Thermoacoustics of CVD graphene

For the first time, direct experimental evidence of the thermoacoustic effect is presented. The results of studies conducted using atomic force microscopy showed that the amplitude of mechanical vibrations of the thermoacoustic transducer does not exceed 161 nm at a sound pressure level of 65 dB at a distance of 2 cm and a frequency of 3 kHz. Mechanical oscillations with such an amplitude at the specified frequency cannot provide the observed level of sound pressure. This indicates that mechanical oscillations do not significantly contribute to the formation of the sound field generated by the thermoacoustic transducer based on a graphene-glass composite. Consequently, the primary mechanism of sound generation in the studied system is the thermoacoustic effect rather than mechanical vibrations of the substrate. It has also been established for the first time that the non-uniform heating and size of the CVD graphene crystallites influence the sound generation process only on scales comparable to the size of graphene crystallites and, under conditions typical for the use of graphene thermophones, do not have a decisive effect on the thermoacoustic effect.