1) Yes, if you possibly have a loose wire connection either inside the main electrical panel or a nearby splice box that feeds the garage and a hot wire shorts out, then an audible arc is usually heard. The sound of an arc is really more of a very quick popping noise and not really a beeping sound. If an arc was present within the main panel or any branch circuit junction box, wall switch or receptacle boxes, yes, this presents a possible safety fire hazard and it should be checked ASAP. Another possibility if the noise was an electrical arc is the circuit breaker contact may have become loose and not making proper contact with the hot bus bar or possibly a loose hot wire connection at the breaker. If an arc, usually you will see some of the insulation on the electrical wires or devices may have become burnt. As you can see, there are many possibilities that can cause an electrical arcing effect.
2) In the interim, I would recommend to leave that circuit breaker in the OFF position until the entire circuit can be checked.
3) If you feel comfortable in doing some electrical troubleshooting and can have access to a 2-prong (contact type) of voltage tester or an AC voltmeter, I can walk you thru the process. Otherwise, I would recommend that a licensed electrician look into the problem.
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