Effects of acoustic source and filtering on time-of-flight measurements

Time-of-flight (TOF) measurements are valuable in the estimation of distances, displacements and velocities of moving objects, phase differences of wave pulses, temperature of the atmosphere, and so on. The effects of sound source on time-of-flight measurements have been investigated in this paper. The sound sources considered are: electric horn, impact noise source, aerodynamic noise from a free jet, and the Hartmann whistle. The focus of the present study is to highlight the advantage of using Hartmann whistle for TOF measurements as this device is simple and attractive, without any moving parts. Time-of-flight of sound waves is calculated by cross-correlating the signals received by two microphones. Further, the effect of signal filtering on TOF measurements is demonstrated. The results indicate that the sound source has considerable effect on TOF measurements, and the accuracy can be significantly enhanced by appropriate signal conditioning. Hartmann whistle proves to be a good candidate as an acoustic source for TOF measurement.