With the advancement and implementation of the national three-network integration policy, TV sets as home entertainment terminals will also bring about some very positive changes. For example, Shenzhen Skyworth took the lead in successfully developing the "chat TV" in February 2010, and subsequently Hisense, TCL and other home appliance manufacturers also launched similar products.
In chat TV, microphone voice collection becomes very important. At present, most chat TVs basically use a single microphone for radio reception, which may be a wired microphone or a wireless microphone. The use of a single microphone for radio will cause the following problems.
â— Bad user experience
That is to say, during the video chat process, the user needs to hold the hand, or speak as close as possible to the microphone, which feels bad; especially when many family members want to chat together, it seems even more crowded.
When using a wired microphone, the connection cable is very long-winded and affects the decoration of the home; the wireless microphone is prone to break sound when people move a little faster; and no matter which method is adopted, after a period of time, the battery needs to be replaced or Charge again.
â— Higher cost
At present, the method of using a wireless microphone with a carrier modulation of 2.4 GHz on a chat TV has become the mainstream, but the cost of this method is significantly higher.
In response to the above two problems, we propose to use array microphones for TV applications, which can solve these two problems. 
Array microphone
Array microphone (Array Microphone), also known as microphone array (Microphone Array), that is, to set up more than two microphones, and use these microphones to detect audio, and the obtained data is passed to the digital signal processor (DSP) for comparison , To restore the original appearance of the sound, and eliminate background noise. Array microphones are currently one of the standards of HD Audio. Windows Vista can already support array microphones.
The array microphone analyzes and processes the picked up multiple voice signals to align the main lobe of the beam pattern formed by the array with the target voice, and the "zero point" points to the interference source to suppress the interference signal, so as to obtain the target voice as much as possible. Among them, the beam direction and the width of the main beam of the beam are closely related to the distance between the microphones, the number of microphones, the placement of the microphones, the incident angle of the sound source, and the sampling frequency. Beam forming not only eliminates the need to manually adjust the microphone directivity when using a single microphone, but also greatly improves the signal-to-noise ratio of the output speech, so that high-quality speech can be obtained without manual intervention.
When using a traditional microphone to speak, one needs to be as close as possible to the microphone. For the system, speaking near the microphone is the "main voice" and the system gets a larger input. For the noise next to it, or the sound output by the interlocutor from the speaker, the amplitude is relatively small compared to the "main sound", which belongs to the "disturbing sound". In this way, the system can more accurately filter out "disturbing sounds" and retain the "main sound". In this traditional microphone pickup process, the problem of echo is not prominent. When using array microphones, echo issues need to be focused on.
Echo means that while the sound broadcast by the speaker is heard by the receiver, the voice signal is picked up by the microphone through various channels and then re-transmitted to the original speaker. The path through which the echo passes is different, and different delayed echoes are generated, including direct echo and indirect echo. Direct echo means that the sound played by the speaker directly enters the microphone without any reflection. The delay of this echo is the shortest. It is the voice energy of the far-end speaker, the distance and angle between the speaker and the microphone, and the playback volume of the speaker. The pickup sensitivity of the microphone is directly related. Indirect echo refers to the collection of echoes generated after the sound broadcast by the speaker enters the microphone after one or more reflections through different paths (such as a house or any objects in the house). The movement or change of any item in the house will change the echo channel. Therefore, the characteristics of this echo are multipath and time-varying.
In array microphone applications, because people no longer need to cling to the microphone when speaking, relatively speaking, the influence of the person's "main voice" on the microphone may be reduced, that is, the "interference sound" next to it may interfere with " "Voice", causing the system to be unable to correctly identify which is the real "Voice". Especially during the chat, the other party ’s voice comes out from the speaker. If the sound is louder, it will be retrieved by the microphone, and the other party will hear what he said once or more times. This is the biggest problem faced in the application of array microphones.
In short, during the application of array microphones, it is recommended to pay attention to the following issues: whether the range of the radio is wide enough; whether the distance of the radio is far enough; whether the effect of the radio is clear enough; whether the problem of echo can be better eliminated. The radio range can be adjusted by changing the number of microphones and the placement of the microphone; and the distance and clarity of the radio can be adjusted by adjusting the sensitivity of the microphone. This article does not make too much discussion. Since the problem of echo is the most difficult to deal with, this article also attempts to put forward some personal ideas. 
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