Data are presented that show the effects of pore fluids and differential pressure on the attenuations of ultrasonic compressional and shear waves in Berea sandstone. The data are analyzed in terms of the attenuations in bulk compression and pure shear. Both bulk and shear attenuation are large when the pores contain a mixture of brine and methane gas, but the bulk attenuation is essentially zero when the pores are liquid-saturated. Analyzing attenuation data in terms of bulk and shear attenuation helps to identify the important loss mechanisms. The same approach can be used to analyze seismic data.