In the implementation of surround sound, both Dolby AC3 and DTS have a characteristic that they require multiple speakers during playback. However, 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 that can process multi-channel signals and play them back in two parallel speakers, and make people feel the surround sound effect. This is virtual surround sound technology. The English name for virtual surround sound is Virtual Surround, also called Simulated Surround. People call this technology non-standard surround sound technology.

The non-standard surround sound system is based on two-channel stereo without adding channels and speakers. The sound field signal is processed by the circuit and then broadcast, so that the listener can feel that the sound comes from multiple directions and produce a simulated stereo field. The value of virtual surround sound The value of virtual surround technology is to use two speakers to simulate the surround sound effect. Although it cannot be compared with a real home theater, the effect is okay in the best listening position. Its disadvantage is that it is generally incompatible with listening. Sound position requirements are high, so applying this virtual surround technology to headphones is a good choice.

In recent years, people have begun to study the use of the fewest channels and the fewest speakers to create three-dimensional sound. This sound effect is not as realistic as mature surround sound technologies such as DOLBY. However, due to its low price, this technology is increasingly used in power amplifiers, televisions, car audio and AV multimedia. This technology is called non-standard surround sound technology. The non-standard surround sound system is based on two-channel stereo without adding channels and speakers. The sound field signal is processed by the circuit and then broadcast, so that the listener can feel that the sound comes from multiple directions and produce a simulated stereo field.

Virtual Surround Sound Principle The key to realizing virtual Dolby Surround Sound is the virtual processing of sound. It specializes in processing surround sound channels based on human physiological acoustics and psychoacoustic principles, creating the illusion that the surround sound source comes from behind or to the side of the listener. Several effects based on the principles of human hearing are applied. Binaural effect. British physicist Rayleigh discovered through experiments in 1896 that the two human ears have time differences (0.44-0.5 microseconds), sound intensity differences and phase differences for direct sounds from the same sound source. The hearing sensitivity of the human ear can be determined based on these tiny The difference can accurately 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 spatial sound source.

Auricular effect. The human auricle plays an important role in the reflection of sound waves and the direction of spatial sound sources. Through this effect, the three-dimensional position of the sound source can be determined. Frequency filtering effects 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 mid-range of 300-4000 Hz is located by sound intensity difference, and the treble is located by time difference. Based on this principle, the differences in language and musical tones in the replayed sound can be analyzed, and different treatments can be used to increase the sense of surround. Head-related transfer function. The human auditory system produces different spectrums for sounds from different directions, and this spectrum characteristic can be described by the head-related transfer function (HRT). To sum up, the spatial positioning of the human ear includes three directions: horizontal, vertical, and front and back.

Horizontal positioning mainly relies on the ears, vertical positioning mainly relies on the ear shell, and front and rear positioning and the perception of the surround sound field rely on the HRTF function. Based on these effects, virtual Dolby surround artificially creates the same sound wave state as the actual sound source at the human ear, allowing the human brain to produce corresponding sound images in the corresponding spatial orientation.