• ### Browse All Lessons

##### Assign Lesson

Help Teaching subscribers can assign lessons to their students to review online!

 Tweet

# Properties of Sound

This lesson aligns with NGSS PS4.A

Introduction
Imagine your friend comes to your door and presses the doorbell. You will hear the sound of the doorbell from inside. Similarly, when we usually go to the swimming pool at weekends or especially in summer. We experience different kinds of sounds as we float on the surface of the water. Some are low e.g. talking of adults, some are high like the laughter and yelling of small children having fun. Furthermore, some sounds are soft, like the splashing of water on the edges of the pool, and some are loud like the boing of the diving board. The difference between the sounds can be characterized by the properties of sound waves. In this article, we will learn about the speed of sound, medium dependence, and the impact of temperature on the speed of sound.

Properties of Sound
A sound is a form of energy produced by vibrations that propagate through the air or other mediums and can be perceived when it reaches our ears. Sound helps us to communicate with each other. The characteristics of sound are speed, pitch, loudness, or amplitude.

Speed of Sound
The speed of sound is the rate at which sound waves propagate through a medium. For instance, in air, sound travels at approximately 343 meters per second at room temperature, while the speed of sound in water is about 1,480 meters per second. The speed of sound in water is more than four times faster than in air. This speed can vary depending on the factors like temperature and humidity.

Speed of Sound Formula
The speed of sound can be calculated using the formula

$v = lambda f$

where v represents the velocity, λ is the wavelength of the sound wave, and f denotes the frequency.

The correlation between the speed of sound, its frequency, and wavelength remains consistent across all types of waves. The wavelength of a sound wave corresponds to the distance between consecutive compressions or rarefactions. Similarly, the frequency represents the number of wave cycles passing through a specific point within a given time period and aligns with the source's frequency."

Medium Dependence
If your two friends shout simultaneously from opposite edges of the pool, is it possible to hear one friend’s voice before the other? The answer is no, the sound of their voices will reach you at the same time. The arrival time of the sound does not depend on who or how loudly the friend shouted. The speed of sound is solely depending on the medium through which the sound wave is traveling. In this scenario, the sound travels through the air to your ears, therefore, travels at the same speed.

Speed Changes When Medium Changes
The speed of sound remains constant through a medium as long as there are no changes in its properties. However, if the properties of a medium do undergo modifications, the speed of sound traveling through that medium will be altered accordingly.

Now we will observe how the speed of sound in the air is affected by changing one property which is temperature.

Impact of Temperature
In 1947, Chuck Yeager, an American pilot, achieved the historic feat of surpassing the speed of sound. However, his actual speed was only 293 m/s, which is lower than the speed of sound in air, recorded as 343 m/s. The explanation lies in the temperature of the air.

In general, lower temperatures correspond to slower speeds of sound. This phenomenon occurs because particles in colder materials exhibit slower movement compared to those in warmer materials. Slower particle movement results in a slower transmission of energy, thus causing the sound to travel at a slower pace in cold air compared to hot air.

At the altitude of 12,000 m above sea level, Chuck Yeager flew in an environment. At that height the temperature was significantly low, causing the speed of sound to decrease to 290 m/s. Consequently, when he flew at 293 m/s, he exceeded the speed of sound by 3 m/s.

Summary
• A sound is a form of energy produced by vibrations that travel through a medium, typically in air or water. These vibrations create waves that reach our ears, enabling us to experience sound.
• The speed of sound is the rate at which sound waves propagate through a medium. It solely depends on the medium through which the sound wave travels.
• The speed of sound in the air can be influenced by factors such as temperature, and humidity.
• Warmer air tends to have a faster speed of sound than colder air.

Related Worksheets: