CANOBLE: New cockpits for reducing cabin noise
Cockpit and cabin noise is of primary importance in the design of new aircraft. Cabin noise is a source of discomfort, whereas cockpit noise is a source of risk for pilots resulting in communication difficulties and fatigue.
Cabin noise is a combination of several acoustic sources which differ according to the configuration of the aircraft, the operating conditions and the transmission path (structure-borne or air-borne). A dominant noise source while in cruise mode is the aerodynamic noise and more specifically the turbulent boundary layer (TBL). It generates a turbulent wall pressure fluctuation along the fuselage that induces vibrations and, by transmission, generates interior noise.
Mastering the excitation, the transmission path and the noise radiation is a key challenge to design the next generation of aircraft. The CANOBLE project aimed at developing and validating innovative engineering methods and tools up to TRL5, enabling researchers and engineers to study, in design phase, the noise generated inside the cockpit and cabin by the external turbulent boundary layer.
The first two years of the project have been dedicated to the development of the technologies:
- A smart thin sensor equipped with a large number of MEMS (MicroElectrical-Mechanical System) digital microphones to measure the wall pressure excitation;
- A numerical workflow combining RANS computational fluid dynamics (CFD) data, empirical models coupled to a vibroacoustics finite element method (FEM) solver.
A dedicated academic wind tunnel has been developed in Ecole Centrale de Lyon to validate the technologies successfully.
In parallel, a full-scale aircraft cockpit and cabin mockup has been designed and manufactured, and various structural components of interest have been instrumented. A dedicated interior cavity welcomes the acoustic interior measurements including intensity probes and 3D acoustic arrays.
By the end of 2018, wind tunnel test campaigns had been conducted covering a large range of configurations and for various flow conditions up to Mach 0.2. These involved more than 500 sensors, measurements covering static and dynamic aerodynamic data, wall pressure measurements, vibration and acoustic responses.
The last part of the programme has been focused on exploitation. This has been realised through the setup and the analysis of the full scale test data base. Numerical prototypes have been developed. Predictions have been compared with measurements from the quality of the excitation up to the acoustic radiated power level.
The CANOBLE project is a major breakthrough towards the state of the art offering new engineering methods, including both prediction and test solutions, to address interior noise. Validated at full scale on an aircraft mockup, the CANOBLE technologies also open up new fields of investigations within the automotive and railway transportation industries.
Check out this video to learn more about the project: https://youtu.be/3jGqhrsusWI