Need help, want to make explosion sounds

[Vandar]

I'm currently playing a game that has quite some cool explosion sounds. That made me want to make some of my own. But I have no good idea how to start. Record something and edit the recording? What would be good sounds to start with?

Or work with envelopes and noise and try to synthesise the sound?

I've not done a lot of sound editing so far, so any tips will be welcome. Thanks!

PS: Sadly I can't record real explosions, there are no explosives for sale here and even fireworks only in the days before new years. So I need something else.

[Julius]

The term you need to search for is "foley".

https://en.wikipedia.org/wiki/Foley_(filmmaking)

[smcameron]

I made an explosion sound making program one time. It works by shaping white noise. I really don't know what I'm doing with DSP though, so the results are not what you'd call high quality. Anyway, it's here: https://github.com/smcameron/explodomatica

Here are some sounds I made with it:
https://freesound.org/people/smcameron/sounds/51428/
https://freesound.org/people/smcameron/sounds/51464/
https://freesound.org/people/smcameron/sounds/51497/
https://freesound.org/people/smcameron/sounds/51463/
https://freesound.org/people/smcameron/sounds/51429/
https://freesound.org/people/smcameron/sounds/51427/

It's possible some of those sounds were made by hand in audacity by shaping white noise before I made my program to more or less automatically do what I was doing by hand in audacity, and I might have done further post-processing one the basic explosion noise that came out of explodomatica. The basic idea is you make some white noise, you taper it off in volume, and as time passes, you e.q. out higher frequencies, so by the end, only low frequencies are playing. That is, you kind of apply a sliding low pass filter, with the cutoff frequency starting off high and quickly sliding down to lower frequencies as time passes. Also, you might make two (or more) explosions offset in time, the first one being the "ka" and the second one being the "boom" in "ka-boom", with the first one having higher initial cutoff frequency (or vice versa? I can't remember) and the first "ka" being quieter than the 2nd "boom". Of course maybe add reverb if you want. You can add secondary effects like falling debris / dust at the end, but that's really out of the scope of the "basic" explosion noise. This technique is very basic though, and it sounds that way.

[Vandar]

@Julius

Thanks for the link. I knew about the approach but I didn't know the name. So that will help for further searches. Also, the article already has a nice list of effects to try. I was wondering if popping a baloon or "bang-ing" a air filled paper bag will make good bases for explosion sounds. But at the moment I lack the resources and all shops are closed ... and I'll need a few tries to even get the microphone setting right ... no clipping and good use of the dynamic range.

@Smcameron

Yes, that's what I meant by synthesising the sounds. I had some very limited success with an approach similar to the one you describe, but I lack experience and knowledge to do better there. Your sounds are quite good. I like the use of the echo and reverb effects. I think I already learned a bit just from listening and trying to find out how you made those. My latest idea was to record something and use that instead of the white/pink noise with an appropriate envelope and filters to make a good semi-synthetic explosion sound.

Thanks for the help!

[smcameron]

I forgot, there was a thread about explodomatica back when I made it, here: https://forum.freegamedev.net/viewtopic ... 50&p=21217

Maybe there are some hints in there. Also I found this extremely low quality video (lol) I made a long time ago demoing what I figured out for explosions in audacity: https://www.youtube.com/watch?v=HRypuCJH9OI (In my defense, the video was shot on a potato, uploaded to google videos, then transcoded to youtube when google shutdown google videos in a process that did not help the quality.)

[Vandar]

Thanks to all for the help! Still working on it, but this video uses one of the explosion sounds for the vortex projectiles:

https://www.youtube.com/watch?v=Xpi2I7QvMr4

Still room for improvement. Just wanted to let you know that your input was helpful!

Edit: Another explosion type used in this one - sounds less "bucket" than the former one:

https://www.youtube.com/watch?v=AXn25l84ec4

[smcameron]

Nice!

Visually, spawning a bunch of sparky particles traveling in random initial directions and slowly shrinking in size can go a long ways towards make a decent explosion effect. In your case you could exclude "downwards" from the "random initial directions" and add some gravity to affect the particles velocity, and maybe have them bounce off the ground. Would probably look pretty good and not be too difficult.

"sparky particles" just means billboards with a texture something like this: https://github.com/smcameron/space-nerd ... exture.png (in case it wasn't obvious, but from your video, you already have something like that texture so it probably is obvious.)

[Technopeasant]

Or you could put a microphone to your mouth and go pechew!

[Vandar]

Smcameron, yes, I have a similar texture but only for the light and fade. The idea to add some particles or some effect to the explosions is a good one. I'll try to work on some suitable graphics for that.