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Full Spectrum Led,Full Spectrum Led Grow Lights,Best Led Grow Lights,Plant Lamp, led grow light, grow lights Shenzhen Wenyi Lighting Technology Co., Ltd , https://www.wycngrow.com The importance of acoustic design
In recent years, people have paid more and more attention to acoustics, and discussions on acoustic design in international forums and magazines are becoming more and more common. When the frequency response of the monitor and the microphone is more and more straight, when the digital recording solves the noise problem in the analog era, a new audio era has arrived. The gap in the device is gradually shrinking, and the quality of the recording is basically determined by the sound engineer's technique and the acoustic design of the studio and the final mixing room. So from an objective perspective, acoustic design is more important than recording for any other factor.
Ensuring that the frequency response of the control room is straightforward is very important for mixing and monitoring, but a large part of the control room does not handle this. Worse, many people don't know anything about it and don't know what way to solve it. The monitor sound is distorted and it is impossible to make high-quality recordings anyway. The design of the studio is completely different from that of the control room. The studio needs to adjust the sound field according to the needs of the recording, instead of a strong sound absorption. In this way, the needs of various sound source recordings are met, and the effect of the previous recording is more perfect.
About sound insulation
In daily life, the building can reduce the noise by 6dB every time it is far away from the street or the noise pollution source, and the green trees in the community can reduce the noise by about 4dB.
(1) Noise propagation
Noise propagation can take two forms: airborne noise, solid-borne noise.
1, airborne noise
The most basic mode of propagation of sound waves is airborne, and airborne noise is the noise that external noise propagates through the air into the room. A cloth with a small hole and a heavy metal plate, the small hole area accounts for about 13% of the metal plate, and when there is sound hitting the surface, nearly 97% of the sound will pass through. The ability of sound to propagate through the pores is quite amazing, and a subtle crack can destroy a complete sealed acoustic system. Therefore, the strict sealing of the room is necessary to isolate the air noise.
2, solid load noise
Sound can be transmitted by mechanical vibration of solids such as wood, metal, concrete, etc. Since the air transmission efficiency is very low and it is difficult to drive solid vibration, the main source of solid-borne noise is due to the vibration source contacting the surface of the solid medium, such as underground generators or some home appliances. The loss of solid sound transmission is smaller than that of air, and it can travel a very long distance without significant loss of energy. The longitudinal vibration of wood, concrete, etc. is about 2dB lost by about 304.8 meters. If the transmission medium is steel, the loss will be reduced by a factor of 20.
(2) Sound insulation treatment
There are many methods for sound insulation. Because of the strict requirements on the noise floor, the studio uses a suspension structure. The suspension structure can greatly improve the sound isolation, and is especially suitable for recording studios in the city. The suspension structure can separate the room from other building structures, so that a cavity can be formed between the floating wall and the original wall, the cavity is filled with soft sound absorbing material, and the cavity absorbs sound waves, thereby reducing air and solid noise to at the lowest limit. However, the suspension structure must meet the load-bearing requirements of the building.
About diffusion and sound absorption
Many people put sound-absorbing materials on the wall, thinking that this is enough to eliminate the reflection, because they feel that when they clap their hands, there is no echo, but this does not make any sense to control the reflection of low frequencies. The wall structure and the concrete structure of the wall, the low frequency problem is particularly serious. The more rigid the wall, the stronger the reflection.
Most people blindly believe that a good studio should try to absorb the reflected sound as much as possible. However, the sound field shaping is not simply a reflection of the reflected sound, but the optimization of the listening and recording of the room, that is, the best consideration for the work of the sound engineer.
(1) Diffusion and its function
The diffuser plays an important role in improving the sound field and the sense of hearing. The quadratic residue diffuser is widely used due to its good diffusion ability and ease of installation. The formula of the quadratic residue diffuser is hn = (λ0/2N)‧'Sn, where Sn is the remainder of dividing n square by N, λ0 is the wavelength of the diffusion center frequency, and N is the number of diffuser lattices (must be prime ), h is the height of the grid, n=0, 1, 2, 3, 4, 5, 6...
The lower limit of the diffusion frequency of the quadratic residue diffuser is about half the frequency at the center frequency, and the upper limit depends on the number of grids, which can reach N-1 times the center frequency.
The diffuser can effectively avoid acoustic focusing compared to a smooth reflective surface. When the sound wave is reflected by the smooth wall, all the sound energy will be reflected in the same direction, and its reflection direction is fixed, depending on the position of the sound source. When the sound waves are reflected by the surface of the diffuser, the sound energy will be scattered and reflected in different directions and have different phase differences.
