iDevGames Forums
iPhone/iPad Audio Glitch - Double Hiss/Static - Printable Version

+- iDevGames Forums (
+-- Forum: Development Zone (/forum-3.html)
+--- Forum: Graphics & Audio Programming (/forum-9.html)
+--- Thread: iPhone/iPad Audio Glitch - Double Hiss/Static (/thread-8395.html)

iPhone/iPad Audio Glitch - Double Hiss/Static - reapz - Dec 8, 2010 05:39 PM

Hi there,

We are developing a game for the Apple devices (iPhone/iPad), and initially resorted to using OpenAL for sound. We didn't have any major issues with this library choice, however after adding complexity to our sound engine, we noticed a strange "double static" sound (sometimes) being played after (some) various .wav sound effects. We assumed that this was an issue with the OpenAL library, and re-factored our engine to use the FMOD library in place of OpenAL. Surprisingly, the strange"double static" sound still plays using FMOD! I have recorded this "double static" sound which can be heard here:

Naturally, one would assume that it's the sound file itself that is corrupt, however we have tried replacing the sounds to no avail. We have also tried converting all files to .caf format, still plays static. We have tried re-encoding the sound files to FMOD friendly (i.e. PCM/ADPCM); still plays static sound Sad

Does anyone have any ideas?

RE: iPhone/iPad Audio Glitch - Double Hiss/Static - AndyKorth - Dec 8, 2010 05:50 PM

If you have very short sounds, pad them with a little bit of silence at the end. We ran into problems with our sound if the sound is longer than a frame of audio. I think padding to half a second or a full second fixed it.

I can't quite tell from your youtube video how long the sound was.

RE: iPhone/iPad Audio Glitch - Double Hiss/Static - reapz - Dec 8, 2010 06:22 PM

I doubt that our sounds are shorter than a frame of audio. Is this what you mean? Did you have problems when the sound was longer or shorter than a frame of audio?

We tried half a second padding but it didn't seem to help. We will try a full second and let you know.


So the problem is fixed. I figured I'd go through a bit of embarrassment to make sure that other people know why we were having this problem. The problem as it turns out was not the explosion sound but the throw sound. It had a long silent gap followed by the two static bursts.

The reason we didn't pickup on it is, first we assumed the sounds were OK. Lesson learned! Second, when a grenade is thrown we have two sounds which are randomly selected so sometimes we'd never hear it. I guess next time we will just check all the sounds to make sure...

I swear this always happens the day I post a problem on the forums Rasp