Because sound travels through any medium, including water, it would make sense for microphones to be waterproof.
So are microphones waterproof? Typical microphones are not waterproof and many will actually be damaged by water and even by excess humidity. That being said, there are waterproof microphones on the market and there are methods to make certain non-waterproof microphones at least water-resistant.
In this article, we’ll discuss how water and humidity affect microphones along with the waterproof mics on the market and tips on improving the resistance of regular mics to humidity and water.
How Water And Humidity Effect Microphones
Most microphones are not waterproof and many microphones perform poorly in high humidity. This makes sense since they are electrical devices, but why exactly do microphones not like water and humidity?
Water And Microphones
It’s important to note that pure distilled water will not damage electronic devices (including microphones). This goes for passive mics and active mics (whether they are on or off). This is because distilled water is a very poor electrical conductor.
The issue is that most water in everyday life is not pure and is contaminated with minerals that do conduct electricity.
Therefore, if electricity (including the mic signal and the power for active mic components) is flowing in a wet microphone, the water will likely cause electrical shorts. These shorts cause current to flow to places it shouldn’t be and if the current is too strong, it will severely damage the electronics.
Basically, if a microphone is plugged in, it’s not waterproof.
That all being said, if a microphone is not plugged in and has no electricity running through it (this is important for battery-powered mics), water should not cause any electrical damage. So long as you make sure that no contaminants are left behind and that the microphone is dry before you plug it in, there should not be an issue.
If you happen to spill water (or any liquid) on a microphone that’s plugged in or submerge the microphone while it’s plugged in, disconnect it as soon as possible before the water has a chance to cause electrical shorting.
Once disconnected, dry the microphone near a heater and store in a dry place with desiccants. Ensure the microphone is completely dry before ever plugging it back in. Do not use a hairdryer to dry your microphones as the movement of air could damage the mic’s diaphragm, worsening the situation.
Humidity And Microphones
Though not nearly as intense as liquid water entering a microphone, humidity has a few negative effects on microphones.
Regular humidity (below 70%) generally won’t cause any issues. However, keeping microphones exposed to prolonged humidity above 70% could potentially lead to the following issues:
Moisture can and will cause atmospheric corrosion on the metal parts of microphones.
These metal microphone parts include:
- Ribbon diaphragms (often aluminum)
- Moving-coil (often copper)
- Magnets (often neodymium or iron)
- Printed circuit boards (with solder, copper, and more)
- Grilles (often brass)
- Bodies (often steel)
- Output pins (especially when silver plated)
Corrosion may also affect the non-metal parts of microphones, such as:
- Plastic diaphragms (often Mylar)
- Acoustic foam (often polyurethane)
- Capsule rings (often PVC)
Note that gold is sometimes used to sputter condenser diaphragms and is very resistant to corrosions. However, even gold can become tarnished over time.
As mentioned before, impure water will potentially short active electronics.
At extreme humidity, this is something to consider, especially when working with active microphones (condensers and active ribbons) that have much more inner circuitry than passive microphones (dynamics and passive ribbons).
Condenser Capsule Malfunction
A typical condenser capsule is known as an AF (audio frequency) capsule. These capsules work like parallel-plate capacitors that store a constant electric charge. Any movement in the front plate (diaphragm) changes the distance between the front plate and the stationary backplate. This change in distance causes a change in capacitance which produces and inversely proportionate change in voltage (mic signal).
Unfortunately, these capsules are inherently in a high-impedance circuit (> 1 GΩ).
Therefore, in humid conditions, this electricity will often have an easier time escaping on airborne water molecules than through the impedance converter (the capsule output). This causes noise, crackling, diminished frequency response, and a reduced output level.
To read more about microphone capsules, check out my article What Is A Microphone Capsule? (Plus Top 3 Most Popular Capsules).
Therefore, it’s best to keep microphones in relatively dry conditions. Try keeping your recording spaces dry with dehumidifiers and store microphones in dry places with desiccants when not in use.
Once again, humidity often isn’t a huge issue unless it’s above 70% and persistent.
Hydrophones: Waterproof Microphones
I would be remiss if I did not mention hydrophones in this article.
A hydrophone is simply a microphone designed for underwater applications. Hydrophones allow us to record underwater sounds.
The vast majority of hydrophones are based on piezoelectric transducers. Piezo mics work with piezoelectric materials (known as crystals) that, when subjected to varying pressure, produce a voltage (mic signal). They have very high output impedances and are capable of handling high-pressure environments.
Because a typical hydrophone is designed to capture sound in water, it does a relatively poor job at capturing sound in air. This is because sound travels much differently in water than in air:
- Sound travels 4.3 times faster in water than in air.
- Sound waves in water will exert 60 times the pressure they do in air at the same amplitude.
Waterproof Microphones On The Market
A quick Google search will show many online retailers of hydrophones. Here are a few common sellers:
- Aquarian Hydrophones (affordable)
- Cetacean Research Technology (high end)
- Brüel & Kjær (high end)
These companies have excellent waterproof microphones for your needs.
