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

Although there are many sharp intervals, most notes are generally close enough to the resonance being excited.  

The low-end within this range is quite intriguing: several notes of the violin bass (196 Hz G and 208 Hz G #) fall to the edge of the frequency response envelope.  

But our ears can infer these notes from the high-order harmonics they contain.  

In addition, investing money in home audio equipment with a response frequency of over 15 kHz will not improve the sound of the violin!  

Each note on the violin has its own specific timbre.  

The fundamental frequency and its harmonics will be amplified at different positions in the response spectrum.  

The waveform of the empty string sound on the E string of a violin played with a bow is shown in the upper right image, which corresponds to the harmonic series.  

The fifth and sixth harmonics of this note are three times and two times greater than the fundamental wave.  

Its seemingly rapid oscillation is the result of these harmonics, which slowly interfere with each other, and the (slow) overall envelope modulation is at the fundamental frequency of 660 Hz.  

Yes, we heard the note E, but we quickly identified it as coming from the violin.  

It is the presence of these harmonics that enables us to identify the source of sound.