Sound travels slower in cold air than in hot air

Does sound travel faster in warm or cold air?

I was asked this by the principal of a school I was visiting during Science Week last year. I gave him the short answer… it travels faster through warm air.

Technically that is correct.. it does travel faster through warm air… the molecules in the warm air are more “excited” and will vibrate more easily. Sound needs vibration in order to work so the sound is carried more easily through the air with the more excited molecules than through air with more “still” molecules (cold air).

A good way to think of it is to imagine a line of dominoes. The air molecules are the dominoes.
Sound makes air molecules around the source vibrate and hit off the next molecule which vibrates and hits of the next (just like the dominoes hitting off each other) and the chain keeps going until the sound reaches your ear… and then the vibrations get carried on to your middle and inner ear until they are changed to electrical pulses that are sent to the brain!

And there was me thinking I was keeping this simple… back to the dominoes… just keep thinking of it like a string of dominoes. Actually that is not quite true…. for the domino model to really mimic the movement of sound you have to arrange the dominoes in concentric circles, not in straight lines. Sound travels outwards from the source in all directions.

So there you have it sound does travel faster in warm air BUT it may appear to travel farther in cold air.

This is how that works…

…if the air close to the ground is colder than the air above it then sound waves travelling upwards will be bent downwards. This is called Refraction.  These refracted sound waves can act to amplify the sound to someone standing far away.

“Sound” about right to you?

The speed of sound is determined by the density of the medium through which it travels. It also depends on the temperature and pressure of that medium. So, does sound travel faster in cold air? Keep reading to find out.

Learn in This Article

• Does Sound Travel Faster in Cold Air
• How Does Temperature Affect the Speed of Sound
• Cold vs. Hot Air
• What Is the Difference in the Speed of Sound on a Warm Day Versus on a Cold Day
• What Other Factors Affect the Speed of Sound

The answer to this question isn’t a simple yes or no. The speed of sound is determined by many factors, such as the density and temperature of the medium. Science says that sound travels faster in warmer air.

How Does Temperature Affect the Speed of Sound

Temperature can affect the speed of sound in a few different ways. So, why does sound travel faster in warm air? Well, since air molecules at higher temperatures vibrate faster, they allow the sound to move through them quicker. 

Sound in Cold vs. Hot Air

So, how does temperature affect sound waves? Let’s take a look at how fast and how far sound travels.

Sound Travels Faster in Hot Air

It all comes down to the molecular structure of the air and sound. In warm air, the sound molecules pass through the air molecules faster. So, the scientific measurement of the speed of sound is 767 mph at a temperature of 70°F at sea level. However, sound will travel fastest in air at higher temperatures such as 212°F when its speed is 872 mph. At freezing temperatures, it travels at 740 mph. 

Sound Travels Further in Cold Air

Even though sound may travel slower in cold air, it can travel further distances. This is because the sound wave is refracted away from the pockets of warm air and back towards the ground. This wave then oscillates between the cold air, warm air, and the surface, making it travel further.

What Is the Difference in the Speed of Sound on a Warm Day Versus on a Cold Day

As we saw above, the way sound waves travel through air is somewhat affected by the temperature and sea level.

However, other factors can affect the speed of sound, such as humidity and pressure. The speed of sound in humid air is 0.35% faster than in dry air.

Many factors contribute to the speed of sound, and to a person, these differences will matter little in day-to-day life. But for science, all of these figures are very important. 

What Other Factors Affect the Speed of Sound

A few different factors can affect sound speed, such as the medium in which sound travels. Is it solid, liquid, gas, or vacuum?

Speed of Sound in Solids

Because solids are incompressible, the speed of sound in solids is always higher than the speed of sound in gasses. In general, the speed of sound in solids is around 13,000 mph. The speed of sound in a material can also be affected by its microstructure. For instance, the speed of sound in diamonds is 35 times faster than the speed of sound in air.

Speed of Sound in Liquids

In general, the speed of sound in liquids is faster than the speed of sound in gasses. The speed of sound also decreases as the temperature of the liquid decreases. This is because colder liquids are more viscous than warmer liquids, and thus sound waves have to travel through them more slowly. The speed of sound in water is only slightly faster than the speed of sound in other liquids, such as oil.

Speed of Sound in Gasses

The speed of sound in a gas depends on the properties of the gas and the temperature. With ideal gasses, which we don’t have in nature, the speed of sound is proportional to the square speed of the absolute temperature measured in Kelvin.

Speed of Sound in Vacuum

The speed of sound is the distance traveled per unit of time by a sound wave as it propagates through an elastic medium. There is no medium for sound waves to travel through in a vacuum, so the speed of sound in a vacuum is effectively zero.

Key Takeaways

• The speed of sound is affected by the temperature of the air.
• Hot air makes sound travel faster, while cold air makes it travel further.
• Other factors, such as humidity and pressure, can also affect the speed of sound.
• The speed of sound in liquids is faster than in gasses but slower than in solids.
• The speed of sound in a vacuum is effectively zero.
• All of these factors are important for science, but they likely won’t make a difference in day-to-day life.

Frequently Asked Questions

Why do things sound louder at night?

The vast majority of the time, sound waves travel through the air at roughly the same speed. However, some factors can affect the speed of sound, such as humidity and pressure. In colder temperatures, sound does travel further, so it may seem like it’s louder because other sounds are absent.

Does snow absorb sound?

While snow doesn’t absorb sound as well as other materials, such as cloth or foam, it can still reduce the amount of noise that travels through it. A few inches of snow can absorb up to 60% of sound. So yes, snow does absorb sound.

Does sound travel up or down?

Sound waves travel in all directions. However, the vast majority of sound waves are transmitted through the air, so they will typically travel horizontally. Sound waves can also travel through other mediums, such as water or solid objects. In general, sound waves will travel in a straight line until they hit an obstacle, at which point they will be reflected.

Does sound travel faster in water or air?

The speed of sound is around 3,243 mph in the water and around 767 mph in the air. Therefore, the speed of sound in water is faster than in air. Now that we’ve touched upon the speed of sound vs. temperature debate and answered the question “does sound travel faster in cold air,” we can conclude that sound doesn’t travel faster in cold air but it travels further distances.