Article details

Conference system audio interference solution

2017-04-22handler681

Conference system signal flow

Branch field equipment including conference terminals and related external equipment, equipment types and functions. Audio signal transmission process is divided into two parts:

The end of the sound through a microphone pickup, the voice will be converted into electrical signals sent to the mixer for amplification, mixing, distribution, quality and effect of modified processing, divided into two road: the road to the end of a signal power amplifier are amplified by the speaker to restore the sound; the other way by the auxiliary signal the output of the mixer (AUX OUT) sent to the conference terminal transmits to the remote processing.

The signal sent by the remote terminal through the conference terminal, the audio signal into the mixer for processing, and then sent to the end of the power amplifier for amplification, reduced to sound by the speaker. The above analysis shows that the mixer is the signal processing point of convergence, how to adjust the sound of the various knobs and function keys, debugging is the key.

Two, audio interference problems

The Organization Department of the video conference system debugging and regular meetings, the quality of sound reduction has been significantly improved, but the individual provinces and the problems still exist, mainly for noise, distortion, frequency response level is not standardized, uneven, voice disorders, reverberation delay problems.

1, loud noise, it affects the clarity of the sound, soft and bright brightness, will cover up the voice of the venue seriously.

Background noise. Because the gain is too large, the automatic gain control, impedance mismatch and so on, the background noise will appear.

Microphone flutter. The microphone is the first link amplifying system, the signal quality directly affects the whole meeting, so we should choose and set reasonable according to the relative relationship between the characteristics of its features and performance, the sound source and the sound source to reproduce. For broken voice strong speaker, should be used to prevent "flutter" sound microphone.

2, distortion, which is related to the nonlinear distortion and human factors. Its characteristic is hoarseness, breakage, high pitched, serious will affect the sound clarity, brightness, softness, fullness and sense of the scene. The distortion caused by many reasons, such as the high sensitivity of the microphone, microphone placed power supply position is not appropriate, with phantom power is not normal, the level of the mixer, adjusting the impedance between the equalizer adjustment is not appropriate, the equipment does not match.

3, the level is not standardized. Before debugging, the mixer, equalizer and other equipment are not adjusted, resulting in the signal level is too high or too low. In addition, the unbalanced line output is directly connected with the balanced line input, which causes the signal level to drop.

4, uneven frequency response. It is related to the frequency response and equipment and human factors, such as deviation from the sound source, intermediate frequency and low frequency attenuation and too long transmission line to the microphone microphone, will affect the sound clarity and sense of hierarchy and fullness.

5, the proportion of voice disorders. If the total control room, the main venue, the voice of the game between the speakers of the three areas of the imbalance, it will affect the balance of other venues to restore the remote sound balance, resulting in a decline in the overall effect of the meeting.

6, reverberation delay improper. Different types of meeting and pickup environment have different requirements for reverberation and delay, so it is necessary to adjust the parameters of reverberation and delay according to the acoustic characteristics.

The size of the venue affects the reflection time and the sense of time in the sound field.

Reverberation time reflects the sound from the sound source through the absorption and reflection around the process, reverberation time depending on the size of the venue, the larger the space, the greater the reverberation time. To make up and modify some of the sound defects through the audio processing equipment, but improper adjustment, it will backfire. If the reverberation time is too long, the sound will have a "muddy" feeling, so to combine the actual, reasonable to add reverb effect, in order to enhance the longitudinal sound. Delay processing is also true.

The frequency characteristics of reverberation reflect the reverberation effect and sound quality at different frequencies. To be familiar with the frequency characteristics of the reverberation, adjust the proportion of the microphone to pick up the direct sound and reflected sound, increase the sense of reality and clarity.

Sound diffusion is the parameter that reflects the acoustic characteristics of the venue, the microphone should be set reasonably to make up for the defects of the sound diffusion conditions at the venue.

Three, common interference

There are many kinds of interference in the transmission of audio signals, such as power supply interference, interference between devices, lighting interference and so on.

1, power interference. The power supply wire between power supply grounding device, bad bad contact and impedance mismatch and equipment without purification processing, audio line and communication wire tube, with the same ditch or the same bridge laying, will be on the audio signal generating clutter, form a low-frequency AC buzzing sound.

2, interference between devices. "Whistle" is caused by a positive feedback between the speaker and microphone, the main reason is that the microphone is too close to the speaker or microphone to the speaker. "Sound" is produced by the acoustic delay, if the microphone is picking up the sound source signal and amplifying the signals picked up from the reduction, two microphone sound source distance and different or the same sound source signal, or a microphone signal from another microphone sound after reduction, will have the corresponding difference caused by time delay. When these signals are superimposed, some of the frequency components cancel out to form an "empty sound."".

3, light interference. If the venue

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