How to Eliminate the Noise in Professional Performance Sound System?

- Aug 21, 2018-

As we all know, noise problems are a common and very headache in sound systems such as stage performances and live sound reinforcement. The noise generated by a sound system is not the same. It may come from many aspects. The sound engineer should analyze and judge the complicated situation and deal with it separately. The general noise may come from three aspects: First, the connection of the device is improper: Second, the inherent noise of the device: Third, the interference noise of the power supply.

Tip 1: Eliminate noise caused by improper connection of equipment

In the audio system, there is a common problem of interconnection of devices. If the connection is improper, the lighter causes the system index to drop, causing noise, and even when the device is not working properly. Make the following points when connecting:

Impedance matching: In the audio system, almost all devices use the bridging method, that is, the output impedance of the device is designed to be small, and the input impedance is large. This is due to the fact that in the system, unless the signal is transmitted over long distances, it is generally treated as a short line. Moreover, the signal level is low, and the signal is required to be transmitted at a high quality, and the change of the load does not substantially affect the quality of the signal.

When the signal source is designed as a constant voltage source, or the load is much larger than the internal impedance of the signal source, the above requirements can be met. In fact, the impedance of professional audio equipment is designed according to the above principles. The interconnection of devices is connected by means of jumper. This is the impedance matching of audio equipment.

When designing a sound reinforcement system, it is generally unnecessary to consider the impedance problem. However, when the output of one device needs to connect multiple devices, that is, one source must drive an active or passive source signal distributor when driving several loads to meet the requirements of device impedance matching (if two devices, Generally available directly at the output of the preamplifier).

The amplifier and speakers are connected according to the nominal output impedance and the input impedance of the speaker. The output impedance of the amplifier is 4Ω and 8Ω, which can be connected to 4Ω speakers or 8Ω speakers. When connected to a 4Ω speaker, the output power of the amplifier is larger than that of 8Ω. Two 8Ω speakers can be connected to the output of the amplifier for 4Ω operation.

 Tip 2: Eliminate the inherent noise of the device itself

The sound system is made up of multiple devices, such as microphones, DVD decks, mixers, effects, equalizers, compressors, actuators, electronic crossovers, power amplifiers, speakers, etc., each device May be the source of noise. In order to find out and determine from which unit the noise is generated, it is necessary to detect the inherent noise of each unit.

Turn on the sound system: the order of booting is turned on step by step in the order of the signal flow. After the power is turned on, there is noise coming out of the speaker. First, you can turn off the power of the wireless microphone receiver and hear if there is any noise. If the noise disappears, it proves that the noise is generated by the wireless microphone receiver: if there is still noise, it proves that the noise is not generated by the wireless microphone receiver. Other units can be detected again.

Tip 3: Eliminate interference noise from power supplies

Noise interference of light thyristor: On the stage, the biggest interference from power supply noise is the noise from the light thyristor, because the brightness and intensity of the theater and dance hall are not changed by changing the voltage of 0~220V. Instead, the conduction angle of the thyristor is controlled by an electronic circuit, and the conduction area of the sine wave of the alternating current is changed to control the change of the power transmission.

Therefore, the positive f-chord waveform in the power supply is changed to a saw-like waveform, and a significant 50 Hz ripple is generated in the power supply, which is manifested in the sound system, and significant noise appears. In order to eliminate the interference noise of the thyristor, the most effective way is to provide two phases of the three-phase power supply to the light, and another phase as the sound system. This will avoid the interference of the light thyristor.

 

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