SOUND MODES OF SUPERFLUID HE-3 IN AEROGEL

We present the results of experiments on sound propagation at audio fr equencies in He-3-filled aerogel. Sound modes were observed at tempera tures of 0.8-100 mK in an aerogel sample of 98% porosity. We find that below T-c for superfluid He-3 in the aerogel matrix the speed of soun d in the composite system increases by as much as 1.5%. Also below the aerogel T-c new modes appear which correspond to propagation speeds o f up to similar to 10 m/s.