The image at the top of this page is a cross-sectional view of the violin at the position of the instrument code.  

The body of the qin is essentially an empty thin-walled box.  

Its panel, or "speaker," is usually two to three millimeters thick, while the back panel, with a similar thickness around its periphery, can be 5 millimeters or thicker near the center.   

The surrounding wall is about one millimeter thick, except for the reinforcing adhesive of the speaker and the backing strip.  

At the foot of the keyboard, corresponding to the position of the E-string, a small wooden pillar mechanically connects the panel and backboard.  

There is a longitudinal reinforcing rib under the other foot of the piano, called the bass beam  

These two components not only have a significant impact on sound production, but are also crucial structurally, as the piano code, due to the tension of its four strings, exerts a downward force of approximately twenty pounds.  

The body of a violin is essentially a resonator, driven by the vibrations of the piano code caused by the motion of the Helmholtz type strings mentioned above.  

However, only frequencies that roughly match the natural resonance frequency in this system will result in any noticeable sound.  

A pure sine wave (without harmonics) vibration code can be used to measure its frequency response.  

This can be achieved by connecting a lightweight acoustic transducer to the piano code and scanning its frequency while maintaining its driving amplitude unchanged.  

The corresponding sound output can be recorded (see the opposite page of the left image).  

Although the details of the data in this figure are quite complex, some overall features are easy to understand.  

The first to appear is a resonance region that extends from approximately 200 Hz to around 15 kHz.