SHOT-NOISE ACOUSTIC RADIATION GENERATED BY PHASE SLIPPAGE IN SUPERFLUID HE-4

We present a model calculation and measurements of the acoustic radiat ion spectrum generated by thermally activated phase slippage driven by a constant pressure head. The calculation of the spectrum, which is s imilar to that for shot noise in an electrical current, takes into acc ount the stochastic nature of phase-slip vortex nucleation. The observ ed acoustic amplitude depends on the driving pressure Delta P, the fre quency omega, and the quality factor Q of a coupled cavity, as (Delta PQ/omega(5))(1/2), consistent with the model predictions.