Separate the two complaints
If traffic is audible while the door is closed, ask about the assembly’s sound-transmission data and other paths into the space. If the sound occurs only during opening, describe the squeak, scrape, vibration or motor noise for service assessment. An acoustic rating does not diagnose worn rollers or a poorly operating door.
Read the type of acoustic claim
DASMA describes Sound Transmission Class (STC) and Outdoor-Indoor Transmission Class (OITC) as different sound-transmission ratings and notes that the sound source matters. Ask what test and configuration support a product claim. Insulation thickness or a thermal rating alone should not be presented as proof of a particular acoustic result in your garage.
Define a realistic result
Keep the intended use and surrounding construction in the discussion. A quieter operator may address its own operating sound without improving the closed door’s barrier performance. For a demanding room-acoustics project, obtain suitable design advice instead of expecting a door change to control every sound path.
Your questions
Does an insulated door automatically have a stated sound rating?
No. Request the relevant acoustic data if sound transmission is part of the purchase decision. Thermal performance is a separate measurement.
Will acoustic information explain a new grinding noise?
No. A change during operation needs mechanical assessment. Avoid repeated cycling of a damaged or unstable door.