When you get sick, especially with a cold or respiratory infection, you often lose your voice or it becomes hoarse because your vocal cords become inflamed and swollen — a condition called laryngitis. This swelling causes your vocal cords to vibrate more slowly and less freely, which changes the pitch and quality of your voice, making it sound deeper, scratchy, or raspy. Mucus buildup from the cold can coat the vocal cords, further preventing smooth vibration. Additionally, coughing and throat clearing during illness strain the vocal cords, making your voice sound tired or shredded.

The swelling adds mass to your vocal cords, lowering their vibration frequency, similar to how thicker guitar strings produce lower notes. This physical change is why your voice sounds deeper or different when you're sick. Typically, this hoarseness lasts about a week or two as the inflammation subsides. Resting your voice, staying hydrated, and keeping the throat moist can help speed healing. If hoarseness lasts more than two to three weeks, it could signal a more serious issue and should be checked by a doctor.