Microphone hiss and noise occur due to so-called feedback. Anyone who has worked with microphones knows about feedback in sound equipment. But how to remove this unpleasant hum? Knowing the main points of occurrence of this interference is a significant step towards its prevention.
Audible feedback is a loud noise (often described as a screeching, hissing, humming, buzzing, etc.) that is sometimes present in sound systems. It is caused by a "looped signal," that is, a signal that moves in a continuous loop.
From a technical perspective, feedback occurs when the gain in a signal loop reaches "unity" (0 dB gain).
One of the most common causes of feedback is when a microphone feeds a signal into a sound system, which then amplifies and outputs the signal from the speaker, and this signal is picked up again by the microphone. 
Of course, there are many situations that lead to feedback. For example, a microphone can be replaced by the pickups of an electric guitar. (In fact, many guitarists use controlled feedback to create a certain sonic effect. This is what happens when you see a guitarist bring their guitar close to a speaker.)
To eliminate feedback, you must break the feedback loop.
Here are some suggestions for controlling feedback:
• Reposition the microphone or speaker so that the speaker output is not feeding directly into the microphone. Keep the speakers closer to the audience than the microphones. • Use a more directional microphone. • Speak (or sing) close to the microphone. • Turn off the microphone when not in use. • Flatten the signal by reducing the frequencies that cause feedback. • Use a noise gate (automatically cuts off the signal when it drops below a certain threshold) or filter. • Turn down the speaker output so that the microphone does not pick up the sound coming from it. • Try not to point the speakers directly at reflective surfaces such as walls. • Use personal monitoring systems instead of lower stage monitors.
You can also purchase a “feedback suppressor” – this device is an automatic equalizer that can detect noisy frequencies and automatically reduce them when unpleasant hissing and humming occurs. There are different models with different levels of efficiency. The best of them are known to give reasonable results. Press a button – and the noise disappears! Such devices are available in small sizes and in professional versions – for mounting on racks.
Modern feedback suppressors are equipped with additional functions such as a compressor, gate, limiter, as well as equalizers of various types - that is, everything you need for dynamic signal processing in real time.
By the way, many acoustic guitars with an amplifier (in electro-acoustic guitars) often have this function already built in.
What else should you know about feedback?
Feedback can occur at any frequency. The frequencies that cause the most problems will depend on the situation, but key factors include the resonant frequencies of the room, the frequency response of the microphones, the characteristics of the musical instruments (e.g. the resonant frequencies of an acoustic guitar), etc.
Feedback can be almost constant or intermittent. For example, you can turn down the microphone volume to stop continuous feedback, but when someone speaks into it, you may still notice a faint ringing or unpleasant tone of voice. In this case, feedback is still a problem and further action is needed.
As you can see, solving the feedback problem is real, you just need to approach it correctly. Our online store KumCenter will easily help you with this! On our website you will find a wide range of feedback suppressors, unidirectional microphones (cardioid, supercardioid, hypercardioid), high-quality sound equipment, mixing consoles and much more, which will help you minimize or completely eliminate the occurrence of whistling and hum during your performances in front of the audience. It is very easy to purchase musical equipment - thanks to the convenient online ordering service, and the goods will be delivered by our postal and courier services to any corner of Ukraine. Call, order and enjoy high-quality and clear sound!
