I’d call that a metallic “chirping” more than beeping, since “beeping” is generally reserved for tones created on purpose, but this is definitely not intentional.
Anyway, you’ve left out some other key info: does the cooktop actually work? What are the test conditions here: Does this sound occur only when turned on? Or turned off? (I can’t quite make out if the cooktop is powered on or not.)
It’s definitely not coming from the plug itself. It’ll be sound coming out into the cabinet where the socket is, but not coming from the plug. It sounds to me like a power supply trying to start up, but it’s also a very similar sound to an induction stove actually heating a pan. You get a similar interrupted metallic chirping when an induction stove is having trouble detecting a pan, and keeps cycling a burner on and off as it tries to turn on, doesn’t detect a pan properly, and then turns off and tries again a moment later.
It looks like it’s plugged into a 230V socket. Is the cooktop configured for 230V single-phase, or is it configured for 400V three-phase? (Some can be configured for either.)