| 5.1 Audio processing is currently the most perfect sound solution, which can meet the super requirements of computer games and home audio and video, and the traditional two-channel audio has therefore withdrawn from the stage of advanced audio. In order to fully utilize the multi-channel capabilities, it is necessary to clearly understand how to configure and use the entire system. |
A brief description of 5.1 channel 5.1 channel is divided into pre-recorded and game. Pre-recording has been widely used in various traditional theaters and home theaters. Some well-known audio recording compression formats, such as Dolby AC-3 (Audio Coding 3, third-generation audio coding), DTS, etc. are based on 5.1 sound system Based on technology. 5.1 Use five directions: left (L), middle (C), right (R), left rear (LS), and right rear (RS) to output sound, making people feel as if they are in a concert hall. The five channels are independent of each other. The ".1" channel is a specially designed subwoofer channel. This channel can produce a subwoofer with a frequency response of 20 to 120 Hz. In fact, 5.1 sound system comes from 4.1 surround, the difference is that it adds a center unit. This central unit is responsible for transmitting sound signals below 80Hz, which is conducive to enhancing the human voice when watching the film, and concentrates the dialogue in the middle of the entire sound field to increase the overall effect.
In addition to the video image quality of DVD movies is much higher than that of VCD, the most important thing is the reproduction of its original sound field. In order to show the sound field effect in the film, it will never be achieved by two speakers. At least four speakers are the basic requirements for a sound field. The overall performance of the six-channel speaker group in the full range will be better. Since this application involves the combination of visual scenes and hearing, there will be quite high requirements for the presentation of the sound field in the film. If it is not matched with a multi-channel speaker set, the accuracy and authenticity of the sound field played by the film will be Suspected of.
Game 5.1 is mainly 3D positioning. From the perspective of the sound field effect, the traditional 3D positioning sound effect is very clear for the front, left, and right sound positioning, but for the rear and high sound, it may be because of everyone â€™s There are differences in feelings, which is undoubtedly a very unfavorable factor for 3D games, because in the game you can only see the scene in front of you, you must rely on the sound to master the dynamics of other positions. If you change to a four-channel or higher product, this problem can be solved.
The correct sound field requires the joint efforts of the sound card and speakers. In the first half of 1999, some sound cards that claimed to support 4 channels appeared, but it was only known after the actual measurement that it was a copy of the original two-channel signal and became a The rear two channels, in this way, naturally the front and rear sounds are the same, not the real four channels. Only by using sound cards and speakers that truly support 5.1, and maintaining the correctness of the angle, height, distance, front, back, left, and right channel connections, can the sound field be truly restored.
The birth of the 5.1 system announced the end of prior technologies such as APX, SpaTIalizer 3D, Q-SOUND, Virtaul Dolby, Ymersion, A3D, etc. It achieved a true 3D surround sound effect. Generally speaking, to implement the game 5.1, only 5.1 sound card and speakers are needed. If 5.1 video playback is required, a Dolby decoder needs to be added.
5.1 channel in DVD
It should be noted that Dolby Digital (Dolby Digital Sound) is not all 5.1 channels, it is just a general term for digital recording, subdivided into:
1. DDM, namely Dolby Digital Mono, Dolby Digital Mono;
2. DDS, namely Dolby Digital Stereo, Dolby Digital two-channel sound effect;
3. DDS, namely Dobly Digital Surround, Dolby Digital surround sound, dual channel storage, surround channel is mono channel, total five channels;
4. Dolby Digital 4.0, namely Dolby Digital Surround Sound 4.0, four-channel storage, the surround channel is an independent mono recording, five channels;
5. Dolby Digital 5.0, namely Dolby Digital Surround Sound 5.0, five-channel storage, the rear surround channel is an independent two-channel, a total of five channels;
6. Dolby Digital 5.1, namely Dolby Digital surround sound 5.1, six-channel storage, surround channels are independent two channels, a total of six channels;
DTS, Digital Theater System, uses a compression technology different from AC-3 to store surround sound effects on DVDs. A special system must be used during playback to release the 5.1 channels hidden in the DVD. The biggest difference between DTS and Dolby Digital 5.1 is that they use different "algorithms". Dolby Digital 5.1 suppresses the same data and takes up the smallest space. DTS does not deliberately pursue the highest compression ratio, so it also has the opportunity to save more information. If handled properly, it can provide better expressiveness than Dolby.
In addition to Dolby Digital and DTS digital surround sound effects, there are also European MPEG 2, SONY developed SDDS, or high-quality stereo-based PCM digital formats. However, DVD currently mainly uses Dolby Digital and Dolby Digital. DTS to record the sound and create a rich surround effect.
