Final answer:
Most deaf children are born to hearing parents, generally due to recessive genetic factors. Calculating the probability of exact cases of deafness in newborns requires additional data. A 60 dB hearing loss at 5000 Hz means much greater intensity is needed for audibility compared to a lower frequency with normal hearing thresholds.
Step-by-step explanation:
Regarding the percentage of children with hearing loss who are born to hearing parents, it is reported that a significant majority of such cases occur in families with no prior history of hearing impairment. Most studies suggest that around 90% to 95% of deaf children are born to hearing parents. This situation often results from genetic factors where the genes responsible for hearing loss are recessive, meaning that a child can inherit the gene from parents who do not exhibit any signs of hearing loss themselves.
In relation to the probability problem provided, we're considering a scenario where, on average, 2 in 1,000 babies in a healthy baby nursery are born deaf. If 1,000 babies were surveyed, the probability of exactly two babies being born deaf can be calculated using the binomial probability formula. However, without the exact figures from the article or additional data, we cannot calculate the probability here.
For the child with a hearing loss of 60 dB near 5000 Hz, we can apply the principles of sound intensity levels and frequency. A decibel (dB) is a logarithmic unit used to measure sound intensity. The formula for decibels is 10 times the logarithm of the ratio of the intensity of a particular sound wave to a reference sound intensity. This means that a 60 dB loss indicates the 5000 Hz tone needs to be significantly more intense than normal for it to be audible to the child compared to a 400 Hz tone with normal hearing levels.