The acoustic design of a private theater is by no means simple as it is acoustically treated on the wall and the ground. There are strict regulations on how much sound is absorbed, how much absorption is in each frequency band, and so on. This requires the selection and matching of the original room measurement and calculation, combined with the laboratory data and actual data of various sound-absorbing materials, and the appropriate amount and position are designed to achieve better room acoustic characteristics.
Then the acoustic indicators of the standardized private cinema acoustic solution are as follows:
1. The reverberation time (t20) is consistent with the expected design parameters to ensure that the overall sound field in the room meets the requirements.
2. The difference of reverberation time between 125Hz and 8000Hz shall not exceed 0.05s, ensuring that the room frequency response curve is straight.
3. Two or less standing wave points below 500 Hz, and it must be ensured that the position is 1.5 s outside the front side of the seat area and 2 s behind the rear of the seat area to avoid obvious standing wave defects from interfering with viewing.
4. Acoustic defects such as silent dyeing and tremor echo, avoiding obvious acoustic defects and disturbing audiovisual.
5. Eliminate the resonance phenomenon and interfere with the audio-visual, and avoid obvious audio defects to interfere with the audio-visual.
Acoustic treatment
When it comes to acoustic processing, you can't help but mention reverberation and reverberation time. Reverberation time is an important evaluation index of hall sound quality or indoor sound quality. Reverberation time has an important influence on people's listening effect. It is still one of the most important reference values ​​for describing indoor sound quality. The reverberation time depends on the building structure, top structure, wall materials and decoration of the room, and the seating arrangement and other indoor devices will affect the reverberation time.
The three-dimensional size of the room determines the presence of three fundamental natural resonant frequencies and harmonics that are integer multiples of the frequency of the three fundamental natural resonant frequencies that interfere with each other as they propagate through the room, creating a complex combined resonant frequency. Acoustically, the room can be regarded as a resonator. When the frequency of the sound source is consistent with the natural resonant frequency (normal frequency) determined by the three-dimensional size of the room, a standing wave will be formed and resonance will occur, which is the phenomenon of acoustic resonance. Sound field uniformity, acoustic staining, and frequency irregularities in the audio-visual room are all related to acoustic resonance. This resonance will add the color of the room's acoustic resonance to the original signal, causing sound pollution. Generally speaking, the loudness of a certain frequency or a certain frequency in the middle and low frequency is excessively strengthened. The acoustic treatment is to arrange the room without changing the original three-dimensional size, and use appropriate sound absorbing materials to increase the damping of the interface of the wall, floor, ceiling, etc., so that the intensity of the resonance of a certain frequency band is weakened. Let the resonance peaks level and widen, reducing the effect of harmful resonance on the overall sound.
Two sound absorption processing
Sound absorption is a phenomenon of energy loss after sound waves hit the surface of the material, and sound absorption can reduce the indoor sound pressure level. There will be different sound absorption coefficients at different frequencies. The sound absorption coefficient frequency characteristic curve is used to describe the sound absorption performance of the material at different frequencies. In order to reduce the echo that sound waves hit the wall, various acoustic treatments can be performed on the wall, such as diffused wall surface or sound absorption treatment. Generally speaking, sound absorption treatment is more common and effective, but sound absorbing materials with a large sound absorption coefficient should be used. The end wall behind the main speaker group should be treated with strong sound absorption. The average sound absorption coefficient should not be less than 0.6 in the frequency range of 125-4000 Hz, and the sound absorption coefficient of 125 Hz should not be less than 0.4.
According to the ISO standard and the national standard, the frequency range of the sound absorption coefficient in the sound absorption test report is 100-5 KHz. The average value of the sound absorption coefficient of 100-5 KHz is the average sound absorption coefficient, and the average sound absorption coefficient reflects the sound absorption performance of the material as a whole. In the engineering, the noise reduction coefficient NRC is often used to roughly evaluate the sound absorption performance in the language frequency range. This value is the arithmetic mean of the sound absorption coefficients of the materials at four frequencies of 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz, rounded to the nearest 0.05. Materials with NRC less than 0.2 are generally considered to be reflective materials, and materials with NRC greater than 0.4 are considered to be sound absorbing materials. When it is necessary to absorb a large amount of sound energy to reduce indoor reverberation and noise, it is often recommended to use a material with a high sound absorption coefficient. Centrifugal glass wool is a high NRC sound absorbing material, and the NRC of a 5cm thick 24kg/m3 centrifugal glass wool can reach 0.90.
