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Static-like noise on IOS


I have encountered a problem with audio while developing for IOS. There is a clicking/staticy noise appearing quite regularly. The same sounds/music play without a problem on PC. It was checked on few IOS devices, with the same result.

My first guess was it had something to do with the buffer(similar sound artifacts appear when there are problems with either size or cleaning/reloading), so i tried adjusting it's size on IOS, but it resulted in either breaking some of the sounds completetly or straight up crashing the app.

Any help with this matter would be appreciated.

Product Version: UE 4.7
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asked May 27 '15 at 04:09 PM in Bug Reports

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avatar image joshbadams STAFF May 27 '15 at 04:24 PM

What OS version(s) are on the devices?

avatar image Zimo May 27 '15 at 05:01 PM

Hi Josh.

The devices we checked it on had 8.3 installed. The whole projects is 8.0+.

avatar image wittlief ♦♦ STAFF May 28 '15 at 02:28 PM

Hi Zimo,

Can you attach the build output logs and the device crash logs to this thread as txt files?


avatar image Zimo May 29 '15 at 09:51 AM


I downloaded logs, but i have a question. Since last update of the engine i think, logs are polluted with messages like those attached below. They repeat tens of times, so currently logs are barely readable. Do you know how to disable this? If i was able to do so, i'd remove thousands of lines of unnesecary clutter.

link text

metalspam.txt (20.2 kB)
avatar image joshbadams STAFF May 29 '15 at 03:03 PM

Sorry about that. The only way now to disable the logs is to remove the logs in the code, or to run a Shipping build. I'll add a bug to remove the logs unless desired.

avatar image joshbadams STAFF May 29 '15 at 03:02 PM

Can you test on a pre 8.3 device? Some things changed in 8.3 with threading that affects sound, but we hadn't seen it in UE4, only UE3.

avatar image Zimo Jun 01 '15 at 10:53 AM

I'm attaching logs from the game, along with some additional info: I checked the game on 8.1, 8.2, 8.3, on iPad Air 2 and mini 3. Pretty much the same result on each one.

And about adjusting buffer size: At first i tried doing something with MONO_PCM_BUFFER size and samples, but it only affects PC, so i tried looking into IOSAudioBuffer.cpp and played around with BufferSize, but i'm not sure it is the right approach, because it seems to work in a different way.

Logs below are for unaltered source code.

[1]: /storage/temp/44819-log.txt

log.txt (172.5 kB)
avatar image Zimo Jun 08 '15 at 11:09 AM

Hi guys.

Any new ideas on how to approach this problem?

avatar image wittlief ♦♦ STAFF Jun 18 '15 at 08:21 PM

Hi Zimo,

Do you mind updating to the most recent release to see if you're still experiencing this issue?


avatar image Zimo Jun 19 '15 at 07:37 AM


I'm during a transition right now, I'll let you know when we get the project running.

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3 answers: sort voted first

Hey there, I just solved this issue today on 4.9.2.

It seemed to be the compression quality setting for each sound file. The "Recommended" sound compression of 40 caused a constant static hiss during the audio play. Turning this instead to 100, thus pretty much turning off audio compression, seems to fix it. I'm not sure if iOS is doing it's own compression on top of the unreal compression, but it worked for me!

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answered Dec 30 '15 at 07:35 PM

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We have tracked down specific sounds which were making those noises and are in the process of replacing them. I'm not exactly sure why those issues happen only on IOS, because on windows everything is fine.

Didn't have a chance to test it on Android yet, because of launching problems in recent versions of UE.

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answered Jul 15 '15 at 03:06 PM

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avatar image Zimo Jul 22 '15 at 09:37 AM

Hi guys, just a final update.

I checked the sounds on Android - no problem there. This is really weird, but i was only able to reproduce this on IOS devices. Anyway, like i said, it's just few sounds, so we'll replace them.

