Francis Speed Mckendree

Portable acoustic intensity measuring device

A portable acoustic intensity measuring device comprising a pair of electroacoustic transducers at a positioned predetermined distance from one another. The measuring device utilizes analog summing, subtraction, integration and multiplier means for measuring an acoustic intensity vector midway between the two electroacoustic transducers. The acoustic intensity measuring device further comprises error correction means connected in circuit with a preamplifier means and a meter means. The error correction means includes switching means comprising a first switch connected in circuit with the preamplifier and summing means and subtraction means and a second switch connected in circuit with the multiplier and the meter for simultaneously switching the first and second preamplified analog signals at the summing input and subtraction input and for simultaneously switching the polarity of the acoustic intensity signal at the meter. The error correction means eliminates any errors induced by phase mismatch and/or any inherent DC component of the device.

Axisymmetric parametric radiation—A weak interaction model

In this paper the difference‐frequency field of a a parametric acoustic radiator is approximated via a weak finite‐amplitude solution of the second‐order nonlinear paraxial wave equation (i.e., the nonlinear optical analog established by E. A. Zabolotskaya and R. V. Khokhlov [Sov. Phys.–Acoust. 15, 35–40 (1969)]) obtained by expressing the primary waves of an axisymmetrically excited bifrequency piston projector in terms of a weighted sum of Gauss–Laguerre eigenmodes. By relating the fundamental (i.e., Gaussian) mode in the farfield of the projector to those of equivalent ’’Bessel beams’’ a closed‐form expression for the difference‐frequency field is thus obtained as a function of range. Following a review of the solution’s phenomenological properties comparisons are made of predicted results and experimental data reported in the literature.

High-volume acoustic transducer

A high-volume source for very low frequency applications in which conventional speakers are inadequate is disclosed. A presently preferred embodiment comprises a reservoir 32 with a pressure relief 33; a controller 34; a supply blower 36; an exhaust blower 38; a positive plenum 40; a negative plenum 42; an orifice plate with valving 44; a horn 46; and pressure transducers 48, 50, 52, 54, feeding detected pressure levels to the controller 34. An electrical command signal s(t) is also input to the controller. The command signal is a voltage analogous to the acoustic pressure or volume velocity to be output by the source.