噪聲大。它影響聲音的清晰度柔和度和明亮度，嚴重時會掩蓋了會場的聲音。
Loud noise. It affects the clarity, softness and brightness of the sound. In serious cases, it will cover up the sound of the venue.
① 本底噪聲。由于增益過大采用自動增益控制方式阻抗不匹配等，都會出現(xiàn)本底噪聲。
① Background noise. Because the gain is too large, using automatic gain control mode, impedance mismatch, etc., background noise will appear.
② 麥克風“撲”聲。麥克風是擴音系統(tǒng)的*個環(huán)節(jié)，其信號質(zhì)量的好壞直接影響到整個會議效果，因此要根據(jù)其特點和性能聲源重現(xiàn)的特征以及各聲源之間的相對關系合理選擇和設置。對于破音較強的發(fā)言者，應選用防“撲”聲的麥克風。
② Microphone "flutter" sound. Microphone is a link of the public address system, and its signal quality directly affects the effect of the whole conference. Therefore, it should be reasonably selected and set according to its characteristics and performance, the reproduction characteristics of sound sources and the relative relationship between sound sources. For speakers with strong breaking sound, anti "flutter" microphone should be selected.
失真大。它與設備的非線性失真和人為因素有關。其特征是聲音嘶啞破損尖細刺耳，嚴重時會影響聲音的清晰度柔和度明亮度豐滿度和現(xiàn)場感。引起失真的原因是多方面的，如麥克風的靈敏度過高擺放位置不合適具有幻像電源的麥克風供電不正常調(diào)音臺的電平調(diào)整過大均衡器的調(diào)整不適當設備之間的阻抗不匹配等。
Large distortion. It is related to the nonlinear distortion of equipment and human factors. It is characterized by hoarseness, damage, sharp and harsh sound. In serious cases, it will affect the clarity, softness, brightness, fullness and sense of scene of the sound. There are many reasons for distortion, such as the sensitivity of the microphone is too high, the placement position is inappropriate, the power supply of the microphone with phantom power supply is abnormal, the level adjustment of the mixer is too large, the adjustment of the equalizer is inappropriate, the impedance mismatch between devices, etc.
電平不規(guī)范。在調(diào)試之前沒有對調(diào)音臺均衡器等設備進行調(diào)校，造成信號電平過高或過低。另外，將不平衡的線路輸出與平衡的線路輸入直接連接，造成信號電平下降。
The level is not standard. Before commissioning, equipment such as mixer and equalizer were not adjusted, resulting in high or low signal level. In addition, the unbalanced line output is directly connected with the balanced line input, resulting in the decrease of signal level.
頻響不均勻。它與設備的頻響指標和人為因素有關，如麥克風的指向偏離聲源中頻和低頻衰減太多麥克風傳輸線過長等，都將影響聲音還原的清晰度層次感豐滿度。
Uneven frequency response. It is related to the frequency response index of the equipment and human factors, such as the direction of the microphone deviates from the medium frequency and low frequency attenuation of the sound source too much, and the microphone transmission line is too long, which will affect the clarity, hierarchy and fullness of sound restoration.
聲音比例失調(diào)。如果總控室主會場發(fā)言的分會場三者之間的聲音比例失調(diào)，就會影響其他分會場還原遠程聲音的平衡度，造成會議的整體效果下降。
The sound is out of proportion. If the voice proportion of the branch venue where the main venue of the general control room speaks is out of proportion, it will affect the balance of restoring the remote voice of other branch venues, resulting in the decline of the overall effect of the meeting.
混響延時不當。不同的會議類型和拾音環(huán)境對混響和延時的要求不同，因此要根據(jù)聲學特性，調(diào)整混響和延時的參數(shù)。
Improper reverberation delay. Different conference types and pickup environments have different requirements for reverberation and delay. Therefore, the parameters of reverberation and delay should be adjusted according to the acoustic characteristics.
① 會場的大小影響聲場混響中反射的時間和聽覺上的時間感。
① The size of the venue affects the reflection time and auditory sense of time in the sound field reverberation.
② 混響時間反映聲音從聲源擴散經(jīng)周圍吸收和反射的過程，混響時間視會場的大小而定，空間越大，混響時間也越大。要通過音頻處理設備彌補和修飾某些聲音的缺陷，但調(diào)整不當，就會適得其反。若混響時間過長，聲音就有“渾濁”感，因此要結(jié)合實際，合理加入混響效果，以增強聲音的縱深感。延時處理也是如此。
② The reverberation time reflects the process of sound diffusion from the sound source through the surrounding absorption and reflection. The reverberation time depends on the size of the venue. The larger the space, the greater the reverberation time. It is necessary to make up for and modify the defects of some sounds through audio processing equipment, but improper adjustment will be counterproductive. If the reverberation time is too long, the sound will have a sense of "turbidity". Therefore, the reverberation effect should be reasonably added in combination with the reality to enhance the depth of the sound. The same is true for delay processing.
