Page 56 - Winter Issue 2018
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Advancements in Thar-mnphanas
oveiau, 10w efficiency, the mcchanica1 fragility of high1y Po. nology 24, 235501.
rous thermophone heaters, and an effective lack of receiv- Ahev’ A‘ E" Luna’  D" mg’ S" and Ba“ghma“’.R‘ H‘ 0010)‘ U“derWa'
_ _ _ _ _ _ _ ter sound generation using carbon nanotube projectors. Nano Letters 10,
ing eaPab1i1tY has innited thetni°Pi1°neS from inaking then 2374-2380. https://doiorg/10.1021/nl100235n.
way into any practical commercial devices. Still, a few niche Aliev, A. E., Mayo, N. K., Baughman, R. H., Avirovik, D., Priya, S.,
use cases exist in which thermophones could outshine their Zfainetaite M- R-3 and Bi°tti'nan- l- 3- (29i4al- "igitetntai tnanagetnent
   due to their broadband ::..:,*:::::::::‘;::‘:1.:::“:.:‘ 332::::::.:::";§..:,.:;:.:::%:‘;:g 3:33:
response and low manufacturing cost. Use as an underwater httPs:/,doi.o,g/10_1083,0957_4484,25,40,405704_ ’
sound projector place thermophones in an ideal environ- Aliev. A. E., Mayo, N. K., Baughman, R. H., Avirovik, D., Priya, S.,
ment where they can be run in their most efficient regimen Zarnetske, M. R., and Blottman, I. B. (2014b). Thermoacoustic excitation
. . . . . of sona.r projector plates by free-standing carbon nanotube sheets. Ioumal
at hlgh P°W°’ “nth ample °°°1mg °“P“b1htY' uf Physics D‘ Applied Physics 47 355302 https-//doi org/10 1088/0022-
Moreover, most thermophone technologies are easily upscaled A1727/:7/:5/::5302N K I d A dud M R bl R O F S
ev,..,ao,..,unen e,.,oes,..,an,.,
With Vaiiens aCtiVe heating eieinents being Pindneed “Sing Baughman, R.  Zhang, M.,gChen, Y., Lee, J. A., and Kim, s. I. (2515).
VLSI processes. New materials are being explored as more me- Alternative nanostructures for thermophones. ACS Nana 9, 4743-4756.
chanically robust thermophone elements, although freestand- i1ttP5=//d°i-°ig/ 10-1°21/nn507ii7a
ing CNT Sheets Currently remain the most efficient transduo Aliev, A. E., Perananthan, S., and Ferraris, I. P. (2016). Carbonized elec-
_ _ _ _ trospun nanofiber sheets for thermophones. ACS Applied Materials and
ti°n inatenai- Ti1enn°Ph°ne eneaPSniat10n Provides a means Interfaces 8(5), 31192-31201.
of protecting the relatively fragile active material from harsh Arnold, H. D., and Crandall, I. B. (1917). The thermophone
environments but also results in a resonant device. This reso- :5 “//§’.°°‘5“’1‘:)  ‘I’: j‘(;"2‘;d' Ph}”““l Rem” 10’ "'38-
nance can be timed independently of the active material that Ba]tlt:'fine(:1'°rSg_/ @932). yfrefifiniliué of microphone Ca1ibmi0n_
is usually suspended from a substrate. Thermophone elements pic lgumul cf ihc Acoustical society of America 3, 319.35()_
are usually arrays of wires or planar films that are suitable for httPS=//dni-nig/10-i121/i-1915555
The future of thermophone projectors is still largely un- ACee5SedA“g“5t 25-2018-
. . . . Bell, A. G., and Tainter, C. S. (1880). On the production and repro-
known' me ablhty to generate Sound wlthout agny rfiechanl duction of speech by light. American Ioumal of Science 20, 305-324.
cally moving parts makes thermophones a fascinating tech- https:/,doi.o,g10_2475,ajs.s3_20_118305.
nology to study for potential applications. However, modern Bouman, T. M., Barnard, A. R., and Asgarisabet, M. (2016). Experimental
thermophones are still a relatively new technology and are q:““"fi°1“_:°‘}‘°fth"it’“‘;l°‘E°‘e“°Y°f;“b"“ ““‘:’“‘be thi";‘9fi1‘1";:3“";“6‘;‘
_ , . t t’ ' t ' , — .
certainly not an end-all replacement for conventional de- doi.:12”{/1.::94:”61§8f£u may of mmm
vices. Indeed, an inspection of recent thermophone publica- Braun, F. (1898). Notiz iiber thermophonie. Annalen der Phyzik 65, 35s.
tions shows that most studies on the topic have been con- i1ttPS=//d°i-°Fg/ 10-1002/andP-13933010609
ducted from a physics or materials science perspective and Bmwn’ 1‘ 1" M°9'e’ N‘ C" Supekflf’ 0' D" Gensch’ I‘ C" and Bnght’ V‘ M‘
_ _ _ _ _ _ (2016). Ultrathin thermoacoustic nanobridge loudspeakers from ALD on
not for direct applications. Thus, additional evaluation and Polyimida Nummhnology 27 475504_
critique by trained acousticians and engineers is sought to Dutta, R., Albee, B., van der Veer, W. E., Harville, T., Donovan, K. C.,
more rigorously quantify thermophone Performance and Papamoschou, D., and Penner, R. M. (2014). Gold nanowire ther-
. . . . mophones. The loumal nf Physical Chemistry 118, 29101-29107.
help progress this exciting technology. Along with develop- httPS_//doi org/10 1021/jpsougsv
ing the theoretical tonndatien Of thefn10Ph0neSs input from Dzikowicz, B. R., Tressler, 1. F., and Baldwin, 1. w. (2017). Cylindrical heat
biologists, sonar technicians, medical doctors, and many conduction and structural acoustic models for enclosed fiber array ther-
others is needed to highlight the various niche areas in which ‘;‘;l;h1‘:“°5‘ /Z'“.]"“"1";’)l1”1f2il/‘j  S"“”’}’ "f A’””““ 142’ 3187'
the advantages of these projectors can be utilized. Only time Fei)  gin) Silt:/Gu'0) w_ (2015) L(;w_vo1ta e driven Ia hem foam
. . . . 3 S P
will tell as to what other practical devices this technology thermoacoustic speaker. Small 11, 22522255.
can produce. In the meantime, it continues to provide a very Smll-201402981
Curious tabletop demonstration for Students. Heath,  S.,.and Horsell, D.'V\7. '(2017). Multi-frequency sound production
and mixing in graphene. Scientific Repnrts 7, 1363. 1038/
References Herschel, A. S. (1874). Vibrations of air produced by heat. Nature 10, 233-
Aljev, A_ 1-‘,_, Ganstein, Y_ N” and Baughman, R. H_ (2013)_ Increasing the ef. Higgins, B. (1802). On the sound produced by a current of hidrogen gas
ficiency of thermoacoustic carbon nanotube sound projectors. Nanntech- paffing through a tube. Iaurnal of the Natural Philosophy. Chemistry. and
54 | Acnuseics Thday | Winter 2018

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