Vocal rest is the process of resting the vocal folds

Vocal folds

The vocal folds, also known commonly as vocal cords, are composed of twin infoldings of mucous membrane stretched horizontally across the larynx...

 by not speaking or singing, which typically follows vocal disorders or viral infections which cause hoarseness in the voice, such as the common cold

Common cold

The common cold is a viral infectious disease of the upper respiratory system, caused primarily by rhinoviruses and coronaviruses. Common symptoms include a cough, sore throat, runny nose, and fever...

 or influenza

Influenza

Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...

. The purpose of vocal rest is to hasten recovery time. It is believed that vocal rest, along with rehydration, will significantly decrease recovery time after a cold. It is generally believed, however, that if one needs to communicate one should speak and not whisper. The reasons for this differ; some believe that whispering merely does not allow the voice to rest and may have a dehydrating effect, while others hold that whispering can cause additional stress to the larynx

Larynx

The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...

.