Inspired by how bats navigate, a team of university inventors has built a device that enables blind people to 'hear' objects in their path and manoeuvre without the help of guide dogs or walking sticks. The Electronic Bat Ears look like a pair of hi-tech sunglasses with built-in earphones. Using echo-location technology, they emit ultrasonic waves that can be interpreted by wearers to let them know what obstacles lie in their path. The Hong Kong Polytechnic University inventors won a silver award at the International Exhibition of Inventions, New Techniques and Products in Geneva, Switzerland, last month. 'Blind people may not be able to see, but their hearing is very good. They can understand where the sound source is,' said He Jufang, associate professor of rehabilitation sciences at the university and one of the researchers. 'The problem is that the objects in front of them do not make sounds, so if we can somehow make those objects make sounds, then blind people will know there is something in front of them.' The device uses the same echo and ultrasound method used by bats to locate insects in the air. He said all objects could be 'heard' if a person emits ultrasound, but the sound echoes back at a frequency too high to be heard by humans. With this new invention, the sound frequency has been lowered so humans can hear it. One of the first users of the electronic bat ears is visually-impaired writer Christina Wong, 26, who frequently needs her mother's assistance to find her way around. She said she could move about on her own when wearing the device. The university has made 40 sets of the bat ears, funded by a $1.6 million donation from the government. Gold award-winning inventions included solar-powered, energy-saving lighting by Megain which can last for 50,000 hours. Another inventor showed off his 'Fridge To Go' - a portable refrigerator ideal for golfers that requires no electricity or ice to keep drinks cold. Polytechnic University was also awarded a top prize in Geneva for a new drug to treat liver cancer, and a gold award for iScream - an intelligent system for construction and real-estate management. iScream enables contractors to install CCTV cameras to monitor quality control on building sites and sets up a communication link between contractors, developers and builders. It also includes a database which investors, real estate agents and evaluators can check to monitor the value of buildings. Another university winner in Geneva was the Basic Competency Assessments - an online testing of students in Chinese, English and mathematics that is being used by 600,000 pupils across Hong Kong. The Logimizer, also developed at the university, is a logistics planing software system for the air freight forwarding industry which can calculate the optimum use of space in cargo containers. It won a silver award.