Audio issues on iOS when launching via Windows Editor

I seem to have encountered a bug. After launching my project on iPhone 5s via the Editor on Windows 7, I noticed that the audio quality has deteriorated quite badly - I could hear noise and crack through my headphones, and at the part the music loops there is a slight, but noticeable gap. Changing the compression to anything from 1 to 99 doesn’t seem to do anything, but changing it to 100 removes the noise and cracks, but the Stereo sound turns to Mono for some reason. The audio files I used were exported from Cubase 7, in 44100 Hz 16 bit WAV files.

Hey Kunning Fox,

Sample rate and the number of bits per sample have a direct impact on the size of your audio files. If you need to play many such sounds, or long-duration sounds, consider reducing these values to reduce the memory footprint of the audio data.

For example, rather than use 44.1 kHz sampling rate for sound effects, you could use a 32 kHz (or possibly lower) sample rate and still provide reasonable quality. Using monophonic (single-channel) audio instead of stereo (two channel) reduces file size. For each sound asset, consider whether mono could suit your needs.

Perhaps what is occurring when you set the compression to 100 is that it defaults to Mono in order to optimize space. In order to verify this, I would need a minimal test case where the issue occurs (crackling).

Thank you,

Hello Andrew,

Thank you, I will consider lower sampling rate for SFX. I don’t think anything lower than 44.1 KHz would be good for music, though.

I have made a new project to test the issue. So far it occurs even if I drop the sample rate down to 22050 Hz. I sent you the download link for it over PM on Forums.

So I do not believe this is a bug after testing the project. If the issue is resolved by setting the compression quality to 100.0. The fact it goes to mono is part of setting the compression quality itself as you have reduced the file size as much as possible.

If this can be reproduced with the starter content sounds, then I might be able to turn this into a bug report. If you cannot reproduce this with other sound files as well, then there is just an issue with the files themselves.

Let me know if you have further questions.


The starter content indeed plays ideally, if I don’t attempt to change compression settings. When I do try to change the Compression Quality to, say, 99, or 60, it introduces the sound artifacts (My guess is it forces the audio file to cook again).

I will install the UE4 engine on a laptop and attempt to launch the project on it to see if it is perhaps a hardware issue - I have ESI MAYA44 soundcard installed on my main PC, maybe it’s the culprit of the artifacts I’m experiencing.

Best Regards,

Kunning Fox.