DESIGN AND CHARACTERIZATION OF ACOUSTIC COMPARISON COUPLER AS A PORTABLE CALIBRATION MEDIA AND MECHANICAL SOUND SOURCE FOR CALIBRATION OF ACOUSTIC MEASUREMENT INSTRUMENTS

Abstract

Design and characterization for an acoustic comparison coupler has been carried out at Deputy of National Measurement Standard-BSN by Research Group for Acoustics and Vibration. The aim of this work is to contrive a design and characterize this prototype that has an ability to be used either as the portable of calibration medium or as the sound source for calibration of the acoustic instruments. This prototype is consists of two main sections that made from aluminum material. The first section is a body part that is assembled some components such as a super low noise connector, a glass wool, and a loudspeaker. Meanwhile for a head part as the second section, it is formed a concave space inside, and a coupler hole of microphones. In addition, some stages of testing of this prototype are also reported in this paper, consists of measurement of insulation level, frequency response, maximum of sound pressure level (SPL), long term stability, and total harmonic distortion (THD), respectively. From the first stage, the difference of SPL between the two rooms and its background noise is not significant where it shown that the deviation of SPL values are 15.0 dB and 0.9 dB, respectively. Subsequently, the SPL maximum and long-term stability test is obtained at range of SPL of 118.0 dB – 124.0 dB, and 0.1 dB – 0.5 dB respectively at the frequency of 63 Hz – 8000 Hz in one third octave band. Moreover, the total harmonic distortion that measured in the final stage is still in a tolerance limit, where it has a value as 1.88 % for the aforementioned frequencies.