Multilevel Pistonphone for Producing Low-Frequency Sinusoidal Pressure Fields.
FInal rept. Feb 72-Nov 75,
AEROSPACE MEDICAL RESEARCH LAB WRIGHT-PATTERSON AFB OHIO
Pagination or Media Count:
This pistonphone is a mechanical device that can generate high-level, low-frequency, sinusoidal pressure fields in small closed volumes over a wide dynamic range for purposes of microphone calibration and laboratory tests. This report describes the device, its performance characteristics, and operationalmaintenance procedures. The pistonphone uses two interchangeable pistons 0.39 and 2.05 cm. diameter and four interchangeable cylindrical chambers 17, 99, 310, 1105 cc. to produce sound pressures at 8 discrete levels ranging from 109 to 174 dB re. .00002 newtonsq over a frequency range of 0.5 to 90 Hz. Tables and graphs present those factors required to compensate for atmospheric pressure changes, isothermal losses, wavelength effects, nonsinusoidal piston motion, nonlinear compressibility of the gas media, vibration, and microphone equivalent volume. This system provides the capability to measure microphone linearity, frequency response and absolute sensitivity to within or - 0.2 dB at all levels except 174 dB or - 0.35 dB for acoustic pressure fields within the limits indicated. Author
- Biomedical Instrumentation and Bioengineering