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.
replyI 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!
replyAlso triggered by baby screams unfortunately
replyAn evolutionary adaptation to ensure parents wearing headphones don't ignore their babies.
replyWe don't ignore him. I wear headphones while soothing him.
replyI have a new idea for a bike horn.
replyPlease do not duct tape a baby to your handle bars.
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