Microphones and earphones depend on vibrating diaphragms to convert sound into electrical signals and back to sound again, so you can speak into your earphones to record audio. The audio quality of re-purposed earphones is inferior compared to purpose-built microphones, but they can be improved slightly using audio settings in the computer.
Find the microphone, also known as audio input or line-in, jack on your computer and plug your earphones in to the jack.
Type manage audio devices in the search box and click Manage audio devices in the results to open the Sound control panel.
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Click the Recording tab on the Sound control panel. Continuously blow on or tap your earphones and watch for green bars to react, indicating that your device is picking up the noise. After you confirm that your improvised microphone is listed and working, select it and click Set Default button. Click the OK button, and you are ready to use your earphones or earbuds as a microphone.