| Carbon nanotube film loudspeaker is a new kind of speaker based on thermoacoustic effect in recent years. The application of carbon nanotube film loudspeaker in active noise control has been proposed for the first time in this paper. The purpose in this paper is probing the feasibility of carbon nanotube film loudspeaker as secondary sound source.The main work and achievements are as follows:First of all, the acoustic characteristics of the carbon nanotube film sound source is analyzed theoretically. The sound source system of the carbon nanotube film sound source is constructed. The near-field acoustic pressure and far-field sound pressure is tested respectively to compared with the theoretical calculation results. And then revise sound pressure formula to make the test results are in good agreement with the theoretical calculation.Secondly, the factors which influence the carbon nanotube film sound pressure are analyzed. Accordingly, a parallel structure of thin film loudspeaker is designed to increase the output sound pressure of thin film by reducing the resistance of the film.Afterwards, in view of the carbon nanotube film output sound pressure and the input voltage is 2 times the frequency, the frequency distortion caused by thermoacoustic effect is analyzed and solved by series dc voltage in the circuit or adding clamping circuit, and the output pressure of the film is significantly increased.The last but the most important, with the carbon nanotube film as the secondary acoustic actuators, the monopole and structural acoustic radiation are active controlled respectively. With the minimum total sound power as control purpose, the optimal control voltage of film sound source is derived and the total sound power after control is obtained. According to different film loudspeakers and different cloth way of them, active control effect is compared to verify the feasibility and effectiveness of the carbon nanotube film as secondary sound source. |
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