The recent trend of automotive industry is to optimize vehicle passengers comfort both at noise and vibration level: this study is the core of Noise Vibration and Harshness (NVH) branch. This work is focused on Structure-Borne Noise (SBN), the noise generated by structures vibrations caused by the propagation through solid bodies of the forces coming from the tyres and on Air-Borne Noise (ABN), the noise transmitted by air in form of pressure wave coming from the tyre-road interaction, friction and air compression. This thesis subject is the paths characterization through which the noise propagates both as vibrations and sound pressure from the tyre to the vehicle interior in order to determine the main sources and to be able to estimate the driver comfort. In order to achieve a first approximation of the noise perceived by the driver’s ear some tests are conducted on the outdoor test track on a rough asphalt: relations between sources and receivers are determined adopting the Operational Transfer Path Analysis (OTPA) approach in order to define the Operational Transfer Functions (TF). Indoor tests are then conducted to simulate the sources and the Transfer Functions are applied: results are validated by comparing the simulated overall signal and the measured response signal. The aim is to check whether the differences between two tyres types perceived by the driver are denoted in the simulated signal starting from the indoor tests.
La tendenza dell’industria automobilistica è di ottimizzare il comfort dei passeggeri a bordo del veicolo sia a livello di vibrazioni sia di rumore: questo è l’aspetto principale della branca dell’NVH (Noise, Vibration and Harshness). Questo lavoro si concentra su Structure-Borne Noise (SBN), ossia il rumore generato dalle vibrazioni della struttura causate dalla propagazione attraverso i corpi rigidi delle forze provenienti dallo pneumatico e su on Air-Borne Noise (ABN), il rumore trasmesso via aerea in forma di onda di pressione prodotta dall’interazione tra strada e pneumatico. Uno scopo è la caratterizzazione dei percorsi del rumore attraverso i quali esso si propaga per determinare quali siano le maggiori sorgenti e per stimare il comfort interno al veicolo. Per ottenere una prima approssimazione del rumore ci si basa sui test condotti sul tracciato di prova su un asfalto ruvido: le relazioni tra le fonti del rumore e i punti dove esso viene acquisito sono determinate con la Operational Transfer Path Analysis (OTPA) che mira a definire le Operational Transfer Functions (TF). Inoltre sono stati svolti dei test indoor in modo da simulare le fonti del rumore e le Funzioni di Trasferimento sono applicate: il risultato è validato comparando il segnale stimato con quello misurato in Outdoor. L’obiettivo finale è di valutare se le differenze riscontrate tra due coperture nei test outdoor, a livello di rumore interno all’abitacolo, sono riprodotte nel segnale ricostruito a partire dai test indoor.
Vehicle internal noise prediction due to rolling tyres with noise paths characterization
MANTOVANI, ANDREA
2019/2020
Abstract
The recent trend of automotive industry is to optimize vehicle passengers comfort both at noise and vibration level: this study is the core of Noise Vibration and Harshness (NVH) branch. This work is focused on Structure-Borne Noise (SBN), the noise generated by structures vibrations caused by the propagation through solid bodies of the forces coming from the tyres and on Air-Borne Noise (ABN), the noise transmitted by air in form of pressure wave coming from the tyre-road interaction, friction and air compression. This thesis subject is the paths characterization through which the noise propagates both as vibrations and sound pressure from the tyre to the vehicle interior in order to determine the main sources and to be able to estimate the driver comfort. In order to achieve a first approximation of the noise perceived by the driver’s ear some tests are conducted on the outdoor test track on a rough asphalt: relations between sources and receivers are determined adopting the Operational Transfer Path Analysis (OTPA) approach in order to define the Operational Transfer Functions (TF). Indoor tests are then conducted to simulate the sources and the Transfer Functions are applied: results are validated by comparing the simulated overall signal and the measured response signal. The aim is to check whether the differences between two tyres types perceived by the driver are denoted in the simulated signal starting from the indoor tests.| File | Dimensione | Formato | |
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2020_04_Mantovani.pdf
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https://hdl.handle.net/10589/152982