Many houses of worship seem to be talking about receiving an electrical shock while performing or speaking during a service or a rehearsal. Electrical shocks happen when a relatively large amount of current flows through your body. If you get shocked when touching a microphone, there is a grounding issue somewhere in the electrical system, and you’ve become part of the shortest path to ground. These shocks are potentially lethal. Getting electric shocks unexpectedly is no fun at all, especially not when it has to do with working with microphones. As a technician, I’ve experienced electrical shocks multiple times when touching the mic and guitar strings at the same time. These shocks could potentially be lethal.
Don’t become the shortest path
Electrical shocks happen when a sufficient current at a high enough voltage travels through our bodies. So, let’s think of a situation where an external electrical current would flow through our bodies when we touch a microphone. This electrical shock happens when your body becomes the “shortest path” for the electrical current to get to ground. If all the electrical equipment is grounded properly, there shouldn’t be a situation where you’re the shortest path to ground.
However, sometimes audio equipment can be faulty. Other times it’s the AC power outlets that may have grounding issues. If either of these cases is true, your gear may be carrying stray voltage (electrical potential) that will flow toward a lower potential if given the opportunity. Unfortunately, that path may, at some point, be you. Note that the issue is very rarely, if ever, the microphone itself. Typically, it comes from the difference in ground potentials or the lack of proper grounding in other parts of the system.
The Usual Suspects
Let’s look at the 3 most common scenarios that present a shock hazard when touching a microphone:
Ungrounded Mixing Console
An ungrounded mixing console chassis could potentially have stray voltage on it, which proves to be dangerous.
The outer case/chassis of a microphone typically connects to its input on a console via the ground pin of the XLR cable.
When a microphone is connected to an ungrounded mixing console, there is always a risk of that stray voltage reaching the microphone. The voltage may very well travel through you as you touch the microphone if you’re the shortest path to ground.
When using any mixing consoles, please ensure they’re grounded properly.
Ungrounded Guitar Amp
If an electric guitar is connected to the amp via a cable, the strings are connected via the cable to the metal chassis of the guitar amp. If the guitar amp chassis is ungrounded, it could have stray AC voltage/current on it.
Many guitar amps are ungrounded to prevent the dreaded “ground hum,” which is sometimes brought about by a grounded connection causing unwanted noise in the amp’s output. If this happens to be the case, there usually isn’t a huge issue with just playing the guitar. Although touching the strings would make you part of the circuit, your body, shoes, and the floor will likely not allow electricity to flow through you.
The issue, then, is when you touch a microphone and the strings (or any other conductive part of the guitar) at the same time. In this scenario, the stray voltage from the ungrounded guitar amp would flow through you into the microphone and then to the mixing console, AC mains, and ultimately a ground somewhere.
Essentially, you’re closing a circuit and allowing stray voltage to pass through you, resulting in a shock. To make things worse, your lips are typically the first point of contact with the microphone.
To prevent this, always make sure guitar amps are grounded properly.
Faulty AC Outlets
Often, we believe all our equipment is properly grounded, but the power mains have different ground potentials. If any of the AC power outlets are wired with different ground potentials, there is a likelihood that there will be shock hazards with the audio equipment. In these situations, electricity will flow from higher potential to lower potential. Therefore, if socket grounds have a difference in potential, electricity will flow to whichever ground is lower.
Let’s say we have a microphone plugged into a grounded mixing console connected to one wall plug and a grounded guitar amp plugged into another wall plug with a different ground potential. In this case, if we were to touch the guitar strings and microphone simultaneously, we would create the electrical connection and the voltage would flow to the lower ground potential. This may very well result in a shock, particularly if there is a significant difference between the socket ground potentials. The same goes for any wall socket that is not grounded properly.
I would always suggest that you test the power outlets of any new room you plug into. I’d even suggest testing your regular performance area from time to time. We can easily test our outlets with an inexpensive receptacle tester. I suggest the Sperry Instruments GFI6302 .
If you have a discrepancy between power outlet ground potentials, a common strategy is to plug all equipment into one socket to ensure a common ground. This isn’t always possible, but it’s worth a shot for smaller setups. Use a power bar if need be.
If you’re getting shocked, please don’t ignore the problem. This dangerous situation requires fixing. Get your audio equipment inspected by a qualified technician and get a qualified electrician to fix the AC outlets.
Shocks vary by victim
Electric shocks happen when a sufficient current at a high enough voltage travels through our bodies. Notice that the electricity must travel through our bodies and not just be present in our bodies. This is why we can often avoid shocks in faulty systems up to the point where we touch a microphone and close a circuit, allowing electricity to travel through us.
