[McDiams]

Hi ! Can you tell me How to reduce speechchat voice volume please ?

Ty ^^

[Gallaway PT]

What I do to reduce the TTS voice volume is on the windows mixer and adjust the level of the audio you want.

P.S- sorry for my bad english

[@HypoSyringe]

What I do to reduce the TTS voice volume is on the windows mixer and adjust the level of the audio you want.

P.S- sorry for my bad english

This is a poor workaround, because it requires adjusting a global control for app-specific behavior.  Solutions address the root issue, they never focus solely on the symptoms.  For example, your workaround would prove disruptive to users who stream music or similar audio integrations from other tabs.

As posted earlier:

Microsoft Edge (Chromium): Speech Chat works well, and we really need a volume control for this utility.

+1 ...because it's 2021, and volume is an HTML 5 element.  Please let me know if you can use developer help.    ♥

HTML Audio/Video DOM volume Property (w3schools.com)

HTMLMediaElement.volume - Web APIs | MDN (mozilla.org)

[Gruntled]

Any updated on this?  The volume is really loud and I don't want to lower the system volume then I can't hear the game when I'm streaming.

[IvanDSaboya]

this should work . I modified the pitch and speed using this codes before the text I wanted to modify. 
howeverIi didnt achieve to work in the $username$ field, but just in the $message$.

try this example as a message first:

 <volume level="100"> hey how is everything <volume level="50"> hey how is everything 

see more here: (not everything works, but play with it.)

XML TTS Tutorial (SAPI 5.3) | Microsoft Learn