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Author Topic: Does heat make a sound?  (Read 5839 times)

Offline bizerl

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Does heat make a sound?
« on: 17/08/2012 07:15:21 »
From what I know (not much), heat is the expression of rapidly vibrating particles. Sound is also vibrating particles that radiate out in a wave.

Are these the same thing? Heat doesn't appear to make a sound unless activating some secondary vibration and sound waves don't seem to noticeably cause warmth, but the principles of both seem the same. Or is there something more subtle going on?


 

Offline Emc2

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Re: Does heat make a sound?
« Reply #1 on: 17/08/2012 07:31:57 »
there are a lot of sounds inaudible to the human ear,

Earth's atmosphere, water, and virtually any physical phenomenon, such as fire, rain, wind, surf, or earthquake, produces (and is characterized by) its unique sounds

  The perception of sound in any organism is limited to a certain range of frequencies. For humans, hearing is normally limited to frequencies between about 20 Hz and 20,000 Hz (20 kHz)[3], although these limits are not definite. The upper limit generally decreases with age. Other species have a different range of hearing. For example, dogs can perceive vibrations higher than 20 kHz, but are deaf to anything below 40 Hz.

 As a signal perceived by one of the major senses, sound is used by many species for detecting danger, navigation, predation, and communication. Earth's atmosphere, water, and virtually any physical phenomenon, such as fire, rain, wind, surf, or earthquake, produces (and is characterized by) its unique sounds. Many species, such as frogs, birds, marine and terrestrial mammals, have also developed special organs to produce sound. In some species, these produce song and speech. Furthermore, humans have developed culture and technology (such as music, telephone and radio) that allows them to generate, record, transmit, and broadcast sound. The scientific study of human sound perception is known as psychoacoustics


http://en.wikipedia.org/wiki/Sound

http://en.wikipedia.org/wiki/List_of_unexplained_sounds   ( these are interesting )
« Last Edit: 17/08/2012 07:35:16 by Emc2 »
 

Offline RD

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Re: Does heat make a sound?
« Reply #2 on: 17/08/2012 07:48:48 »
...  sound waves don't seem to noticeably cause warmth

Quote
Ultrasonic welding of thermoplastics causes local melting of the plastic due to absorption of vibration energy.
https://en.wikipedia.org/wiki/Ultrasonic_welding#Process

 
 

Offline syhprum

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Re: Does heat make a sound?
« Reply #3 on: 17/08/2012 08:15:21 »
To answer the inverse does sound make heat the actual power inherent in common sounds is very low, I once read that a symphony orchestra produces about 1 watt I do not know if this is correct
 

Offline bizerl

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Re: Does heat make a sound?
« Reply #4 on: 20/08/2012 01:06:52 »
The perception of sound in any organism is limited to a certain range of frequencies. For humans, hearing is normally limited to frequencies between about 20 Hz and 20,000 Hz (20 kHz)[3], although these limits are not definite. The upper limit generally decreases with age. Other species have a different range of hearing. For example, dogs can perceive vibrations higher than 20 kHz, but are deaf to anything below 40 Hz.


I should have specified, I'm aware of the limitations of human hearing. I understand sound to be the detection of compression waves through what is usually air by our peripheral hearing mechanism (or "ear"). If something vibrates - say a string for instance, the vibrations push the air around it in and out, and this chain reaction eventually pushes the air molecules right next to our eardrum, forcing our eardrum to move and go through the ossicles, cochlea etc.

I guess the question was more trying to determine whether heat is caused by the same sort of movement on a smaller scale? Is it a different manifestation of the same atomic or molecular movement or something else entirely?
 

Offline damocles

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Re: Does heat make a sound?
« Reply #5 on: 20/08/2012 01:16:22 »
I suppose that part of the answer is to recognize that the increased motion designated as "heat" is a random motion, with all local particles moving fairly independently, while "sound" is a coherent motion with local groups of particles moving in the same direction to produce a series of pressure waves.
 

Offline yor_on

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Re: Does heat make a sound?
« Reply #6 on: 20/08/2012 12:46:08 »
heh, so what we hear should then be organized 'heat'..
Explains a lot at times, that one :)
 

Offline bizerl

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Re: Does heat make a sound?
« Reply #7 on: 20/08/2012 22:47:18 »
I suppose that part of the answer is to recognize that the increased motion designated as "heat" is a random motion, with all local particles moving fairly independently, while "sound" is a coherent motion with local groups of particles moving in the same direction to produce a series of pressure waves.

That makes sense, although it also seems counter-intuitive that the random motion seems to have more energy than the motion which is organised and synchronous.
 

Offline yor_on

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Re: Does heat make a sound?
« Reply #8 on: 23/08/2012 16:15:52 »
Wow, that's a really cool questions Bizerl :)

How do the molecules arrange themselves to create the sound, voices etc we hear? What I mean is that we must be really keen differentiating those 'waves', but how do they do it on a molecular level? Setting themselves up (self organizing) into waves and frequencies?

As for the energy I'm sort of thinking that if they all move the same way they create lesser interactions than if the motion is a random one, but that may be naive :)
 

Offline evan_au

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Re: Does heat make a sound?
« Reply #9 on: 24/08/2012 13:51:19 »
Sound is perceived in the cochlea by sounds of specific frequencies causing particular hair cells to resonate, triggering nerve impulses to the brain. http://en.wikipedia.org/wiki/Cochlea#Summary

Sounds like speech and music trigger these resonances strongly, and the mix of different frequencies can make these sounds pleasant (harmonic) or unpleasant (dissonant).

Random noise, or "white" noise does not trigger a strong resonance because the sound has a random frequency and phase. White noise has been used to make offices seem quieter, even though you are injecting more noise into the environment!

Heat, or thermal noise is also random in frequency and phase, and so does not set up resonances in the hairs in the cochlea. I imagine that the hairs also have a threshold of excitation that would not trigger nerve impulses, or all of us would be continually annoyed by the sound of the air - a continual, broadband tinnitus.

The movement of atoms in the air due to heat has a particular random velocity distribution - see the graph at: http://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_statistics     

When a gusty wind is blowing, we can hear the eddies of the air in our ears - this is strong enough and non-random enough to trigger nerve impulses to the brain.
 

Offline yor_on

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Re: Does heat make a sound?
« Reply #10 on: 25/08/2012 13:59:37 »
Interesting Evan.
 

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Re: Does heat make a sound?
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