Visualization of Ultrasonics Interference Patterns in Front of Radiating Quartz Discs by Optical Illumination in the Direction of Sound Propagation

Normally investigations on the structure of an ultrasound field are carried out in such a way that the field is illuminated perpendicular to the direction of the ultrasound propagation. In the present publication however the illumination is carried out through a translucent quartz disc and parallel to the ultrasound propagation. Two cases of interference phenomena are obtained: In the one case with small angles between the quartz disc and the reflecting walls of the vessel bands of interference arise. The number of these bands increases with increasing angle. In the second case with parallelism of the quartz transducer and the reflecting walls concentric interference circles are produced.

To avoid a disturbance of the amplitude distribution on the quartz disc by thermal effects it is necessary to observe the phenomena immediately after switching on the source of sound.