We present the results of experiments on sound propagation at audio frequencies in 3He-filled aerogel. Sound modes were observed at temperatures of 0.8-100 mK in an aerogel sample of 98% porosity. We find that below Tc for superfluid 3He in the aerogel matrix the speed of sound in the composite system increases by as much as 1.5%. Also below the aerogel Tc new modes appear which correspond to propagation speeds of up to ∼10 m/s.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- General Materials Science
- Condensed Matter Physics