③ 混響的頻率特性反映在不同頻率下聲音的混響效果和音質(zhì)。要熟悉混響的頻率特性，調(diào)整好麥克風拾取**聲與反射聲的比例，增加聲音的真實感和清晰度。
③ The frequency characteristics of reverberation reflect the reverberation effect and sound quality of sound at different frequencies. Be familiar with the frequency characteristics of reverberation, adjust the proportion of * * sound and reflected sound picked up by the microphone, and increase the realism and clarity of the sound.
④ 聲擴散是反映會場聲學特性的參數(shù)，要合理設置麥克風，彌補會場聲擴散條件的缺陷，同時要避開具有顫動回聲區(qū)域和強反射的方向。
④ Sound diffusion is a parameter reflecting the acoustic characteristics of the venue. Microphones should be set reasonably to make up for the defects of sound diffusion conditions in the venue. At the same time, areas with vibrating echo and directions with strong reflection should be avoided.
常見干擾
Common interference
音頻信號在傳輸過程中產(chǎn)生的干擾是多方面的，常見的有電源干擾設備之間干擾燈光干擾等。
The interference of audio signal in the transmission process is multifaceted, including power interference, interference between equipment, light interference and so on.
電源干擾。
Power interference.
電源接地不良設備之間的地線接觸不良和阻抗不匹配設備的電源未經(jīng)“凈化”處理音頻線與交流電線同管同溝或同橋架鋪設，都會對音頻信號產(chǎn)生雜波干擾，形成低頻的交流“嗡嗡”聲。
Poor power grounding, poor ground wire contact and impedance mismatch between equipment, the power supply of equipment is not "purified", and the audio line and AC line are laid in the same pipe, ditch or bridge, which will produce clutter interference to the audio signal and form low-frequency AC "buzzing" sound.
設備之間干擾。
Interference between devices.
“嘯叫”是揚聲器與麥克風之間發(fā)生正反饋引起的，其主要原因是麥克風離揚聲器過近或麥克風指向揚聲器。“空聲”是由聲波延時產(chǎn)生的，若麥克風既拾取聲源信號又拾取經(jīng)擴音還原的信號，或者與聲源距離不同的兩只麥克風拾取同一聲源的信號，或者一只麥克風拾取經(jīng)擴音還原后的另一只麥克風的信號，都將產(chǎn)生相應的路程差而造成延時。當這些信號疊加后，某些頻率成份相互抵消，形成了“空聲”。
"Howling" is caused by positive feedback between the speaker and the microphone. The main reason is that the microphone is too close to the speaker or the microphone points to the speaker. "Empty sound" is generated by sound wave delay. If the microphone picks up both the sound source signal and the amplified and restored signal, or two microphones with different distance from the sound source pick up the signal of the same sound source, or one microphone picks up the signal of the other microphone after amplified and restored, it will produce corresponding distance difference and cause delay. When these signals are superimposed, some frequency components cancel each other to form "empty sound".
燈光干擾。
Light interference.
會場若采用鎮(zhèn)流器方式間歇啟動的照明燈，燈管激發(fā)時將產(chǎn)生高頻輻射，并通過麥克風及其引線串入，出現(xiàn)“噠噠”聲;麥克風線離燈線太近，也會出現(xiàn)“吱吱”聲;另外，外界的高頻電磁也會產(chǎn)生干擾。
If the lighting lamp is intermittently started by ballast in the venue, high-frequency radiation will be generated when the lamp tube is excited, and it will be connected in series through the microphone and its lead, resulting in a "clatter" sound; If the microphone line is too close to the light line, there will also be a "squeak" sound; In addition, external high-frequency electromagnetic interference will also occur.
會議系統(tǒng)音頻干擾處理方法
Audio interference processing method of conference system
視頻會議的聲音還原，應根據(jù)聲學的理論知識，按照不同的實際情況，靈活調(diào)整調(diào)音臺和均衡器，對聲音進行加工和美化，彌補聲場的缺陷，營造較為理想的聲學環(huán)境;適當調(diào)整壓縮限幅器，遇到突發(fā)性的大峰值信號不過載和不失真，同時又要避免壓縮限幅器長時間處于壓縮狀態(tài)，使聲音銜接平滑圓潤。
The sound restoration of video conference should flexibly adjust the mixer and equalizer according to the theoretical knowledge of acoustics and different actual conditions, process and beautify the sound, make up for the defects of sound field and create an ideal acoustic environment; Properly adjust the compression limiter to avoid overload and distortion in case of sudden large peak signal. At the same time, avoid the compression limiter in the compression state for a long time, so as to make the sound connection smooth and round.
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