LED based Low-Cost Photo-Acoustic Setup by Using Stethoscope

In this study, design and characterization of a low-cost photo-acoustic setup is presented. Photo-acoustic effect is a very intriguing photo-thermo-acoustic effect having applications in a wide range from biomedical science to material characterization. The basic components of a photo-acoustic setup are a sound detector with or without an acoustic cell, a modulated light source preferably with enough power, and an absorbing object. One of the challenging problems is to couple the produced photo-acoustic waves into the detector and this problem was solved by using a commercial sound sensor module connected to a stethoscope. As a modulated light source simply a high power flashlight driven with an amplifier and MOSFET circuit was used. Both detection and light modulation were designed and operated to be via sound card input/output (I/O) of a computer and/or cell phone. Light power and frequency response of the system were presented and 523 Hz was determined as a resonance frequency of the system.