  We report the results of high frequency acoustic shear impedance measurement
on superfluid helium-3 confined in 98% porosity silica aerogel. Using 8.69 MHz
continuous wave excitation, we measured the acoustic shear impedance as a
function of temperature for the sample pressure of 28.4 and 33.5 bar. We
observed the A-B transition on warming in zero magnetic field. Our observations
show that the A and B phases in aerogel coexist in a temperature range of about
100 micro-Kelvin in width. We propose that the difference in the relative
stability of the A and B phases, arising from anisotropic scattering, can
account for our observations.
