Does sound travel faster in warm or cold 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).

photo credit: Micah Taylor via photopin cc
photo credit: Micah Taylor via photopin cc

 

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.

Refraction of sound waves amplifies and focuses the sound so that it can be heard from farther away
Refraction of sound waves amplifies and focuses the sound so that it can be heard from farther away

“Sound” about right to you?

nao

Science blogger and writer; Owner of Dr. How's Science Wows; Mother of three junior scientists who have taught me that to be a great scientist you need to look at life through the eyes of a child!

9 thoughts on “Does sound travel faster in warm or cold air?

  • Pingback: Environment Boost Sound Amplification | Science on Campus

  • February 18, 2015 at 4:36 pm
    Permalink

    Oh it was just great ! It helped me alot !
    Thankyou so much for such a beautiful explanation ☺☺☺☺☺☺

    Reply
    • February 18, 2015 at 8:03 pm
      Permalink

      Really glad it helped Mariam and thanks for stopping by the blog

      Reply
  • Pingback: 14 from '14 - a little blog reflection - Science Wows

  • December 31, 2014 at 3:43 pm
    Permalink

    Sound appears to transmit farther, louder, and more clearly in cold air. I’m wondering if humidity might have anything to do with this? When the air is cold, it cannot hold as much moisture, and the moisture drops to the ground as dew or frost. When the air is warm, it can hold more moisture, so humidity may be higher. I’m wondering if more water particles in the air mutes the sound? For example, when you try to speak underwater, the sound is muffled and muted. The more water in the air, the more muted the sound, perhaps? The less water in the air, the farther the sound goes and the clearer the sound is?

    Reply
  • November 23, 2014 at 11:46 am
    Permalink

    hi, this is best crisp and short explanation available on internet
    Shrimati Naomi Lavelle u should do your science blogging more often

    thanks for the beautiful explanation

    Reply
  • January 9, 2014 at 9:35 pm
    Permalink

    All I know is that I tried to guess the right answer before reading and I got it wrong 🙁 So much for LC physics 😉

    Reply
    • January 9, 2014 at 10:31 pm
      Permalink

      Guessing is better than not answering at all ;0) Although I didn’t feel that way when played a safari quiz game with my son the other night hand I lost!!!

      Reply

Leave a Reply

Your email address will not be published. Required fields are marked *

CommentLuv badge