Gnome 46 port of the extension: https://extensions.gnome.org/extension/6027/mic-monitor/
Toggle microphone monitoring from the top panel
The Mic Monitor Gnome extension adds a microphone icon to your Gnome desktop's status area. Clicking this icon lets you hear your microphone input through your speakers or headphones, allowing for effortless toggling of real time monitoring. Its lightweight design and easy to use functionality make it perfect for users who frequently test their microphone settings or want live feedback.