In this work we present some experiments which can be performed in college or on the first courses
of university to acquire knowledge about resonant acoustical phenomena in closed cavities in a
tangible way, through experiments based on the photoacoustic effect in gases. This phenomenon
consists in the generation of acoustic waves after optical excitation of an absorbing gas and
further local heating of the non-absorbing surrounding gas by energy exchange through collisions
between molecules of both species. Simple experiments, performed with daily live elements, can be
very useful for teachers and students to get in touch with the phenomenon of acoustic resonances
with the addition of concepts about light–matter interaction. The setups consist of the resonant
cavity, the illumination source and the signal detection-acquisition scheme. In this paper a closed
glass test tube is used as the resonant cavity and is filled with a mixture of nitrogen dioxide and
air. The illumination …