Why do you speak louder in an empty auditorium than in a crowded auditorium?

After a sound is emitted in a building, it often reflects back and forth hundreds of times between walls, ceilings and floors, and it takes a long time to disappear. The so-called reverberation is around the beam. The bigger the room, the more empty it is, the smoother and harder the walls are, the harder it is for the sound to disappear and the longer it lasts. This phenomenon is called reverberation. After the sound is emitted, the time it takes for the sound intensity to decrease to one millionth in the indoor space is called reverberation time.

If the reverberation time in the room is too long, it will make the sound buzzing and vague, giving people a noisy and turbid feeling. In this case, to make the sound clear, it is best to open the window and let the sound escape; You can also spread carpets or hang tapestries, curtains and other soft, porous and energy-absorbing materials on the wall to absorb sound. In addition, the soft cloth or cotton-padded clothes worn by people are also good sound-absorbing materials, so when the theater is full, the time for sound reflection back and forth will be shortened.

When China architects built the Great Hall of the People, they made great contributions to solving the acoustic problems of huge buildings. The auditorium of the Great Hall of the People has a large volume and a large surface area, which requires even sound, appropriate reverberation time and noise less than 35 decibels. When speaking at a meeting, every seat can hear 70 decibels; When playing music, the intensity should reach 80 decibels. Therefore, China's vocalists have spent a lot of time.

In order to make the sound evenly distributed and have no obvious echo, audiologists installed small speakers in front of each seat in the Great Hall of the People. Each of the 8000 speakers has a power of 0. 1 watt, producing a sound intensity of 75 decibels, making the sound field uniform. At the same time, because the current travels faster than air, it also makes the audience feel that the mouth gesture of the performer or speaker is synchronized with the sound. The design of reverberation time takes into account the characteristics of Chinese characters, and the reverberation time is 1.6 seconds when the house is full, which makes the characters sound clear. The sound-absorbing material adopts plastic splint to strengthen the absorption of low-frequency parts. There is a perforated sound absorption structure under the 7000 leather chair on the second and third floors. When the seat is empty, the bottom of the chair can be turned over to replace some people's absorption of sound.