Sound field design art professional sound engineering can not be ignored work

HC sound lighting network reported

To give a similar example: everyone knows the relationship between the speaker unit and the cabinet in the speaker. Many people return the famous foreign speaker unit including the crossover, but they can't make a good speaker anyway. The reason is that the acoustic structure of the cabinet is not solved. The design of the sound field in professional audio engineering is as important as the design of the cabinet. The design of a good sound field is as important as the design of the cabinet. The sound field will fully play the advantages of the audio equipment, which makes people sound very comfortable, and an unreasonable sound field will not only give people a wonderful sound experience, but also reduce the performance level of the equipment.

Of course, due to the level of architectural decoration and the user's understanding of the sound engineering, many projects are in contact with the sound construction unit very late, so that the design of the sound field cannot be completed completely, and the sound field design must rely on the architectural decoration to achieve, so A large number of sound projects are indispensable in the lack of sound field design, and only the sound design and construction unit fully recognizes the importance of sound field design, so that users can realize its importance.

A basic sound field design includes sound insulation processing, site noise reduction, building structure requirements, sound uniformity to achieve acoustic tremor, focus, feedback and other issues to avoid, indoor calculations, etc., the following classification for analysis.

Professional sound engineering

First, the sound insulation treatment

In order to create a quiet sound field and avoid affecting the units and residents in the surrounding environment, at the beginning of the sound field design, the sound insulation should be considered first to provide a good innate condition for the sound field. The sound insulation involves the construction. Sound insulation with the outside world, sound insulation of each room in the building; sound insulation parts include: sound insulation of the partition wall, sound insulation of the doors and windows, and sound insulation of the ceiling of the room connected to the top.

For the sound insulation with the outside world, the general building structure can achieve the basic sound insulation requirements, but if the architectural design does not consider the need of sound engineering at all, it is necessary to conduct an investigation of the sound insulation, and if necessary, should design the building. The unit conducts consultations and knows the local noise restrictions from the public security organs.

Usually do not use the height of the floor as sound insulation for the sound insulation between the rooms. If the wall is too thin, it will bring some difficulty to the project. This time, in consultation with the decoration unit, add a layer to the wall during decoration. Intermittent to solve the high and medium frequency sound insulation.

It is more difficult to completely solve the sound insulation of the low frequency band, because there is no other more effective way to increase the weight of the sound insulation. Doors and windows are the weak link of the sound insulation treatment. For their sound insulation, it can be recommended to the decoration unit. Improve the quality of the production of doors and windows, if necessary, use leather door and double glazed windows, or add isolation channels outside the door and heavy double-layer curtains hanging on the windows, etc., the ceiling sound of the top communicating room is also more critical.

Especially in some large-scale entertainment venues built in recent years, the sound of the hall has a great influence on the surrounding rooms. Some of the disturbances are from the top of the ceiling. This part of the sound insulation scheme cannot be raised too late, otherwise it is difficult. Implementation, so audio designers are required to ask questions to the decoration unit as soon as possible to coordinate a feasible solution.

For example, the ceiling is covered with a layer of fire-resistant sound-absorbing cotton or a layer of suspended ceiling at a certain distance above the ceiling of the ceiling. In short, the sound insulation treatment of the project is of great significance, which improves the quality of the project and facilitates the normal use of the user. Care should be taken to consider whether the sound insulation treatment is necessary and whether the processing method is feasible, otherwise it will increase unnecessary work and expenses.

Second, the reduction of noise on site

For the background noise of the scene, many people do not pay attention to it, but in the relevant national standards, they all put forward corresponding requirements, such as: the first-level karaoke should be less than 35dB, and the first-level disco should be less than 40dB.

The reason is that the increase of background noise correspondingly reduces the signal-to-noise ratio of the sound reinforcement system and affects the quality of the project. To effectively solve this problem, it is to limit the above-mentioned sound insulation. For example, whether the air outlet noise of the central air conditioner allows the installation unit to help solve the problem; the noise, size, installation position of the exhaust fan is appropriate.

Third, the situation of the building structure

It should be said that the general sound is not capable of letting the building structure completely designed according to its own intentions. However, for the part where the engineering quality requirements are strict and the construction engineering is processed on the reconstructed structure, it is necessary for the sound designer to make corresponding requirements as much as possible. The optimum proportion of the length, width and height of the structural part, the shape of the wall, and the position setting of the control room have already been mentioned in the overall planning of the front. Here, some architectural partial structures related to the engineering installation are mainly mentioned here. Happening.