The irregular reflection of these uniform energy causes the human ear to subjectively create a sense of space, while at the same time using the mid-high frequency diffusion will increase the "brightness" of the sound. Its reflection direction is roughly a semicircle, and the sound energy spreads evenly. The diffuser has another function. When the sound source sounds, the sound wave is reflected by the back wall. If the reflective surface is a smooth wall surface, only a fixed reflection path of a certain frequency band points to the position of the sound engineer. When the reflecting surface is a diffusing body, since the sound waves are diffused in a semicircular direction, there are numerous reflection paths of different frequency bands converge at the position of the sound engineer, and so on, there are countless convergence points of the same nature, thus expanding invisibly. The best listening area.
(2) Sound absorbing materials (structure) and their effects
Sound absorption can be divided into two cases, medium and high frequency absorption and low frequency absorption. Sound absorption can reduce the echo, and can also effectively control the reverberation time, which plays an important role in improving the frequency response of the listening area. In this way, you can create a mixing environment that is more clear and more standard.
1, medium and high frequency absorption
High-frequency absorption is mainly for the sound field design, for early reflection of sound wave interference, reverberation and echo control. Sound absorption is usually performed using a full-band sound absorbing fiberglass board and combined with a diffuser for sound field shaping.
2, low frequency absorption (low frequency sound sink)
(1) role
The role of the low frequency sound trap is to avoid low frequency standing wave and low frequency frequency response distortion caused by sound interference. As shown, when the sound from the monitor speakers hits the wall, the reflected sound waves interfere with the sound waves that the monitor speakers continue to emit. Depending on the wavelength, the sound pressure is either enhanced or cancelled, and different locations have different frequency response. In an untreated room, when the sound waves interfere with each other, up to 25 dB or more can be generated.
Many people mistakenly believe that the use of near-field monitor speakers can eliminate acoustic defects. In fact, there will be a standing wave problem, but the energy of the direct sound at the listening position is greater. Although the high-frequency reflected sound gradually decreases due to the masking effect when the human ear is close to the speaker, low-frequency interference still exists.
Another misunderstanding is the use of an equalizer to change the frequency response caused by the phase cancellation of the sound waves. Acoustic interference is related to the structure of the room and exists objectively. Unless the direction of sound wave transmission is changed, the use of equalization cannot change the frequency response distortion caused by acoustic interference. And the frequency response curves obtained at different locations are completely different, so it is impossible to rely on the equalizer to compensate for acoustic defects.
Although the use of headphones can avoid the acoustic problems caused by the room, the sound of the headphones is only direct, making it difficult to control the volume of certain tracks. When we use headphones, the main instrument or lead singer can even hear very clearly at very low volume, so our final mix, the level of the lead singer will be slightly lower than the level that should be. Similarly, there is no accurate judgment of reverberation and delay.
In a room without sound sinking, the decay time of some frequencies is as much as 300ms, which will have a great impact on other low frequency tones, destroying the clarity, and even making the sound not Xie.
In general, a room needs as many sound sinks as possible. Although he may change the room to "dead", there must be no mixed low frequencies in the room. Sound sinks can be installed in the corners, walls, floors and ceilings of the room. The larger the processing area, the better the low frequency effect.
(3) Commonly used low frequency sound traps
a. Helmholtz resonator
The Helmholtz resonator is also a low-frequency sound trap that differs from the soot formed by glass wool, which absorbs lower low-frequency components. It has an adjustable cavity structure that is very effective for absorption in a certain frequency band. The absorption frequency range is related to the quality factor Q. The cavity structure absorption bandwidth formula of the Helmholtz resonator is: f2-f1=fr/Q, and fr is the resonance frequency, which is the maximum absorption frequency. The absorption band can be broadened by adding glass wool or by adding several openings of different sizes. There are many types of Helmholtz resonators. The usual design is to use a large box filled with glass wool inside, and the front end is covered with a series of thin planks of different sizes. This design is called a slab resonator. Although the Helmholtz resonator can effectively absorb a certain frequency band, its absorption range is limited, and the use of multiple resonators to broaden its frequency absorption range has an impact on the activity of the sound field, so it must be used with great care.
b. Panel sound trap
The panel sound trap is a narrow-band sound trap that absorbs about one octave of bandwidth. It can cover the entire low frequency with a series of panel sounds of about one square meter without using very heavy materials to increase the sound absorption range. Since the low frequency component has nearly 4 octaves, the low frequency of different frequencies can be absorbed by the combination of panel sound sinks of different thicknesses, and since the high frequency components can be reflected by the panel, installing multiple panel sound traps will not cause The sound energy is completely absorbed, causing the sound field to be too quiet. The front panel can also be of other shapes or combinations, and can be diffused if placed on the back wall.
c. Acoustic suspension body sound absorption structure
Due to the wide range of low-frequency radiation and high energy, when the low-frequency sound waves enter the suspension system, the suspension bodies are swung together by the influence (not visible to the naked eye), thereby converting their kinetic energy into their own kinetic energy and thermal energy. Because the angles of the suspensions are different, the direction of transmission of the sound waves also changes, which is equivalent to a labyrinth of sound. The sound waves constantly collide and are absorbed until they remove almost all of the energy.
