Hi guys, I'm looking for advice on how to go about building a circuit that will delay a signal by about 30 microseconds. The delay needs to be adjustable, say between 10-50 microseconds. The signal is audio frequency. Basically I'm trying to make a noise cancelling device, i.e. a microphone picks up incoming noise, then inverts the signal, amplifies it, and puts it out a nearby speaker. I need the delay circuit because there is about 1cm of distance between the speaker and mic, so the signal has to wait for the sound wave to reach the speaker before cancelling it. I got the impression that this would best be done using digital memory. Is this true, and if so, what does that involve? Thanks for your help guys!