# What is the fastest speed of sound? **URL:** \ **Category:** Factual Questions\ **Created:** [December 6, 2011, 4:28am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236 "2011-12-06T04:28:41Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [December 6, 2011, 4:28am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236/1 "2011-12-06T04:28:41Z")
Ok. In air, dependent on pressure, temperature, etc., shock waves, bullwhips, I get it. Ditto water. In other materials, so-so. A strike (not necessarily producing a “ping”) also produces a shock wave–is that the right term?–measured in speed of sound. Why do they call that wave sound? In plasma–which I looked up in Wik–it’s used at the atomic level. I have no clue. Any help? ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [December 6, 2011, 5:27am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236/2 "2011-12-06T05:27:12Z")
Mostly has to do with density, isn’t it? So, the speed of sound in a long steel beam is higher than the speed of sound in water, and in water faster than in air. If your plasma or other gas were under super high compression (would it still be a gas?) the speed of sound might get really high. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [December 6, 2011, 5:28am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236/3 "2011-12-06T05:28:38Z")
In very rigid solids the speed of sound can be quite a bit higher than in air. Here’s a [table](http://hyperphysics.phy-astr.gsu.edu/hbase/tables/soundv.html#c1) that shows some sample values. It gives the SoS in diamond as 12,000 m/s - about 35 times the SoS in air. ---
**Author:** ![coremelt](https://avatars.discourse-cdn.com/v4/letter/c/4491bb/32.png) [@coremelt](https://boards.straightdope.com/u/coremelt)\ **Post date:** [December 6, 2011, 5:30am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236/4 "2011-12-06T05:30:13Z")
previous thread implies that in a neutron star it could approach the speed of light. > **[Which material has the fastest speed of sound?](https://boards.straightdope.com/sdmb/showthread.php?t=449378)** > > Sound travels faster in water than air. Sound travels faster in steel than air. But in which substance does it travel the fastest? Obviously there’s an upper limit of the speed of light, but would any material support near that? A neutron star? A... ---
**Author:** ![Naxos](https://avatars.discourse-cdn.com/v4/letter/n/50afbb/32.png) [@Naxos](https://boards.straightdope.com/u/Naxos)\ **Post date:** [December 6, 2011, 5:36am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236/5 "2011-12-06T05:36:44Z")
> [@Leo\_Bloom](#): > > Any help? Is this your homework? We call “sound” a wave that would excite the human auditory system. So your question should be: how fast can a wave travel that can still be detected by the human ear? ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [December 6, 2011, 6:00am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236/6 "2011-12-06T06:00:33Z")
> [@Naxos](#): > > Is this your homework? > > We call “sound” a wave that would excite the human auditory system. So your question should be: how fast can a wave travel that can still be detected by the human ear? No, and no.😛 ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [December 6, 2011, 6:07am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236/7 "2011-12-06T06:07:06Z")
> [@coremelt](#): > > previous thread implies that in a neutron star it could approach the speed of light. > > [Which material has the fastest speed of sound? - Factual Questions - Straight Dope Message Board](http://boards.straightdope.com/sdmb/showthread.php?t=449378) Great thread, that, thanks. It covers basically the question–except for the plasma one. One of the respondents defined sound as “basically the speed of stuff bouncing against stuff.” Is it because of the ingrained response that it refers to air-based–and human sensed-- phenomena that makes me uncomfortable with the term? ---
**Author:** ![Naxos](https://avatars.discourse-cdn.com/v4/letter/n/50afbb/32.png) [@Naxos](https://boards.straightdope.com/u/Naxos)\ **Post date:** [December 6, 2011, 6:09am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236/8 "2011-12-06T06:09:15Z")
> [@Leo\_Bloom](#): > > No, and no.😛 For the second “no”, you’ll have to define how the initial vibration is created, what is it that is vibrating, and what is the material through the vibration is propagated. The upper limit, of course, would be light and the speed of light accordingly. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 6, 2011, 6:17am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236/9 "2011-12-06T06:17:12Z")
> [@](#): > > In other materials, so-so. A strike (not necessarily producing a “ping”) also produces a shock wave–is that the right term?–measured in speed of sound. Why do they call that wave sound? It’s just a wave, not a shock. And it’s the same kind of wave as a sound wave, a lateral compression wave. Back to your OP, I gather that you’re asking what material has the highest sound speed? The answer, then, is probably a photon gas (or I suppose a graviton gas), in which case the sound speed is c/sqrt(3). As an aside, I wonder: There’s no reason one couldn’t also have a phonon gas in some material, and one could have soundlike disturbances in that phonon gas. One would then have a sound propagating through a medium which was itself composed of sound. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [December 6, 2011, 6:27am UTC](https://boards.straightdope.com/t/what-is-the-fastest-speed-of-sound/605236/10 "2011-12-06T06:27:10Z")
[quote=“Chronos, post:9, topic:605236”] … > [@](#): > > Back to your OP, I gather that you’re asking what material has the highest sound speed? The answer, then, is probably a photon gas (or I suppose a graviton gas), in which case the sound speed is c/sqrt(3). sqrt(3) to account for 3-d spread?