Noise transmission in vehicles

The vehicle transfer function shows the proportion of noise that reaches one part of a vehicle from another, for example the proportion of noise from the engine bay that reaches the driver or passenger in the passenger compartment, or the noise from the exhaust reaching the passenger compartment.

Just a few years ago measuring vehicle transfer functions was a specialist task and most often used to diagnose specific problems. There was not even a robust technique available to quantify airborne noise transfer routes. In recent times every major vehicle builder has developed or adopted a set of techniques for quantifying vehicle acoustic response and these have become central to the design process. ISVR has pioneered much of this development over the past 20 years.

The Engine Noise Simulators, developed in conjunction with the Ford Motor Company still provide one of the most robust ways to quantify the multiple airborne routes between engine bay and passenger compartments both objectively as well as subjectively.

As development times have reduced so the more rapid results available from smaller omni-directional sound sources have become more attractive. The high frequency source nozzle with its miniature reference microphone mounted directly in the orifice is small enough to work within the confined spaces found in a typical engine bay. Both the high frequency and low frequency sources are suited to both direct and reciprocal measurement.

More recently, attention has been directed towards the implications and significance of the phase part of these transfer functions especially in terms of sound quality.

As well as continuing to develop faster and more efficient methods, ISVR Consulting provides a reliable measurement service to the industry for all forms of transfer function, both airborne and structure-borne, from all the recognised excitations within the vehicle.