Perhaps everyone has heard of THX, which is the movie theater playback standard proposed by the American director George Lucas. Its purpose is to improve the sound quality of the movie theater movie, so that the audience can fully feel the director's attempt to express. Therefore, it has quite strict regulations on the space of the movie theater and all audio equipment, and even the brightness of the screen when playing. There are certain requirements on the screen, and after the cinema is issued a THX license, it must be reviewed every six months to avoid aging of the equipment. Not up to standard. The THX specification was later extended from the cinema to home-use equipment, which has the same strict specifications as the cinema. Currently, many manufacturers have produced audio-visual equipment that meets the THX standard. An AV system composed entirely of THX-standard equipment should be able to achieve the following effects: full-range treble and bass, more smooth and natural sound, minimum bass distortion in the hearing range, and clearer vocal positioning.
The equipment that can get THX certification is very expensive, and most of them have to be matched with Hi-End audio equipment to exert their effects. Therefore, home audio and video systems that usually have THX effects are mostly expensive.
After the 5.1-channel system speakers are added, it is not necessary to put them next to the computer in a mess. In order to highlight the effect of 5.1, there are strict requirements for the position of each speaker. The PC system serves individuals. You cannot absolutely place speakers in the same way as home theaters. However, there is still a simple rule: the tweeters are placed high and the bass speakers are placed low.
The front speakers are placed facing the listener in a line-by-line arrangement, with one speaker left and right, and the center speaker placed on the desk in front of the monitor or on top of the monitor. The height of the front speakers and the center speaker should be the same as possible, and the front of the three speakers should be on the same plane, or the center speaker should be slightly backward, but the front should be parallel to the front of the front speaker. The distance between the front left and right speakers is related to the position of the listener. In the normal viewing position, the angle between the speaker and the listener is 45 degrees.
The surround speakers are placed on the left and right sides of the listener. The two speakers face the listener face to face. The distance between the two speakers is the same as the listener. Place the two speakers 60 to 90 cm above the head when the listener is sitting. Office. The second solution is to hang the speakers on the wall behind the listener, surround the speakers toward the front or face to face.
Humans are not sensitive to the orientation of the accent, and the placement of the subwoofer is more casual. However, the low frequency range of computer speakers is not as low as expected, but it is better to put it on the ground in front of the listener. If the subwoofer has resonance phenomenon, that is, when there is abnormal vibration sound after turning on the large volume, you can install rubber pads or place heavy objects such as books on the subwoofer to eliminate resonance.
Sound transmission and speaker placement The sound waves directly transmitted from the sound source to the listener are called direct sounds.
Since sound waves are spread to a certain extent in all directions during transmission, when we enjoy home theater programs, most of the sound waves emitted from the sound source will be reflected into our ears through the walls, ceilings and other objects in the room. This kind of sound wave transmitted by reflection is called reflected sound.
The earliest reflection to your ear is a reflection. A reflection sound has a short reflection time, so its shape is very close to the direct sound.
Delayed reverberation is the reflected sound that reaches your ear after a reflection. It has no directivity during transmission, so if too much delayed reverberation occurs, it will seriously affect the clarity of the reproduced sound. The amount of delayed reverberation is closely related to the shape, size and material of the listening environment.
When the satellite speakers are placed a little further away from the indoor wall, it is easier to obtain a good sound reproduction effect. Not only the sound is natural, but also the sound image positioning is better. At the same time, the sense of space and depth of the sound will be stronger. The reason is that after the speakers placed in this way, the time they reach your ears after they directly emit sound (direct sound) can be the same as the sound (reflected sound) that reaches your ear after being reflected from the walls and ceiling of the room later. Obvious difference. This time difference is preferably not less than 10ms. Only in this way can the human brain have enough time to complete the analysis and processing of the originally heard sound signal, so as to avoid the interference of early reflected sound.
If the reflected sounds are heard within a short time, the human brain will treat these reflected sounds as part of the original sound, which tends to obscure the spatial characteristics of the sound. Starting from this characteristic of the human brain, placing the speaker about 0.6m away from the rear wall and about 0.9m away from the side wall (this is a ratio that can be changed dynamically) makes it easier to obtain better sound reproduction.
After the placement, the volume should be adjusted to make the listener feel that the volume of each speaker is equal on the seat. If the surround speakers are closer to the listener, the volume control must be lowered accordingly, without feeling noisy, in order to obtain a balanced sound experience.