Digby,

A couple of things.

Hearing loss can also occur because of illness.   Viruses or bacteria involving high fever are a significant cause of sudden hearing loss at any age.   The younger this happens, the more serious this can be, especially if speech hasn't fully developed.   In those cases, speech therapy is needed.   And, for the record, an otolaryngologist told me the best thing for parents to do for children with hearing loss was to read aloud to them regularly and a lot, sitting with the text visible to the child. 

Sudden ear pressure change can burst the ear drums.

Research shows that children with early hearing loss are more likely to struggle in school (regardless of the use of hearing aids) and if the diagnosis is delayed or missed, they are more likely to be incarcerated as adults.   In addition to the social problems caused by miscommunication, people assume they are insubordinate and respond with punishment.   This can escalate and become a serious problem.