How to play "sound"
The sound environment of the sound room determines the sound quality of the sound to a large extent. The hard equipment is good, the listening environment is bad, and it is difficult to have good results, but this is often overlooked. The acoustic characteristics of the room are largely related to the interior and room layout. The shape and size of the ideal listening room should be in the golden ratio, and the three sizes (length, width, height) are not integral multiples, so that the influence of standing waves in the room is reduced, and the sense of hearing is improved. Secondly, it is necessary to make sound insulation, so that the inside and outside of the room will not interfere, and the sound will spread, and appropriate sound absorption should be provided to avoid repeated reflection of sound waves, which will stimulate the sound interference of some natural frequencies (normal frequency), resulting in acoustic dyeing. Each sound space will have its own different sound characteristics; each sound space will have its own unique sound characteristics because of different space size, proportion and interior decoration. In other words, there are very few sounds in two acoustic spaces that sound the same. Therefore, even if the same audio equipment is used, different sound characteristics are generated as long as the sound space is different. "Reverberation" for room acoustics In fact, reverberation (reverberation, also known as reverberation) refers to the phenomenon that the sound formed by repeated reflections from walls, ceilings, floors, furniture and people in the room persists and gradually decays. It is different from echo, which is not a smooth decay, but a sudden return of sound. For the most important indicator of room acoustics, the first is the reverberation time, which is the time required for the attenuation of sound energy to drop to one millionth of the original intensity (60db). For a certain room, the reverberation time mainly depends on In the sound absorption process. For the reverberation time of the Hi-Fi listening room, it can take 0.4~0.5 seconds. The reverberation time is moderate, the music is full, the voice is full, the reverberation time is longer, the sound is more lively and rich, but when it is too long, the sound is easy to be ambiguous, the speech intelligibility is degraded, the tone lacks strength and rhythm, and the reverberation time is too short. The sound is harder, lacks anger, and there is no reverberation sound (such as outdoor) often has a sense of dullness, so it is necessary to have an appropriate reverberation in an audio room. Why should the room absorb sound? If there is no sound absorption in the room, the room itself does not absorb sound. What kind of scene will it be? That is, once the sound is emitted, it will continue to reflect, and the sounds that are emitted before and after will be mixed. For example, when a language broadcast is played in such a room, the first word sound is still ringing when the second word sound appears, and the sound of the first two words is still ringing at the same time when the third word sound appears. In addition, it will evoke resonance sounds of different frequencies, so whether it is language or music, we will be completely indistinguishable (except for the first sound), let alone appreciate it, and only hear a noise! Of course, these are just imaginations in an extreme situation. In fact, since the walls, the air, and the human body absorb sound energy, the reflected sound always disappears gradually. However, through such imagination, we can further understand the importance of sound absorption in the room. How to create an optimal sound-absorbing environment In general, most of the places we live in are brick walls. This traditional brick wall, especially after being painted, is highly reflective of high, medium and low frequencies, especially high frequencies; therefore, "appropriate" sound absorption is a top priority. The so-called appropriate is not too much, if the sound is sucked dry and has no charm, it is counterproductive. In principle, if you want to pursue the true original sound during playback, you should not be disturbed by the reflected sound, but only listen to the direct sound; thus you need a complete sound-absorbing environment, and this is the general living environment. In terms of it, it is often impossible, so it is usually a partial sound absorption of the room, and some reflection sound is reserved for use. The sound absorption and diffusion of the room in the room are rigid walls that are parallel to each other, and the height is below 3M. For a room of about 16M square, it is easy to generate resonance in the low frequency band, so that the sound of a certain frequency is abnormally strengthened. It causes the bass roar, which seriously affects the quality of the replay sound. This kind of acoustic dyeing is the most common problem in the home listening room. This kind of room resonance also makes the sound distribution of some frequencies (mainly low frequency) very uneven in space. The frequency at which the possibility of acoustic dyeing is greatest is 100 to 175 Hz, and around 250 Hz. A side benefit of how the doors and windows of the room are soundproofed is that the sound insulation of the room is improved, allowing us to enjoy the music in a better environment. In addition to the recording room, the room listening to music also requires a fairly low noise level - 30db! What is this concept? The sound level of the general conversation is around 60db, so the noise level of 30db is a very quiet environment. In such an environment, you can clearly hear the faint snoring of the quartz clock on the wall, even the sound of a steel needle landing, and only in this quiet environment, it is possible to go deep into the details of the music and hear the real Good music, especially some symphonic