Hearing 'helped by touch'

Research has shown that “sensations on the skin play a part in how people hear speech,” BBC News reported. It said that the findings could lead to better hearing aids.

This study in 66 people without hearing impairment investigated whether tactile sensation (touch) can aid hearing. The research was based on the principle that when some sounds are spoken, they are accompanied with a short burst of air (“pa” for example, compared to “ba”). In experiments, people had puffs of air directed at their hands or neck while they listened to sounds. Speech that was accompanied by the puffs of air was more accurately interpreted.

The study suggests that, like visual clues, tactile sensations may aid hearing. However, further research would need to establish if a device based on this principal would improve communication for those with impaired hearing.

Where did the story come from?

This research was carried out by Bryan Gick from the University of British Columbia in Vancouver and Donald Derrick from New Haven, Connecticut, USA. It was funded by a Discovery Grant from the Natural Sciences and Engineering Council of Canada and by a National Institutes of Health grant.

The study was published in the peer-reviewed science journal Nature .

What kind of research was this?

This study investigated whether tactile sensations can affect how sounds are heard. The researchers say that visual cues, such as lip reading, can help people with a hearing impairment to understand speech. In this study, they performed several tests on human volunteers without hearing loss to see if the same was true of the tactile sensation of a puff of air.

The researchers were careful to set up the tests so that the location of the air puff (to the hand or neck, or no puff but sound only) were tested separately. The sound that was produced was also standardised (“pa”, “ba”, “ta” and “da”) and the participants were blindfolded to ensure the results were as reliable as possible.

What did the research involve?

The research was carried out in three experimental groups with a total of 66 male and female participants. There were 22 people in each of three experimental groups (hand trial, neck trial and an auditory-only trial). How the participants were recruited, their age and the male and female composition of the groups were not reported.

Before the experiment began, the participants were told that they would experience some background noise and unexpected puffs of air. They sat in a soundproof booth and were told they would hear a series of pairs of sounds (either “pa” and “ba”, or “ta” and “da”). Their task was to identify which of the sounds they heard by pressing a button. They were then blindfolded and listened to the sounds through sound-isolating headphones. The equipment to deliver the tactile stimuli of puffs of air was set up after the participants were blindfolded to conceal the body location of air puffs.

In each of the three groups, half received the “pa”/“ba” pairs of sounds (sounds made with the lips) first and then the “ta”/“da” sounds (sounds made with the tongue on the back of the teeth). The other half heard the sounds the other way around. Within the hand trial and the neck trial groups, the participants listened to 12 sounds (six with air puffs and six without). The auditory trial group listened to 12 sounds without puffs.

In the following test sequence, the participants heard a random assortment of sounds ("pa", "ba", "da" or "ta") either with or without the burst of air. These combinations of interventions left the researchers with 64 sets of results across the “pa”/“ba” and “ta”/“da” groups.

What were the basic results?

The researchers say that in the hand-puff experiment, participants got more of the “pa” sounds correct when they had an associated puff of air on the hand than without the puffs. The same was true for the “ta” sound.  Both these sounds are usually associated with a puff of air from the speaker.

The reverse was true for the “ba” and “da” sounds. Fewer participants got the sound correct if these sounds were delivered with a puff of air. These sounds are not normally made when the speaker exhales air.

A similar pattern was seen when air was delivered to the neck. No pattern was seen at all in the auditory-only experiment, which the researchers took to mean that the participants could not hear the airflow or compressor activation.

How did the researchers interpret the results?

The researchers say that their findings support the theory that human appreciation of voice and language combines information from touch with sound in much the same way as vision and sound, as has been previously been shown.

Conclusion

The results of this experimental study suggest that the sensation of air being blown on the hands or neck can help people interpret a selection of sounds.

Although theses participants did not have a hearing impairment, the study raises the possibility that the sensation of touch may help those who have hearing loss distinguish these pairs of sounds. A hearing aid that uses touch has not yet been developed, so as yet it is unknown how useful this new finding will be in improving communication for people with hearing impairments.