Fig. Labelled diagram of larynx

The larynx or the voice box produces sound. Two vocal cords are stretched across the larynx while leaving a small slit between them for the passage of air. When the lungs force air through the slit, the vocal cord vibrates and produces sound. The muscles attached to the vocal cord can make it tight or loose, if it is tight the sound produced is of high frequency and if it is loose then the sound produced is of low frequency.