I've never heard of using vinegar as a way to "lose your voice." There are some benefits to vinegar. So far as the throat goes:
"It kills bacteria. Vinegar is thought to have antibacterial properties that can fight the infection behind a sore throat."
You can read about other benefits, like heart health and blood sugar levels here:
http://www.doctoroz.com/article/people-are-drinking-vinegar-should-you?page=1
Whoever said you'd lose your voice has lost their mind. (joke) ; )