MULTI PHYSICS MODELING AND VALIDATION OF CARBON NANOTUBE LOUDSPEAKERS

Carbon nanotube (CNT) thin film speakers produce sound with the thermoacoustic effect. Better understanding the physical acoustic properties of these speakers will drive future design improvements. Measuring acoustic properties at the surface of the CNT thin-film is difficult because the films, themselves, do not vibrate, they are fragile, and they have a high surface temperature. In order to measure the surface particle velocity and sound pressure level, near-field acoustic holography (NAH) has been used by employing probe microphones. NAH images the acoustic quantities of the source system using the set of acoustic pressure measurements on a hologram parallel to the source surface. It is shown that the particle velocity at the surface of an open-air, double-sided speaker is nominally zero, as expected. However, the sound pressure level distribution is not uniform on the source surface, contrary to common lumped parameter model assumptions. Also, particle velocity and sound intensity distributions on the hologram and directivity pattern of the CNT speaker have been obtained in this study. In addition, developing a multi-physics (Electrical-Thermal-Acoustical) model, for planar CNT transducers is studied. The temperature variation on the CNT thin film is obtained by applying the alternating electrical current (AC) to the CNT film. The surface temperature variation is then used to simulate the pressure distribution in the open medium. To validate the model, the results of simulation are compared to the experimental data and traditional lumped-parameter models