Diagnosis
This is a classic dynamic range issue. The soundbar is playing the full spectrum of sound (quiet whispers, loud gunshots) as it receives it, compressing the mid-range where dialogue usually lives.
How to Fix It
Your soundbar has a specific mode for this. Grab the remote and press the 'Sound Effect' (or sometimes labeled 'EQ') button. You'll cycle through options like 'Movie', 'Music', 'News', etc. Stop on 'News' or 'Dialogue' mode. This mode is specifically tuned to boost the vocal frequencies and compress the extreme highs and lows, making speech clearer and reducing the jump in volume for loud effects.
If That Didn't Work
Check your source settings. On your TV, go into the audio output settings and see if there's a 'Dynamic Range Compression' or 'Night Mode' option. Turn that ON. This tells the TV to pre-compress the audio signal before sending it to the soundbar, further leveling out the volume. Also, on some TVs, you need to set the audio output to 'PCM' instead of 'Auto' or 'Bitstream' for the soundbar's modes to work correctly with all content.
Heads Up
Using 'News' mode will make movie soundtracks and music sound flatter and less exciting—that's the trade-off. Switch back to 'Movie' or 'Music' mode when you're not watching dialogue-heavy content.