First of all, the building unit must be recognized for the load-bearing capacity of the wall or roof that needs to be hoisted in the sound engineering. Especially when the weight of the light shed is large, the safety of hoisting is more important. Secondly, it needs to be in the existing building. The structure of the room, the location of the pre-buried pipeline, and the export have a more detailed understanding, in order to facilitate the possible insertion of the pipe, wiring construction, and then to understand the weak links of the internal structure of the building, to find out what landlord can change, where not .

Fourth, the realization of sound uniformity

The concept of sound uniformity is generally not very clear. There is not too much consideration in the project. Is it not important, right? It is not only important, but also very important.

For example: When you go to an entertainment hall, you find that the sounds in different places are different. Some places are very beautiful. Some places are like faults. The sound is erratic. For example, the volume in the front stage is very high. Big, but the audience behind it said that the sound is small (of course, some entertainment halls are designed to make the back area easy for the audience). These phenomena are caused by poor uniformity. In the relevant national standards, it is uneven in sound field. The concept of degree to the table, generally requires that the field pressure level test value deviation is less than 2dB at each point, how to achieve a uniform sound field?

First of all, there should be no obvious defects in the building structure. For example, there should not be too many columns in the room, and the walls should avoid trapped arcs, especially the wall on the side of the stage should not have a large structure; Large acoustic shadow areas appear in the interior, but since a large number of changes cannot be made to meet these requirements after the completion of the construction of the building structure, it is necessary to use the experience in the sound engineering to skillfully arrange the sound reinforcement area and avoid the comparison. Large defect structures that minimize their impact;

Secondly, it can provide some simple solutions to improve the sound diffusion effect to the decoration unit in a timely and effective manner. For example, all concert halls have good sound diffusion effects because a large number of sound diffusers of various shapes are used inside, and These structures can be completed by some simple decoration methods, so as long as the method is right, the better results can be achieved. Of course, it is not easy to properly and properly design the shape, position and quantity of the diffuser. The feasible method is to use the wall cement to pull the hair. Although this method is relatively old and not very beautiful, it can play a very effective role in the sound diffusion of the hall;

In addition, the sound system should be arranged reasonably, especially the position of the speaker must be strictly required. If the computer design software provided by some speaker manufacturers can be used in the design, the sound field simulation is better. If not, it should be Adjust in practice until the sound field is optimal.

Fifth, the avoidance of sound, focus, feedback

For the problem that the sound vibration, sound focus, and sound feedback bring poor sound reinforcement, some people can only say that the sound effect is not good, and all of them are classified as equipment. This is not appropriate. In fact, they should all belong to the sound field. Category, usually these problems do not happen from time to time, so in general engineering, often can not attract enough attention, even if these problems occur, many people do not realize that this is caused by the unreasonable sound field, or that is known as the sound field Unreasonable, there is no way to solve it.

The above phenomenon, the sound system work is generally normal, but occasionally suddenly on the scene can hear rhythmic pulse-like "bashing" or "beep" sound, usually in a place in the middle and low frequency band is the easiest Occurs, when the hall is large, the sound is far from the direct sound, which makes people sound very uncomfortable.

The reason is: the sound is reflected back and forth between the parallel walls in the hall, and the reflection of the wall is very strong, and the sound energy is hard to be weakened. Therefore, it is required to check whether there are two reflectives in the hall at any time during the decoration. Large areas of parallel surface, there are not too many glass, stainless steel structure, because these things that seem normal in the decoration unit, may cause problems; the curved surface of the sound focus occurs to put some large decorative items Or suspend curtains, curtains, etc., to reduce the possibility of acoustic focusing; pre-prevention of acoustic feedback is more difficult, and the frequency of feedback occurs cannot be accurately predicted during design, but the prevention of acoustic feedback is more important for practical applications.

Therefore, when the selection of decorative materials is carried out in the early stage of design, the sound absorption coefficient at different frequency points can be analyzed, and the calculation of the reverberation time can be roughly judged to provide necessary reference for construction and debugging. Of course, it is necessary to completely solve the problem. The above problems are solved by the later equipment debugging. Generally, after the completion of the project, the signal generator and the spectrum analyzer are used to detect the sound reinforcement area, and the repeated debugging of the equipment is used to compensate for the lack of the sound field.

