Abstract
The signal compression method is used to measure the acoustic particle velocity by a constant temperature hot wire anemometer. The signal compression method, which was proposed by one of the authors, was proved useful to improve S/N ratio in measuring the impulse response and the frequency response of any linear system. It is necessary to add bias flow about 1-2 m/s to measure the particle velocity by a hot wire. Four methods were tried, using (1) natural air convection by the hot wire, (2) steady flow in a pipe, (3) vibration of the hot wire, and (4) air suction by a pipe. Methods (2) and (4) were successful to measure the particle velocity with sufficient accuracy. From measured waveforms of particle velocity and acoustic pressure, acoustic intensity acoustic impedance and reflection coefficient were calculated and showed good agreement with theoretical values. Methods (1) and (3) were not so good because sufficient bias flow could not be generated. Nevertheless apparent particle velocity pulse signal could be detected by virtue of the signal compression method.
