I have had problems with low volume sound coming from Brave. I even experienced the same from other web browsers. But it began with Brave. I got an ASUS TUF Gaming F15 with Nvidia RTX 3050, Intel Core 5 11th Gen, Windows 11.
Re-installing Windows didn´t solve.
The only way I found solution was by going to Nvidia GeForce Experience App, and then choosing Studio driver instead of Gaming driver. Then The app installed the latest Studio driver for my Nvidia card and voila, the sound increased to normal volume from Brave.
I don´t know if this is going to last as a definitive solution for my case, but if it happens again I plan to uninstall sound drivers from Nvidia and try again.
Hope this is hopeful for the Nvidia / Brave users with problems with the sound level.