Aircraft

Two universities involved in the partnership for air transport noise and emission reduction (Partner) programme are making headway in better understanding the connection between certain types of aircraft noise and community discontent.

Under Partner's source emission and propagation initiative, better known as "Project 2", Pennsylvania State University and Purdue University researchers are delving into the finer aspects of modelling three specific types of community disturbances - thrust-reverser noise, acoustic propagation around airports and realistic sonic boom portrayal.

The work, funded by the US Federal Aviation Administration, Transport Canada and NASA, is part of the broader palette of Partner programmes that are designed to generate technological advances in areas including national security and the environment.

Project 2 in part picked up where Project 1, a study of the effects of low-frequency (below 50Hz) airport noise on communities, left off. Project 1 findings included that take-off thrust and reverse thrust "can be annoying" in terms of window rattling to people living within 915m (3,000ft) of a runway.

One prong of Project 2 will be to test actual noise results from reverse thrust events measured in Project 1 to verify whether today's integrated noise models (INM) accurately represent the noise. The FAA uses the INM to assess aircraft noise on surrounding communities.

To further refine the INM, Project 2 will also study acoustic propagation of aircraft noise from the airport into the community to create better noise algorithms. Included will be topography dependent elements of propagation like grass, concrete and water.

A third arm of the project is not specifically linked to airports, but to communities that could lie below a new class of "quiet" supersonic aircraft now on the drawing boards. Researchers will attempt to generate realistic computer-generated sonic boom signatures based on ground noise measurements taken from a series of NASA supersonic test flights.

Included will be the effects of terrain on boom propagation and an understanding of the "post-boom", an after-effect that is not well understood but one that researchers say is a key distinguisher between how people perceive real versus computer-generated booms today.

• For more on the Partner activities on noise visit www.noisequest.psu.edu