Intermittent audio fluctuation is a common external source issue seen with incoming broadcast signal, and is not related to the internal TV components.
Samsung states there are various audio settings that could help assist with leveling out the different audio levels being received from each broadcast program when scenes either change or broadcast changes from commercial to commercial (not all incoming broadcast signal is created with the same audio level or quality which will present a fluctuation in audio)
1. Go to settings, select sound, select expert settings , select HDMI Input Audio Format, change 'Bitstream' to 'PCM'
2. Go to audio settings options of your TV and locate Auto Volume adjustment option (AVL)
3. Go to audio settings and update 'surround sound' to 'stereo'
These steps will help improve the audio fluctuation issue, although the root cause of the issue is being caused from the incoming broadcast audio signal in which not all programs are rendered the same (ie. TV is set at a constant 40 lvl volume, but broadcast show intermittently has softer audio than the programmed commercials -or- between different cut scenes)
Note: There are features within the TV such as enabling the audio settings "SRS" which will help improve the fluctuations, but will not resolve them entirely (see below for reason)
Here is a link to an article explaining why commercials are louder than normal broadcast programs:
"The Federal Communications Commission does not specifically regulate the volume of TV programs or TV commercials. However, broadcasters are required to have equipment that limits the peak power they can use to send out their audio and video signals. That means the loudest TV commercial will never be any louder than the loudest part of any TV program.
A TV program has a mix of audio levels. There are loud parts and soft parts. Nuance is used to build the dramatic effect.
Most advertisers don’t want nuance. They want to grab your attention. To do that, the audio track is electronically processed to make every part of it as loud as possible within legal limits. “Nothing is allowed to be subtle,” says Brian Dooley, Editor-At-Large for CNET.com. “Everything is loud – the voices, the music and the sound effects.”
Spencer Critchley, writing in Digital Audio last month, explained it this way: “The peak levels of commercials are no higher than the peak levels of program content. But the average level is way, way higher, and that’s the level your ears care about. If someone sets off a camera flash every now and then it’s one thing; if they aim a steady spot light into your eyes it’s another, even if the peak brightness is no higher.”