What is virtual surround sound

In the realization of surround sound, whether it is Dolby AC3 or DTS, there is a feature that multiple speakers are required for playback, but due to price and space reasons, some users, such as multimedia computer users, do not have Enough speakers. At this time, a technology is needed, which can process the multi-channel signal and play it back in two speakers placed in parallel, and can make people feel the effect of surround sound. This is the virtual surround sound technology. Virtual surround sound in English is Virtual Surround, also known as Simulated Surround, people call this technology non-standard surround sound technology.

The non-standard surround sound system is based on the two-channel stereo, without adding channels and speakers, and processing the sound field signal through the circuit to broadcast, so that the listener feels that the sound comes from multiple directions, generating a simulated stereo field. The value of virtual surround sound The value of virtual surround technology is to use two speakers to simulate the effect of surround sound. Although it cannot be compared with a real home theater, the effect is ok at the best listening position. The disadvantage is that it is generally The sound position is higher, so it is a good choice to apply this virtual surround technology to the headset.

In recent years, people have begun to study the use of the fewest channels and the fewest speakers to create a three-dimensional sound with a three-dimensional effect. This sound effect is not as realistic as the mature surround sound technology such as DOLBY. However, due to the low price, this technology is more and more widely used in power amplifiers, televisions, car audio and AV multimedia. People call this technology non-standard surround sound technology. The non-standard surround sound system is based on the two-channel stereo, without adding channels and speakers, and processing the sound field signal through the circuit to broadcast, so that the listener feels that the sound comes from multiple directions, generating a simulated stereo field.

The principle of virtual surround sound The key to realizing virtual Dolby surround sound is the virtualization of sound. According to human physiological and psychoacoustic principles, the surround channel is specially processed to create the illusion that the surround sound source comes from the back or side of the listener. Several effects of the human ear listening principle are applied. Binaural effect. The British physicist Rayleigh discovered in 1896 that the two ears of the human have a time difference (0.44-0.5 microseconds), a difference in sound intensity and a phase difference to the direct sound of the same sound source, and the auditory sensitivity of the human ear can be based on these tiny The difference is accurate to determine the direction of the sound and determine the location of the sound source, but it can only be limited to determining the sound source in the horizontal direction in front, and cannot solve the positioning of the three-dimensional airborne sound source.

Auricle effect. The human pinna has an important directional effect on the reflection of sound waves and the orientation of spatial sound sources. With this effect, the three-dimensional position of the sound source can be determined. The frequency filtering effect of the human ear. The sound localization mechanism of the human ear is related to the sound frequency. The bass of 20-200 Hz is located by phase difference, the midrange of 300-4000 Hz is located by sound intensity difference, and the treble is located by time difference. According to this principle, the difference between language and musical sound in the reproduced sound can be analyzed, and the sense of surround can be increased through different processing. Head related transfer function. The human auditory system produces different spectrums for sounds in different directions, and this spectrum characteristic can be described by the head related transfer function (HRT). In summary, the spatial positioning of the human ear includes horizontal, vertical, and front-back directions.

Horizontal positioning mainly depends on the ears, vertical positioning mainly depends on the ear shell, and front and rear positioning and the perception of the surrounding sound field depend on the HRTF function. Based on these effects, virtual Dolby surround sound artificially creates the same sound wave state as the actual sound source at the human ear, so that the human brain produces corresponding sound images in the corresponding spatial orientation.