A baby may be born deaf because of cochlea damage before birth as the result of infections during pregnancy. Mumps and meningitis can damage the cochlea. Meniere's disease also causes sensori-neural deafness. The effects of sensori-neural deafness High frequency hearing loss means you can hear people speaking, but can't always make sense of what they are saying. This is because you can't hear high frequency sounds, and most consonants are high frequency.
Consonants make up most of our speech.
Without them we can't make much sense of the words. Background noise is also a problem, especially if it is low frequency such as a car engine. Those with high frequency loss may hear the background noise clearer than the high frequency speech. Unfortunately there is no cure for sensori-neural deafness. Scientists have regrown hair cells in pigs, but not yet in humans.