8 November 1999
Automotive music
by Kate Melville 
Cars are full of technology and science, but car stories are not something we would normally inflict on Science A Go Go readers. But research from Ohio State University that uses computer analysis to 'listens' to the sounds coming from a racing car is an exception. This new technique can be used to reveal engine performance, driving technique, and team's strategy, but could also be used to measure the performance of any complicated piece of machinery (like power plant turbines). According to Yann Guezennec, an associate professor of mechanical engineering at Ohio State's, "Racing has become an extremely technical field and racing teams use a wealth of sophisticated equipment to analyse the performance of their own cars and their competitors". Unfortunately deciphering useful information from engine noise isn't easy as an engine roars at several different pitches simultaneously. "The key is to simplify all the noise down to one thing, such as engine RPM, so we can present information that is not directly available," said Guezennec. The research team developed equations to analyse the change in frequency of car sounds over time. From trackside, they record the sound of a car and then use a computer to calculate its instantaneous speed and trajectory. "From those two pieces of information we can figure out most everything we want to know -- the strategy of the team, the engine capability, how the driver shifts gears," said Guezennec. As an example the Ohio State team was able to decode a cars gear ratio - racing teams change gears frequently during practice and try to keep the final gear ratios secret. The engineers recorded sounds of McLaren/Mercedes and Ferrari racing cars during the 1998 at the 1998 San Marino Grand Prix. The sound analysis as the two vehicles ran along a straight-away and two curves showed that McLaren's transit time was as much as 0.5 seconds quicker than that of Ferrari.
The military have used similar technology for some time particularly to identify submarines by signature sounds made by their propulsion systems. According to Guezennec, "We have advanced that technology to obtain more information efficiently and inexpensively." So far the research has centred on sounds recorded outside of vehicles but researchers think that the same technique will work for sounds recorded inside a vehicle (for example from in-car audio/video footage recorded by racing teams). Given that the cost of campaigning a Formula 1 team may be as much as US$60 million per season we may soon see acoustic recording devices at ever circuit (or perhaps they will try to mask the sounds of their cars - both inside and out).
| 
