a CdS crystal annealed in an inert atmosphere at a temperature and for a period of time to provide {HEAD ~ substantially maximum acoustic attenuation} at {TAIL ~ the operating frequency} of the crystal; and 
at
a CdS crystal annealed in an inert atmosphere at a temperature and for a period of time to provide { HEAD ~ substantially maximum acoustic attenuation } at { TAIL ~ the operating frequency } of the crystal ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH