Hearing Maps are Real Conversation Starters 

An audibility map showing the intelligibility that would be experienced by a listener in every part of a room with a lot of echoes. Intelligibility is best (red) near where the person is talking and weakest at the blue area which is close to a noise source. The software can make similar predictions for any number and distribution of noise sources.

Innovative sound-mapping software based on human hearing has been developed to help architects design out unwanted noise by generating audibility maps of proposed room designs. These maps show hotspots where conversations would not be intelligible if the room were busy. Architects can then adjust their designs to reduce reverberation until the hotspots are eliminated and audibility is maximized.

Software already exists to help architects predict how a building will perform acoustically for an audience in places like theatres and concert halls. This new software is specifically designed to improve the acoustic design of indoor spaces where a large number of people meet, chat and interact. It could be used for business as well as social purposes, for example, in designing open-plan offices, cafes and reception areas.

 

The Engineering and Physical Sciences Research Council (EPSRC) project has been developed at Cardiff University.

 

“A lot of work has been done to understand acoustics in places used for public performances,” says Professor John Culling, project leader. “But little has been done to improve the acoustics of day-to-day meeting-places, even though this would help all of us in our working and social lives.”

The new software also produces results much more rapidly than other acoustic software. The key to its capabilities is the unprecedented sophistication and computational efficiency of the unique mathematical equation that underpins it.

The equation has been built up using the project team’s cutting-edge research looking at how people take in sound through both ears as it travels round busy rooms and how noise sources are affected by each other. This means it can accurately predict acoustic quality at every point in an indoor space where people are likely to gather and talk.

The mathematical equation treats the binaural system (i.e. the use of two ears to perceive sound) as a bank of directional microphones, each of which operates at a different frequency and has a single-directional null (i.e. an area where the signal is cancelled out completely).

The architect will be able to call their proposed design onto their computer screen and run the software, which will ask them to specify the locations of the main sound sources in the room. An audibility map will then automatically be produced and the architect will be able to change the room’s dimensions, its shape and/or the materials to be used, until hotspots are eliminated. This means that rooms could be tailor-made to suit their purpose. The work also will make a significant difference to areas where audibility is important, such as rail and airport announcement waiting areas. In emergency situations, such clarity could be vital in saving lives.

Cafeterias, lobbies and other interior spaces that are badly designed from an acoustic viewpoint tend to have one thing in common: too much reverberation, resulting from design aspects such as low ceilings or the use of materials that are good sound reflectors. By modeling such rooms at the design stage, it will be possible to determine exactly how this reverberation could be reduced. Options could include adding sound-absorbent tiles or panels. Reverberation occurs when sound waves are reflected in a confined space, causing the sound to persist even after it has ceased to be created. High ceilings are generally better than low ceilings, in terms of reducing reverberation, as the space they provide acts like a sound absorber.

The new software is intended to be used in conjunction with standard architectural computer programs widely employed in room design.

The research also will help in the future development of hearing aids and cochlear implants.

“Our objective now is to identify and work with a software company to help us develop the software further and market it,” says Professor Culling. “Hopefully, it will be available for architects to use within the next 12 months.”

The three-and-a-half year project ‘Effects of Reverberation on Conversation in Rooms’ is receiving EPSRC funding and is due to run until July 2010.