Supplementary Materials for Increasing the efficiency of thermoacoustic carbon nanotube sound projectors. Ali E. Aliev 1† , Yuri N. Gartstein ‡ and Ray H. Baughman † † Alan G. MacDiarmid NanoTech Institute, University of Texas at Dallas, Richardson, TX, 75083 ‡ Department of Physics, University of Texas at Dallas, Richardson, TX, 75083 Contents S1-S4. Detailed description of theoretical model. S5. Experimental part: Acoustic measurements in air and underwater. S6. Temperature on the surface of MWNT sheet. S7. Enhanced heat dissipation: Thermoacoustic projector on the heat sink. S8. The sound generation efficiency for flat encapsulated projector with fixed geometry and different filled gases. S9. Modulation of high frequency carrier current with low frequency sound signal. S10. Fabrication and properties of tested encapsulated sound projectors. S11. List of symbols and notations. S1. Comparing surface and volume heaters: With the aerogel nature of the multiwalled carbon nanotube (MWNT) heater, the gas inside of the heater is also heated – unlike the usually discussed surface-only heaters. Here we compare both heating models in the traditional planar geometry for the normal regime that can be related to other published results. Figure S1(a) shows the schematics diagram of aerogel heater with used notations. The wisdom of the standard normal regime treatment is that one considers the expansion of the heated air and finds the velocity of the molecules υ ∞ at the front of the temperature wave. This velocity then serves as the piston velocity to address the sound-wave pressure variations p rms (υ ∞ ). For the benchmark surface heater, one specifies the variation amplitude of the surface temperature T a . The pure temperature wave (no pressure variations) in region II of figure S1(a) is then determined by , = 2 2 0 x T T C i p      (S1.1) hence . = , = ) ( 0 2 1 ) ( 1   p h x ik a C i k e T x T  (S1.2) The respective heat current density at the surface a a T k i x T j 1 = =       , (S1.3) where ț,  0 and C p are thermal conductivity, density and heat capacity of the gas respectively, ω=2πf is the angular frequency of the temperature variation. The energy balance for the surface heater is then just 1 Corresponding author. Tel.: +1 972-883-6543; fax: +1 972-883-6529. E-mail address: Ali.Aliev@utdallas.edu.