Touch bar MBP Mid 2017 Speaker issues

hi, have real strange problem speakers on 15" tmbp mid 2017.

after resume sleep, (which how use 90% of time, shut lid , sleeps) , play videos youtube, audio, sound switch mono , sound muffled.
doesn't matter browser happens in both safari , chrome. reboot fixes it. until next time resume sleep.

when issue occurring, launch itunes , play music, start off in stereo, switch mono.
doesn't matter if streaming music, or local files.

know whats going on? , how begin diagnose this?
accessibility setting "stereo mono" not selected.

don't recall happening when got machine, since updated high sierra think.

--- post merged, jan 3, 2018 ---

ok did smc, , nvram reset, same result. think issue persistent after reboot, shutdown/resart. sound starts off stereo , changes muffled mono.

if plug earphones in, sound fine in stereo. when unplug them i'll few seconds of speakers sounding in stereo, change muffled mono.

next might wipe it, , reload fresh copy of high sierra. unless there other suggestions?

 

do have 15 inch or 13 inch macbook pro? make weird popping noise before switching mono? 15 inch macbook briefly had similar problem before heard loud pop noise coming right speaker , whirring grinding noise coming right side of macbook. right speaker sounds muffled.

it's not hardware problem suspect mine is.

 

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