Christian Doppler's Tie

Origin
Christian Andreas Doppler (November 29, 1803-March 17, 1853) was an Austrian mathematician and physicist. He is celebrated for his principle, known as the Doppler effect, that the observed frequency of a wave depends on the relative speed of the source and the observer. He used this concept to explain the color of binary stars.

Effect
When worn, the user can alter the volume, by either raising, lowering, or even muting the volume of nearby sounds. Only the user can notice the effect.