Hey! I got two questions. Hoping someone can please help me out. 1) I'm doing a physics assignment and there's a question about constructive/destructive interference of sound. One wave is square and its on top of and the other wave is a triangle and its on the bottom. The square is bigger than the triangle. I'm thinking its a destructive interference since they are both on a different plane. Therefore, when the waves meet, I have the square with a missing portion of the shape of the triangle. Something like this: http://img503.imageshack.us/img503/6374/physicsinterferencefu3.png [Broken] Can someone help me with this. This is what I have but my friends have something else. 2) An ambulance is moving away from you and its siren is making a sound with a frequency of 457 Hz. It the original frequency was 620 Hz and the temperature is 25 C, how fast is the ambulance going? Someone please help. I'm desperate.