Source Path Contribution - SPC

In today’s competitive automotive industry, it is crucial to quickly and accurately evaluate the noise and vibration perceived. Meeting the regulations and improving the experience requires knowing more than just the levels and perceptions people encounter. It is important to know the contributions of the different sources in detail to find the right source of vibroacoustic phenomena. And to mitigate the paths that vibroacoustic energy takes to people, it is crucial to understand how it travels through the structure and through the air.

In today’s competitive automotive industry, it is crucial to quickly and accurately evaluate the noise and vibration perceived. Meeting the regulations and improving the experience requires knowing more than just the levels and perceptions people encounter. It is important to know the contributions of the different sources in detail to find the right source of vibroacoustic phenomena. And to mitigate the paths that vibroacoustic energy takes to people, it is crucial to understand how it travels through the structure and through the air.

Source Path Contribution and Time Domain

Is it the source that is too loud, or the path that transmits it too easily? Many technical questions arise when refining development vehicles. Source Path Contribution (SPC) analysis, or transfer path analysis, is a technique for evaluating noise contributions from suspected sound or vibration sources through various acoustic or vibroacoustic paths to a desired receiver location.

With SPC analysis, it is possible to categorize the effects perceived by the observer (receiver) as airborne or structure-borne, and drill progressively deeper into their origins, tracing them back to their source, such as a specific engine mount. Dominant sources with respect to a given receiver can be highlighted to help focus engineering effort where it has the greatest impact. This helps automotive engineers and managers improve their engineering decision-making process and enables parallel evaluation of design alternatives and product variants throughout the vehicle development process.

For effective SPC on vehicles, it is important to analyse transient events, such as run-ups and run-downs and play back modified signals to simulate design changes. Time-domain SPC software allows listening and modification of noise source strengths or path sensitivities to set target levels for individual component sources or transfer paths. Time-domain SPC data can also be transferred to an NVH Simulator model for virtual drive assessments. 

While SPC methods are often used for interior cabin noise analysis, with sources and paths being both acoustic and vibratory, they can also be used for analysing vehicle pass-by noise using an indoor pass-by setup. In some cases, the operating measurements can be combined, for example, measuring with a Head and Torso Simulator (HATS) binaural microphone inside the vehicle whilst also measuring with an indoor pass-by microphone array.

Source Path Contribution for Vehicle Exterior Noise

The BK Connect® Pass-by SPC solution is specially designed for analysing vehicle exterior noise (pass-by noise) using measurements on a chassis dynamometer in a hemi-anechoic chamber.