Brief review of primary methods applicable to key comparisons in acoustics

Abstract

Historically, various techniques have been used in acoustics to attempt to establish and measure sound pressures (spatially uniform amplitude of sound pressure, as in a suitable coupling cavity that is small compared with a wavelength of sound) and in the free field (plane progressive sound wave at a specified angle of incidence, in the absence of reflecting surfaces). At present, over a broad range of frequencies the most accurate, precise, and convenient methods involve the primary calibrations of laboratory standard microphones by reciprocity techniques. Some issues and parameters in these techniques that must be considered in comparisons, and selected previous interlaboratory comparisons themselves, are discussed. Recommendations relevant to a key comparison already identified, as well as future work areas, are presented.

Membrane actuation by Casimir force manipulation

“…However, this procedure, familiar in acoustics, is well known to only yield reliable results as a secondary calibration, mainly because of difficulties to accurately measure the distance between the electrostatic actuator and the microphone membrane. In addition, the entire process typically neglects fringing effects and it assumes that the electrostatic pressure is a constant everywhere on the membrane [43][44][45][46][47][48][49][50][51][52].…”