Question

Which of the following frequencies of sound can be heard by a dog but not by a man?
A) $50,000{\text{ hertz}}$
B) $15,000{\text{ hertz}}$
C) $42000{\text{ hertz}}$
D) None

Answer 1

Hint: An acoustic wave that propagates through vibrations through a medium such as solid, liquid, or gas is called sound in physics. According to human physiology, the reception or perception of these kinds of waves by the brain is called sound. Acoustic waves lying only in a particular frequency can be perceived by human ears.

Complete step by step solution:
There is a particular frequency range that human ears can receive. The range of frequency lying between ${\text{ 20 hertz}}$ and ${\text{ 20000 hertz}}$is perceivable to humans. Sounds that have frequencies greater than ${\text{ 20000 hertz}}$ are called ultrasonic sounds. Some animals can hear ultrasonic sounds.

Dogs can hear sounds greater than ${\text{ 20000 hertz}}$ but humans cannot hear such sounds. The frequency range that dogs can hear varies from${\text{ 67 to 45000 hertz}}$. The frequency that lies between ${\text{ 20000 hertz}}$ and ${\text{ 45000 hertz}}$can be heard by dogs but not by humans.

The answer is Option (C): $42000{\text{ hertz}}.$

Note: The sounds that have a frequency of less than ${\text{ 20 hertz }}$is called infrasound. This range of sounds is also inaudible to humans. The capacity of perception varies in different animal species. Many animals use sounds for different purposes like communication, predation, detection of danger, navigation, etc. Some animals have special organs to produce sounds. Animals like whales, animals, etc. can detect infrasound and use it for communication.

Unwanted sound is called noise. Ultrasound is used for many medical and research purposes. Infrared sound can be used to detect volcanic eruptions. The speed of the sound depends on the medium through which it passes. The speed of sound will move through solids. The physical properties of sound are not constant through a medium.