Having someone’s breath on your neck may help deaf people to hear what you are saying. In tests researchers found that: “In speech, the ‘aspirated’ syllables ‘pa’ and ‘ta’ are accompanied by a puff of exhaled air, whereas ‘ba’ and ‘da’ are not. Such puffs aren't always detected when someone is speaking, but Gick's team reasoned that the brain might learn to use puffs to modify its perception of certain sounds. They had 66 volunteers listen to a male voice saying all four syllables against background noise that made it hard to distinguish them. At the same time as some of the syllables, they delivered a puff of air to the hand or neck. Although many volunteers could not consciously feel the puffs, they were still more successful at correctly identifying ‘pa’ and ‘ta’ when these sounds were accompanied by air puffs.” This development could lead to the creation of hearing aids which produce puffs of air.