Aircraft cause considerable noise, both to the outside world and inside the cabin. The INTONATE project is investigating how cabin noise is created and how it affects flight comfort. The main goal is to set up a digital thread for calculating the cabin acoustics of aircrafts still in the design phase.
Start of the INTONATE project - Future Aircraft INTeriOr Noise and VibrATion Evaluation
Transmission paths for structure-borne and airborne noise in aircraft - digital chain
Future aircraft should offer as much comfort as possible
In future of aviation three factors are becoming ever more important: sustainability, reduced exterior noise near airports and, of course, flight comfort. Reducing fuel consumption is the main driver for sustainability. This leads to new engine designs and aerodynamic drag reduction technologies. The second problem can be improved by smart placement of the engines, e.g. on the plane. However, the resulting aircraft configurations also have a strong, and often negative, effect on cabin noise and thus comfort.
Last but not least, a new development must be accepted by the customer. For the development of new aircraft, it is therefore particularly important to be able to predict cabin noise as early as possible in order to avoid subsequent noise reduction measures and thereby not delay or even jeopardize the development process.
The digital analysis method is important for new configurations, as there are no empirical values for estimating cabin noise from similar configurations. Cabin acoustic assessments have so far been an afterthought of the development process, but could be a decisive factor in the choice between otherwise economically and ecologically equivalent configurations.
Starting the INTONATE project
Within the INTONATE project DLR is researching a continuous analysis capability for cabin noise. The different aspects of cabin noise are scientifically evaluated at various DLR institutes. The Institute of Aeroelasticity, which leads the project, the Institute of Aerodynamics and Flow Technology in Göttingen and Braunschweig, the Institute of Propulsion Technology, the Institute of Composite Structures and Adaptive Systems, the Institute of System Architectures in Aeronautics and the Institute of Aerospace medicine are involved.
Noise and vibration sources and their transmission paths to the aircraft cabin to the receiver
Due to the novelty and complexity of the topic, prior to the project a joint "map" of the participating institutes, their competencies and interfaces was created. This shows the current development status of the various individual disciplines in simulation and experiment. In addition to the possible sources of cabin noise, the various transmission paths were identified, which now need to be established as new interfaces between the institutes.
Sources of noise are, for example, the flow in the turbulent boundary layer which affects the fuselage, as well as the engines, which introduce vibrations into the fuselage and also emit noise that is directly transmitted through the air towards the aircraft. All these sources act on the fuselage and are transmitted from it to the cabin and the interior cavity.
Goal: consistent digital analysis capability for cabin noise
The aim is to set up a continuous digital chain for the analysis and evaluation of cabin noise, for which the establishment of interfaces must be considered in addition to method validation in the individual disciplines. The long-term goal is the ability to digitally (i.e. completely numerically) evaluate new aircraft designs with regard to their cabin noise.
A virtual environment for test subject experiments will be developed to investigate the comfort level of the passengers. The numerical analysis results of the sound and vibration investigations will come alive with the help of a virtual reality environment in order to assess at which point in the cabin what kind of noise is particularly discomforting. For this purpose, requirements are defined, virtual reality models of cabins are set up and a methodology for making the calculated cabin noise tangible (auralization) is developed.
Finally, the functionality of the continuous digital chain will be demonstrated using the comparative analysis of two different aircraft configurations.
Author:
Rene Winter, DLR-Institute of Aeroelasticity, Department Structural Dynamics and System Identification
