Humans Found Able to Hear at High Levels

Researchers reported Friday that both hearing and deaf people were able to understand words transmitted at high frequency levels once thought to be outside the range of humans.

Deaf people and older, hearing-impaired individuals were among those able to understand words that had been translated into the ultrasonic range and transmitted through a vibrator placed against their skulls, the researchers reported in Science magazine.

Dr. Martin L. Lenhardt of the Medical College of Virginia said the study suggests that high-frequency sounds, conducted by bones in the head, “may provide an alternative therapeutic approach for the rehabilitation of severe hearing loss.”

Lenhardt reported that, when a vibrating device was placed against the skulls of study participants, “the signal was clearly perceived as speech. The temporal quality was well preserved such that syllables could be clearly and accurately counted.”

Study participants listened to words transmitted at ultrasonic ranges through the device and were instructed to pick between six pictures to report which one illustrated the word.

Young adults with normal hearing were able to pick the right word with a mean score of 83%, well above the chance level of 16%. Scores were similar for older people who had suffered hearing loss typical of age-related deafness. Three deaf individuals scored about 40% in similar testing.

The study said the results “confirm the ability of human subjects to detect sounds in the ultrasonic range despite a significant hearing loss normally associated with aging.”

And it said they suggest even profoundly deaf people may be capable of understanding words “when these speech signals are modulated into the ultrasonic frequencies.”

Lenhardt said that it was possible some other organ within the ear, such as the saccule, may respond to ultrasonic vibrations rather than the cochlea, which detects sounds in the normal range.