Experimental quantification of the true efficiency of carbon nanotube thin-film thermophones

Troy M. Bouman, Andrew R. Barnard, Mahsa Asgarisabet

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Carbon nanotube thermophones can create acoustic waves from 1 Hz to 100 kHz. The thermoacoustic effect that allows for this non-vibrating sound source is naturally inefficient. Prior efforts have not explored their true efficiency (i.e., the ratio of the total acoustic power to the electrical input power). All previous works have used the ratio of sound pressure to input electrical power. A method for true power efficiency measurement is shown using a fully anechoic technique. True efficiency data are presented for three different drive signal processing techniques: standard alternating current (AC), direct current added to alternating current (DCAC), and amplitude modulation of an alternating current (AMAC) signal. These signal processing techniques are needed to limit the frequency doubling non-linear effects inherent to carbon nanotube thermophones. Each type of processing affects the true efficiency differently. Using a 72 Wrms input signal, the measured efficiency ranges were 4.3 × 10-6 - 319 × 10-6, 1.7 × 10-6 - 308 × 10-6, and 1.2 × 10-6 - 228 × 10-6% for AC, DCAC, and AMAC, respectively. These data were measured in the frequency range of 100 Hz to 10 kHz. In addition, the effects of these processing techniques relative to sound quality are presented in terms of total harmonic distortion.

Original languageEnglish (US)
Pages (from-to)1353-1363
Number of pages11
JournalJournal of the Acoustical Society of America
Issue number3
StatePublished - Mar 2016

All Science Journal Classification (ASJC) codes

  • Arts and Humanities (miscellaneous)
  • Acoustics and Ultrasonics


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