baby with
respect to its hearing. Our interest here is, of course, in the tests of
hearing that do not require special apparatus and special training. In
the case of a child less than two years of age we must rely upon merely
attracting his attention by various sounds, judging the effect upon him
by his expression and actions. We cannot, at that age, establish a
system of responses, nor expect him to imitate the sounds he hears.
Sounds should be used for testing that disturb only the air, and are
not sufficiently low and powerful to set in vibration the floor, chair,
or any other object with which he may be in contact. Deaf children
rapidly become abnormally sensitive to vibrations, which are to them
what noises are to us. A rather smooth, not too shrill, whistle is one
excellent sound to use. Not a fluttering whistle like the postman's, nor
a heavy tone like an organ pipe or bass horn. Clapping the hands is a
good initial test of a crude nature; then a moderate whistle, varying
the pitch, for sometimes high sounds are perceived, but not low ones, or
vice versa. Then a bell, such as a small table bell, the telephone,
electric door bell, etc. Lastly, the human voice in various pitches,
volumes, distances, and vowels. Little by little it can be determined
whether the child hears all the sounds, and if not, then which, if any,
he perceives. A totally deaf child may often deceive the investigator by
turning his head at the critical moment, apparently in response to the
sound that was made, while, on the other hand, a child very slightly
deaf, or not deaf at all, may completely ignore the sounds made for the
purpose of attracting his attention. Therefore, it takes time and
repeated tests under varying environments to gradually eliminate
possible errors and coincidences.

It must be remembered that the intensity with which a sound affects the
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 ser