'Chirping' sound through PA system.

[Stereo Joe]

At my Saturday gig this weekend, I experienced something strange with the sound system.

I first noticed a problem when our female lead was singing. Once in a while (on average every 30 sec, but not at regular intervals) a horrible 'chirp' would come through the PA that distorted the singer's voice. I thought it was preamp clipping, but I verified that the singer's channel on the board was not overloading (the clip light never lit and the the PFL never showed any red). Also, the meter on the master channel wasn't showing any clipping either.

I was going to switch out the female singer's microphone when the same problem started happening with the male lead's vocals as well. Same thing - no clipping indicated on the board.

The 'chirps' always seemed 'triggered' by the vocals, but not necessarily when the singers were hitting their highest or loudest notes. It seemed wildly inconsistent and didn't sound like normal clipping, but had more of a harsh digital quality to it.

The PA belongs to the club, but I'm fairly familiar with it - Allen & Heath board, 2 ceiling-mounted EV mains and 2 EV monitors. I don't have access to the power amps for the mains (they're in the DJ booth), so perhaps that could be the problem area. The subwoofer was out of commission, so two extra mains were placed on the floor (sounded terrible, but that's another story).

The chirping was definitely coming through the mains, and didn't seem to be coming through the monitors. I could hear it once in a while when the DJ was playing in between our sets as well.

Anyone have any idea what this is? I'm not exactly an experienced sound tech, but I have a basic knowledge and can usually troubleshoot typical problems. Yet this issue outwitted me! Grr...

I play at this club often and I'd like to have some suggestions for things to try if I experience this again. Thanks in advance, TB!

[Munjibunga]

Wireless mics? Sometimes cell phones (especially on stage) will do this.

[Stereo Joe]

Originally Posted by Munjibunga

Wireless mics? Sometimes cell phones (especially on stage) will do this.

Wired mics - Beta 58s if I recall correctly...

[acleex38]

I've experienced it even with wired stuff. I hear it with my amp (as well as my computer speakers) all the time if someone nearby is getting or sending a call or text.

[sevenyearsdown]

Originally Posted by Munjibunga

Wireless mics? Sometimes cell phones (especially on stage) will do this.

I had a cell phone a few years doing this through my bass stack. Like an idiot, I set my cell phoe on top of my rack. As soon as I turned it off the problem went away.

[steve_rolfeca]

+1

GSM cel 'phones tend to be the worst, for some reason.

[dannylectro]

Apple iPhones can cause this too. No cell phones on or near the stage! Band guys - turn yours off. If you're on a stage that's very close to the audience, I'd give up the wireless mics too.

[One Drop]

Could also be caused by air leaking from an unplugged screw hole on a plastic box PA speaker.

[Phalex]

Check the crossovers. If the kick drum is coming out of the horns it makes a horrible chirping noise..... and then a horrible silence.....

[Vanceman]

Sometimes when we finish a song that we really sucked on, we hear chirping, but more like the sound of crickets.

Seriously, I've heard that before, but don't know what it is because it is so random.

[John D]

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