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Author Topic: Large buzz/blast sound from our school audio system -please help  (Read 3623 times)

Todd Bearson

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Hi there.  Let me start by saying that I am in no way an audio technician, but I know a little...enough to plug stuff in and get it rolling.  Anyway, we are a rebuilt school and we had a very nice audio/pa system put into out gym/meeting space.  It's wireless and works great.  However, once a day or so, it emits a large 1/2 second, extremely loud buzz.  It sounds kind of like something getting electrocuted.  We can't seem to trigger it on purpose - it just happens randomly and basically freaks the kids and teachers out.  It doesn't seem related to volume and there's no residual buzzing or problems.  I thought it could be a ground loop, but I know those are more of a low-level buzz that continues over time.  This just sounds like a capacitor or something rapidly discharging.  The people who have installed it can't seem to figure it out and haven't really made it a high priority to help us out.  Any ideas on what it could be?  Many thanks for any ideas,

CC 
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TJ (Tom) Cornish

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Re: Large buzz/blast sound from our school audio system -please help
« Reply #1 on: January 15, 2015, 10:22:06 am »

Hi there.  Let me start by saying that I am in no way an audio technician, but I know a little...enough to plug stuff in and get it rolling.  Anyway, we are a rebuilt school and we had a very nice audio/pa system put into out gym/meeting space.  It's wireless and works great.  However, once a day or so, it emits a large 1/2 second, extremely loud buzz.  It sounds kind of like something getting electrocuted.  We can't seem to trigger it on purpose - it just happens randomly and basically freaks the kids and teachers out.  It doesn't seem related to volume and there's no residual buzzing or problems.  I thought it could be a ground loop, but I know those are more of a low-level buzz that continues over time.  This just sounds like a capacitor or something rapidly discharging.  The people who have installed it can't seem to figure it out and haven't really made it a high priority to help us out.  Any ideas on what it could be?  Many thanks for any ideas,

CC
Before anyone can reply, you must change your username to your full real name per forum rules.
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Todd Bearson

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Re: Large buzz/blast sound from our school audio system -please help
« Reply #2 on: January 15, 2015, 11:23:31 am »

Before anyone can reply, you must change your username to your full real name per forum rules.

Got it.  Change made.

Thanks,

T.
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Corey Scogin

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Re: Large buzz/blast sound from our school audio system -please help
« Reply #3 on: January 15, 2015, 11:34:27 am »

Hi there.  Let me start by saying that I am in no way an audio technician, but I know a little...enough to plug stuff in and get it rolling.  Anyway, we are a rebuilt school and we had a very nice audio/pa system put into out gym/meeting space.  It's wireless and works great.  However, once a day or so, it emits a large 1/2 second, extremely loud buzz.  It sounds kind of like something getting electrocuted.  We can't seem to trigger it on purpose - it just happens randomly and basically freaks the kids and teachers out.  It doesn't seem related to volume and there's no residual buzzing or problems.  I thought it could be a ground loop, but I know those are more of a low-level buzz that continues over time.  This just sounds like a capacitor or something rapidly discharging.  The people who have installed it can't seem to figure it out and haven't really made it a high priority to help us out.  Any ideas on what it could be?  Many thanks for any ideas,

CC

Can you give us more information about what equipment comprises the system? 
What do you mean by "It's wireless"?  Are there wireless microphones used?  What else is wireless?

One common issue with wireless microphones is that if the transmitter (microphone) is turned off but the receiver is on and unmuted, the receiver may sometimes pick up interference from the environment if that interference is strong enough.  It sounds like some machine may be kicking on and emitting interference that is then picked up by a wireless microphone receiver.  Try muting the channels you aren't using or turning off any unused wireless microphone receivers.

If your name is Todd Bearson, why did you sign the post "CC"?
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TJ (Tom) Cornish

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Re: Large buzz/blast sound from our school audio system -please help
« Reply #4 on: January 15, 2015, 11:35:06 am »

Hi there.  Let me start by saying that I am in no way an audio technician, but I know a little...enough to plug stuff in and get it rolling.  Anyway, we are a rebuilt school and we had a very nice audio/pa system put into out gym/meeting space.  It's wireless and works great.  However, once a day or so, it emits a large 1/2 second, extremely loud buzz.  It sounds kind of like something getting electrocuted.  We can't seem to trigger it on purpose - it just happens randomly and basically freaks the kids and teachers out.  It doesn't seem related to volume and there's no residual buzzing or problems.  I thought it could be a ground loop, but I know those are more of a low-level buzz that continues over time.  This just sounds like a capacitor or something rapidly discharging.  The people who have installed it can't seem to figure it out and haven't really made it a high priority to help us out.  Any ideas on what it could be?  Many thanks for any ideas,

CC
Divide and conquer.  Does it happen with just the mixer/amps/speakers on?  Is it a certain channel that does it?  Try to eliminate parts of the system to make the problem easier to locate. 

Could be wireless interference on your microphone.  Try to change channels.
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John Roberts {JR}

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Re: Large buzz/blast sound from our school audio system -please help
« Reply #5 on: January 15, 2015, 11:42:39 am »

An audio signal cable with an open or intermittent ground wire can cause a loud buzz momentarily. To troubleshoot wiggle the wires while turned on at reduced volume and see if noise problem is correlated to one specific cable.

Fix or replace any bad cables.

JR 

Note: Do not plug cables in or out with volume turned up full because the ground and signal do not connect simultaneously.
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Todd Bearson

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Re: Large buzz/blast sound from our school audio system -please help
« Reply #6 on: January 15, 2015, 12:16:17 pm »

Thanks, everyone.  I'll get the system information for you (yes, wireless mics) and start trying to isolate the components.

CC/T.
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Jonathan Johnson

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Re: Large buzz/blast sound from our school audio system -please help
« Reply #7 on: January 15, 2015, 03:02:13 pm »

Try turning up the squelch on your wireless receiver.
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Greg_Cameron

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Re: Large buzz/blast sound from our school audio system -please help
« Reply #8 on: January 15, 2015, 03:31:26 pm »

Try turning up the squelch on your wireless receiver.


+1


And if the mic starts cutting out/muting after this change, it's likely you have interference problems in that frequency area. Changing channels might help, as well as locating the receiver(s) closer to the mics.


Pro tip: you may not be able to mitigate the issue with cheaper, older wireless mic systems. One facility in town here has nearly 10 year old bottom-of-the-line Audio Technica wireless mics that will cut out even with the receivers 8 ft. away from the mics on any channel due to local interference. Those models need to go to an e-waste facility.
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Mike Sokol

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Re: Large buzz/blast sound from our school audio system -please help
« Reply #9 on: January 15, 2015, 04:04:04 pm »

If your receivers have RF level meters, turn off all the transmitters and see if any of the receivers see RF signal. If they do, then they're tuned to an outside RF source and need to have their frequency changed. I've also seen a fluorescent light ballast arc internally and make a big blast of noise in a sound system. That can be intermittent and drive you crazy.
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Mike Sokol
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Re: Large buzz/blast sound from our school audio system -please help
« Reply #9 on: January 15, 2015, 04:04:04 pm »


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