In fact, there are many types of sound absorbing panels. From the shape and material, there are wooden sound absorbing panels, fabric sound absorbing panels, wood sound absorbing panels, strip sound absorbing panels, diffused sound absorbing panels, dry hanging decorative panels, three-dimensional wave panels, etc. species.
Triple diffusion treatment
The so-called diffusion is a phenomenon in which the sound is irregularly reflected, refracted and diffracted in many directions, and the diffusion makes the indoor sound field uniform. The sound diffuser can improve the sound field distribution in the room, shorten the sound level difference between the front and rear rows, adjust the balance of sharpness and fullness, eliminate echo, and suppress sound feedback. In general, the purpose of using a sound diffuser is to achieve a balanced state by supplementing the deficiency of a certain sound frequency band in a room by using a diffuser of a specific material.
When designing and configuring the sound diffuser, it should be noted that:
1. The diffuser cannot be a sound absorber at the same time.
2, the material of the diffuser should be as large as possible and have a certain rigidity of materials, such as concrete, plastering brick, marble, granite and so on.
3. If wood is used, solid hardwood should be used. A multi-layer composite board is applied to the surface of teak, oak, rosewood or hardwood. Do not use a thin plate such as plywood or plywood to make a hollow body, which will form a strong absorption of low frequency.
4. Avoid casting the diffuser with gypsum as much as possible. Although the production cost is very low, it will produce metallic acoustic dyeing, which is unfavorable to the sound.
5. The geometry of each diffusing surface of the diffuser must be sufficient to have a good diffusion effect compared to the wavelength of the acoustic wave.
Four standing wave processing
What is Standing Wave? The scientific explanation is: waves formed by superimposing two columns of waves with the same frequency and amplitude, the same direction of vibration, and opposite directions of propagation. When the wave propagates in the medium, its waveform continuously advances, so it is called a traveling wave. After the two columns of waves are superimposed, the waveform does not advance forward, so it is called a standing wave. In a regular room, if you don't make any acoustic design, then the speakers in the room are playing, the sound we hear, in addition to the direct sound of the speaker and the reflection of the wall, there are standing waves. Harmonic sound exists. In the past, we have repeatedly stressed that the low frequency standing wave of a small room determines the overall sound of the low frequency. Only by reducing the influence of the low frequency standing wave can the low frequency effect be improved. Therefore, the phenomenon of standing waves in the room is eliminated, mainly for the low frequency part.
Five shading and soundproofing
Shading is one of the more important parts of the home theater system, but this has a very close relationship with the properties of the room. If there is no window in the room, then this part can be ignored. If it has windows, then we have In addition to adding shading materials, soundproofing or other acoustic materials should be added around these windows. Secondly, it is necessary to say that the proportion of the sound insulation treatment of the private cinema door in the overall space is also very important. The sound pressure maintained in the interior is not exposed, and the external environment is not affected.
Acoustic design and processing is a systematic project that only uses the above points to have a good listening environment.
HDI is the English abbreviation for High Density Interconnector. High-density interconnect (HDI) manufacturing is one of the fastest growing areas in the printed circuit board industry. From the first 32-bit computer from HP in 1985 to the large client server with 36 sequential multi-layer printed boards and stacked micro-vias, HDI/mini via technology is undoubtedly the future PCB architecture. Smaller ASICs and FPGAs with smaller device spacing, I/O pins, and embedded passives have shorter rise times and higher frequencies, all of which require smaller PCB feature sizes, which drives Strong demand for HDI/mini vias.
HDI process
First-order process: 1+N+1
Second-order process: 2+N+2
Third-order process: 3+N+3
Fourth-order process: 4+N+4
Buried Hole Pcb,Blind Hole Pcb,Buried Blind Hole Pcb,Multilayer Blind Buried Hole Pcb
Chuangying Electronics Co.,Ltd , https://www.cwpcb.com