Hmmmm, good question, I had to look that one up, here's what I found ... "Bell's father, grandfather, and brother had all been associated with work on elocution ..." And of course I had to look up elocution too ... here's what I found ... "Elocution is the study of formal speaking in pronunciation, grammar, style, and tone." Makes perfect sense!
Alexander Graham Bell's area of specialization in sciences was in speech and sound. He developed an interest in sound ever since he was young. He went to the University of Edinburgh to study this and later moved to University of Canada.