music with a wide dynamic range. It is a pity that most people living in the city today do not have such a blessing. The indoor noise is usually above 40db. At home on the roadside, they are often more affected by the noise of sound levels above 60db. Therefore, in order to listen to music, but also for physical and mental health, we must pay attention to reduce noise. As a room for the listening room, it is better to choose it properly. It is not suitable to be on the side of the road. How to absorb sound on the four walls, floors and ceilings of the room. How to handle the wall treatment? How to absorb the sound on the four walls? Let's talk about the two side walls; here is the first reflection sound from the horn. Why do you want to absorb the first reflection? If the first reflection is too much, it will cause the positioning to be unclear, and the sound will sound too noisy, so be sure to suck. You don't have to do a sound-absorbing process on the entire wall, as long as it is about the middle of the speaker and listening position. The area of ​​this sound absorption must be at least 1 to 1.5 meters wide and two thirds of the height of the wall. In terms of materials, you can't absorb sound with a cloth as thin as a general curtain, because the effect is not good, at least the thickness of the terry cloth can be used; and if you want to hang on the side wall like a curtain, please pay attention to wrinkles, just like curtains. The same as the processing. The rear wall of the processing horn must be strong and hard so that it does not absorb the low frequency, and it will double the power of the amplifier. If you nail the cavity in the back wall of the horn, no matter how thick the plank or sheet is, there is absolutely no negative effect, and there is no positive effect. The most common negative effects are that the sound is illusory, the low frequency is not enough, not strong and low, and not clean. The processing of the back wall corner is between the opposite walls. Due to the multiple reflections of the sound, standing waves are generated. When the standing wave occurs, resonance can occur. The frequency depends on the distance between the walls. It is a resonator. The place where the standing waves cause the most sound staining in the room is on the two corners of the back wall of the speaker, which reflects the unclean bass. This effect is called room booming. This low frequency standing wave is a common acoustic defect that causes the bass clarity to drop and requires careful handling. A good way to control the reflection of standing waves is to use the bookshelf filled with books, the irregular shape of the books and the less strong sound absorption to scatter the sound waves, thus reducing the effects of sound reflection. You may be confused when you listen to the wall behind the position. I have already sat on the back wall. What can I do with this wall? Honestly, sitting against the back wall is the worst, because the sound will be awkward at this time, unless your system is not low enough, you must be close to the back wall to enhance the low frequency. In general, your seat will be at least half a meter away from the back wall, so that the sound will be relatively clean. Second, the floor and ceiling treatment of the poor treatment of the floor will make the low-frequency reflection too strong, if the living room inside, has been laid with wooden floor, it is ideal, its sound absorption characteristics are more uniform. If it is a hard floor such as glazed brick or stone, it should be covered with a thick carpet that can be moved, because the sound absorption effect of the thick carpet is enough. If you only want to use a small thin carpet, it will only have a decorative effect, but no substantial sound absorption. effect. As long as it is a thick carpet and wool, you can buy cheaper machine fabrics. In order to facilitate walking, the area of ​​the carpet can also be limited between the speaker and the listening position. The key is to have a thickness, which can be achieved by using a cardboard, a board, a fiberboard, etc. underneath. The ceiling is treated on the ground, and we can focus on only a carpet, and on the ceiling, there are more patterns. Please note that it is a pity that you should never leave an empty ceiling. We eliminate tooling costs and save customers money by offering hundreds
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The sound from the sound source in the room is transmitted to the listener's ear through six channels: the direct sound from the speaker, the reflection from the floor, the reflection from the ceiling, the reflection from the back wall of the speaker, and the walls on both sides. The reflected sound, the reflection of the wall behind the listener. As long as any reflection condition of the sound wave is changed, the sound changes. It can be seen that sound waves, like light waves, reflect light to the mirror. The walls, floors and ceilings of the house will reflect the sound. Unfortunately, the sound waves cannot be seen. This phenomenon is often overlooked. Sounds from a certain part of the house will spread in waves and reach the listening position from countless ways. Due to the existence of the reflection phenomenon, in the listening position, what we actually hear is not the sound that is purely emitted by the horn. It is the direct sound of the horn and the effect of superimposing the reflected sounds. So, what is the effect of this superposition? The concept of "reverberation time" is more common and important. It refers to the time course in which the sound waves are gradually reflected and the energy is gradually reduced after the direct sound. The application of the word "mixed" here is very image, because the sound heard somewhere indoors is not a single one, but a chaos from all directions. The reflected sound is generally referred to as a reverberant sound. 
