Simulator at http://sakshat.amrita.ac.in/VirtualLab/
An A.C sonometer is an apparatus by which the transverse vibrations of strings can be studied. On the box are two fixed bridges, near the ends, and at one end is a pulley. A string, often a steel wire, is fastened at one end, run over the bridges and the pulley, and attached to a weight holder hanging below the pulley. Weights can be added to the holder to produce tension in the wire, and a third, movable bridge, can be placed under it to change the length of the vibrating section of the string.