TABLE OF CONTENTS Sandrine Vergne, Jean-Marc Auger, Fred P ri , Andr Jacques, and Dimitri Nicolopoulos
Aerodynamic noise is one of the major contributors to internal vehicle noise; it becomes dominant above 400 Hz at driving speeds exceeding 100 km/h when compared with structure-borne, power train, and tire noise for which substantial noise reduction has been achieved. The interaction of the flow with the geometrical singularities of the vehicle body produces transient turbulent flows, often detached, resulting in an increased aerodynamic noise generation. Two main phenomena are involved:
Aeroacoustic noise: The production and decay of turbulent structures within the flow yields the generation of acoustic sources. That is propagative pressure waves by opposition to the mostly convective nature of the flow around the car. The pressure waves produce a loading of the vehicle body and side windows which do transmit part of the noise inside the vehicle.
Aeroelastic noise: The convected pressure waves fluctuations (pseudo noise), although not propagative, do also load the vehicle structures and therefore induce vibrations that will radiate noise inside the passenger compartment.
This section focuses mainly on this second kind of noise, which is also named aerovibroacoustics.
Flow-induced vibration phenomena are a ubiquitous feature in numerous engineering applications from dynamic stability (e.g., airplane stability, deformations of building structures, and bridges under wind loads) to structural radiation (e.g., the trailing-edge noise described in Howe (2000) or the flow-induced sound inside a plane or a car due to the pressure fluctuations...
