High Resolution Mechano-Optical Method for Acoustic Field Measurements in Air (Postprint).

摘要

Acoustic fields are typically visualized by measuring spatial variation of pressure in a medium, using optical (ie: Schlieren, laser interferometry) and electro-mechanical (ie: transducers, micro-electro-mechanical sensors) methods. These methods have limited ability to visualize acoustic fields in air, especially at high spatial resolution (< 0.5 mm). This paper presents a method to detect and quantify the acoustic fields in air by measuring the displacements of a micro-reflector attached to fiber with a laser interferometer. The potential of the method is demonstrated by measuring acoustic pressure of an air coupled transducer, and the variation of acoustic pressure in the focal region of an air coupled acoustic lens. In the current experimental arrangement an approximate spatial resolution of 250 microns and an approximate acoustic pressure of 7 mPa have been demonstrated. A physics based mathematical model is presented that has been used to analyze the spatial resolution and acoustic pressure. Limitations of the method and possible improvements to achieve higher spatial and temporal resolution are discussed.