A Japanese researcher has suggested that an ultrasound transmitter could help profoundly deaf people hear.

Dr. Hiroshi Hosoi of the Kinki University School of Medicine in Osaka used a brain-imaging technique called magneto-encephal-ography to see if the auditory cortex, the part of the brain that processes hearing, responds to ultrasound.He tested 53 profoundly deaf people and found that 28 could detect ultrasonic stimuli and 11 could differentiate the ultrasound modulated by different speech signals.

"We found that bone-conducted ultrasonic stimuli activate the auditory cortex of man. Furthermore, ultrasound modulated by different speech sounds can be discriminated in the auditory cortex," he said in a letter to The Lancet medical journal.

"These results provide the rationale to develop ultrasonic hearing aids, which do not require surgery, for the profoundly deaf who can sense ultrasound," he added.

Ultrasound uses sound frequency well above the limit of the human ear. It is an inexpensive and versatile tool in medical diagnosis.

Ultrasound images, or scans, are used to determine the extent of a pregnancy or any abnormalities in the fetus, as well as tumors in the liver, kidney, ovaries, pancreas and bladder.

Hosoi said ultrasound hearing aids could be a replacement for the electric implants which have helped profoundly deaf children hear sounds and speak.

The electronic, or bionic ear, is surgically implanted. Electrodes in the inner ear bypass the damaged area and create a nerve impulse which stimulates the auditory cortex of the brain.