An acoustic transfer function (ATF) is defined as the relationship between a sound level of a source, and the sound level at some remote point known as the receiver. A practical example of a sound source on a vehicle might be the engine, an exhaust tailpipe orifice or an individual component such as a steering pump. The receiver in this context is often simply the driver or passengers ear.
Why are ATF’s important?
ATF’s describe how much the noise of a source is attenuated or reduced before it reaches the receiver. For example how much lower the noise of the vehicles engine is inside the passenger cabin, than inside the engine bay. Along with the source’s sound level, the ATF plays an important role in how much sound is observed by the receiver, or in practical terms how isolated the driver or passenger feels from the vehicles noise sources such as the engine, or tyres. Optimisation of the vehicles ATF’s therefore plays a crucial role in the overall refinement of a passenger vehicle.
Types of ATF’s
The most common types of airborne transfer functions are:-
Other types of transfer functions deal with the relationships between a vibrating source and an acoustic receiver (NTF), and where both the source and receiver are vibrating (VTF).
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