Fortunately, we are not living in an environment that does not absorb sound at all, otherwise it is really unimaginable! Although the real room can absorb some sound energy, it is often not ideal. If a good audio equipment is purchased, the standard Hi-Fi sound is emitted, but it is a pity that the sound absorption characteristics of the sound room are not good, the reverberation and resonance that should not be there, and the original sound is seriously distorted. Yeah! Therefore, the real fever family should also be the pursuit of reasonable sound absorption in the room.
Usually, the number of sound absorbing materials in the room is always too small, which means that the best listening environment is produced in a messy room. Let's talk about this kind of non-quantitative sound absorbing treatment. law. Hanging sound absorbers around the walls: all kinds of soft materials, such as cotton, hemp, silk, wool, or other fiber-like fabrics, wall hangings, etc. are available. For example, hanging a 1mm thick velvet (or other similar texture) curtain on the wall, it can only absorb about 1/5 of the sound energy (in the middle and high frequency bands, the low frequency is worse), and the rest is reflected out, so It is not possible to eliminate the symmetry of the low frequency; the solution is: do not stick the curtain cloth to the wall, leave a distance of about 10cm (add other sound absorption in the gap); discount the curtain fabric or multi-layer suspension, and then use the low-frequency sound absorption A large soft sofa with good characteristics can achieve certain effects. Generally, in a playback environment with poor sound absorption characteristics, it is not suitable to use that kind of hardwood sofa.
The sound absorbing properties of various materials will vary, and it is best to use them selectively. The goal is to achieve symmetrical and balanced absorption of high, medium and low frequencies. Sometimes, you can also combine the characteristics and hobbies of your own equipment to achieve unbalanced absorption. If someone prefers the bass and the output power of the amplifier used is not large enough, or the low-frequency response of the speaker is not good, it can be appropriately reduced. Low frequency absorption. Although this is not a high-fidelity choice in the general sense, it can still be used when there is some defect in the audio equipment itself.
Acoustic treatment of the room, focusing on the side walls and ceiling. In principle, the treatment of indoor sound waves should be more diffuse than absorption. The purpose is to reduce the resonance intensity. To prevent excessive use of sound absorbing materials, the reverberation time of the room is too short (<0.3 seconds), and the sound is not smooth. For the wall behind the speaker, it is best not to have a large piece of sound-absorbing material, usually no need to deal with it, brick wall or cement wall will make the sound full and full of vitality.
The side wall can evenly and appropriately set some sound absorption and diffusion materials. For example, a thick wool blanket is an excellent full-frequency sound absorbing object, and the thin carpet and the tapestry only absorb the medium and high frequency. The wooden doorless bookcase is a good sound diffuser, which is good for adjusting the low frequency. In addition, furniture such as tables, chairs, mattresses, and sofas can adjust the sound transmission and can be used as an acoustic treatment. In the sound absorbing process, the lower half of the wall is more important than the upper half, and can be treated with a resonant sound absorbing structure such as a perforated plate or a thin plate.
Thin carpets, curtains, tapestries, etc., mainly absorb the middle and high frequencies, and have low absorption effect on low frequencies. Too much use will cause the reverberation time of the medium and high frequency sounds in the room to be short. The lack of color is not bright enough. The wooden low cabinet can effectively absorb the low frequency, but there should be a proper space between the wall and the wall, and if necessary, a sound absorbing material should be placed between them. But remember not to nail a large number of splints to the wall, and do not apply a large number of sound-absorbing blankets and curtains in the room; otherwise, because the high-frequency is absorbed a lot, the sound will be sluggish, the details will be reduced, and the volume will be reduced.
