Material and system modification for sound pressure enhancement of the carbon nanotubes thermoacoustic devices

Abstract

The thermoacoustic loudspeaker, which has no vibrating membrane with omnidirectional sound generation, would be a candidate for the next generation loudspeaker. However, there is a physical limit of sound pressure caused by the nature of driving mechanism. Therefore, it shows performance below the sound pressure of the conventional dynamic loudspeaker. In this paper, we propose the material and system improvement to overcome low sound pressure performance of the thermoacoustic loudspeaker. One of the advantages of thermoacoustic sound is that the sound pressure is proportional to the input power. Therefore, it is possible to achieve sound pressure performance similar to that of a dynamic loudspeaker in a high power situation. In the first chapter, we propose an insulator coated transducer to withstand high power. Insulator coating improves maximum input power by more than 40% without degrading sound pressure performance. In the second chapter, we apply the thermoacoustic resonators to reinforce the low sound pressure of the thermoacoustic loudspeaker in the low-frequency range. The design of a multiway loudspeaker with three thermoacoustic resonators is discussed to reinforce the sound pressure in wide band low-frequency region. The fabricated multiway loudspeaker has an improved sound pressure level of more than 10 dB at 500 Hz compared to conventional thermoacoustic loudspeakers.