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Message: <blockquote data-quote="Orionblamblam" data-source="post: 124484" data-attributes="member: 90"><blockquote data-quote="quellish">Many modern consumer electronics have active noise cancellation...</blockquote>Which works when the receiver - a specific human ear, for example - is at a well defined point in space. The source of the sound produces spherical waves; the cancellation system produced spherical waves. At specific locations, the waves cancel; at others, they amplify. Like so:<img src="http://www.faculty.virginia.edu/consciousness/images/water%20wave%20interference.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />This works at the small scale, where the receiver is essentially *inside* the sound cancellation system. But to cancel the noise of a rocket, a jet engine or a helicopter blade for the *outside* universe, the source of the sound cancellation would have to be precisely co-located with the source of the sound to be cancelled. But rocket, jet engines and helicopter blades are *not* point sources, but instead large complex structures that make noise not only in themselves, but attoparsecs and even fathoms away. A lot of the noise for rockets and jet engines is created at the shear plane between the supersonic exhaust and the static air; as the exhaust grinds to a relative halt, several percent of the kinetic energy is transformed into noise. And this can take place a rod or two aft of the exhaust nozzle. You'd have to perform active sound cancellation all along that length. This would not only require a whole lot of computational power, but powerful Star Trekkish tractor beams that can manipulate air at the molecular level over an area of perhaps several dozen picoTexas.</blockquote>

Verification: What company designed the famous Spitfire?