A new apparatus for investigation of sound propagation constants for large amplitude audiofrequency vibrations in metals is described. One novel feature of the apparatus is the use of tuned resonant supports that are tilted with respect to the specimen. The tilting minimizes the tendency to chatter due to the Poisson effect. Because the supports are driven at their resonant frequency, large amplitudes may be achieved without the occurrence of an energy loss due to slipping at the contact surfaces between supports and test specimen. Auxillary equipment permits determination of the resonant frequency of the specimen to better than 1/1000. The error in the determination of the logarithmic decrement varies between 2 percent and 5 percent. The error caused by energy dissipation due to the internal friction of the support is, in most cases, negligible. In those cases where it is not negligible, it can be closely estimated and corrected for. Preliminary results for 61S‐T6 aluminum alloy show the decrement to vary as the14power of the stress amplitude.