Upon the production of sound by radiant energy

Between Invention and Discovery: A. G. Bell's Photophone and Photoacoustic Research

“…And his discovery of the emission of sounds under modulated light, the photoacoustic effect which could be applied to an essential part of the photophone, gave him good chance to enter into the scientific community and he took advantage of this unexpected opportunity. he could hear the loudest sound from it [7] . Thus, Bell tried lampblack in the photophone to get satisfactory results.…”

“…When the light is cut off, the converse process takes place that a wave of rarefaction is originated from the contraction of the material [8] .…”

“…Bell's subsequent research led to the spectrophone, which opened the possibility of spectrum analysis by ears, especially through the effects of producing sounds by invisible light [11] . Bell removed the eye-piece of the spectroscope and put photoacoustic material in the focal point of the instrument behind a diaphragm containing a slit.…”

High Resolution Biological Visualization Techniques

“…4.1 Photo-acoustic imaging mechanism of action It was Alexander Bell who reportedly first described the phenomenon of sound generation in materials by light (Bell, 1880). As he shone chopped light on strongly absorbing substances he observed that audible sound was generated.…”

Effect of Sample Preparation Route on the Thermal Diffusivity of Nd2O3 - A Laser Induced Photoacoustic Study

“…The photoacoustic (PA) effect has been revived as a very useful technique for measuring the optical [1][2][3][4][5][6][7] and thermal [8][9][10] properties of materials because of its high sensitivity and non destructive nature. The basic principle of photoacoustic effect is that a sample illuminated by periodically modulated (chopped) light undergoes optical absorption and gets heated by nonradiative transitions.…”