[mightysashiman]

On my wh-1000xm2, wh-1000xm3, wf-1000xm4 and lastly wf-1000xm5, there is a quite high frequency pitch (usually coincides with some public transport beeps, and some accidental squeaking of doors) that toggles ANC to transparent mode automatically. I remember reading something about this on Sony's support website.

[bmicraft]

My XM4's always do that at the beeps from the cash register, although I always attributed that to their volume rather than frequency. My theory was that they refuse to produce sound loud enough to cancel the beeps for safety reasons.

[ziml77]

I suspect as much too. If there's a failure to match the noise perfectly then the headphones are just going be be blasting a loud sound into your ears. And if it matches the frequency correctly but lines up with the sound instead of being out of phase, then it's acting as an amplifier!

[walthamstow]

Also triggered by baby screams unfortunately

[haritha-j]

An evolutionary adaptation to ensure parents wearing headphones don't ignore their babies.

[walthamstow]

We don't ignore him. I wear headphones while soothing him.

[jkestner]

I have a new idea for a bike horn.

[RobotToaster]

Please do not duct tape a baby to your handle bars.