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A Fessenden oscillator is an electro-acoustic transducer invented by Reginald Fessenden, with development starting in 1912 at the Submarine Signal Company of Boston. [1] It was the first successful acoustical echo ranging device.
Using piezoelectric transducer, the wave propagation angle in the test part is affected by Snell's law. As a result, a small variation in sensor deployment may cause a significant change in the refracted angle. Easier to generate SH-type waves. Using piezoelectric transducers, SH wave is difficult to couple to the test part.
Generally, the electro-acoustic transducers are of the Tonpilz type and their design may be optimised to achieve maximum efficiency over the widest bandwidth, in order to optimise performance of the overall system. Occasionally, the acoustic pulse may be created by other means, e.g. chemically using explosives, airguns or plasma sound sources.
This loudspeaker enclosure or speaker box isolates the acoustic energy from the front of the cone from that of the back of the cone. A horn may be employed to increase efficiency and directionality. A grille , fabric mesh , or other acoustically neutral screen is generally provided to cosmetically conceal the drivers and hardware, and to ...
Collinear transverse acoustic waves or perpendicular longitudinal waves can change the polarization. The acoustic waves induce a birefringent phase-shift, much like in a Pockels cell [dubious – discuss]. The acousto-optic tunable filter, especially the dazzler, which can generate variable pulse shapes, is based on this principle. [6]
The term tonpilz or "acoustic mushroom" may refer to a certain type of underwater electro-acoustic transducer. By sandwiching active (i.e. piezoelectric or magnetostrictive) materials between a light, stiff radiating head mass and a heavy tail mass, the transducer can effectively operate as either a projector (source) or a hydrophone (underwater acoustic receiver).
Surface acoustic wave sensors are a class of microelectromechanical systems (MEMS) which rely on the modulation of surface acoustic waves to sense a physical phenomenon. The sensor transduces an input electrical signal into a mechanical wave which, unlike an electrical signal, can be easily influenced by physical phenomena.
Data acquisition hardware for acoustic measurements typically utilizes 24-bit analog-to-digital converters (ADCs), anti-aliasing filters, and other signal conditioning. This signal conditioning may include amplification, filtering, sensor excitation, and input configuration. Another consideration is the frequency range of the instrumentation.