The vibrations in this speech method are generated pneumatically by an external battery operated vibrator (called electrolarynx or artificial - larynx) which is usually placed on the cheek or under the chin.  

It makes a buzzing vibration that reaches the throat and mouth of the user. The person then modifies the sound using his/her mouth to articulate the speech sounds.

See also

Voice and speech rehabilitation following laryngectomy

The first aim of this study is the compilation of the various methods of voice and speech rehabilitation following laryngectomy. Therefore, this book gives a detailed survey of these voice rehabilitation methods, with emphasis on the tracheo-esophageal shunt method with a valve prosthesis in respectively Chapter II, Chapter III and Chapter IV. The development of these valve prostheses, which are inserted into a surgically created tracheo-esophageal shunt, has presented a giant step forwards in the voice and speech rehabilitation of laryngectomees.