IDEA PACI - IDEntification of an Aircraft PAssenger Comfort Index

In terms of general performance, air transport technology is very advanced. Due to the increased use within the typical distances and area of the European Community, not only environmental impact, but also the Internal, particularly Vibro-Acoustic, Comfort has to be considered in the design process. Already a standard approach in cars, "design to noise" has become more and more accepted in aeronautics.

In the efforts aimed at improving the interior comfort of aircraft or other means of transport, attention has recently moved towards active, as opposed to the usual passive systems. These methods appear as complementary rather than alternative, both showing qualities and faults. It is to their application credit, that certain thematic aspects have been deepened, and some unexpected results have been pointed out. The link between noise and vibration levels appeared to be ruled by complex relationships, and results following the application of pure noise abatement systems were surprising. People interviewed stated a preference for high noise instead of low sound but high vibration levels. Then, by lowering interior noise levels, comfort was decreased.

Assuming that passenger welfare inside the aircraft is a complex function of both noise and vibrations (and other surrounding characteristics) is almost trivial. Also, to imagine that the design objective is to improve the comfort and not to suppress the noise, seems obvious. Because comfort is a subjective matter, psychological studies play a fundamental role. The target of this basic research project is to define a general Subjective Comfort Index for commercial aircraft. The objective will be reached by developing a "Virtual Passenger", defined on the basis of an Artificial Neural Network (ANN), that simulates the Transfer Function between the external stimuli (physical variables) and the generic passenger response (subjective impression). Both acoustic and vibration data will be taken into account. The main steps of the research may be summarised as follows:

• A psycho-acoustic study will be carried out to develop a tool that allows to translate the environmental solicitation in subjective impressions. Suitable descriptors will be identified.
• Experimental investigations, both on the ground and in flight, will be performed to produce a wide data-base, fundamental for statistical investigations. Different helicopter and aeroplane test articles will be used.
• The architecture of the ANN will be defined. The network will be trained and assessed on available experimental data. The Net performance will be preliminarily evaluated. The Virtual Passenger will be defined.
• ANN will finally predict comfort levels on both experimental and numerical (FEM) data. The main physical parameters that affect the passengers' welfare during the flight will be identified through a sensitivity analysis, relative to the "design to comfort" concept.

1. A "design to comfort" tool will be addressed, able to provide the necessary information to improve aircraft characteristics according to customers' necessities and taste.
2. A global index concerning both vibration and acoustics will be issued, so that aircraft will be classified in terms of comfort as well as other performance characteristics like maximum speed, take-off distance, etc.
3. The public opinion demand will be met, so qualifying the European aircraft companies to commercial airlines and their customers.
4. Specifications for active or passive noise suppression systems will be improved, through effective identification of the final target.