Active Noise Cancellation - feasibility

Question

I'm planning a micro-controller project on active noise cancellation.

The idea is:

• Speaker_1 generates 100-200 Hz noise (constant frequency).
• Microphone records Speaker_1.
• Signal is passed into micro-controller for DSP.
• Output from micro-controller is 180 degree phase shift of input.
• Output signal goes to Speaker_2.
• Sound from Speaker_2 cancels sound from Speaker_1. Room is silent

My questions are:

1. Is this idea feasible? (I saw demo here: https://www.youtube.com/watch?v=UyN1TACCbHE)
2. Once the noise-cancellation does start to work, then wouldn't the microphone receive no input? Thus no signal equates to no noise cancellation?

Answer 1

Before you waste too much of your time try this: Take two speakers. Reverse the speaker wires on one to switch the phase. Now play a mono signal through them. You'll find pretty quickly that the room is not silent. There will be some cancellations at some frequencies but that will be highly dependent upon your listening position and the speaker locations.