Common Noise Problems
Operating, maintaining, and troubleshooting church sound systems can be one of the most difficult challenges for church production volunteers. In many cases, the equipment is old and the limited knowledge of the volunteer often means that hums and buzzes go undetected, or are misguidedly corrected with hum eliminators and noise gate devices. As a result, service quality can suffer as sounds become unclear and unintelligible to those in attendance.
In this article, we’ll explore some common noise problems plaguing churches and offer some solutions to help you troubleshoot them so that future church services will be hum, buzz, hiss, pop, or crackle-free!
Snap, Crackle and Pop!
First of all, let’s identify, explain and phonetically describe the most common noise problems that occur within sound systems. I have then offered some “quick-fix” troubleshooting tips for each issue.
Hum – “Hmmmmmmmm”
What is it?
Hum is a low-level, continuous noise that is in the low-frequency spectrum. Think the hum of an air conditioner.
Common Causes
Ground loops in the signal path between devices are notorious for creating buzz, especially if you are forced to plug the gear into multiple power outlets around the sanctuary – for example plugging instruments and amplifiers on stage and then the mixing console, wireless receivers, etc all the way up at front of house. Hum is generally caused when there is a difference in voltage between two devices and nearly always manifests as a 50Hz tone as that is the frequency of power distribution in Australia. (60Hz for our North American or European friends.) A 1/4 “unbalanced” instrument cable greater than 5 metres can also cause hum issues.
Quick Fixes
- Run a long power cable from one to the other to ensure that all equipment is plugged into the same source. Note: It is important to ensure that the overall current draw does not exceed the rating of the power circuit – generally, 15-20Amps. You can easily check the rating on the circiut breaker. To calculate this, use the formula P=VA or Total Power Draw in Watts (P) = Voltage (V) (240 in Aus) x Current (A). ie 2400W = 240V x 20Amps. Many new auditoriums are designed so that there are multiple outlets for the same circuit distributed around the building and that multiple circuits for common purpose use, such as sound systems, are all on the same earth pole, which helps reduce the occurrence of pesky hums.
- The same phenomenon very often appears in acoustic guitar, keyboard or electric bass channels, as well as computer soundcard outputs when connected via 3.5mm aux cables. Very often hum can be eliminated by breaking the connection on pin 1 of the cable (shield). This is what the “ground-lift” button on the DI box is for.
- Ensure all instrument cables are less than 5 metres long and don’t run too close to power cables.
- Sometimes there is hiss and hum printed into the audio signal itself. Speakers are meant to reproduce audio signals and so any noise in the audio will often come out of the speaker as hiss and hum. Don’t be sent on a wild goose chase trying to troubleshoot a sound that is embedded in a recording.
Other Fixes
- Buy an isolation transformer that connects in-line in the signal path and allows clean audio to pass whilst blocking the hum.
- Use an audio interface or USB DI box to connect any computer audio via analog connections.
Buzz – “Zzzzzzzzzzzzzz”
What is it?
Buzz is different to hum, but often misquoted as being the same thing. Buzz is a higher-pitched noise that can even crackle at times. Buzz can be caused by a hum or it could also represent electrical interference from fluorescent lights, power lines, and other electronic devices.
Common Causes
Buzzes are caused by electrical interference. Common culprits are fluorescent lights or refrigerators that are plugged into the same circuit as audio equipment, or a bad “dirty” power supply. If there is a light dimmer on the same circuit, or even just nearby, having it set to anything but 0% or 100% output can cause an audible buzz in the system. Lastly, poorly shielded, unbalanced, damaged, or cheap, low-quality audio cables are susceptible to interference and likely to cause a buzz, especially when placed near other electrical equipment or power cables.
Quick Fixes
- Double-check that the cables connecting your bass guitar or keyboard to a stage amp are instrument cables that are less than 3-5m long. Also, inspect the quality of all cables connected to the system for damage.
- Turn off any equipment that is not sound related that is on that power circuit, or switch them to a different circuit. ie: Use dedicated power circuits for all audio components.
- Keep any low-voltage audio cables away from high-voltage power cables. Don’t let them run parallel with each other and if they have to cross, make sure it is at a 90-degree angle. (Mileage may vary).
- As buzzing could also be caused by an unsafe ground in your power distribution, make sure all of those connections are grounded properly.
Other Fixes
- Consider investing in a power conditioner to condition, seperate, and isolate electrical interference from a bad power supply. Note, some cheap power conditioners are nothing more than a rack-mountable surge protected power-board. It is important to research for an appropriate unit.
- Wireless mics can be a source for noise. Try changing the frequency or channel it transmits on or conduct a frequency survey of the environment.
