FAA paper Noise Attenuation Properties of Noise-Canceling Headsets

Larry Dighera wrote:

That might be an adequate number of inputs in most cases, but it's
still going to require equipment manufacturers of stall warning
systems, autopilots, etc to provide the audio outputs in addition to
their horns and bells.

Have you ever used an ANR headphone? Most don't attentuate
frequencies that the various alarms (my gear alarm, the cessna
stall party horn, etc...) much more than the passive headphones
do.

Even engine noises are frequently enhanced by ANR. I kept hearing
a clanking noise in the ANR. I pulled off my headphones for a "better
listen" and couldn't hear it. With the ANR I heard it. On landing
I found my exhaust pipe had busted a weld and was flapping around.