1) It is required that low background noise is used as a hall where sound expansion and room must have low background noise. Noise may come out of the outdoor or indoors, such as air conditioning, ventilation equipment, and noise generated during the movement of light equipment. Measures should be taken to reduce the noise of the listening environment as much as possible. Excessive noise will cause the sensitivity of the soundtime dilatation system to decrease, which is difficult to make the audio system achieve the sound quality of hope. Instead, it may cause sound feedback when the output sound pressure level may cause the system to be unable to work stably. The problem of indoor noise control must be fully considered during construction and renovation, and necessary sound insulation measures must be taken. The background noise of the general movie theater is 25 ~ 30DB, the lecture hall is 30 ~ 35DB, and the gymnasium is 47 ~ 56DB.

2) There should be a uniform and reasonable sound pressure level that requires indoor sound pressure levels to reach a certain value according to different types of sound expansion. Specifically, the sound dilatation of music should reach the average sound pressure level of 80 ~ 85DB, the voice enlargement is 70 ~ 75DB, the background music is 60 ~ 70dB, and the unevenness should be controlled within ± 4dB. This requires that the soundproofing system should have sufficient output power and sound gain. The indoor sound field should be spread evenly. The recent reflex sound shadows should be fully and reasonably utilized. The radiation characteristics and placement of the speaker should be reasonably selected.

3) Ensure that the understanding of the sound expansion system should ensure the understanding of the language. This requirement is particularly important for the occasion of language dilatation. It is generally believed that the maximum consonant loss rate allowed not to exceed 15%. This indicator can be relaxed appropriately for the hall that is dominated by music replacement or sound expansion, but it requires a better sound effect.

4) When ensuring that the system can stabilize the working audio system, when reaching the specified average sound pressure level, it should have sufficient sound feedback stability and stability. Generally requires feedback stability and margin 6DB.

5) Basic consistent successful soundplay systems of sound statues and images should ensure the consistency of the sound and the image, so that the audience can not detect the existence of the sound expansion device, as if they directly hear the sound from the stage.