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Trevor Cox is Professor of Acoustic Engineering at the University of Salford in the North of England.
He's an adviser to the Save Our Sounds project taking place on BBC World Service.
His main job is designing spaces so that they sound good. This can include public spaces such as town squares, or inside rooms such as school theatres.
He says that every country has its own distinctive sounds. For example, taxis in London sound different from taxis in other cities because of the type of diesel engine they have.
Transport sounds often connect people instantly to a certain city - from rickshaws in India to the subway in New York City.
As part of Save Our Sounds, Trevor has been recording some sounds on the streets of Hong Kong. He asked Outlook's Lucy Ash to guess what they were.
Can you work out what the sounds are before the answers are revealed?
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