A Reference Infrasound Source with Low Distortion Based on Laser Pistonphone Technology

A study on the pressure leakage correction of pistonphones at infrasonic frequencies

“…It is reasonable to substitute Δ op into Eqs. (12) and (13) to get the actual adiabatic pressure step response and the actual T a of the pistonphone, which is shown in Fig. 5.…”

“…Furthermore, according to Eqs. (12), (13), (26) and (33), it could be found that δ and ε always appear simultaneously as a combined expression (1 þ1.5ε 2 )δ 3 , so a new variable Δ is defined as…”

“…In order to get the precise sound pressure in the chamber, extra corrections for effects of sound pressure leakage, heat conduction and wave motion are always made [7,9,12,13], which results that the final corrected values of sound pressure level (SPL) in the chamber of a pistonphone is…”

“…where p ref is the reference sound pressure, p ref ¼20 μPa; L LC , L HC and L WC are the values in dB of the pressure leakage correction [7,9,12,13], heat conduction correction [13,15,16] and wave motion correction [7,18], respectively, and each correction is independent [7,13]. A thin slit between the piston and its guide is usually designed to equalize the static pressure in and out of the chamber [7,13].…”

“…A thin slit between the piston and its guide is usually designed to equalize the static pressure in and out of the chamber [7,13]. In all references, the pressure leakage correction of pistonphones is done as the method proposed by NPL [7,9,12,13]. As stated in this report, by ignoring the heat conduction effects at low frequencies and wave motion effects at high frequencies, the acoustical impedance of pistonphones is expressible as the acoustical compliance of the chamber C, in parallel with the acoustical resistance of the leakage path R. Accordingly, the correction in dB for the sound pressure leakage effect is [7] L LC ¼ À10log 10 …”