Hey @psychosys , this appears to be an issue specific to the Android/IOS/Unity systems. It seems that iOS automatically converts all audio through unity to its own format: https://forum.unity.com/threads/audio-quality-issue-on-mobile-platforms.285230/
From past experience I’ve noticed that Mono formatted sound seems to have a greater disparity between devices than Stereo, so you can try seeing if you are able to make a switch with your current sound files.
The last 2 links are really basic suggestions which may also cause an issue (increasing the audio source volume)
Try one of these suggestions and see which works best for your application. Please let us know which option works best for you, it would be of great help to the community.