Architectural acoustic design points for home theater audio

The sound reproduction of audio equipment has a very close relationship with the acoustic characteristics of the building environment. In order to maximize the performance of the sound system, the listening room must be acoustically treated.
There are four aspects to consider for the architectural acoustic characteristics of the listening room, 1 reverberation time, 2 diffusion characteristics of reverberation attenuation, frequency characteristics of 3 rooms, and 4 ambient noise levels.

The acoustic characteristics of the building in the listening room vary, and the reflection and absorption of sound by different objects are also different. Therefore, the acoustic processing to improve the listening environment and the improvement of acoustic defects are very complicated. Whenever possible, it is best to avoid the size of any two sides of the room being equal, or one side that is exactly twice the other side, that is, a room with a square or aspect ratio, because this ratio of room will produce standing waves, low frequency acoustic resonance. , causing sound staining. China Home Theater Network

The sound formed by the repeated reflection of walls, ceilings, floors, furniture and people in the room continues to fading and is gradually attenuated, called reverberation (also known as reverberation). It is different from echo, which is not a smooth decay but a sudden return of sound. For the most important indicator of room acoustics, the first is the reverberation time, which is the time required for the attenuation of sound energy to drop to one millionth (60dB) of the original intensity. For a certain room, the reverberation time mainly depends on In the sound absorption process. For the reverberation time of the Hi–Fi listening room, it can take 0.4~0.5 seconds. The reverberation time is moderate, the music is full, the voice is full, the reverberation time is longer and the sound is more lively and rich, but when it is too long, the sound is easy to be ambiguous, the speech intelligibility is degraded, the tone lacks strength and rhythm, and the reverberation time is too short. The sound is harder, lacks anger, and there is no reverberant sound (such as outdoor) often with a sense of dullness.

The diffusion characteristics of the room are good, the sound attenuation is smooth, and the sound throughout the room feels even. Any convex surface has the ability to diffuse sound waves, including bevels, curved surfaces, and convex arc surfaces. When the diffuse acoustic wave frequency is required to be convex, the diffuser can be used for processing.

When a certain frequency in the sound is excessively strengthened or weakened for some reason, the uniformity of the sound in the room will be destroyed. This phenomenon is called sound coloration. For example, standing waves can change the original characteristics of the sound, and peaks appear in some frequency bands. The improvement is that indoor objects are placed to avoid symmetry.

The large space listening room not only helps the low frequency extension, but also makes the sound feel easier and more lively. China generally uses the room area of ​​the listening room to be about 14m2, about 2.8m high, and the volume is about 40m3. In this kind of room, as long as the acoustics are handled properly, it should be able to have a good listening effect. Since the wavelength of sound below 100 Hz is greater than 3.4 m, which is the same order of magnitude as the size of the room, only a few resonant frequencies can be generated in its space, and the low-frequency sound waves have less mutual interference, which sounds natural and round. However, the wavelengths of the medium and high frequency sounds are much smaller than the space size, and a large number of standing waves will be generated indoors. Under the mutual interference of the standing waves, the acoustic characteristics of the room at 100~500 Hz are generally poor, and the audio energy of this frequency band is very high. High, so pay attention and make appropriate treatment.

In the room between the opposite walls, standing waves are generated due to multiple reflections of the sound. When the standing wave occurs, resonance occurs. The frequency depends on the distance between the walls. The room is actually a resonator. The place where the standing waves cause the most sounding of the sound in the room is the corners of the two sides of the back wall of the speaker, which will reflect the unclean bass. This effect is called room booming. This low frequency standing wave is a common acoustic defect that causes the bass clarity to drop and requires careful handling. A good way to control standing wave reflection is to use a bookshelf full of books, the irregular shape of the book and the less powerful sound absorption to scatter the sound waves, thus reducing the effects of sound reflection. Marble and granite floors and floor-to-ceiling glass are the first choice for modern home improvement, but they are the enemy of sound effects. Frequently, the sound is blurred and noisy. The method of improvement is to place a properly sized carpet in front of the speaker and a thick curtain in front of the glass.

The ambient noise level refers to the noise sound pressure level when there is no sound source in the room. If the ambient noise is too high, sound insulation, vibration isolation, etc. may be adopted, or a certain sound absorbing material may be laid indoors. The sound insulation of the current living room is usually not enough, and the sound insulation of the solid wall is the best in the whole room, and the sound insulation of the door and the window is the weakest, so the important factors determining the sound quality of the room interval are the door and the window.

The living room in the living room is not ideal as a listening room, because the living room is an open space, the aisle creates asymmetry in the space, and the floor-to-ceiling window causes low frequency loss. The extended space makes the sound reflection not well controlled, resulting in a sound image bias. shift. As long as there is not much furniture, the bedroom is a better choice for the listening room, because the confined space is easy to grasp the sound reflection problem.

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