File:PHYS Wiki Figure 2.jpg

English: Figure 2: A trumpet is playing three notes with a straight mute inserted. The first note is low in pitch and has a low-frequency wave. As the wave terminates closer to the back of the bell, the note it produces is largely absorbed by the mute. The second wave, which has a higher frequency and thus terminated farther along the bell, is also partially absorbed, but also escapes somewhat along the edges of the mute to project out of the trumpet. The final wave, which has the highest frequency, almost entirely escapes along the sides of the mute. In this way, one can see how a straight mute quiets notes of a certain low frequency while allowing higher frequency notes to resonate.