Question about Sennheiser Pxc 550

No, unfortunately these headphones are not really suitable for that. I have the feeling that when there is no signal (music, film,...), the noise-cancelling function is not very effective. In any case, not better than simple earplugs from the supermarket for 50 centimes.

I often wear the headphones in an open-plan office without listening to music. The effect takes a little getting used to, but ambient noise is clearly attenuated. Naturally, noise cancelling works best with uniform broadband noises, which are almost completely gone (e.g. air conditioning or other uniform noise such as on an aeroplane, no matter how loud). Conversations are muffled but still audible. The effect is completely sufficient for me to be able to concentrate well even in a noisy environment.