Mono (Monaural or monophonic sound reproduction)

Mono has audio in a single channel, which is a more primitive form of sound reproduction. It is intended to be heard as if it were a single channel of sound perceived as coming from one position. From the perspective of nowadays, it may be considered as outdated since it uses a recording method lacking of sense of location, but it is already a quite advanced technology when the audio card just began to appear.  

Monaural sound has been replaced by stereo sound in most entertainment applications. However, it remains the standard for radiotelephone communications, telephone networks, and audio induction loops for use with hearing aids. A few FM radio stations, particularly talk radio shows, choose to broadcast in mono, as a monaural signal has a slight advantage in signal strength over a stereophonic signal of the same power.

Stereo (or Stereophonic sound)

Stereo is the reproduction of sound using two or more independent audio channels in a way that creates the impression of sound heard from various directions, as in natural hearing. Stereo sound is particularly useful in music appreciation, as the audience can clearly distinguish the direction from which a variety of musical instruments play, thus making the music more imaginative and feeling personally on the scene. After the appearing of Sound Blaster Pro , the stereo technology is widely used in lots of following audio cards. It has become a far-reaching audio standard. Up to now, stereo is still a technical standard abide by lots of products.

Stereo sound is preferred for listening to music, in theaters, radio stations dedicated to music, FM broadcasting and Digital Audio Broadcasting (DAB).

Prospective stereo

The basic concept of prospective stereo audio card is that adopting mono  when recording sound, but what is reproducing can be stereo and mono sometimes. The audio card with this technology has also been popular in the market for some time, but now has disappeared.

4.0 surround sound

Also called quadraphonic sound. It uses four channels in which speakers are positioned at the four corners of the listening space, reproducing signals that are (wholly or in part) independent of one another. It includes four points of articulation: left on the front, right on the front, left on the back, and right on the back, while the audience is surrounded by the sound.

It is suggested to add a subwoofer to enhance the playback processing of low-frequency signal.

As far as the whole is concerned, the four-channel system can bring the surround sound from a  different directions, allowing you to get immersed in a variety of  auditory experience in different environments. Now 4.0 surround sound technology has been widely integrated into the design of all kinds of high-end sound card, becoming the mainstream trend of future development.

5.1 surround sound

A 5.1 surround sound system uses 6 channels (5 standard + 1 subwoofer) to create surround sound. It includes a center speaker, subwoofer (for low frequency effects, such as explosions), left and right front speakers, and left and right rear speakers. In the system, ‘.1 sound channel‘ is a specially designed subwoofer channel, which has a frequency ranging from 20Hz to 120Hz. As it has a smaller number of speakers and is the industry standard, it is simpler to set up, cheaper and suitable for small or medium-sized rooms.  

5.1 surround sound is achieved with AC-3 (Dolby Digital) or DTS. DTS uses less compression but is also less common than Dolby Digital.

5.1 is the industry standard and is used by most DVDs and Blu-ray disks, as well as by HDTV and video games. It is also the most common sound system in commercial theaters.

7.1 surround sound

7.1 surround sound systems use 8 channels (7 standard + 1 subwoofer). It uses the same 6 speakers as above, plus an extra two side speakers. The extra two speakers add more depth to the surround sound experience. As it uses more speakers, 7.1 surround sound is more expensive and is only suitable for large rooms. 

7.1 surround sound can be achieved using Dolby TrueHD or DTS-HD Master audio. These are considered lossless audio, identical to the movie studio’s original.

Most Blu-ray players support 7.1 sound, as does the PS3. Most DVDs, Blu-ray disks and games are still produced using only 5.1 audio, but an increasing number of Blu-ray disks are being released with 7.1 sound as well.