if a wired microphone fell into pool would you be electrocuted?
August 1, 2017 5:11 AM   Subscribe

I read a story about a pastor being electrocuted from a wired mic at a baptismal, but the blame was put on faulty heater wiring and grounding. If the heater had not been faulty, would touching a wired mic or it falling into be fatal or would it just give a shock? if someone jumped in after (let's say to save the person) would they also be shocked? Like does the water become a hotbed of electricity or would it wear off?
posted by soooo to Science & Nature (8 answers total) 1 user marked this as a favorite
 
Microphones of this type are, generally-speaking, passive: there's a small diaphragm that moves inside a magnetic coil which induces a really, really small voltage change that goes down the wire to an amplifier. It's possible that there's 48v of "phantom power" coming from the amplifier to the mic, but it wouldn't be deadly, and it's usually not used with that type of mic.

What happened to the pastor was probably an ungrounded circuit in the pool heater finding a ground through the pastor and into the (grounded) mic. It's the same thing that happens to singing guitarists all the time (because we are stupid and don't ground our guitar rigs, or lift the ground to eliminate hum), although that's generally just a sharp shock on the lips (which hurts like hell, but usually doesn't kill).
posted by uncleozzy at 5:44 AM on August 1 [11 favorites]


Like does the water become a hotbed of electricity or would it wear off?

Someone else would have to speak to how much power is going through a mic and what fuses might be in place but the water does not become a "hot bed of electricity," any more than a wire does.

All that's happening is that the water (actually impurities in the water) is serving as a conductor for the electricity continuously coming out of the mains. Baring some very unusual chemistry that I can't see any plausible way of happening, the water in a baptismal font will be able to hold approximately 0 charge. So as soon as the path back to main current is cut (whether by physical removal of the wire, circuit breaker, fuse, etc), there'll be no electrical current flowing through it or charge stored in it.
posted by PMdixon at 5:47 AM on August 1 [2 favorites]


Someone else would have to speak to how much power is going through a mic

Very little under normal circumstances. Dynamic mics, as uncleozzy noted, don't receive power and the types of condenser mic that a preacher might be using is 48VDC at most. If whatever the mic is plugged into was malfunctioning, it's possible that it could send electricity down the mic cable.
posted by Candleman at 7:36 AM on August 1 [2 favorites]


The most power a mic would carry would be roughly the same as that of an analog telephone line. You could put both bare wires in your hands and not feel a thing. Maybe if you put them in your mouth you'd get a small shock. But the analogy continues, because people do get electrocuted by phone lines when the line is struck by lightning. So it's never about the mic or the phone per se, but the path provided by the wire hooked up to the device. It's a low-voltage cable, but is capable of carrying a lethal amount of current for a short time if something goes badly wrong.
posted by wnissen at 9:42 AM on August 1 [3 favorites]


It used to be the case that certain kinds of public address amplifier could suffer from a fault that turned the case of the amp (to which the microphone will be connected via the mic cable) live, but didn't affect the sound - so you couldn't tell. If the microphone was well insulated, then you might not notice even when holding it, but if you touched a metal part of the mic (or if it fell into water to which you were also in contact) then you'd get a severe shock and perhaps even get electrocuted.

In rock music, the Death Amplifier is a thing.

So, perhaps the pastor was using an old amplifier, or one that had been miswired to the mains, or a modern one that had a rarer fault - there are quite a lot of safety features in modern, well-designed amplifiers, and they use much lower voltages internally anyway. Having said that, I've seen some literally shocking things in the very cheap modern equipment you can buy online.

I can't offhand think how a faulty heater could be to blame, but perhaps there was a chain of bad wiring which cascaded faults on top of each other.

In general - if someone is being shocked by contact with high voltage DO NOT try and pull them away, or jump into the pool, or whatever. You stand a very good chance of getting a lethal shock yourself - plus, electric shocks can cause muscle spasm, so if they're holding onto something that's shocking them you won't be able to pull them away - nor, quite possibly, will anyone be able to pull you away from them.

The first and most important thing is to isolate the supply. If the offending device is connected to the wall current by a (dry, intact, insulated) power cord, yank it. (If there's a lot of liquid around, don't do this). Or find at turn off the building supply, or do whatever is safe to stop the current.

There can be faults which can't be isolated, if there's some contact with the main supply before the building's main distribution panel, or if the wiring in a building is really cock-eyed. So if you're not sure the current's disconnected, be extremely cautious.

