London, Apr 26 : iPods and mobile phones may soon become theftproof, thanks to the unique sounds made by our ears.

Southampton University researchers have discovered that they can identify individuals from the faint sounds made deep inside the human ear. And, therefore, by using this technology they''re developing security devices.

Personal music players could be fitted with antitheft devices that detect "acoustic fingerprints" so they only work when they are being used by the registered owner.

"The sounds produced are not audible to the human ear and people are unaware they are being produced in their own ears," The Telegraph quoted Dr Stephen Beeby, a reader in engineering at Southampton University who is leading the research, as saying.

"With a sensitive enough microphone, these sounds can be captured with a standard computer sound card and the signal can be analysed. We found that they were different from person to person, which gives us a really nice biometric tool," he added.

As for how the technology works: it uses extremely faint sounds that are produced inside the human ear called otoacoustic emissions. The emissions are produced by hair cells in the cochlea, which are responsible for detecting sound waves and turning sound into the electrical message that is received by the brain.

It is believed that hair cells vibrate to help amplify the signal they receive through the ear. While doing so, they produce their own sound. However, the human ear can''t detect the noise, but sensitive microphones can do so.

The researchers found that when they compared the sounds produced by hair cells in different individuals they were able to distinguish them.

It is thought that each person''s hair cells produce a slightly different noise, but as the sound travels through the bones in the ear, the ear drum and along the ear canal, which are subtly different in each person, the noise is changed further to make it unique.

Dr Beeby said: "Otoacoustic emissions have been used by the medical profession for many years and anecdotally clinicians could tell different people''s traces apart.

"When we looked at it we found that otoacoustic emissions really are unique from person to person. As the sound produced will change with the signal put in, we can use standardised signals that produce traces that can be compared.

"It could be surreptitious as you don''t necessarily know when your emissions are being captured. When you phone your bank, they could send out a series of clicks through your headset or phone and analyse the response to confirm whether you are who you say you are." (ANI)