Author Topic: The effect of temperature on sound frequencies  (Read 13959 times)

0 Members and 1 Guest are viewing this topic.

Offline Rider

  • Ur-Quan Lord
  • *****
  • Posts: 2302
  • Karma: 25
    • View Profile
    • Cubicle Webcomic
The effect of temperature on sound frequencies
« on: December 01, 2007, 03:50:49 am »
A friend of mine, and myself, where curious if there's any kind of paper or whatever about the effects of temperature on sound frequencies.

She thinks that warm air decreases the 'weight' of air, and thus (much like helium) will heighten the sound frequencies.

I on the other hand believe that because of warm air's decreased resistance, it will simply travel faster at the same frequency strength, thus providing lower sound frequencies.

I wonder if either of these hold any truth.
You wish you had a signature like mine

Valaggar Redux

  • Guest
Re: The effect of temperature on sound frequencies
« Reply #1 on: December 01, 2007, 04:55:10 am »
The speed of sound in a gas is directly proportional to temperature. This means that, in warm air, sound will propagate faster.
Frequency = Speed / Wavelength; since the wavelength remains constant (as we don't change anything regarding the sound source), frequency will increase too in warmer air.

Thus, you were both right and wrong at the same time. You might ask "But how can a wave that has both a higher speed and a higher frequency still have the same energy as the one with lower speed and lower frequency?". But do not forget that energy, in a wave, is stored in the form of amplitude too.

See also here.

[Also, the weight of air doesn't change with temperature; only its pressure and/or volume do, per the ideal gas law.
« Last Edit: December 01, 2007, 08:50:27 am by Valaggar Redux »

Offline Sedodes

  • Ur-Quan Lord
  • *****
  • Posts: 3737
  • Karma: 6
  • Ironic self-hating narcissist superhero!
    • View Profile
    • Clickity
Re: The effect of temperature on sound frequencies
« Reply #2 on: December 01, 2007, 07:47:07 am »
Wow, go VR.  Very thorough and understandable (even for Rider) explanation.  I hope you stick around these forums rather than disappearing like the vast majority do...
In a world where one man could change the world,
One man changed the world!


The day the world changed
Will be known as the day that changed the world


Offline Lukipela

  • ZFP Peace Corps
  • Ur-Quan Lord
  • *****
  • Posts: 4326
  • Karma: 29
  • The Ancient One
    • View Profile
Re: The effect of temperature on sound frequencies
« Reply #3 on: December 02, 2007, 02:52:13 am »
Yeah, I didn't even understand the question the way it was phrased. Somewhere along how warmth decreases weight I got lost and just started crying.
Round and round it goes, where it stops nobody knows