution of axial velocity in the measured cross-section of the pipe or the vessel, u(x,y); and integrating the distribution of the axial velocity u(x,y) along the cross-section to obtain a flow rate. A system is also provided to measure an axial velocity distribution and a flow rate in a pipe.

A measuring apparatus includes a determining unit configured to determine propagation paths through which acoustic waves propagate. The acoustic waves are transmitted from one or more transmitters, pass through a predetermined region and are received by one or more receivers. The measuring apparatus includes a controlling unit configured to control the transmitters such that acoustic waves are transmitted and propagate through the propagation paths determined by the determining unit. The measuring apparatus includes an identifying unit configured to identify each of propagation times required for each of the acoustic waves transmitted in response to the control by the controlling unit to propagate each of the propagation paths. The measuring apparatus includes a measuring unit configured to measure an air characteristic of the predetermined region based on the propagation times identified by the identifying unit and length of the propagation paths.

An acoustic air data system includes first and second acoustic transmitters, an array of acoustic receivers, and control circuitry. The array is positioned to receive first and second acoustic signals. The control circuitry determines time difference of arrival (TDOA) of the first and second acoustic signals. The control circuitry determines, for each of a first and second set of acoustic receiver pairs, a signal velocity of the first and second acoustic signals, respectively, based on a distance between an inner acoustic receiver and an outer acoustic receiver and a corresponding TDOA for each pair of acoustic receivers. The control circuitry estimates one or more of wind angle, speed of sound, Mach number, and true airspeed of the airflow about the exterior of the vehicle based on parameters of a best fit circle.

Realized is a device capable of measuring a wind speed and a wind direction with high precision while reducing the effect of ambient noise. The device includes an acoustic wave transmitting section that transmits a measurement acoustic wave, an acoustic wave receiving section that receives the measurement acoustic wave transmitted from the acoustic wave transmitting section, a signal selecting section that determines a characteristic of the measurement acoustic wave, and a wind speed calculating section that calculates a wind speed by analyzing a signal received by the acoustic wave receiving section. The signal selecting section selects, as the measurement acoustic wave, an acoustic wave that mainly includes a low-intensity frequency bandwidth selected from a noise signal which the acoustic wave receiving section receives when the measurement acoustic wave is not transmitted. Alternatively, the plural acoustic wave receiving sections are disposed at different relative positions with respect to the acoustic wave transmitting section, and the wind speed calculating section functions as a wind direction-and-wind speed calculating section to calculate a wind direction as well as a wind speed by analyzing signals received by the respective plural acoustic wave receiving sections.

An acoustic air data sensor for an aircraft includes an acoustic transmitter, an acoustic receiver, an acoustic signal generator, timing circuitry, speed of sound determination circuity, and communication circuitry. The acoustic transmitter is located to transmit an acoustic signal through an airflow stagnation chamber that is pneumatically connected to an exterior of the aircraft and configured to receive and stagnate airflow from the exterior of the aircraft. The acoustic receiver is positioned at a distance from the acoustic transmitter to receive the acoustic signal. The pulse generator causes the acoustic transmitter to provide the acoustic signal. The timing circuitry determines a time of flight of the acoustic signal from the acoustic transmitter to the acoustic receiver. The speed of sound determination circuity determines, based on the time of flight and the distance, a speed of sound through air in the stagnation chamber. The communication circuitry outputs the speed of sound.

An electronic device for measuring a speed of flow of a fluid that includes at least two electroacoustic transducers adapted for emitting and/or receiving acoustic signals through the flow of the fluid, the electronic device being adapted for determining a measurement of the speed of flow of the fluid from the characteristics of an acoustic signal emitted and one or more acoustic signals received, these received acoustic signals corresponding to reflections of the emitted acoustic signal.

Apparatus and associated methods relate to detecting turbulence of an airstream over an airfoil surface of an aircraft using a sequence of acoustic transducers attached to the airfoil surface of the aircraft along a path. Each of the sequence of acoustic transducers is configured to detect acoustic waves indicative of airstream condition proximate the acoustic transducer. A processor is configured to determine, for each of the sequence of acoustic transducers, a level of turbulence of the airstream proximate the acoustic transducer.

Apparatus and associated methods relate to determining airspeed and/or altitude based on acoustic waves caused by airflow. One of more acoustic transducers are positioned along an exterior surface of an aircraft. Each of the one or more acoustic transducers is configured to detect acoustic waves caused by the airflow. The acoustic waves detected are indicative of an airstream condition proximate the acoustic transducer, such as, for example, airspeed and/or altitude. A processor is configured to determine airspeed and/or altitude of the aircraft based, at least in part, on the acoustic waves detected.

Method for measuring a speed of a fluid and ultrasound fluid meter suitable for implementing this method. The method comprises the step of measuring a travel time taken by a measurement ultrasound signal to travel a path of defined length, the measurement ultrasound signal being generated by a transducer subjected to an excitation electrical signal (16). The excitation electrical signal (16) includes a first signal portion (17) followed by a second signal portion (18). The first signal portion is a periodic signal having a pattern (19) and a decreasing amplitude. The second signal portion is a periodic signal having the same pattern (21) and a constant amplitude.