Sound reproduction using the photoacoustic effect

One possible solution for generating point sound sources in mid air is the photoacoustic effect: energy transduction from light energy to sound energy. The photoacoustic effect generates sounds from the alternate current components of air expansion due to the heat generated by light absorption of a material when light modulated with acoustic signal is radiated to a material. In order to confirm sound reproduction using the photoacoustic effect, the experiments to reproduce a pure tone and a musical sound is performed. In order to generate louder sound, the light from the halogen lamp is focused on a charcoal, which has high absorptive power since a charcoal is black and spongy. It is shown that a halogen lamp can be modulated with acoustic signal although the amplitude of higher frequency components is reduced because of the response speed of halogen lamp. Next, the experiments of sound reproduction using a halogen lamp and a charcoal were performed.