Each time my central A/C starts, there is a loud buzz for 1 second. The unit is new and works fine - just wondering if this is unusual. I've been told its probably the relay sending power out to the outside condenser. Anyone else familiar with this?

Really depends on where the sound originates from, odd buzzing is never acceptable for motors, relays, circuit breakers, etc.

If pipes or metal enclosures are causing the noise, then most likely all is needed is more straps or tighten a loose bolt.

If any of the electrical or mechanical parts is the source, then call in a tech .