Hi! Thanks for the question!
You can indeed run both models with the power and noise-cancelling turned on, but no music playing.
You’ll hear your surroundings become magically muffled, which is cool…but you’re not going to block out quite as much noise as you would with the music on.
Both systems are designed to perform optimally with music playing. First, the music itself helps to block out some background noise. Secondly, each headset has internal mics designed to listen to your music, which in turn helps it decide what is noise and what is music, which in turn allows the cancellation to perform a little bit better.
It’s not a night and day difference, but it’s there. If you’re looking for something that just blocks out outside noises, you’ll still get better performance from dedicated hearing protection headphones, ear plugs, or even deep-insertion in-ear monitors.
But yes, you could theoretically run them without music playing and the ANC turned on. This works best with an AUX cable plugged in, because then you can prevent the power-saving circuit from kicking on inside the headphones. I think the Bose app also now includes a toggle to extend the power save time when running wirelessly.
Hope that helps you out!