Sir Joseph: Can you sing?
Ralph: I can hum a little . . .
Not only Ralph Rackstraw hums a little. Babies hum at the breast, and mothers hum while rocking them. Children hum at play; workmen hum at work. No company is without its office hummer who strides the halls humming his favorite pop or Paganini. Pablo Casals hums while playing the cello. Why do humans hum? In the current Journal of Auditory Research, a psychiatrist offers a couple of answers.
Dr. Peter Ostwald, 33, of the University of California School of...