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Noise!


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Noise!

Noise is something that every DJ or sound technician has to deal with at some point or another. Excessive buzzing can be really distracting, good sound should be clear with little to no noise. If you are considering renting speakers from us you might find this article useful. Our DJs are trained to trouble shoot noise and create clean audio, it’s not always an easy task. This is an area where more experienced DJs tend to shine.

The cause

Noise in audio is usually caused by one of three issues; grounding/power issues, signal to noise, interferance or feedback.

Grounding hum or noise can be caused the wiring in the venue (especially if it’s older) or something plugged into the same electrical line as your speakers. Common culprits are laptop power supplies and older lighting. Most LED lights don’t seem to create ground noise.

Solutions

Try some of the following for grounding or electrical problems

A direct box is one of the best ways to ensure that you don’t introduce noise into the sound system – they are specifically designed for this exact purpose. All computers and musical equipment (except microphones) should be run through a direct box, all the trouble shooting below might be unnecessary with an inexpensive DI. Search for our other article “Magic Box” on this blog for more info.

Some commercial self-powered speakers have a ground shield switch, simply flicking this switch can make a significant difference. For example our Yorkville NX250P speakers have this switch.
A ground lift is a device that removes the grounding pin from a laptop power supply. It’s easy to test by simply unplugging the laptop power supply and running the computer on battery power – if the noise goes away you know it’s the power supply. Basically it’s a device that physically removes that centre round pin on the plug from the circuit. Be aware that there are certain risks associated with using a ground lift, please use this solution at your own risk. Here is an article that discusses opinions on those risks https://www.native-instruments.com/forum/threads/is-it-safe-to-remove-the-earth-from-a-laptop.61815/. We’ve used this solution in the past with positive results and it’s possible to make your own ground lift.
A power conditioner is a device that fixes dirty power noise. They can be expensive but usually clean up the audio if the venue has a grounding or power issue. This solution usually replaces the need for a ground lift without any added risk.
Make sure that all lights are plugged in on different electrical circuits, older style lighting really needs to be separate. Remember that some plugs can still be on the same circuit.
Signal to noise problems are created when the audio gain isn’t set properly at the audio source, mixer or speaker. Self-powered speakers need a strong signal from the laptop and mixer to create clean sound – otherwise the speaker just winds up amplifying static. Be careful with the mixer gain control, it’s possible to overdrive the signal and create clipping – or a loud harsh distortion. In most cases the volume at the laptop should be set to maximum and the speaker should be set to unity (on most self-powered speakers it’s the middle or max setting). Your volume is then controlled at the mixer but you usually don’t want the mixer turned above zero or unity. The red clipping light on most mixers should never glow solid red, but an occasional flicker is ideal. The speaker should never be over-driven, most have a flashing red light. You should never hear distortion.

Feedback is another noisy issue. Audio feedback (also known as acoustic feedback, or the Larsen effect) is a special kind of positive feedback which occurs when a sound loop exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for example, a loudspeaker). This loop will increase in volume rapidly and tends to occur in a specific frequency spectrum. Our latest Behringer X Air mixer is the best tool in are arsenal for eliminating feedback, this digital mixer actually shows us where the frequencies are “freaking out.” The most obvious solution is to turn the microphone or pickup down and keep the microphone pointed away from the speaker. Sometimes professional DJs will use a graphic EQ to target frequencies that are too strong in a room and lower those specific frequency volumes – digital mixer now have this technology built-in. It allows the microphone to get louder without feedback but does require a bit of skill. The simplistic version is to try turning down the bass, mid or treble on the microphone channel – using your ears affords better guesswork. The human voice does not require any bass, you can usually turn that down on a vocal microphone.