active noise reduction

Today I was 'ploguing around', trying to test out the phenomena of wave cancellation. I really wanted to find out whether 'noise cancellation' can occur binaurally. Unfortunately, I couldn't get the cancellation working through headphones, nor even speakers. I could not get phase cancellation happening in the physical world - the only way the signals canceled out was if I ran them through the same channel inside Bidule. Thinking that perhaps the latency created by using the phase-invert unary operator was offsetting the waveform enough to ruin the cancellation effect, I recorded a sine wave, then inverted it in Peak. I placed both these sound files in a 'dual mono' sound document but to still no avail. It seemed however that there was some reduction in the sound, like maybe the fundamental had been lost/changed.

Any thoughts?
Maybe I need an anechoic chamber for this.