The body is the actual soundbox of the instrument. It amplifies the vibrations of the strings and accounts for the distinctive sound of each instrument. The body consists of the belly (spruce), the ribs and back (both generally made of maple), and the inside structures. The shape of the outline, the type of arch and the various thicknesses, along with the quality of the wood, are responsible for the sound of the instrument. Even though science has frequently tried to find a body shape superior to the gold-standard classical model developed by Amati, Stradivari and Guarnieri by employing various physical calculations and digital simulations, it has not succeeded so far. The body may be subdivided into three sections: The upper bout (including the neck to body transition), the middle bout (also known as the C-bout, the narrowest part of the body to the left and right of the bridge), and the lower bout.