A well log of the vibrations of an ultrasonic acoustical signal as it passes through a four-phase system of fluid, pipe, cement and formation. If the pipe is not acoustically coupled tightly with a dampening material such as cement, very little of the acoustical energy signal is lost. If the cement is bonded or acoustically coupled tight to the pipe, the energy is extremely dampened and the signal nearly disappears, thereby indicating that the casing is well cemented.