New 3D Modelling Technology for Hearing-Aids Offers High Accuracy

This 3D scan of the ear canal, taken with new imaging technology developed at MIT, could be used to manufacture better fitting hearing aids. Image courtesy of Federico Frigerio.

Researchers at MIT are working to improve the fit of hearing aids through the development of new 3D modelling software. The ability of hearing aids to amplify sound depends on the fit between the device and the ear canal. Plaster moulding, which is the method now commonly used to model hearing aids to patients’s ears, offers limited accuracy, leading to a poor fit and efficacy of the hearing aids.

Douglas Hart, MIT professor of mechanical engineering, has developed a novel, patented method of scanning the ear canal that is said to be faster, simpler and more accurate than the plaster moulding technqiue. Hart plans on marketing the technology to hearing-aid makers first but the technology also could be potentially used for earphone and earplug applications as well.

Obtaining a precise 3D scan of the ear canal is the “Holy Grail of the hearing-aid industry,” says Scott Witt, head of research and development for hearing-aid manufacturer Phonak. “Taking these impressions is still the messiest, least-exact part of the process,” he adds.

With the new system, a stretchy, balloon-like membrane is inserted into the ear canal and inflated to take the shape of the canal. The membrane is filled with a fluorescent dye that can be imaged with a tiny fibre-optic camera inside the balloon. Scanning the canal takes a few seconds, and the entire fitting process takes only a minute or two.

Witt believes the scanner has more potential than other proposed imaging systems he has seen in recent years. “What really interested me is, they say they can determine the physical properties of the ear canal, such as how soft the tissue is,” he says.

Because the camera captures 3D images so quickly, it can measure how much the surface of the ear canal deforms when the pressure changes, or how the canal shape changes when the wearer chews or talks. That could help hearing-aid manufacturers design devices that keep their tight seal in those situations.

The new technology could be seamlessly integrated into existing manufacturing practices, says Witt. “We could do it right now. The rest of our manufacturing process is set up to receive digital scans,” he says.

More information on the research is available from the Technology Review.

Tags: 3-D modelling technology, Dentistry, Douglas Hart, ear canal, hearing aids, MIT