These are noisy. Buzzing/humming/electronic sounds heard from outlet.

When connected to a USB charging load that varies its power draw (i.e. a Qi wireless charging pad for mobile devices), an regular intermittent humming sound can be heard from the outlet. It's loud enough to be noticeable in a quiet room (especially at night). I found it disturbing enough after a couple of weeks that I ordered a similar product from an alternate manufacturer (which was/is completely silent). I believe the circuit design/build quality to be poor. Steer clear and choose alternatives (readily found on Amazon).

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