Sixth, the calculation of reverberation time

For the sound field design, the average person can understand intuitively, and the more contact is the reverberation time, because it is the most controllable quantitative indicator in the design. The importance of reasonable reverberation time is reflected in the design. The sound field will make the sound system perform very well, giving the impression that the sound is full and round, not dragging, and not disturbing. It can be said that if the requirements of the sound field design in the front can be satisfactorily satisfied, the reverberation time can be controlled. If you are good, you can add a lot of sound effects. You must first choose a reasonable reverberation time target value before calculation. The selection of this value is generally based on the volume and purpose of the hall.

On the specific value, most designers prefer to make the recommended sound field reverberation time smaller. The reason is: the sound field reverberation time can not be adjusted after a long time, so it is suggested that the hall should be more natural. The better, the more you want to add artificial reverberation to the system to achieve reverberation requirements during commissioning and use.

At the same time, in recent years, the interior decoration materials are increasingly updated, and materials with high sound absorption coefficient are widely used, which makes the reverberation time of a large number of halls generally small. It can be seen that the starting point of this design principle and the influence of objective conditions There is no doubt, but you must know that the reverberation sound in the sound field is the natural reverberation sound produced by the sound source. It is based on the direct sound to show its particularity. It is an important characteristic in the sound field and is used in the system. Adding artificial reverberation is equivalent to adding the direct sound in the signal to the reverberation. At this time, the sound played by the speaker is no longer the direct sound of the sound engineer who wants you to hear the period, even when recording the program. Usually, different levels of reverberation are added, which is equivalent to destroying the source (sound source), so this method not only disturbs the good relationship between the direct sound and the reverberation, but also violates the sound field reverberation in order to make the room properly The purpose of the "Tong Yin", which I believe can be put forward, for the engineering design sales staff to discuss.

The brief reverberation time is calculated as follows:

General engineering can be carefully calculated at home at 500 Hz or kHz. The sound absorption coefficient of various materials should be strictly in accordance with the data provided in the product parameters or the building materials manual. Otherwise, the calculation results may be larger and larger, of course, with the recommended values. Nearly the calculation results, the designer does not need to ask the decoration unit to improve too much, because the reverberation time requirement is not a specific absolute value, as long as the disparity is not too large, the calculation should also consider how many pairs of the audience The impact of time.

Seven, the calculation of sound pressure level

The purpose is not only to provide users with feasible engineering electroacoustic parameters, in order to facilitate their safe and correct use of equipment, to create a healthy listening environment, but also to provide a basis for electrical design in sound engineering. The selection of the model provides a reference.

Before calculating the sound pressure level, it is necessary to select a corresponding appropriate environment for its quasi-sound pressure level, and the selection of the reference sound pressure level must understand the equal-acoustic curve of the normal human ear, namely the Fletcher-Munson curve.

The curve reflects the auditory response of the human ear to different frequencies and different sound pressures. The numbers on the curve indicate the loudness values ​​at the corresponding frequencies and sound pressures, in units of: Phono.

The human ear responds differently to sounds of the same sound pressure and different frequencies. The sound of the low-frequency sound of the same sound pressure level in the human ear is lower than the high-frequency sound of the same sound pressure level; The loudness produced in the human ear is basically the same. If there is no shortage of hearing in some frequency bands, the sound pressure must be sufficient to achieve the sound pressure level. This is the basis for the selection of the reference sound pressure in the sound pressure calculation.

For the language sound reinforcement project, since the language signal is mainly concentrated in the middle frequency band, the equal response curve degree is less correlated here, so the reference sound pressure level can be 70~80dB; for the sound engineering of general music playback, this reference sound The pressure can take 85~90dB as the basis for calculation; at the same time, leave the peak of 12~18dB peak and the ambient noise margin of 1~3dB for the sound reinforcement of the system, then the rated spread of the design on the average listening distance The sound pressure level should be: P = (85 ~ 90) dB + (1 ~ 3) dB and then the average listening distance L needs to be determined according to the actual sound range of the hall. The rated sound pressure level should be at this position. The actual sound pressure level.

According to this, the 1m position sound pressure level P of the speaker can be calculated:

According to the above mentioned: the distance change is doubled and the sound pressure changes by 6dB. The sound pressure level that the speaker needs to provide at 1m is: P=P amount +6LogL. The design of the sound is basically finished, and the subsequent work is completed. It is to work closely with the building decoration unit to put the design requirements into practice.

Editor in charge: Liu Chaozong