physics and sound

[scionicboom]

So ima college student and in my physics 101 class we were learning about sound now what I learned is that sound travels fastest in solids...so wud this apply if u built a box out of steel or something...just wondering

[will77530]

i assume thats why ppl build boxes from mdf and birch which are quite dense

[scionicboom]

Well yea but would u get better results with something that's more dense

[C-Fizzy]

Mdf is cheaper than .75 inch steel. You gonna weld the box together?

[IH8PunkRok]

Nope you are way off. But I'm drunk and tired. I'll yell at you tomorrow

By your theory if you fill your car with steel you always win competitions. Think about it

[IH8PunkRok]

It has to do with the space between atoms. Sound travels fastest in solids due to the minimal spacing between atoms. It had nothing to do with what you are contemplating

[TheBetterMethod]

SPL has nothing (for all intents and purposes) to do with the speed of sound. We're measuring pressure not velocity.

[scionicboom]

True ....sorry now that I think about it ...it doesnt apply.... it was just a thought

[HHR Ed]

Lots of guys in the SPL world have built boxes from Steel or concrete, or both sandwiched together, or glass, or granite, and all types of wood.

But they do this for the rigidity properties of the materials, not the density.

See, when any part of the enclosure moves, or flexes, it takes away from the acoustical energy applied to the microphone sensor. (or your ears).

So an enclosure must be as rigid as possible.

Now here is what happened with the steel boxes. Even at 0.5" thick or more, the steel had shown to flex from the woofers. This is because steel is flexible.

So wood shows an advantage over steel in this case because it can be made to be more rigid in terms of woofer enclosures.

Now, in relation to your thoughts on speed of sound. These steel boxes produces a "ringing" noise which is a harmonic from the vibrations the steel incurs when the woofers play. This "ringing" not only sounded annoying, it also created an unwanted harmonic that partially cancelled the initial source wave as it coupled with the mic sensor, reducing the total SPL score.

So, since we see that these harmonics can decrease SPL, can they be made to increase SPL?

Yes

For years, the top SPL guys have learned to adjust the rate of flex of different parts of their enclosures and vehicles to create supporting harmonics. This can be something as simple as building one side of the box out of 1 layer of wood and the other side out of 2 or 3. There is an art to it, and some trial and error. But usually it is done in the range of frequencies less than 1 octave higher than the initial source frequency.

[IH8PunkRok]

spl secrets right there ^