The Sennheiser HD 350BT headphones do not have active noise cancelling (ANC) capabilities, but they do have a passive noise isolation mode that can help reduce ambient noise. To activate this mode, simply put on the headphones and adjust them to ensure a comfortable and secure fit. The earcups should create a seal around your ears, which will help block out some outside noise and enhance the overall listening experience. If you have any further questions or concerns about the noise isolation mode on your Sennheiser HD 350BT headphones, please consult the user manual or contact Sennheiser customer support for assistance.