Bit of thread drift here, but:

I don't think any manufacturer has developed a noise cancelling sound system specifically designed for a motorcycle helmet because the very nature of a helmet precludes the usual strategy of sensing unwanted sound at a central boom microphone, then cancelling it out at the speakers.

The nature of unwanted sound in a motorcycle helmet is quite different from the nature of unwanted sound in (for example) an aircraft. I specified and used a noise cancelling headset in the aircraft I was responsible for. The noise present at the boom microphone (engine sound, propeller thrumming, rain hitting the windshield, etc.) was pretty much identical to the noise present at the two earcups, hence, the boom microphone could be used to detect and identify the sounds to be cancelled.

In a motorcycle helmet, the unwanted sound present at the rider's ears is quite different from the unwanted sound present at the microphone (located near the rider's lips). Wind buffeting noises at the sides of the helmet will be different than wind buffeting at the lower front of the helmet where the microphone is. Likewise, engine noise sensed at the rider's lips will be different in both amplitude and frequency from the engine noise that makes its way up to the rider's ears, this due to the internal sound insulation properties of the helmet.

For a motorcycle helmet noise cancellation system to work, each earpiece (presumably an earplug, because over the ear cups used in most noise cancelling systems would not be possible in a motorcycle helmet without compromising head impact protection, the primary purpose of the helmet) would have to have its own microphone located very close to the outside of the earpiece. Two signal processing systems would be needed (one for each side) because ambient noise within the helmet will vary from side to side depending on how the rider turns his head, or what the crosswinds are, or where the big truck you are passing is relative to the motorcycle.

Such technology could be developed, but it would be both complex and expensive. It would also probably require a cable connection between the helmet and motorcycle to power it, because the electrical demands would be too great to permit the system to be powered by a battery small enough to be acceptable for mounting within the helmet.

The use of an earpiece to deliver sound, as opposed to small flat speakers mounted within the helmet, also presents problems. I'm opposed to the idea of using an earpiece (earplug) to deliver sound because it presents a very great risk of skull injury if I take a tumble off the moto and the side of my helmet has a hard impact with the ground. It is for this reason that all the aftermarket helmet sound systems use speakers and not earplugs. The designer of a motorcycle helmet noise cancelling system would have to find a way to effectively cancel sound without using either earcups (like an aircraft headset) or earplugs (like pedestrian systems that plug into phones, etc.), and that would present a major challenge.

Michael