4. Acoustic radiation from the complete GMP

The term "acoustic radiation" refers to the overall level of noise from an engine and its peripheral components, radiated from all sides and across the entire frequency band. Noise is generated by vibrations from all surfaces of the engine trunk and peripheral parts, and transmitted to human ears or measurement microphones via the air.

Motor excitation → Vibration of external walls → Overhead transmission

By definition, the acoustic radiation from an engine excludes gearbox-related noise. In general, however, an engine operates with a gearbox. When the engine is measured with its gearbox, it is referred to as the "sound radiation of a GMP". However, it is possible to measure only the acoustic radiation from an engine without its gearbox, by adding soundproofing...