Automotive thermal systems are of major importance in ensuring optimum operating of thermal engines and in preserving battery capacities. These systems involve various components with a wide range of technologies, designs and subcomponents as HVACs, compressors or fan systems.
Currently, as thermal engine noises are reduced and electrification trends are continuously increasing, thermal systems can be a major source of noise and vibration. These NVH issues can emerge inside the car cabin inducing significant discomfort to passengers and can also emerge outside the car causing major disturbances to passersby.
During development stages, NVH issues are mastered and contained by suppliers according to internal specifications in addition to complying with OEM requirements. However, NVH issues may not be well detected when using regular NVH metrics. This raises concerns about the limitations of the regularly used metrics to ensure specification compliance and furthermore to depict a subjective assessment at component level and afterwards at vehicle level.
Throughout some recently encountered examples, this paper first focuses on the discrepancies between the data provided by traditional NVH metrics and subjective evaluations. Furthermore, a deeper analysis involving psychoacoustic criteria provides a relevance overview of the applied metrics depending on the encountered issue and compared to a subjective assessment. Finally, from a technical responsibility perspective, these findings raise questions about the relevance of regular metrics used in OEM specifications and the wright way to handle NVH topics nowadays.