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Hi Zimo,

We're gonna mark this resolved until you're able to try with the newest version. If when you get to test you are still seeing this problem with the latest, post here and we'll continue our investigation of your issue.


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answered Jun 19 '15 at 01:37 PM

avatar image Zimo Jun 25 '15 at 02:55 PM


Unfortunately problem persists in 4.8.1. I'm quite sure now that it has something to do with the buffer and not sounds themselves. I tried changing the sound files, disabling some of the sounds etc. The clicks still appear, and the more sounds are active, the more often it bugs out.

Also, whenever a sound hasn't been used for a few seconds, and then it is played, the static appears every time without fail.

avatar image joshbadams STAFF Jul 01 '15 at 06:30 PM

Have you tried any of our samples? Are these sounds marked as streaming or anything like that? Are all sounds that misbehave stereo?

I can't see how the not playing for awhile thing could make a difference.


avatar image Zimo Jul 03 '15 at 10:45 AM

Sounds are not marked as streaming, and majority of them are mono, including those, that are problematic. I'm currently in the process of replacing them one by one and checking for exact spots that are making this noise. Still, what's most interesting, is that everything is fine on PC, while IOS version is broken.

I'm going to make an Android build soon and check it out there.

avatar image wittlief ♦♦ STAFF Jul 14 '15 at 04:29 PM

Hi Zimo, are you still experiencing this issue? Were you able to reproduce on an Android device?

avatar image mrgrimm01 Jul 22 '15 at 08:40 PM

I'm experiencing this as well. On UE4.8, iOS 8.2. Lots of static on almost all sounds, and clipping/cutting off of some sounds (footsteps played via anim notifies, for instance.)

I've been experiencing this problem since UE3 and it seems as though it's never been resolved.

avatar image wittlief ♦♦ STAFF Jul 22 '15 at 08:51 PM

Hi mrgrimm01,

As Zimo discovered, this does not appear to be a problem with UE4 directly, in as much as we can't reproduce it internally by any method. If you've been experiencing it since UE3 you may need to re-evaluate your development sound processes, especially if you're only able to reproduce this on a selection of devices or one platform vs another.

Good luck!

avatar image Zimo Aug 21 '15 at 02:25 PM


I'm updating this topic with new info, because the problem still persists with numerous assets for no obvious reasons. Below is a comment from our sound designer:

Recently I found a major issues with sound in Unreal Engine 4.

When we build a game for iOS something strange is happening with stereo files. For sampling frequency different than 44.1kHz right channel is playback with wrong speed and pitch. For 22.05kHz - right channel is playback to fast, for 48kHz is playback to slow. Please find a recorded audio files attached.

Other thing is very low sound quality. even when compression quality is high a lot of drops and pops appears. Please find a recorded audio files and print screen from Pro Tools attached.

I try to fix this issues but with no luck. What I tried was: - adding short silence at the beginning and end of sound asset - various sampling frequency, 44.1kHz, 48kHz, 22.05kHz - send all sounds only to default Master Bus - various compression quality 1 to 100 More info: - drops and pops appears often just after some sounds - making new build with the same setup can change drops and pops

So far we tried replicating the issue with template project and the same assets, but with no luck. So the same assets will cause problems in one project, but not the other.

Link to dropbox with sounds and screens mentioned above: https://www.dropbox.com/sh/2099yzrxq1bnqg7/AADiBk_7k8DcgqAd7hCd6UWGa?dl=0

Any help or idea how to pinpoint the problems would be appreciated.

avatar image Samantha Sutton ♦♦ STAFF Aug 25 '15 at 09:13 PM

Hey Zimo,

So I have added your sound files to a project and pushed the project to both an Android device as well as an iOS device. Both devices played the sound exactly the same.

With that being said, I've requested some additional feedback from our Developers regarding the frequency for mobile devices. I'm hoping to hear some more information within the next couple of days.

Please let me know if you have any further questions, thanks!

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