Propagation, interférence, réflexion, absorption, diffusion des ondes sonores et ultra-sonores visualisées par la méthode des stries

Observation by strioscope of sound and ultrasonic waves allows one to study their propagation, reflection and absorption without disturbance. Usually frequencies of 69 and 23 kc/s have been used but it is possible to go down to 4 kc/s. Applications in architectural acoustics (role of balconies, circular galleries, cavities in the ceiling, etc.). By using ultrasonic waves reflected between two parallel mirrors the acoustic analogue of the electromagnetic wave-guide has been realised.