Noise measurement appts. in pipes conducting rapidly flowing air - using external slit-coupled narrow tube with microphone fitting

摘要

The appts. gives easy access to the measurement microphone, thus facilitating calibration. It requires no special fittings, thus eliminating turbulence and acoustic noise, and does not obstruct the measured pipe inlet and outlet flow conditions. It enables measurements to be made in pipes whose dias. are smaller than that of the microphone. The microphone system is mounted outside the pipe (2) whose noise is being measured. An approximately 400 mm long pipe (1) of internal dia. approx. 6 mm is mounted along the measured tube in the direction of flow. It is connected to the main pipe via a 1 mm wide slit, or senses of holes, covered with glass fibre or similar material. The narrow pipe is sealed at its forward end (5) and terminates at the other end in an inclined microphone adapter member (7).