Default Own Notification Sounds quiter

Hi all i have a Problem with my Notification Sounds on my LG G33 32GB. When i select a own mp3 as Notification its quiter then the original LG Sounds ;( but when i select the samt Tone as Ringtone its loud as the LG One. Can someone confirm this? Is it a Hard or Software Problem? Swap the Device or hold it and wait for Software Update?

Thanks and Greetz v0dKa
Smartphone: OnePlus One 64GB Sandstone Black
ROM: CyanogenMod 11S
Recovery: TWRP 2.8.0.0
Tablet: Apple iPad Air 32GB Space Grey