Let's take a look at the following discussion:

The noise and "wolf sound" in erhu performance

"wolf sound" exist in the whole family of stringed instruments, but the vibration of the wooden board is smaller than the wolf sound produced by the vibration of the leather membrane and is easy to control. Wolf sound is a difficult problem to solve in erhu performance. Nowadays, the way to suppress the wolf sound of erhu is to put a sponge under the bridge. Although this method is effective, it has certain influence on the timbre and volume of erhu.

I have done some experiments on the suppression of the wolf sound in Erhu, which proved that the tightness of the Erhu's leather membrane, the strength and angle of the bow, and the proper selection of the piano and horse all have influences on the generation and suppression of the wolf sound.

It is necessary to mention here that the definition of wolf sound is not listed in Cihai and Encyclopedia of China, Volume of Physics, because it is too specialized. In my opinion, beginners of erhu are unlikely to encounter wolf sounds, but noise. It is precisely because the definition of wolf sound is unclear that noise is mistaken for wolf sound.

actually, there is a difference between wolf sound and noise. In my opinion, the difference lies in the fact that wolf sounds mostly appear near half of the string, while noise may appear anywhere in the string. Secondly, the timbre of wolf sound is similar to overtone, but it is obviously different from overtone: overtone means that fingers must be pressed in half, one third, one quarter of the string, and it can be played with a gentle bow or plucking the string, with stable pitch and clear and transparent timbre. Wolf sound is the sound produced by pressing the finger on the string, the phoneme is mostly in half of the string, the pitch is not very stable, and the timbre is dry and heavy. It can be seen that the general erhu beginners encounter noise, but it is unlikely to be wolf sound. The main reason is that this noise will not only appear near half of the string, but also be generated at any handle, especially at the lower handle. Then, the difficulty of controlling noise is very different from that of wolf sound: if you can control the wolf sound, you will certainly be able to control the noise, but those who can control the noise may not be able to control the wolf sound well.

Wolf sounds exist on all stringed instruments, which is familiar to all people who play stringed instruments, and no physicist does not know it. Then why didn't the Encyclopedia of China Physics Volume accept this title? There is some truth in thinking about it. There are opposing musical sounds and noises, as well as real sounds and overtones, so this wolf sound is obviously not musical sounds or overtones. Is it noise? Neither does it. How do physicists define it? I suspect that the timbre of "Dong Xiao" imitated by blind musician Sun Wenming in "The Sound of Xiao at Night" is probably the alienation of this "wolf sound". Mr. Sun Wenming was a part-time teacher in the Department of Folk Music of Shanghai Conservatory of Music. I majored in flute, but Mr. Sun's erhu art failed to attract the author's attention. Unfortunately, none of his descendants can master the charm of Mr. Sun's performance now. The author intends to discuss this issue in "Sun Wenming Erhu Playing Art". Here, we will discuss the control of erhu noise. Controlling the noise is not far from controlling the wolf sound.

The noise on the erhu is caused not only by improper production and accessories of the erhu, but also by the mismatch between the speed of carrying the bow and the strength of pressing the bow. For beginners, we should remember this point: besides the speed of bow transport, the strength of bow transport must match the strength of bow transport, otherwise it is very easy to produce noise (not wolf sound). This is the reason why beginners often make "creak, creak" noise when playing the erhu no matter how good it is. At this time, it should be noted that the slower the bow is transported, the smaller the strength of the bow to press the string; When the string is pressed hard, the bow must be pushed and pulled quickly. In addition, when playing, the strength of lifting and closing the bow is small, and the change of strength and speed in the whole process of carrying the bow is olive-shaped: the speed of carrying the bow at both ends is slow, the strength of pressing the string is small, the strength in the middle is large, and the speed of carrying the bow is fast; The stronger you play, the greater the amplitude ratio between the two ends and the middle. It's just that the process from weak to strong is extremely short, but it can't be cancelled.

except that the relationship between the speed and the strength of the bow is extremely important? Besides mastering the cultivated land, I have proved through practical verification that the direction of carrying the bow (that is, the angle between the bow and the piano) also has enough influence on the noise and timbre. Every erhu has an optimal included angle, and this included angle can be slightly changed by the slight movement of the position of the bridge and horse. I suspect that Mr. Gan Tao took advantage of this relationship to improve the timbre of erhu with the help of carrying a bow. I have seen all Mr. Gan Tao's expositions on erhu, but unfortunately Mr. Gan has never talked about the wolf sound. The author has been staying in Shanghai since he was admitted to the folk music department of Shanghai Conservatory of Music in 1959, and he has been out of the music industry for decades, and his major is not right, so he has no intention to ask about it. Now that Mr. Gan has passed away, I have to find out for myself.

I'm afraid the noise and wolf sound on the erhu are also influenced by the skin (snake skin). What is the basis? You see, when making erhu, the tension around the drum is always required to be equal, whether it is round, hexagonal or octagonal. But after the bridge is suppressed by the tension of the strings, will the tension around it be equal? At this time, the tension around the membrane is not equal, so the vibration of the membrane cannot be balanced. How can it not produce noise and wolf sound? People often put a sponge under the bridge, and it is a fact that noise and wolf sound will be suppressed to some extent.

In order to improve the sound quality of erhu, I have done a detailed study on the Qin Ma. It is necessary to use extraordinary thinking to solve this problem. The author once made a horse with colored wood for a noisy huqin. As a result, the sound quality has been greatly improved-there is no sponge under the horse, so long as the bow is handled carefully, the third one is not noisy. This shows that Qin Ma plays an important role in erhu timbre. It should be noted that the production of this horse took three days, and the price seems to be a little too expensive. But if we continue to study, the second and third horses will not need so much time, right?

From the above facts, it can be inferred that during the performance, not only the section below the weight of the string but above the bridge is vibrating, but also the string at the lower end of the bridge, and the vibration of the string at the lower end of the bridge deteriorates the sound quality of the erhu. I have achieved the purpose of improving the sound quality of the erhu by choosing the height and base of the bridge. In addition, I tilted the bridge slightly upward to reduce the pressure on the strings at the lower end of the bridge, and tied the two strings at the lower end of the bridge with silk or thread to restrain the vibration of this short string, which also further improved the sound quality of the erhu.