Sounds very much like you don’t have the right sound settings activated in your TV’s settings. The Arc Ultra can only play the sound it is sent - it doesn’t do anything with it.

What sound settings do you have set on the TV?

If you have an external device connected like a cable box or Apple TV or Firestick, you should have Passthrough enabled in the TV sound settings so the TV does not process sound before it is sent to the soundbar.

I and/or others can perhaps advise more if you let us know the TV model and the sound settings you have set currently.

Hi, let me explain better, overall the volume behaves well... I mean that in some particular cases, with some YouTube songs or with some movies on TV, i have to go over half (50) of the maximum volume of the soundbar to hear well... It would be nice to have a fairly high volume even at 40... For example, if i watch the movie "Dune", the volume is already high at 30 or 40 and that's fine. However, i don't have any connections to an external device and so i don't use the pass-through. These are the specifications of my TV and settings:

• Samsung Neoqled QN90BA
• Audio output: Hdmi e-Arc
• Hdmi e-Arc mode: Auto
• Digital output audio format: Auto
• Dolby Atmos: On

Sonos App:

• Trueplay: Done
• EQ: 0, +10, volume On
• Audio Sub: +2
• Audio height: +10
• Volume limit: Off
• 3D music: On
• Speech enhancement: Off
• Night sound: Off

It’s probably already set correctly and in general, it would be good to also reach volume 40 and already hear high... Without reaching up to 60-70 in some cases…
That's all...

As I understand it, there is no “standard” volume level for film makers or program broadcasters to meet. Thus there can be differences in the relative volume of one program or film to another. This is not a “fault” in Sonos devices; nor, I believe, is it something Sonos can fix in the app. 

I agree with ​@nik9669a 

However, there’s a software trick in some devices called Volume Leveling or Sound Check used by Apple. It’s mainly used for music tracks or AV broadcasts (by some Tv’s) to lower commercials.

That said whether or not Sonos would invest in software development to implement similar technology in its soundbars IMO would be a major undertaking if not unprofitable. Sound bars typically take what is sent to them and delivers it to the audience unabridged. Sonos, however does allow for speech enhancement.

What follows is an AI Generated explanation. Take from it what you will. Although I find it to be one of the better AI generated explanations.

Volume leveling, also known as automatic volume control, is a feature that automatically adjusts the volume of audio content to maintain a consistent listening experience, regardless of the source or content type. It prevents drastic volume changes when switching between different audio sources, like between a movie and a commercial, or when playing tracks from different albums or playlists. 

Here's a more detailed explanation:

How it works:

• Compression and Normalization:

  . 

  It often involves a form of compression or normalization to bring the overall volume to a target level. 

• ReplayGain:

  . 

  Some systems use algorithms like ReplayGain to analyze audio files and calculate volume adjustments, which are then applied during playback. 

• Per-Track or Per-Album Adjustment:

  . 

  Volume leveling can be applied to individual tracks within a playlist or to entire albums, preserving the intended dynamic range between tracks on the same album. 

• Dynamic Range Reduction:

  . 

  Volume leveling analyzes the audio signal and reduces the dynamic range, which is the difference between the loudest and quietest parts of the sound. 

Benefits:

• Consistent Listening Experience:

  Prevents sudden jumps in volume when switching between different audio sources. 

• Reduced Need for Manual Adjustment:

  Users don't need to constantly adjust the volume when listening to various types of content. 

• Improved Clarity:

  In some cases, it can enhance dialogue clarity and make it easier to hear quieter sounds. 

• More Enjoyable Experience:

  Overall, it creates a more comfortable and consistent listening experience, especially when switching between content with varying loudness levels. 

Examples:

• TVs:

  . 

  Many TVs have an "auto volume" or "volume leveling" feature that balances the volume between programs and commercials. 

• Streaming Devices:

  . 

  Roku and other streaming devices offer volume leveling options to maintain a consistent volume across different apps and content. 

• Audio Players:

  . 

  Music players like MediaMonkey and Roon offer volume leveling features to ensure a consistent listening experience when playing music from different sources or albums. 

• Audio Software:

  . 

  Volume leveling is also a feature in audio editing software to help create a more balanced and professional-sounding mix. 

​@MicheleM24 

On Samsung TVs, I believe “Pass-Through” simply means “send the raw encoded audio (Dolby Digital, DD+, Atmos) unchanged over HDMI ARC/eARC - so in fact, even if you aren’t using an external device, it might be worth setting it as Pass-through (provided that is presented as an option while you are playing YouTube videos and also other content, like movies), to see if it helps. 

Also, on your TV, ensure you have Auto Volume enabled:

Settings → Sound → Expert Settings → Auto Volume → On

(OR if you have it enabled already, try it without!)

Samsung state to have Auto Volume Off when using a soundbar.

“You'll need to turn Auto Volume off if you want to control the volume of the TV through a soundbar or external speakers. If you use the Auto Volume function with external speakers, the speaker's volume control may not function properly.”

https://www.samsung.com/au/support/tv-audio-video/use-auto-volume-on-a-samsung-tv/

​@Mr. T 

Thanks!