Dell XPS 7390 2 in 1 : Low and hissing sound issue

I am having sound issued with dell xps 13 2 in 1. Hissing and low sound. While testing sound using MaxAudioPro it starts with hissing low sound but after playing testing sound for few minutes sound returns to normal.

Issue returns after few minutes of inactivity or changing the speaker status to mute/unmute etc. I tried everything mentioned on the forum even restored to factory default but unable to resolve this annoying issue. 

Any help in this regard is highly appreciated.

Thanks