The sound window is an important part to adjust the sound quality of the Erhu sound.

1. Strengthen the reflection of sound waves to gather sound energy, which is conducive to the vibration resonance of the erhu air column. Filter high-order disharmonious sound waves, which is beneficial to adjust the timbre and sound quality of the erhu.

2. Now the sound window occupies about 30% of the opening area of the rear opening (the patterns are basically evenly distributed), adjust the air column frequency and frequency response range of the erhu drum (the natural frequency of the air column with sound window is lower than that of the piano without sound window) cylinder).

3. The sound of erhu with sound window is more concentrated, pure and mellow. But the higher harmonics are attenuated and the volume is moderate.

The sound of the erhu without the sound window is relatively loud, which is easy to cause the sound phenomenon of empty and scattered erhu sound. The sound is concentrated and rounded, and the sound quality is slightly poor.

Excerpted from "Summary of Several Questions in Erhu Sound Test" on the experiment (part) of the sound window of the erhu sound window, mainly to understand the influence of the structure of the sound window on the volume and timbre, and to further find the best sound window . Its opening area should account for how much of the total area.

1. Use a drill to drill three holes each time on a sound window panel without openings. The diameter of the drill is 0.55 cm, and the area of the three holes accounts for about 2.3% of the total area of the sound window (the total area of the sound window is : 30.6 cm²).

2. During measurement, adjust the position of the microphone until the sound intensities of the three tones of d1; a1; a2 are the same (the reading of the voltage is 500 mV).

3. The measurement result of the inner string d1 (293.66 Hz) is: when the sound window is fully closed, the voltage reading is: 250 mV; when the sound window is fully opened: 500 mV; when the sound window is opened with 15 holes, that is, the area of the hole accounts for the sound When the total area of the window is 11.5%, the sound intensity is the same as when it is fully open.

4. The measurement result of the outer string a1 (440 Hz) is: when the sound window is fully closed: 180 mV; when it is fully open: 500 mV; and when the sound window is opened with 33 holes and 36 holes, the The volume reaches a maximum of 650 mV at 25.3% and 27.6% of the total area of the sound window.

5. The measurement result of the outer string a2 (880 Hz) is: when the sound window is fully closed: 150 mV; when it is fully open, it is 500 mV; When the area is 27.6%, 29.9%, and 32.2%, the volume reaches 250 mV, which is lower than the volume when it is fully turned on.

6. From the analysis of measurement records, if the opening area of the sound window is appropriate, not only will it not hinder the volume, but it will increase the volume (referring to a certain frequency range).

7. The influence of the sound window on the timbre, due to the limited instrument conditions, no systematic data has been obtained, but it is certain that the sound window can change the timbre (it can be clearly heard by the subjective hearing of the human ear).

Therefore, since the sound window affects the timbre, we can use the sound window to adjust the timbre according to different wishes.

8. Using the sound window to adjust the sound of the erhu is only one aspect of determining the sound of the erhu. It cannot be assumed that the sound of the entire erhu can be adjusted with the sound window. In addition to the sound window, the timbre of the erhu also depends on factors such as strings, yardsticks, membranes, and the structure and material quality of the piano barrel.

9. The sound window can beautify the appearance of the erhu piano, which has always been recognized by people. A sound window with a good pattern will add a lot of brilliance to the erhu, but because the opening area of the sound window is closely related to the sound effect, it is hoped that when designing the sound window, in addition to considering the aesthetic appearance, it is also necessary to pay attention to the consideration of sound and sound. tone effect.

The role of the sound window of the erhu piano

a. Increase or decrease the volume to change the resonance characteristics of the resonator.

b. Adjust the tone.

c. Beautify the appearance. According to preliminary experiments, the area occupied by the sound window preferably accounts for about 30% of the total area of the rear opening.