If the shaft is not aligned properly, moving equipment will vibrate.20 Shaft couplings between parts, such as an electric motor and centrifugal pump, are particularly vulnerable.21 The centre lines of both shafts should match.22 Limiting vibration will significantly help with HVAC noise reduction.23 A quiet HVAC system is the result of addressing vibration at the design stage.24 Otherwise, components may malfunction, which in turn can lead to system failure.