Possibility of ESPI visualization
Zdenek Otcenasek; Pavel Dlask

Electronic speckle pattern interferometers (ESPI) are prominent helping tools for non contact observations of movements of an object surface. Their functionality is based on speckles, which are products of the interference effect between both the laser beams scattered from separate unevenness of the object rough surface and the reference beam originated from the same laser source. This method is applicable on rough surfaces of solids. In the case of acoustic fields the air particles don’t give speckle patterns. Also in this case ESPI visualization can be used, but based on a principle of changes in the air refractive index when air pressure is changed. The aim of this contribution is to explain basic know-how and possibilities of ESPI (especially double pulse TV ESPI method) visualizations of a sound pressure distribution in a defined space. The practical output is focused on applications on wind musical instruments (presented is an example of sound pressure distribution inside and outside of an organ pipe in the process of normal excitation).