Plug in or connect your headphones, then open an online speaker test. The test plays tones to the left and right channels separately so you can verify both drivers work. Check that audio is clear without crackling, buzzing, or distortion. If only one side plays, check the headphone cable for damage, try a different audio port, and test the headphones on another device to rule out hardware failure. For Bluetooth headphones, make sure they're selected as the output device in your OS settings. On Windows: Settings > Sound > Output > select your headphones. On Mac: System Settings > Sound > Output. If the headphones sound tinny or lack bass compared to speakers, check for audio enhancement settings or equalizer presets in your OS or headphone app that might need adjusting.