I have the iso tunes free aware ear buds, they are actually rated as proper 32db snr ear defenders. Wearable all day and ip rated.
As they are proper ear defenders I'm sure they don't use noise cancelling so there isn't that question mark for if they are just cancelling out the sound but still causing damage with the negative soundwave
They do have microphones built in that will amplify sounds. Settings are something like 4 options, completely off (no sound amplification so straight ear defenders) then 3 levels of sound amplification, which is still rated as an defender but will blend outside sounds so speech, buzzers is more audible but if the levels rise it drops the sounds out, so if you turn an engine on or use a impact/nail gun it cuts out.
To be honest I generally use them as a straight ear defender, with amplified ambient sound off, there is times I'll go up a setting or two but if you're somewhere windy, the mics blend in the wind sound which can be annoying.
Only issue is the cost, they are £180