I tried 2 tsp of unfiltered cider vinegar in 12 oz. of water 3 times a day because I was losing my voice, or at least finding it difficult to force out a high-pitched rasp, by mid-day every day. It worked immediately, even allowed me to speaker at a lower pitch than normal. But I've been doing it for two weeks, and the effect is wearing off. Maybe I'll try using it on and off.