Code for a Unity3D component. Attach to a GameObject. AudioSource will generate automatically; make sure it is 2D. With "negation mode" to "negate one", if speakers are next to each other, they should jam each others' signal, mimicking an active noise cancellation system.

Noise Cancellation Experiment

using UnityEngine;

[RequireComponent(typeof(AudioSource))]
public class NoiseCancellationExperiment : MonoBehaviour {
	public enum Mode {
		Direct, NegateOne, NegateBoth
	}

	public int samplesPerSecond = 44100;
	public double[] tones = new [] { 350.0, 440.0 };
	public Mode negationMode;


	const int channels = 2;
	int offset;
	// Use this for initialization
	void Awake () {
		var audioSource = GetComponent<AudioSource>();
		audioSource.loop = true;
		audioSource.clip = AudioClip.Create("Tone", samplesPerSecond, channels, samplesPerSecond / channels, true, Produce);
		audioSource.Play();
	}

	void Produce(float[] samples) {

		double factor = 2.0 / (double) samplesPerSecond;

		for(var i = 0; i < samples.Length; ) {
			double builder = 0.0;
			for(int j = 0; j < tones.Length; j++) {
				builder = builder + System.Math.Sin((double) (offset + i) * factor * tones[j] * System.Math.PI);
			}
			double alfa, bravo;
			alfa = bravo = builder / (double) tones.Length;
			if(negationMode == Mode.NegateOne) {
				bravo = -bravo;
			} else if(negationMode == Mode.NegateBoth) {
				alfa = -alfa;
				bravo = -bravo;
			}
			samples[i++] = (float) alfa;
			samples[i++] = (float) bravo;
		}

		offset += samples.Length;
	}
}