I know what you mean, sometimes the engine noise through the intercom can vary enormously. Just to be clear, you are not talking about 'noise cancelling' as in ear phones. I assume what you are referring to is a sort of 'dolby noise reduction' effect in the ground operator's mike to stop engine noise feeding into the intercom system. This wouldn't be practical- it would end up having to account for quite a large range of engine sounds for different types which would seriously attentuate the ground operators own voice as well! This doesn't happen. I would guess maybe the particular headset was over amplifying sound, maybe the operator was holding his mike further from his mouth to compensate. The effect would be too much engine noise/voice ratio. The only noise cancelling effect to affect you would be the ANR effect in your own earphones.