Drink non-caffeinated beverages such as water, herbal tea, juice, or decaf coffee. Try to drink 6 to 8 8-ounce (240 ml) glasses of water a day. Drinking plenty of fluids will keep the vocal folds in your voice box hydrated so they move easily. Avoid alcohol if you'll be speaking or singing soon because alcohol irritates the mucus lining of the throat. You'll damage your vocal folds over time if you consistently scream or use your voice loudly. The folds can become swollen and red which will make your voice raspy or hoarse. Whispering also damages the vocal cords because they're tightly squeezed. It's hard to give your voice a rest if you're constantly performing, but your voice will become strained and overworked if you don't. It's also important to rest your voice if you start to become sick. To rest your voice, try to talk or sing as little as possible for a few days. Plan on taking "vocal naps" according to your schedule. For example, avoid speaking or singing during your lunch break or on your commute home. Since coughing can harm your vocal folds and cold medication such as decongestants may dry them out, sip water instead. You can also try clearing your voice by gargling salt water for about 30 seconds. Sucking on a cough drop or lozenge is safe for your vocal cords and will stop a cough. If you've rested your raspy voice but it hasn't gotten better after 2 to 3 weeks, schedule an exam with your doctor. If you don't have any other illness and you don't smoke, there may be a problem with some part of your vocal box. The doctor might refer you to an ear, nose and throat doctor for a diagnosis.

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Write a summary of the previous text in Vietnamese:
Dưỡng ẩm cả ngày. Không đẩy giọng vượt quá giới hạn tự nhiên, ví dụ như thì thầm hay la hét. Cho giọng nghỉ ngơi. Uống nước từng ngụm nhỏ hay súc miệng nước muối để làm sạch họng. Liên hệ với bác sĩ nếu tình trạng khản tiếng kéo dài.