Inside the chamber of secrets
Ann Dowling is a world authority on noise and acoustics and the public face of Cambridge University’s engineering department. PE hears her plans for better collaboration
- Published in Cover Story.
An encounter with Concorde ignited Ann Dowling’s interest in acoustics
Cambridge is given its unique character by the strength and reputation of its university. Even on a grey day, with the rain lashing down, tourists mill around the streets in their droves, visibly awestruck by the imposing colleges and well-kept courtyards that are dotted liberally around the city.
You might expect the head of the engineering department at such an august institution to exude an air of scholarly seriousness befitting their seniority. But Professor Dame Ann Dowling is happy to break the mould – she’s far more likely to be wearing a radiant smile. And it doesn’t take long to discover the reason for her seemingly perpetual good mood.
“Who wouldn’t want to work at a place like the University of Cambridge?” she asks. “I’m heading up one of the best engineering departments in the world. That means I get to work with some wonderfully talented people carrying out some amazing research. And our collaborative engagement with industry means we get to work on projects that can make a real difference in a commercial setting. It really is a fantastic job to have.”
Dowling’s elevation to the role of head of the department of engineering at the University of Cambridge is the latest chapter in a glittering career which sees her widely acknowledged as one of the world’s most respected authorities in the fields of combustion, acoustics and vibration. Mathematics was her first love, having studied the subject as an undergraduate at Cambridge in the 1970s. But a summer job at the Royal Aircraft Establishment in Farnborough researching aircraft noise helped her identify what was to become her area of specialisation.
“I was at the Royal Aircraft Establishment for two summers and my experiences there helped crystallise what I wanted to do,” she says. “Concorde was carrying out its proving flights and noise had become the issue that would decide whether or not it would be allowed into the US. A whole new field was opening up in front of me. In some areas you can study very hard and only make a small change – but here there was a whole ‘order one’ effect to be found. It was an exciting time that proved crucial in the development of aviation.”
Dowling returned to Cambridge enthused by her experiences at the Royal Aircraft Establishment, immediately switching from mathematics to the engineering department to carry out a PhD in aircraft noise. Her supervisor was part of the Concorde noise task force, and with his guidance she began researching aircraft noise at higher speeds, carrying out fundamental research into the modelling of jet noise and how higher-speed motion affected noise sources. The work showed that it was a more complex relationship than originally thought and that unexpected effects were coming into play. “Previously people had talked about it purely in terms of a Doppler shift,” she says. “But there was more than that going on, there was actually a change in the character of the noise source as well. I wouldn’t say my PhD work solved the problem of aircraft noise at higher speed, but it did go to show that a whole new effect came into being when aircraft moved faster.”
Concorde eventually gained the required acceptances for entry into the US and Dowling’s role in the successful outcome hadn’t gone unnoticed. She was subsequently asked by the Ministry of Defence to expand her research into the area of submarine noise. At that time the next generation of Royal Navy submarines were expected to move through the water listening to very distant passive sounds, while actually existing in an extremely noisy underwater environment characterised by turbulent flow. That environment resulted in pressure fluctuations which were much louder than the distant sounds being listened for. So Dowling was asked to work on ways to model that phenomenon and then to develop compliant flexible coatings that would reduce certain aspects of noise. The modelling work she carried out was passed on to the Royal Navy and eventually shared with the US military through a technology exchange.
“However, I had to wait a long time to see the fruition of my work, as it had been applied strictly on a need-to-know basis,” she recalls. “It was actually some 15 to 20 years later, when I was serving on a promotion board for the Defence Evaluation and Research Agency, that I saw more details of the benefits that my research in this area was bringing. Compliant coatings had found their way onto submarines without me knowing the details of their use. It was rather nice to discover that, albeit after such a long time.”