  We use an optical centrifuge to deposit a controllable amount of rotational
energy into dense molecular ensembles. Subsequent rotation-translation energy
transfer, mediated by thermal collisions, results in the localized heating of
the gas and generates strong sound wave, clearly audible to the unaided ear.
For the first time, the amplitude of the sound signal is analyzed as a function
of the experimentally measured rotational energy. The proportionality between
the two experimental observables confirms that rotational excitation is the
main source of the detected sound wave. As virtually all molecules, including
the main constituents of the atmosphere, are amenable to laser spinning by the
centrifuge, we anticipate this work to stimulate further development in the
area of photo-acoustic control and spectroscopy.
