Question

The grandparents and parents of a two- year old girl are playing with her in a room. A sound source produces a $28\,KHz$ sound. Who in the room is most likely to hear the sound?
A) Grandparent
B) Little girl
C) Both
D) None of them

Answer 1

Hint: The sound is the vibration that is in the form of waves. There are three types of sound. They are audible sound, ultrasonic sound and the infrasonic sound. The human can hear an audible range of sound where the bats can hear ultrasonic sound.

Complete answer:
It is given that the Frequency of the sound source, $F = 28\,KHz$
Approximately, the members in the room are grandparents of the age greater than $60$ and the parents of the age are greater than $25$ and the $2$ year old child. The audible range of the sound that is heard by the human is from $20\,Hz$ to the $20,000\,Hz$ . This range is known as audible limit. The human cannot hear the sound greater than this limit, which is known as ultrasonic sound and lesser than the limit is infrasonic sound. The given sound is $28\,KHz$ , which lies in the audible limit. Though it is in audible range, the persons who are aged cannot hear this sound due to their nature of the less hearing when aged. Since the ear loses its efficiency of hearing at the later part of the life due to many reasons. Hence newborn infants have a high efficiency in hearing when compared to adults. Hence the little girl can hear the sound in the room more than others.

Thus the option (B) is correct.

Note: If the sound range is greater than the audible sound, it is an ultrasonic type of sound and if the sound range is less than the audible range of the sound, it is the infrasonic sounds. The human cannot hear these two types of sounds, but some other organisms can.