Pop – “Puullllfff”
What is it?
A pop is a loud, sudden sound that can sound like something heavy has been dropped or even a bit like a small explosion. It occurs when there is an interruption to the electrical current. It makes a sudden abrupt movement in a speaker’s voice coil and can potentially damage equipment.
Common Causes
Plugging in an instrument cable to a guitar or keyboard with the channel unmuted on the console will nearly always cause a pop. So too when turning on a mixing console if the Master Fader is left unmuted and the power amplifiers are turned on and live. A loose connection between an audio device, instrument, and cable is another cause, as well as phantom power (+48V) not being transmitted properly through a faulty cable.
Quick FIxes
- Always turn power amplifiers on LAST and off FIRST.
- Make sure channels are muted when plugging or unplugging cables or switching +48V Phantom Power on or off.
- Check for any loose connections and replace any damaged, cheap cables.
Hiss – “Ssssssssssssss”
What is it?
Is there a snake in my speaker? A constant “sssss” sound that can be at any volume. An inherent level of hiss is to be expected in any sound system. Computers, power supplies, amplifiers, and transducers all create some amount of noise as electrons flow through conductors creating thermal noise.
Common Causes
Poor gain structure and setup of a sound system, with lots of elements in the signal chain, can cause substantial hiss. Even small amounts of hiss can add up. Old or cheap analog gear and components will cause a hiss as the electrical signal passes through its components. Old (and even new) recordings will also have some hiss.
Quick FIxes
- Review your gain structure by making sure that any gain stages in the signal flow is adding clean gain and not needing to be turned up too high. For example, try turning the keyboard volume up to maximum and turning the gain on the mixing console’s preamp down.
- Swap out or bypass each element in the system (cable, console channel, DI, mic, etc) to see if the hiss can be isolated to one particular source. Replace the culprit.
Crackle – “Crrkkccckkklll”
What is it?
Similar to popping, and often occurs concurrently. The sound is heard when the transducer in the speaker compresses at an accelerated rate and snap back to their original position in rapid succession, which can be caused by various things.
Common Causes
Faulty equipment; possibly a loose connection inside the device. A faulty speaker can crackle if a component inside is damaged, particularly active speakers (amp inside the cabinet). Unstable or loose connections, as well as old analog gear or components, are also culprits.
Quick FIxes
- Swap out or bypass each element in the system (cable, console channel, DI, mic, etc) to see if the problem can be isolated to one particular source. Replace the culprit.
Other Noises:
- White or Pink Noise – equal energy per frequency or octave. Sounds like the radio when changing the channel to an unused frequenct. This can be generated and useful for tuning sound systems.
- Feedback – positive gain loop where sound arrives in a microphone, is amplified and then is picked up by the mic and then amplified, etc – single or harmonic tones build in volume. Reduce the gain of the output fader to break the loop and review gain structure.
- Plosives – the loud “puh”, “duh”, “kuh”,”tuh” sounds in a mic. A pop filter or windscreen on the microphone as well as not speaking directly into the capsule will reduce this greatly. Same effect as wind noise from location recordings.
- Sibilance – “tss”, “fff”, “sss” sounds that occur in the 2-5kHz range and can irritate or even hurt the ears. Some digital mixing consoles have a “de-esser” which can work magic, or you can perform EQ cuts in the 2-5KHz range. Finding a less sensitive dynamic microphone will also help.
- Background Noise – loud stages (loud foldback monitors or drums) can cause “bleed” problems in the mics of other sources (such as vocalists) and result in poor signal to noise ratios. Try lowering the volume of the stage through drum screens, cages and switching to in-ear monitoring.
- Rumble – from microphone handling noises or stage resonances picked up through a mic stand. Ensure the HPF is engaged on all channels of the console where low frequencies aren’t required. Also mute microphones when they are being handed between presenters or picked up off a mic stand. You can also put padding under mic stands to isolate them from the stage.
- Distortion – the “squaring-off” of a sign wave that causes the speaker to move back and fowards quickly and violently. This can cause significant damage if sent loud enough through the system. Avoid digital clipping like the plague or overdriving any gain stage inappropriately.
Helpful Links
There are plenty of helpful links throughout this article (blue text) however here are some other specific ones relating to noise issues is sound systems.
Types of Audio Noise-Hiss,Hum,Rumble & crackle (audioshapers.com)
Fixes to Common Problems of PA Speaker Systems – My Audio Lover
Troubleshooting Your Church Sound System (churchtechtoday.com)
How to Stop Buzz and Hum in Church Sound (churchtechtoday.com)
What Causes Speaker Hum & Hiss (How To Eliminate Them Both) – My New Microphone
