British scientists are investigating the viability of a new biometric technique that would make use of the human ear as a way for a third party to identify the person they are speaking to.

According to a report in the New Scientist, instead of asking for passwords or pin numbers, a call centre or bank would simply use a device on their telephone to produce a brief series of clicks in the recipients ear to make sure the person is who they say they are.

The New Scientist says the idea is based on something called otoacoustic emissions (OAEs), the ear-generated sounds that emanate from within the spiral-shaped cochlea in the inner ear. They are thought to be produced by the motion of hair cells within the outer part of the cochlea. Typically, sounds entering the ear cause these outer hair cells to vibrate, and these vibrations are converted to electrical signals which are transmitted along the auditory nerve, allowing the sound to be sensed. Crucially, these cells also create their own sounds as they expand and contract.

The theory is that supersensitive microphones are able to detect these sounds, as OAEs can be provoked when a series of clicks is played into the ear. The returning sound emissions comprise signals of between 0 and 5 kilohertz, and vary in amplitude. Indeed, click tests are already used today in newborn infants, to check for signs of hearing difficulties, since the OAEs are weaker if the inner ear is defective.

A team at the University of Southampton, UK, has already received funding from the UK's Engineering and Physical Sciences Research Council, to work out if OAE patterns can be used as a viable biometric technology like fingerprints and IRIS recognition.

The research is being led by engineer Stephen Beeby, and the New Scientist quotes Beeby as saying that because "hearing is an active process - the ear actually puts energy into the incoming sound waves to replace energy lost as sound is absorbed by the ear's structure."

"This process helps us hear things we otherwise would not, but as a result some of the energy added by the hair cells escapes as OAEs," he is reported as saying.

Beeby and his colleagues think that the power and frequency distribution in the OAEs provoked by specific series of clicks seem to be highly distinctive, driven by the internal shape of the person's ear. "Anecdotally, audiologists say they can tell different people apart - men, women, even people of different ethnic origins - by the profile of the widely varying types of emissions the clicks evoke," he said.

"In the controlled conditions of a lab, everybody's emissions are indeed different, but whether this is a practical way of telling people apart as a real-world biometric still needs a lot of work," he admits.

Indeed, there seems to be a lot of "what if" questions associated with this approach. Beeby has found for example that with some subjects, who have been drinking alcohol, their emissions are deadened. And different drugs alter the amplitude of OAEs, as do ear infections or wax build-up.

The project has a mid 2010 deadline. The hope is that electronics firms would be interested in making headsets or mobile phones with a supersensitive microphone in the earpiece. Beeby said that the rest would be done with software.

On the surface, the commercial application of this technology remains doubtful. For example, what would happen if someone lent their mobile phone to a friend, but it is only programmed for the owner? Would it think the friend was a thief and disable the handset?

Also, if sending clicks down a telephone line, how do you ensure that background noise is not an issue? And does OAE amplitudes change in size as we age?

And finally of course, what would happen if the user had just come out from a particularly loud AC/DC concert?

There are also some concerns that biometrics are a poor substitute for conventional security measures. After all, unlike biometrics, at least a password or pin number can be changed if it is hacked or compromised.