In order to make the sound spread well and not get together to become a harmful standing wave, it is necessary to change the course of the sound of the frequency. It should be noted that the board or device used to diffuse the sound must have a large enough size, at least Half of the sound wavelength, otherwise it is not enough to achieve the effect of changing the sound wave travel, such as the medium and low frequency requirements of 100Hz, should exceed 3.4m or 1.7m; the intermediate frequency requirement of 1000Hz should exceed 34cm or 17cm. It can be seen that the most practical method for the harmful effects of standing waves is to move the speaker or the listening position, or to use the lattice structure of the bookshelf and the louver to achieve the effect of sound wave diffusion.
The overhead wooden floor absorbs low frequencies and prevents excessive low frequency levels when the room is small. If the low frequency of the sound in the room makes a roar, a thick wool carpet can be laid near the reflection point of the floor near reflection.
When the sound is harsh and the low-frequency sense is thin and not enough. When the volume is loud and noisy, the sound-absorbing material covering treatment should be set at the reflection point of the near-side reflected sound on both sides of the wall. If the sound is found to be too dry, the carpet should be removed first. A sound-absorbing block or cloth cushion made of fiberglass is placed in the corner of the room for final adjustment of the reverberation time.
The sound insulation of the general room is not ideal. The ideal sound insulation of the listening room is difficult for the average family. Doors, windows, walls, floors and ceilings will pass in the outdoor sound and will be indoors. The sound spreads, especially to the low frequencies, and spreads farther. Doors and windows are weak links of sound insulation. They are usually used for sound insulation and only doors and windows. The windows are made into double layers. On the existing windows, a layer of good sealing is added. Window, which is the least costly and effective method; for the sound insulation of the door, a double door with a cavity can be adopted, the panel is made of plywood, and the sound absorbing cotton is laid in the middle. The sound insulation of the wall is related to its thickness and surface treatment. It is the most effective and economical sound insulation method by evenly coating a layer of cement on both sides of the built brick wall to increase the density of the surface. The gaps and holes in the leaking sound also have an effect on the sound insulation of the room, especially for the sound insulation of the intermediate frequency part, which must be sealed. Due to the channel relationship, the living room affects the balance of the indoor sound field. Sound absorption materials can be added to the asymmetrical walls and corners to balance the reflection sounds on both sides.
If you don't want to use the fabric to absorb sound, you can also use the cloth to absorb the sound cotton to make a block of sound absorbing body; you can also hang sheep wool; you can also use a variety of soft materials you can think of. However, please note that you should not think that the nail board can absorb sound. The surface of the board is flat, which is the same as the original wall. The board itself is very hard and it is no different from the wall. It does not have the function of sound absorption. The cavity, although it will absorb sound, but it does not suck high frequency, but will suck the intermediate frequency and low frequency, so that the sound is thin and not full, unless it is absolutely necessary, it is best not to do so.
Huh? Since the back wall of the horn is to be strong, how can I say that I want to suck it? What I call suction is not to make a cavity, but to suck like a side wall. Please note that if the two side walls are used for sound absorption, and the position is accurate, and the sound is not noisy, then the rear wall of the speaker can be used for sound absorption. On the other hand, if you still feel that the sound is too noisy and the positioning is not accurate, then you should do sound absorption on the back wall of the speaker. After the wall is processed, the sound is improved.
How big is the area of ​​sound absorption on the back wall? About two-thirds of the area between the two speakers is enough. If you only hang a small picture, it is not very useful. If you only hang a violin, it is useless. Once again, remind you that hanging thin cloth is useless, at least as thick as a tapestry.
Listening to the wall behind the position can actually absorb sound or spread. When used to absorb sound, if the wall is too close to the back wall, the reflected sound is too strong; when used for diffusion, if it is far away from the back wall, the sound can be made more natural. The best method is to use the sound absorbing material on the surface of the diffused shape, so that the benefits of absorption and diffusion are the same, which is the most perfect.
In general, the ceiling is best combined with sound absorption and diffusion, so that the sound will be the best. If there is only a hard tone spread, the high frequency reflections from the ceiling will be too strong. Different ceiling shapes can spread the frequency that is not easy to break up, and the deep sews can absorb too much energy!