not echo reflections. Example: In a recording studio, sound proofing is accomplished with bass traps and anechoic chambers. Wallace Sabine, an American physicist, is credited with studying sound reverberations in 1900, and Carl Eyring revised his equations in 1930 for Bell Labs. Another example is the ubiquitous use of dropped ceilings and acoustical tiles in modern office buildings with high ceilings. Submarine hulls have special coatings that absorb sound. Acoustic damping: Vibration isolation prevents vibration from transferring beyond the device into another material. Damping mounts have progressed in the industry to offer vibrational resistance in many degrees of freedom. Recent advances include shock isolators damping in at least six degrees of freedom. Acoustic damping also has uses in seismic shock protection of buildings. Motors and rotating shafts are commonly fitted with these mounts at the points where they contact the building or the chassis of a large machine. Acoustic decoupling: certain parts of a machine can be built to keep the frame, chassis, or external shafts from receiving unwanted vibrations from a moving part. Example: Volkswagen has registered a patent for an "acoustically decoupled underbody for a motor vehicle.". Another example: Western Digital has registered a patent for an "acoustic vibration decoupler for a disk drive pivot bearing assembly.". Preventing stalls: Whenever a machine undergoes an aerodynamic stall, it will abruptly vibrate. Preventing cavitation: When a machine is in contact with a fluid, it may be susceptible to cavitation. The sounds of gas bubbles imploding is the source of the noise. Ships and submarines which have screws that cavitate are more vulnerable to detection by sonar. Preventing water hammer: In hydraulics and plumbing, water hammer is a known cause for the failure of piping systems. It also generates considerable noise. A valve that abruptly opens or shuts is the most common cause for water hammer. Shock absorption: Just as automotive shock absorbers are used to prevent mechanical shocks from reaching the passengers in a car, they are also important for quieting shocks. Reduction of resonance: Essentially any piece of metal or glass has certain frequencies to which it is susceptible to resonate. A machine that resonates would make a tremendous noise. Resonance also occurs in enclosures, such as when echoes reverberate in an ocarina or the pipe of a pipe organ. Material selection: By choosing nonmetallic components, the transmission of sound and vibrations can be minimized. For example: instead of