Sound field design for public broadcasting and professional audio

September 05, 2022

Design of sound field for public broadcasting and professional sound reinforcement
Horn Speakers

First of all, it is necessary to clarify what kind of sound engineering is to be designed. It belongs to entertainment venues such as concert halls, theaters, dance halls, karaoke rooms; studios, recording studios and other program production places; conference halls, multi-purpose halls, stadiums, gymnasiums, What kind of places are language-based, such as public broadcasting, or background music, etc.? Then, according to the specific category and the specific situation, it is determined what grade level to reach, that is, what grade to reach the corresponding standard. When there is no corresponding standard, technical indicators can be determined according to conventional requirements, such as sound pressure level, transmission frequency characteristics, sound field unevenness, sound transmission gain, etc. As for the reverberation time, it is mainly determined according to the purpose. If there are clear regulations in the corresponding standard, it will be implemented in accordance with the standard regulations; if it is not clearly stipulated, it can be determined according to some principles. If it is used in language, the reverberation time should not be too long; when used in music, the reverberation time should be slightly longer.

After the technical indicators are determined, the sound field design can be started. The first step is to carefully check the architectural drawings to find out the room shape, specific dimensions, walls, ceilings, floors and other interface decoration. Based on the above data, the reverberation time can be preliminarily estimated. If the estimated reverberation time is found to be significantly beyond the range of reverberation time set according to the standard or application, rectification measures should be proposed, or help modify the selection of decoration materials, or should The required reverberation time range is achieved, and other personnel try to meet the reverberation time range requirements. Under normal circumstances, sound engineering designers can help to put forward specific suggestions for modifying decoration materials for reference.

For the calculation method of reverberation time, the sound absorption coefficient of the seats of the audience should be taken into account when calculating the reverberation in the empty field, and the sound absorption coefficient of the audience in the seats should be taken into account when calculating the full-field reverberation time. If the calculated reverberation time meets the requirements of this project, the next step of sound field design work can be considered. The Ministry of Housing and Urban-Rural Development's JGJ/T 131-2000, J42-2000 "Gymnasium Acoustic Design and Measurement Regulations" standard specifies the specific reverberation time requirements for different frequencies, and the value should be determined according to the standard.

Dance halls, dance halls and theaters are different. Generally, there is no large stage, only a small stage, but it is still suitable for a centralized speaker horn system. The PA Loudspeaker system should be hung obliquely at the upper position near one end of the small stage, and the left and right speakers can be used. Keep an appropriate distance, and at the same time ensure a certain distance between the horn speakers and the walls on both sides, but the distance between the left and right speakers should be greater than the distance between the horn loudspeaker and the near side wall. It should be avoided to place the speaker directly on the ground, because the height of the loudspeaker horn is relatively low when it is placed on the ground, which will cause the sound pressure level near the speaker to be high, the farther the distance, the lower the sound pressure level, the sound field is very uneven, and because the low-frequency components are affected. In addition, the dancers on the dance floor will absorb more sound energy, especially the middle and high frequency sound energy. If the speakers are hung obliquely, the distance difference between the speakers and each point will be reduced, the uniformity of the sound field will be improved, and the absorption of sound waves by the dancers on the dance floor will also be reduced. At present, many dance halls place speaker systems around the dance floor, and they are often placed on the ground to provide sound for the dance floor. In fact, if conditions permit, the speaker system is placed on the top of the center of the dance floor, and the sound energy effect is radiated from the center to the surrounding. would be better. Because the speaker system is placed around the dance floor, there are two defects in radiating sound energy from the surrounding to the center: ① the phenomenon that the sound waves radiated by the speaker system interfere with each other, resulting in a comb filter effect of the frequency response; ② when the dancer is not in the center position , it must be far away from the speaker system at different positions, so the sound of the far speaker system will arrive later than the sound of the near speaker system, and when the dance floor is relatively large, the sound will be unclear. Of course, effect lights are generally placed on the top of the dance floor. In order to place the speaker system in the center or near the center of the top of the dance floor, it is necessary to comprehensively consider the arrangement of the lights and the speaker system. As for the woofer system, you can put it anywhere, as long as it is visually acceptable.

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Ms. Silvia

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