High frequency response of carbon nanotube thin film speaker in gases

The thermoacoustic response of carbon nanotube (CNT) thin films at frequencies ranging from 300 Hz up to 100 kHz has been studied in a variety of gaseous mediums. Theoretical derivations show that the sound pressure generated by CNT thin films is approximately proportional to the inverse of the heat capacity of the gas within the audible frequency range of human hearing, which is consistent with the experimental results in argon, air, and helium. For large size CNT films, a decrease in sound pressure is observed within a higher frequency range in air, which is attributed to the destructive interference of sound waves in the near field zone according to the theoretical calculations. (C) 2011 American Institute of Physics. [doi:10.1063/1.3651374]