[Lord Odin]

brycelarson, on 22 September 2009 - 08:55 AM, said:

Lord Odin, on 22 September 2009 - 08:16 AM, said:

Wouldn't a spectrum analyzer program be better for the sound? I tried to do some SPL measuring before but everything came out the same, even though you could hear a noticeable difference in the sound.

I've got both. I just don't have a calibrated mic for my USB preamp. I can use the SPL meter to eyeball calibrate the computer I suppose. It won't be exact, but for our needs it should be fine. I'll look into this - sounds like a good winter project. I should be able to produce waterfall plots of volume at frequency. That would be a good descriptor of whether it's a thud or a smack sound.

Will doing it indoors cause any problems with sound reflections?

[Leafy]

Lord Odin, on 22 September 2009 - 12:40 PM, said:

brycelarson, on 22 September 2009 - 08:55 AM, said:

Lord Odin, on 22 September 2009 - 08:16 AM, said:

Wouldn't a spectrum analyzer program be better for the sound? I tried to do some SPL measuring before but everything came out the same, even though you could hear a noticeable difference in the sound.

I've got both. I just don't have a calibrated mic for my USB preamp. I can use the SPL meter to eyeball calibrate the computer I suppose. It won't be exact, but for our needs it should be fine. I'll look into this - sounds like a good winter project. I should be able to produce waterfall plots of volume at frequency. That would be a good descriptor of whether it's a thud or a smack sound.

Will doing it indoors cause any problems with sound reflections?

I dont see it being that big of a difference, as long as he's in a big enough room with enough soft surfaces in it, ie not in an utilitarian bathroom.

[brycelarson]

Lord Odin, on 22 September 2009 - 12:40 PM, said:

Will doing it indoors cause any problems with sound reflections?

depends on what the test is trying to do. If the test is to give the real, calibrated SPL readings from guns - then yes, that's not going to happen in my house. You need to get into an anechoic chamber for that - and I don't happen to have one.

If the goal is simply to get comparable number from different barrels - then as long as the setup is repeatable it'll do just fine.

So, even given the bathroom example - as long as the measurements were taken in the same way from barrel to barrel, gun to gun etc. - then it'll give us a useful comparative number.

My thought was to do the test outdoors - to get as clean a signal as I can.

[UV Halo]

Is the Stiffi Barrel you tested ported? If not, I'm expecting that there will be a minimal sound level difference between the two barrels. Even if there is porting, The barrel is so short I'd be surprised if it turned out to be substantial.

[Deadpool]

Spitlebug, on 21 September 2009 - 03:03 PM, said:

I love the sped up footage! It's actually quite interesting to watch.

Yeah it looks like one of those Benny Hill movies... minus the "softlegs"

[Lord Odin]

Do humans interpret things as being louder based on frequency, dB, or a combo? For example, say one TPX barrel has a lower dB but different frequencies that make it more noticeable. Are there certain frequencies that humans will pick up on quicker than others? Which would we consider to be "louder"?

[Leafy]

frequency and dB. I think theres like a graph or something, also dont forget that high frequency is more directed but tends to travel further while low frequency tends to be more omni directional.

[brycelarson]

Leafy, on 22 September 2009 - 10:35 PM, said:

frequency and dB. I think theres like a graph or something, also dont forget that high frequency is more directed but tends to travel further while low frequency tends to be more omni directional.

right, there are actually things called weighting - most common are A and C.

A weighting accounts for the various sensitivities of human hearing - C weighting is more flat - outputting closer to the same volume at all frequencies.

The difference can be heard in Pink vs White noise. human ears are more sensitive to higher frequencies. White noise is C-weighted - so it sounds mostly like a hiss. Pink noise is A weighted so it has more rumble and "body" to the low end.

If you're measuring how loud something sounds - then A weighting is the way to go.

http://en.wikipedia....ting_curves.svg

This post has been edited by brycelarson: 23 September 2009 - 07:59 AM

[Spitlebug]

Deadpool, on 22 September 2009 - 05:45 PM, said:

Yeah it looks like one of those Benny Hill movies... minus the "softlegs"

Yeah that's pretty close to what I was thinking. Not quite as entertaining as Bryce but here you have it:

[pbplayer2327]

Pearlsea, on 21 September 2009 - 02:54 PM, said:

No I can has barrel for my awesome proposal of testing how paintballs would perform in a vacuum we will be colonizing the moon sooner then we thing and I think its a valid experiment so we know we can still shoot each other with gelatin on the moon when we have to abandon the earth in the aftermath of a nuclear world war.

Sooner then we think!

Alright way to think ahead dude