Acoustic design has to achieve the following four purposes:
1. Prevent the standing wave from interfering with the sound wave to ensure the straightness of the frequency response.
2. Reduce the low frequency resonance of the small room and make the sound field evenly distributed.
3. Reduce the low frequency reverberation time of large rooms and obtain better reverberation time frequency characteristics.
4. Use absorption or diffusion to prevent echo and improve stereo positioning.
5, sound insulation needs to meet the requirements of the recording control room.
Important factors to consider
1, early reflection
The initial delay gap is the time difference between the direct sound and the first indoor reflection, that is, the first early reflection, as shown. In the subjective sense of hearing, the initial delay gap leads to the perception of room characteristics. For example, when we are in a closed dark room, we can know the approximate size of the room by clapping. This is precisely the information that the auditory system conveys to a room in the brain as the initial delay gap is perceived. When the initial delay gap is greater than 20ms, the room will have a feeling of openness, and the sound propagation is about 7m. The early reflection point of the side wall of the large and medium-sized control room is at least 3-4 meters away from the listening point, so it is necessary to absorb or diffuse the side wall.
Early reflections play a vital role in the quality of the listening. Rich early reflections can bring a relatively active sound field, and proper early reflections can play a role in improving the clarity of the sound. Early reflections that reach the listening point within 50ms will increase the clarity of the sound, but since the control room cannot add too much room characteristics, early reflections should try to control their energy. The use of a diffuser is a good way to spread the early reflection evenly, so that the sound field enhances clarity and has a sense of space. High-frequency reflection also helps to increase the loudness, while low-frequency reflection makes the sound turbid, so the diffuser should only diffuse high-frequency components (the center frequency is about 1 kHz), and the low-frequency reflection should be absorbed as much as possible.
However, early reflections can also cause sound interference problems such as comb filtering, affecting sound field localization and listening frequency response. Many people are very resistant to the early reflections. They think that the reflected sound has serious interference to the direct sound, which will affect the positioning of the front sound image. Then it will be very dogmatically covering all the reflection points with sound absorbing materials, and even more will The entire room is filled with sound absorbing materials! This will only attenuate the sound energy more, which will cause us to continuously increase the loudness and enhance the reverberation during the mixing.
We perform downmixing and mastering in the control room, requiring a standard space environment where the reverberation time of each band and the frequency response of the room are as straight as possible. At the same time, we also want to ensure that the reflected sounds do not interfere with each other to form a comb filter or affect the frequency response.
2, the size and shape of the room
The impact of the room structure on listening is:
1. Standing waves generated by parallel wall surfaces cause resonance problems
2. Influence of asymmetric structure on positioning
(1) Standing wave and resonance
The standing wave is formed by superimposing sound waves of opposite frequencies and the same frequency in two columns. When the parallel wall spacing is an integer multiple of half a wavelength, an axial standing wave is generated. At the same time, there are oblique and tangential standing waves. When the standing wave persists, resonance occurs.
Where c is the speed of sound, lx, ly, lz are the length, width, and height of the room, and n is 0, 1, 2, 3, 4...
When the resonance frequencies of several resonance modes are the same, a resonance frequency degeneracy occurs. At the degenerate resonant frequency, those with the same resonant frequency are greatly enhanced, which causes severe distortion of the frequency. This phenomenon is particularly severe in the low frequency range.
(2) Symmetric structure
Since the stereo position is generated because the volume and time of the sound emitted by the two speakers are different, in order to ensure accurate positioning of the original signal, the room information received by the bins must be balanced. That is to say, when the speaker plays a single tone test signal, the ears should receive almost the same reflected sound signal. If the room is rectangular, the speakers should be placed symmetrically at the front end of the shorter side, so that the listening position is away from the back wall, thus avoiding the most complicated area of ​​sound interference near the back wall. The figure below is a set of comparison diagrams. The left picture shows the correct symmetrical structure, and the right picture shows the unsatisfactory layout structure. For the picture on the right, the middle and high frequency components of the left speaker can be directly reflected to the listening point, while part of the sound of the right speaker is reflected by the left wall and part of the sound is reflected by the back wall, resulting in different reflections on both sides of the listening point. The offset of the pan position.
4, measurement acceptance
The standards are as follows:
(1) Sound insulation: 55dB or more (2) Reverberation time of each frequency: average reverberation time T=xs (x is determined according to customer needs)
(3) Frequency response of listening area: unevenness is controlled within 10dB 
