Active Noise Cancellation (ANC) is sound field modification, particularly sound field cancellation, by electro-acoustical means. In its simplest form, a control system drives a speaker to produce a sound field that is an exact mirror-image of the offending sound (the "disturbance"). The speaker thus "cancels" the disturbance, and the net result is no sound at all. In practice, of course, active control is somewhat more complicated.

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The name Active Noise Cancellation differentiates "active" from traditional "passive" methods for controlling unwanted sound and vibration. Passive noise control treatments include insulation, silencers, vibration mounts, damping treatments, absorptive treatments such as ceiling tiles, and conventional mufflers like the ones used in today's automobiles. Passive techniques work best at middle and high frequencies, and are important to nearly all products in today's increasingly noise-sensitive world.

However, passive treatments can be bulky and heavy when used for low frequencies. The size and mass of passive treatments usually depend on the acoustic wavelength, making them thicker and more massive for lower frequencies.

Active noise control using Panphonics elements as sensors and actuators makes it possible to change the acoustics of a room according to the special requirements at hand. Passive sound control does not always provide effective sound attenuation. Thick absorption layers and special structures are often required, resulting in higher costs and increased weight. Low frequencies in particular may require a large amount of passive sound absorption material, and in many cases, this is not a feasible solution.