At first glance, a muffler looks like a simple set of pipes with holes in them. However, these tubes and chambers are tuned like a musical instrument and are designed to reflect the sound waves produced by the engine in a way that they cancel themselves out. Sound is a pressure wave formed from pulses of alternating high and low air pressure that make their way to our ears at the speed of sound. How we perceive sound depends on the sound wave frequency (which determines the pitch of the sound) and the air pressure level (which determines how loud the sound is). However, if two sound waves are out of pace with one another, they cancel each other out. This concept is called “constructive interference.” When one wave is at its maximum pressure and another is at its minimum pressure, they won’t produce any sound at all when these waves hit your eardrums.