Wikipedia
Tadoma is a method of communication used by deafblind individuals, in which the deafblind person places their thumb on the speaker's lips and their fingers along the jawline. The middle three fingers often fall along the speaker's cheeks with the little finger picking up the vibrations of the speaker's throat. It is sometimes referred to as 'tactile lipreading', as the deafblind person feels the movement of the lips, as well as vibrations of the vocal cords, puffing of the cheeks and the warm air produced by nasal sounds such as 'N' and 'M'. There are variations in the hand positioning, and it is a method sometimes used by people to support their remaining hearing.
In some cases, especially if the speaker knows sign language, the deaf-blind person may use the Tadoma method with one hand, feeling the speaker's face; and at the same time, the deaf-blind person may use their other hand to feel the speaker sign the same words. In this way, the two methods reinforce each other, giving the deaf-blind person a better chance of understanding what the speaker is trying to communicate. In addition, the Tadoma method can provide the deaf-blind person with a closer connection with speech than they might otherwise have had. This can, in turn, help them to retain speech skills that they developed before going deaf, and in special cases, to learn how to speak brand new words.
The Tadoma method was invented by American teacher Sophie Alcorn and developed at the Perkins School for the Blind in Massachusetts. It is named after the first two children to whom it was taught: Winthrop "Tad" Chapman and Oma Simpson. It was hoped that the students would learn to speak by trying to reproduce what they felt on the speaker's face and throat while touching their own face.
It is a difficult method to learn and use, and is rarely used nowadays. However, a small number of deafblind people successfully use Tadoma in everyday communication. Helen Keller also used a form of Tadoma.