I have an old version of Bose Quietcomfort 2 Acoustic Noise Cancelling Headphones. I put a new battery in and the red "on" light turns on, but I don't hear any active noise cancelling. I haven't used these headphones in ages and I don't have the manual any longer, but I don't recall having to do anything else other than turn them on to get the noise cancelling effect in the past. Suggestions?
Thank you for posting and welcome to the community.
I'm sorry to hear that your having issues with your QuietComfort 2 active noise cancellation. You are correct, once you turn on the headphones, the noise cancellation should start automatically as well. When the headphones turn on, do they work for playing audio, even if the noise cancelling is not working?
It is also worth checking for blockages in the headphone mesh grille and headphone opening as debris can result in issues with the audio and noise cancellation.
It would definitely be helpful to contact your local technical support team for this issue, you can find their contact information from the link here. Just select your region then 'Contact Us'