Speech prostheses

Speech prostheses, or voice prostheses, is a overall term for small, silicon valves that are inserted into the tracheoesophageal puncture of laryngectomy patients. The prosthesis not only safely divides the oesophagus and the trachea, but also allow speech when the outside of the stoma, the opening on the neck to allow air in, is covered with a finger or otherwise occluded.

https://www.inhealth.com/category_s/44.htm

http://www.cancerresearchuk.org/about-cancer/type/larynx-cancer/living/stoma/starting-out-with-a-breathing-stoma

http://www.webwhispers.org/library/tepprosthesis.asp

https://en.wikipedia.org/wiki/Voice_prosthesis

http://medind.nic.in/jat/t07/i4/jatt07i4p188.htm