Bell’s mother and wife were both hearing-impaired.

 A childhood illness left Bell’s mother mostly deaf and reliant on an ear trumpet to hear anything. Young Alexander would speak close to his mother’s forehead so she could feel the vibrations of his voice. Bell’s father and grandfather were both distinguished speech therapists, and from a young age the future inventor joined in the family business. Bell became a voice teach

er and worked with his father, who developed Visible Speech, a written system of symbols that instructed the deaf to pronounce sounds. In 1873 he became a professor of vocal physiology at Boston University where he met his future wife, Mabel Hubbard, a student 10 years his junior who had completely lost her hearing from a bout of scarlet fever. Living and working with the hearing impaired sparked Bell’s interest in the principles of acoustics and his experiments in transmitting sound waves over wires.