Rate of fire help

[Ninthmessiah]

I'm working on a .50 cal sound and trying to get it to match up with the rate of fire.  If I assume that the Browning M2 had a rate of fire of approx. 800 rounds per minute, then that means it fires 13.333 rounds per second.  At 13 rounds per second, that means that  76.92milliseconds [or 0.07692 seconds] elapse before the next round is fired.  I came to this figure at 1000/13.

Is there anything wrong with my math or assumptions?

I made a 76ms clip that sounded terrible and I think it's because 76ms is to small for a digital clip to repeat.  Or it could just be that my .50 cal sample is total crap.

What do you guys think?  If the 76ms part is right, then I need to edit my sample better, or get a better sample alltogether.

[Chalenge]

The fast way round is just to take the number of seconds in one minute and divide by the number of rounds per minute. That's if you want it on the basis of one shot. You can round off to .075 seconds which will fool any human either way. Since you want it to loop you will probably never be able to make it just perfect anyway.

If your recording is clear already then you should not have any problem. Don't be afraid to insert silence at both ends of the clip. Very small segments of silence are easier to loop than trying to match up the waveform of a gunshot, especially a machinegun.

Please, don't be tempted to push the bass boost on your guns. If you check you will see that most gun sounds (especially tanks) are over amplified to impress people. Less is more. The default sounds are just right and make a good example to emulate.

One reason sounds do not loop well is because you have to match up the waveforms properly at both ends. If you snip a segment out on the crest of a -6db wave (some editors will refer to it as +6, which it is not) it will not match the valley of -4db. Your editor should have marks for everything from minus infinity (no volume) to positive and negative running back to zero. Some editors, like Audition have marks beyond 0 on into infinity. The "-1" indication is a measure of the work limitation of any audio channel. If you attempt to amplify beyond that mark you may get clipping and distortion (especially during mixes) and that will ruin a good sound byte. I used to use -5db as a good place to limit some sound bytes, but others I push on up to -1.5db. There is no reason to push the envelope, because good sound is better than loud sound by a long shot. You have to watch your input levels and mix output levels to avoid the peaks crossing over into clipping ground also.

Did you record the HB M2, or the AN M2? Because of the firing rate you mentioned I am assuming it is the AN M2. If you try to use the HB M2 to match the AN M2 firing rate then it will never sound right.

If you ever get around to making engine sounds, then check to see if your editor supports selection snaps to zero-crossings. You do not want to insert silence into a looping engine sound, or tank treads. So, when you work on those sounds the zero-crossings are very important.

[Ninthmessiah]

After playing around some, I think problem is that 75ms is just too short.  The clip repeats so fast that it just ends up generating a resonant frequency based on whatever undeveloped sound wave is playing mixed with a higher octave of 13hz.  I don't have the tools to do a spectrum analysis to notch it out, assuming that would fix the problem.  I'm using some freeware beta software that won't let me analyze in real time.  Tried cross-fading the ends but that wasn't the problem because this isn't a continuous sound such as an engine.  Thanks for the help.  I ended up just expanding the clip to 105ms which although is not accurate, is much easier on the ears. 

No I did not boost the low end.

But...   I did add a 50hz sine wave to give it some beef.  Which is still cheating but eh...  my headphones go that low.

And because you care about these things, the sound I downloaded  falls within that copyrighted but ok for non-commercial use category.

[Chalenge]

Well, for your own use in the game you can actually duplicate just about anything, you just can't inevitably pass it around. Also, if you want to use software that does have everything enabled, then you can download and use Adobe Audition for 30 days free. In fact, their entire suite is available. They have an option for cloud rental usage for $30/month, but I don't know if that extends outside of education.

Audacity is free and I think it can almost do everything Audition can.

Here is how Adobe portrays the AN M2 .50 caliber as it was recorded on a cell phone.



After I have clipped it, inserted tiny silence segments, and amplified:



You can download the final sound here, but note that it is limited precisely because of the limits of the recording device.