Note that the resistance of human skin varies from person to person and fluctuates for each person depending on many factors, including the moisture on and in the skin and if the skin is broken or not. Ohm’s Law tells us that when we’re subjected to electricity, the amount of current that would flow through us is equal to the voltage of the current divided by the resistance of the medium (skin).
Ohm’s Law: I = V/R
I = current
V = voltage
R = resistance
Both alternating current (AC) and direct current (DC) can flow through the body and cause electric shock. The potential amount of AC able to flow also depends on its frequency. AC (typically measured by root mean square rather than peak-to-peak) is considered about 3 to 5 times more dangerous than the same quantity of DC.
The effects of electric shock are determined by the voltage, current; resistance to flow; duration of contact with the source; the pathway of flow; and the type of current (i.e., direct or alternating).
Effects largely depend on the amount of current and the voltage of that current.
Effects range from:
- Tingling sensations
- Skeletal muscle tetany (spasms)
- Respiratory muscle paralysis
- Ventricular fibrillation
- Tissue burns
It’s important to note that the human body actually needs electricity to function.
The nervous system requires electricity to send signals throughout the body and brain, making it possible for us to move, feel, and think. The body’s cells effectively create electricity with charged ions within the body called electrolytes. Our bodies do a great job with what we produce but don’t fare so well with external sources of electricity (especially when these sources provide great amounts of electricity).
What is grounding?
Electrical ground is commonly described as a source capable of absorbing so much charge that it remains unchanged compared to the rest of the system. It is the reference point in a circuit from which voltages are measured. It’s also a common return path for electrical current.
Current flowing to ground can be visualized similarly to other physical occurrences where matter or energy from a higher potential goes toward a lower potential. These occurrences include:
- Objects falling (think of an apple falling from a tree to the earth)
- Fluid moving from higher pressure to lower pressure (think of a vacuum cleaner)
- Heat moving from hotter to colder (convection, conduction, and radiation)
So basically, electricity always wants to get to ground and will do so even if it has to travel through you to get there, shocking you in the process.
How to protect your microphone
There are multiple ways to troubleshoot or prevent the issue of electrical shock from your microphone. Here are a few:
- Outlet Tester
- Ground Fault Circuit Interrupter
- Same Circuit
- Pinky/Forearm Trick
- Voltmeter or Neon Tester
- Go Wireless
By placing a foam windscreen over the microphone, we effectively add a barrier between the microphone chassis/grille and the mouth of the singer/speaker. Although this may prevent some electrical shocks, it does not fix the underlying problem whatsoever, so I would not recommend doing this.
As mentioned before, we can troubleshoot the shock issue by checking the ground potentials of the power outlets in the room. To ensure proper grounding of your equipment, first, check to see that all outlets are in fact grounded and then make sure that the outlets being used have the same ground potential.
Ground Fault Circuit Interrupter
A GFCI protects against the most common form of electrical shock hazard, the ground fault. It also protects against fires, overheating, and the destruction of wire insulation. These devices are put inline and act as circuit breakers designed to shut off electric power in the event of a ground fault.
If it is possible to plug all equipment into one grounded outlet, we effectively ensure that all the equipment is grounded at the same ground potential.
Playing guitar and singing into a microphone is the most common way to get an electric shock from a microphone. An easy test to check if there’s a shock hazard is referred to as the pinky/forearm trick, where the pinky touches the microphone grille, and the elbow touches the guitar strings. If there isn’t an electric shock, the microphone is likely (though not certainly) safe to use. If there is a shock, the electricity is only flowing from your pinky through to your forearm. This is much less dangerous than testing from your mouth to your hand because the heart is not involved in the circuit.
Voltmeter or Neon Tester
A voltmeter can be used to test the potential difference between the guitar strings and the microphone. If there is a significant difference, there will likely be electrical shocks when a circuit is made between the two devices.
A wireless microphone and/or wireless guitar pack will eliminate the direct physical connection to ungrounded consoles, amps, and outlets. A wireless microphone and/or wireless guitar pack will eliminate the direct physical connection to ungrounded consoles, amps, and outlets. Therefore, wireless systems will greatly reduce the likelihood of electrical shocks.
Always take a look around and keep your performance area clear of hazards and you’re in good working order. Most church staff and musicians are volunteers, we should make sure they stay protected. Remember: stay safe out there!
About the Author
Bill Di Paolo has worked in live production for over 30 years, He is the owner and technical director of Entertainment Services, a production company based in upstate New York that handles lighting, audio and video for events of all sizes in the Northeast. If you have questions for Bill you may send them to him at email@example.com.