The gentle whooshing noise of a running air conditioner, on a hot NYC afternoon, is a welcomed sound. When an HVAC system is running optimally, that is the only sound that will emanate from the machine. If you hear any other noises coming from your system, it indicates that there are some mechanical troubles happening within the appliance.
If you experience a rattling sound coming from your HVAC unit, it means that there is something loose within the system. The condenser for most HVAC systems is located outside of home, which means that is exposed to the elements. Things like twigs and rocks can find there way into the machine and cause a rattling noise. If things have fallen into the indoor vents, they will also rattle. This extraction job is best left to air conditioning repair specialists.
Clanking and scraping and metal on metal sounds, indicate that there are parts loose within the HVAC unit. Pipes, fan blades, and other parts can fall out of alignment and cause the appliance to run inefficiently. This is a repair that only an air-conditioning installation or air-conditioning repair specialist should handle.