Information was from the top negative review on Amazon: "I called Bose support and they told me the QC30 was never intended to be a replacement for the QC20. They said the NC wouldn’t be as strong and wasn’t intended to be. That is why one is designated QuietControl and not QuietComfort. "

I missed the reply from Bose: "We apologize for the information you received from our support team as it is not accurate. The Quietcontrol 30 headphones should offer a comparable level of noise cancellation to the previous QC20 model. Although the level of noise cancellation is adjustable on the QC30, they should perform just as well as the QC20."