increased noise from central air conditioner units

My central air conditioner seems to work fine, but lately it is louder than usual. mostly I hear a noise that resembles a "click" when it turns on (coming from the unit--not the furnace) and then the Ac unit just seems to run slightly loud.

I did have a company out to do a spring maintenance and the technician didn't notice anything wrong.

Amps tested fine, freon was fine and he didn't notice any unusual noise, nor did he think the noise was out of the ordinary. but I've had the central ac unit for ten years and it sounds different. any ideas?