How to deal with noise in a sound reinforcement system?

Noise is a common and headache in sound reinforcement systems. Here are some strategies for dealing with noise:

First, source control

Check the device connection

Make sure all audio devices are connected correctly and securely. Loose plugs, broken cables, etc. can cause noise. For example, if the microphone cable has poor contact, it can introduce a "hiss" sound during signal transmission.

For battery-powered devices, such as wireless microphones, make sure the battery is fully charged. When the battery is low, the device may produce noise.

Update or replace your device

If the device ages, its internal circuitry may malfunction, resulting in noise. For example, after many years of use in the amplifier, the capacitor may leakage, resulting in noise in the output signal. In this case, consider updating your device.

For some low-quality audio devices, there may be a large noise floor by itself. For example, some inexpensive microphones can hear a noticeable "hum" sound in a quiet environment, and you should try to choose better quality equipment.

Second, line processing

Shielded signal cables

Use a well-shielded signal cable, especially for microphone cables that are susceptible to outside interference. The shield can effectively block external electromagnetic interference, such as radio frequency interference from nearby electrical equipment.

When laying the signal line, it is necessary to avoid laying parallel to the power line, and if it must be parallel, it is necessary to keep a certain distance (it is generally recommended to have a distance of more than 15 cm) to prevent the electromagnetic field generated by the power line from interfering with the signal line.

Grounding treatment

Proper grounding is an important measure to reduce noise. The grounding of all audio equipment should be uniform, and the grounding resistance should meet the requirements. If the grounding is poor, common-mode interference noise may be introduced.

Avoid situations where there are multiple grounding points, as there may be potential differences between different grounding points, which can lead to the formation of ground loops and thus noise.

3. Audio processing

Use a noise gate

A noise gate is an audio processing device or software feature. It can control the passage or failure of the audio signal according to the set threshold. When the input signal falls below a threshold (i.e., noise level), the noise gate closes, preventing the noise signal from passing through; When the input signal is above a threshold, such as the speaker's voice, the noise gate opens, allowing the signal to pass through normally.

When setting the threshold of the noise gate, it should be carefully adjusted to avoid misjudging the desired signal as noise and cutting it off.

Adopt noise-canceling plug-ins or devices

Many digital audio workstations (DAWs) have noise cancellation plug-ins. These plug-ins reduce noise levels to some extent by analyzing the noise signatures in the audio signal and then processing the entire signal.

There are also specialized noise reduction devices, such as dynamic noise cancellers, which can cancel out noise in a specific frequency range.

Fourth, environmental optimization

Sound-absorbing treatment

Add sound-absorbing materials such as sound-absorbing panels, sound-absorbing cotton, etc., to the room where the sound reinforcement system is located. These materials absorb reflected sound, reducing reverberation time and thus reducing noise due to reverberation.

For some rooms that are prone to echoes, such as empty halls, the acoustic environment can be improved by rationally arranging the location of sound-absorbing materials.

Isolate from outside interference

If the PA system is located close to a traffic artery or noisy machinery, sound insulation can be used. For example, install soundproofing materials such as soundproof felt, gypsum board, etc. on the walls to reduce the introduction of outside noise into the room.

For some unavoidable sources of electromagnetic interference, such as large-scale electrical equipment, shielding measures can be adopted, such as setting up a metal shield around the motor to prevent electromagnetic radiation from interfering with the sound reinforcement system.