There are other hydrophones on the market that are worth mentioning as well. These include (with links to check the prices):
- Point Source Audio CO-8WL (lavalier microphone)
- Sennheiser MKE 2 Elements (GoPro camera microphone)
- Instamic Pro (digital Bluetooth wireless USB lavalier)
There are plenty of other waterproof and water-resistant mics on the market, but these are definitely worth checking out in my opinion.
Humidity Resistant Microphone Types
There are many places (particularly in outdoor settings) where the humidity is high and there’s nothing we can do about it. Fortunately, there are some microphone types that are designed to be quite humidity resistant.
RF Condenser Microphones
RF (radio frequency) condenser microphones have a different capsule design than their regular AF (audio frequency) counterparts.
RF condenser capsules are built into low-impedance circuits and act as tuning capacitors for low-noise RF oscillators.
A high-frequency RF signal is passed through the capacitor at all times. Changes in capacitance, which are caused by diaphragm movement (just like in the AF capsule), alter the resonant frequency of the circuit. These alterations are, of course, proportional to the sound waves at the diaphragm.
An RF demodulator takes this high-frequency alteration at its input and outputs an audio signal.
The low-impedance capsule circuit of the RF condenser makes much more resistant to humidity than the typical condenser microphone. For this reason, RF condensers are preferred and sought after for outdoor recordings.
The Sennheiser MKH line of microphones are the most popular RF condenser mics on the market.
Moving-Coil Dynamic Microphones
Moving-coil dynamic microphones are passive, durable, and quite resistant to humidity.
The diaphragms of moving-coil dynamic microphones are generally made of thin plastic film (Mylar). This Mylar is relatively thick since it has to hold a moving-coil and is very resistant to humidity.
The coil of a moving-coil mic is typically made of copper and the magnets are typically neodymium. Though both these metals are indeed corrosive, they are very resistant to corrosion.
The fact that moving-coil dynamic microphones have simple, spaced-out circuitry with no active components means there’s a very low probability of electrical shorts.
Some more durable moving-coil dynamic microphones have even been able to withstand submersion while connected without being electrically destroyed.
To read more about moving-coil dynamic microphones, check out my article Moving-Coil Dynamic Microphones: The In-Depth Guide.
I would never suggest using tube microphones in outdoor settings due to the inherent fragility of vacuum tubes and the inherent risk of damage in outdoor environments.
However, it’s the vacuum tube that actually makes these microphones humidity resistant.
Vacuum tubes require heat to function properly. In fact, these electric devices have heaters (filaments) built into their designs.
On top of tube functionality, these heaters act to dry the interior of the tube microphones when in use. Thus allowing tube mics to be used in studios with less-than-ideal humidity levels.
Of course, when these mics are not in use, it’s best to store them in a safe dry space.
How To Improve A Microphone’s Resistance To Water And Humidity
There are several strategies to improve a microphone’s resistance to water and humidity. Let’s start with humidity.
Improving Humidity Resistance In A Microphone
Most microphones are naturally sensitive to persistent humidity due to its effects on corrosion. Other microphones perform poorly in humidity due to its effects on their electrical components and circuitry. In either scenario, there are steps that can help save your microphones from humidity.
- Ensure a consistent temperature and humidity in your recording environments. Use air conditioners and dehumidifiers if need be.
- Store microphones in dry spaces (with desiccants if need be) when they are not in use.
- Keep your desiccants dry (rebake silica bags regularly).
- Use pop filters and/or windscreens when recording vocals.
- Use windscreens and dead cats when recording outdoors.
Basically, keeping your microphones out of humid conditions is the best way to go.
Improving Water Resistance In A Microphone
Sometimes we need (or just want) to record underwater or in the rain. In these cases, choosing a waterproof or water-resistant microphone is a great idea. But if not, improving water resistance is paramount.
Microphones have been encased in plastic bags to make them “waterproof.” This technique is best used with inexpensive passive dynamic microphones. In case of a tear in the plastic, we do not want to fry the electronics or an expensive microphone.
This plastic bag technique can be extended to other bag materials (non-lubricated condoms are a popular choice) and waterproof containers that can host microphone(s). Though these setups will effectively waterproof a mic, they do so at the expense of sound quality. The acoustics within these protective layers are poor and put a barrier between the sound wave and the microphone.
Will heat damage a microphone? High and low temperatures can cause damage to the electronics (particularly tube electronics) and to the capsules of microphones. Too much heat from the environment or from the heater of tubes in tube mics will slowly damage the diaphragm and some electronics of the microphone.
Why are outdoor microphones furry? Outdoor microphones are subjected to wind noise. This noise can be greatly reduced by using a furry windscreen (known as a dead cat) that fully encompasses the microphone, which is why you’ll often see “furry” mics outdoors. Wind energy that hits the fur does not cause loud vortexes required for wind noise.
For an in-depth read on furry mics, check out my article What Are Dead Cats And Why Are Outdoor Microphones Furry?