Abstract
Results are presented of calculations made of distortion experienced by ultrasonic pulses in transmission through dispersive constant-group-velocity media, and the effects that it may have on velocity measurements. Three types of pulses were considered: a pulsed sine wave of constant amplitude, a pulsed sine wave with amplitude varying as sine-squared, and a rectangular pulse. It is shown that the individual waves in the pulsed sine waves move with the phase velocity of a continuous wave, and the envelope moves with the group velocity. It was also found that a pulsed sine wave in going a certain distance in a constant-group-velocity medium repeats itself, and midway between these distances is the negative of the values at the repetition distances. Because of this repetition phenomenon it is seen that the pulses propagating through the constant-group-velocity dispersive media do not spread as is normally the case in dispersive media. The envelopes of the propagated waves were also calculated, and in agreement with Brillouin’s results [Wave Propagation and Group Velocity (Academic, New York, 1960)] it was found that if the envelope contains negligible frequency components above the carrier frequency, then the envelope is not distorted in passing through a dispersive constant-group-velocity medium.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call