1. Interference in 2-D

2. How do two sound sources interfere with each other over a two dimensional plane? Key Question:

3. If they have the same f, λ and A: ▫Crest on crest – Supercrest ▫Trough on Trough – Supertrough ▫Crest on Trough – Node What interference patterns do we expect?

4. These areas of constructive and destructive interference move out from the source in symmetrical patterns Nodal lines appear straight but as they move away from the source they curve into a hyperbola

5. Let’s play around with a tuning fork!

6. Applications Noise Cancellation Headphones: use a computer to cancel noise using destructive interference computer receives the sound from a microphone, and creates a wave exactly out of phase with the incoming sound creating a node (no sound) ▫used by pilots for better communication and to protect the ears against engine noise