Click the speaker icon in the taskbar and use the dropdown to select a different output device. For per-app routing: go to Settings > System > Sound > Volume mixer to assign specific apps to different output devices (e.g., Zoom to headphones, Spotify to speakers). If a new device doesn't appear in the list, unplug and replug it, or for Bluetooth devices disconnect and reconnect. Windows remembers your last-used device preference, so if you frequently switch between speakers and headphones, it usually auto-switches when you plug in. For HDMI audio (monitors with speakers), select the display name from the output dropdown. If the device appears but has no sound, right-click it in Settings > Sound > set as default, and check that the volume isn't at zero.