An automobile owner notices that when her car is outfitted with a muffler, the sound from the exhaust pipe is much quieter than without the muffler. When she asks her automobile technician about how a muffler works, he explains that a muffler is a device that matches the sound coming down the exhaust pipe but with waves out of phase from the pipe. What phenomenon is the automobile noticing and the technician describing?

A) Seismic shift
B) Doppler effect
C) Destructive interference
D) Constructive interference