ear varies inversely as the square of the distance from the ear to the
source of the sound. That is to say, if exactly the same sound is
repeated at half the distance, the intensity with which it reaches the
ear is four times as great as before, and if the distance is quartered,
the intensity is sixteen times as great. In other words, if "ah" is
spoken with a certain loudness eight inches from the child's ear, and
then again with exactly the same pitch and volume only two inches from
his ear, it will be sixteen times as loud to him as it was the first
time.

These simple tests will serve to determine whether the child has, or has
not, a normal acuteness of hearing. They will not serve to determine
with any accuracy the degree of impairment, if it is found that the
hearing is impaired at all. More thorough tests will have to be
postponed till the child is two years old or more. But the moment that
impaired hearing is suspected, the best available ear specialist should
be consulted in order to determine whether the cause can be removed, or
measures taken to prevent a progressive increase in deafness.

The visit to the otologist should be repeated at intervals of not more
than eight or ten months, even where there is no question of treatment,
in order that any change in the physical condition of the organs may be
promptly detected.




III

HOW SHALL THE MOTHER GET INTO COMMUNICATION WITH HER DEAF CHILD?