Making loudspeakers resonate like atoms

According to quantum physics, an atom confined in a cavity will emit far more radiation than a free atom (a). Using this idea, Zhang, Wu and collaborators have explained how a specially designed cavity around a loudspeaker can enhance the emission power of low frequency sounds (b).

© 2018 Jiajun Zhao

A new theory about sound transmission uses ideas from quantum physics to explain how small loudspeakers could efficiently produce low-frequency sounds.

It is well-known that small loudspeakers can produce high-pitched sounds, but much larger speakers (called woofers) are usually limited to produce deep bass sounds only. Recently Jiajun Zhao and Ying Wu from KAUST proposed a solution: a small enclosure with coiled air channels that effectively reduces the speed of sound and enhances low-frequency sound power.

Now,  Zhao  and  Wu’s  concept has been verified by an experiment conducted by Maryam  Landi  and  Likun  Zhang  at  the  University  of  Mississippi,  USA.  The  team’s  experiments  in  an  anechoic  (nonsound-reflecting)  chamber confirmed  that  their  10-centimetre-wide  enclosure  greatly  enhanced  the  emission  power  of  low-frequency  sounds  from  a  tiny  loudspeaker.

“Our enclosure produces powerful sounds with wavelengths much longer than the size of the device,” says Zhao, who recently moved from KAUST to take a job with the energy company GOWell International LLC in Texas. “We hope it can be implemented in traditional woofers to make them smaller.”

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