Once that has happened, then there will be no further voltage - it doesn't hang around once the main supply has gone. You can't 'charge up' a baptismal pool or font with appreciable or dangerous amounts of power.

In general, you will not get any kind of a shock from a microphone, even if you jump into a bath with it. You'll ruin the microphone, and it's always best not to rely on safety features working to save you from the stupidity of your actions, but you won't die.

The most power a mic would carry would be roughly the same as that of an analog telephone line. You could put both bare wires in your hands and not feel a thing. Maybe if you put them in your mouth you'd get a small shock

I've done this with telephone wires when someone rang the number (don't ask, just... don't) and it is not a small shock, it is a very painful and memorable delivery of angry demons. However, as you can perhaps tell by the fact I'm still here, it's neither lethal nor particularly injurious. Phantom power - the 48v that some microphones want - is at a much higher impedance than phone circuits, meaning it can deliver very much less oomph, so you'd get a tingle but not feel like your tongue had spontaneously turned to Satan's own hornets' nest.

Don't try this at home, or anywhere else.
posted by Devonian at 1:54 PM on August 1 [2 favorites]


I suspect you're talking about this incident: Family settles lawsuit in electrocution death of Waco pastor.

The output of a microphone is, literally, millivolts. Which in turn means effectively zero current. IOW, a wired mic in and of itself is not dangerous. Chuck the thing in a baptism pool and you might ruin some of the internal parts (although I've had plenty of Shure SM58's get soaked by a sudden rainstorm and they work just fine once they dry out), but if the rest of the audio system is working and wired correctly your chance of electric shock just from touching a wet microphone is essentially none. (And I have touched plenty of said microphones in said rainstorms or standing in puddles onstage in the aftermath and gotten no shock at all. Although, as Devonian says, do not try this at home. I do this because I am very very confident (possibly overconfident) that all my equipment is working correctly and that all electrical connections are correct, because I've made and tested those connections myself.)

The potential danger arises because eventually that microphone is connected to other parts of a sound system, like mixing boards and power amplifiers, that are connected to and drawing electrical power from the electrical mains of a building or venue, a.k.a. the wall outlets that you plug stuff into. Which in the US is 120 volts AC, potentially carrying 15 to 20 amps of current. Much greater than the millivolts of a microphone. And if there's a problem with one of those pieces of equipment, especially with the grounding, then there's a potential situation where either a part of a piece of equipment (like the metal body of a microphone or the metal case of a mixer or power amplifier) that shouldn't have current running through it suddenly does; or where if you are touching a microphone and then touch something else connected to the electrical mains, it completes a circuit, and since (as the saying goes) electricity seeks the path of least resistance/the shortest path to ground, the path of least resistance is through your body.

And that second scenario seems to be what happened to the pastor - insulation burned off some heating elements and resulted in the water pipes coming into contact with electrical wires, which means, as PMdixon says, that the water in the font became a conductor for the flow of electricity; it became part of the circuit. And it's possible that, had the pastor simply stood in the font without touching a microphone (or anything else that would have provided a path to ground), he would have gotten a painful but non-fatal shock, or maybe even just a really intense and painful buzzing and tingling. But when he touched the wired microphone (even if the mic & all parts of the sound system were properly working and grounded) he created a new circuit for electricity to flow down - from the water through his body through the microphone down the wires through the mixer/amps to the wall outlet ground. And that's what killed him, the sudden surge of current as the electrons suddenly "discovered" that they had a new path to follow.

IOW, the microphone is, um, kind of blameless, here.

So . . . . . . the answer to your question: "If the heater had not been faulty, would touching a wired mic or it falling into be fatal or would it just give a shock?" is "Neither, really - assuming all other components of the audio system including the mains electricity are working and wired properly. And we all know the saying about assuming things, so Safety 101 is don't get into a body of water with a wired microphone."

If the pastor had been using a wireless mic he would likely still be alive.
posted by soundguy99 at 6:04 PM on August 1 [1 favorite]


Or if the heater were on an arc fault protected circuit..
posted by wierdo at 6:31 PM on August 1 [1 favorite]


wierdo: "Or if the heater were on an arc fault protected circuit.."

Arc fault doesn't really help in the linked case (it might have detected the faulty heater but it's not designed for that in most failure modes that would have happened in this case); GFCI protection is what you want when dealing with water. From what sparse details are in the article there were at least three mistakes made in the installation that contributed to the death (something wrong that led to overheating; lack of proper bonding; lack of GFCI).
posted by Mitheral at 10:46 PM on August 1 [1 favorite]


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