could someone explain me how VO volume works since iOS 18?

The volume is a little wonky since iOS 18, primarily due to the way Apple restructured "audio ducking". The way it works now, anything at 100% or lower, has to do with VoiceOver volume. Be it VO sounds, VO speech, or a combination of both. More on that later.

Anything above the 100% mark, is exclusively for "audio ducking". As I understand things, you can go from 0% to 100% above all other media when it comes to "audio ducking". Let us say, for example, that you have your volume set to 150%. The 50% in this example, means that when audio ducking is enabled, VoiceOver audio will be 50% louder than all other audio on your device. Period.

When audio ducking is disabled, you can still set these volumes, but anything above 100% is useless. This is where it gets a little wonky.

Now to completely twist your brainmeat. Under VO sounds and haptics, you can adjust the volume here for VoiceOver audio. However, if you uncheck the box to match speech and sound effects, then the volume slider will only adjust the sound effects audio for VoiceOver, and not touch speech volume. It is my belief that this is where a lot of people get confused. Because a lot of people tend to have this unchecked, and they wonder why they cannot adjust VoiceOver speech volume.

On the flipside, if you have the volume rotor enabled, then that volume slider will "only"adjust VoiceOver speech volume, and absolutely nothing else. Again providing that match speech and sounds is unchecked under VoiceOver sounds and haptics.

To summarize, if you want to adjust voice speech volume, make sure you have the volume rotor turned on under settings, accessibility, VoiceOver, rotor, rotor items. If you want to adjust VoiceOver sound effects, go to settings, accessibility, VoiceOver, audio, sounds and haptics. It is totally your choice if you want to match speech and audio volume channels, or leave them separate.

HTH 🙂

PS does your brain hurt yet…? 😇
PPS Edited to appease the grammar police. 😈

FYI, it's audio ducking (with a u), not audio docking (with an o).

Well does not make any difference how it is spell, it is broken. Do not know why apple tried to fix something it was not broken. Nuts.

First. . .: 🐇
1. Go to Settings, Accessibility, VoiceOver, Audio, VoiceOver Sounds & Haptics. Here, check the box to "Match Speech Volume".
2. Double-Tap Back in the upper-right corner, then swipe right until you find "Audio Ducking". Here, Set Audio Ducking to "Off", then swipe to the right until you find a volume slider. Set this to 100%. It should not go above 100% if Ducking is disabled.
3. Double-Tap Back in the upper-right corner, do this twice until you are on the main VoiceOver screen. Now, swipe right until you find the "Rotor" option. Double-Tap here.
4. Here, swipe right until you find "Rotor items". Double-Tap here, then swipe to the right until you find Volume, make sure this is checked. Note: if this has already been done move on to step 5. 😉
5. On any screen at any time, perform your rotor gesture (2 finger rotate clockwise/counter clockwise), until you find "Volume".
6. Swipe up and down until you have VO at your preferred volume.
7. *Very Important* Praise Brian for his awesomeness. . ., even if he cannot spell things properly. 🐰✌️

There is also a podcast on it by Thomas. Check it out.

Something is definitely broken somewhere. Those settings work just fine for me on my iPhone. I wonder what else could be causing your speech volume not to be adjustable? 🙁