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Acoustic treatment of the room

Room, where the acoustic system is placed is practically like a box, but the outside box. Therefore, there is no a crucial difference between a box and listening room. In both cases they have significant impact on the sound, bringing the inequality into a sound with reflection and standing waves. Such waves occur in any room. They do not put out at the same moment but depending of characteristics of specific room, the time of their multiple reflections can be even a tenth of a second. That so-called, parasite sound reflection is inevitably projected on to sound acoustic system, which can cause amplitude-frequency deviations in the value of 50-10 dB. Low frequencies are most susceptible by the influence of room characteristics, where such variations can be even greater than 10 dB. Internal walls of sound box are covered with material that absorbs the parasite resonance, overtones and standing waves. But practically no one, never thinks about the influence of characteristics of the room on a sound of acoustic system. Even some studios do not apply the material that absorbs sound to the walls.

It is totally useless to use even a good two-way system monitors in the room without acoustic treatment. You should be aware that the graph of amplitude-frequency characteristics, which is added along with technical documentation, it is possible to get only in such room where measurements were made and they were made in soundproof room. Flat frequency characteristic showed in the documentation, if it is used in a room without acoustic treatment of walls, is only just emotional satisfaction and nothing more.

Sound proof Acoustic rooms with high ceilings have dimensions no less than 10x10 feet. Their rooms, floor, ceiling are covered with a layer of porous material thickness not less than 50 cm, which absorbs sound. Such characteristics have building thermal insulators like glass wool and basalt wool. The next layer represents a special conical pyramid, height not less than 30 cm. Their role is additional suppression and dispensing of sound transmission, especially at low frequencies. Cone material must have properties similar to the heat insulators and it is usually a sponge. But even at that type of room is not possible to get an ideal amplitude-frequency characteristic. For example, a cone of 1 m height enables linearization at frequencies up to 100 Hz. For linearization of lower frequencies, cone height of 2 m or area big as a hangar is needed, but that is pure fiction. Because of this most home made sound proof rooms can have full linearity of the amplitude-frequency characteristics only at the frequencies 300-500 Hz. That doesn’t mean that DEVIATIONS at lower frequencies would be as if there was no acoustic treatment of the rooms. The situation will be much better and the middle and high frequencies will be free of resonance.

At The audiophile surroundings there is a sustained opinion that is necessary appliance of materials which have properties of sound absorption and dispersion at the same time. Therefore I would like to give a comment for these two mutually contradictory characteristics.

Sound insulation is room protection that controls the sound way in and out of the room. Such structures are made of layers of stone bricks, plaster board, rubber, and plywood ... with the inner layer of material, which absorbs sound. The task of such construction is to tight the sounds in both directions, related to the room.

Sound absorption is decreasing the amplitude of sound waves reflected from the walls of the room. The ideal situation implies complete absence of such reflection, but in real conditions it is impossible to achieve. I guess you will not listen to music in the open field? Materials that can absorb the sound must have porous structure so that the sound wave can pass into the deeper layers of material. In that case sound wave disappears and it doesn’t reflects of the walls in a cacophony of parasite sounds.

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