How Edison Brought Tears to the Eyes of Maria Montessori
(p. 221) Edison's partial loss of hearing prevented him from listening to music in the same way as those with unimpaired hearing. A little item that appeared in a Schenectady, New York, newspaper in 1913 related the story that Edison supposedly told a friend about how he usually listened to recordings by placing one ear directly against the phonograph's cabinet. But if he detected a sound too faint to hear in this fashion, Edison said, "I bite my teeth in the wood good and hard and then I get it good and strong." The story would be confirmed decades later in (p. 222) Madeleine's recollections of growing up. One day she came into the sitting room in which someone was playing the piano and a guest, Maria Montessori, was in tears, watching Edison listen the only way that he could, teeth biting the piano. "She thought it was pathetic," Madeleine said, "I guess it was."
Stross, Randall E. The Wizard of Menlo Park: How Thomas Alva Edison Invented the Modern World. New York: Crown Publishers, 2007.