Rock stars, comedians, gamers, and filmmakers - these are but a few mere examples of why you might be in the market for a microphone. The truth is, there are countless reasons you may need a microphone - too many to list here, that’s for sure. It’s all well and good being given suggestions but we feel it’s more important to have some understanding as to how and why microphones work!

Here, you’ll find our guide to how microphones work where we’ll discuss the basics, the types of microphones there are, their many forms and several factors to consider when exploring your microphone options. 

What is a microphone?

On a basic level, a microphone is a transducer - an energy converter. It can convert sound vibrations into electronic signals that can then in turn be recorded or amplified. 

The first patented microphone was made by Alexander Bell in 1876. This microphone with made using a wire that conducted an electrical current (DC). It could generate and receive audio signals by moving an armature transmitter and receiver, enabling transmission from both directions. Along the way, there have been many versions of the microphone such as crystal microphones that used a piezoelectric crystal to generate electricity under the compression of a diaphragm. Another is the carbon microphone - early models used a platinum bead to press against a hard carbon disc but were surpassed by using loose carbon granule elements instead of the hard carbon disc.

These two early types of microphones took hold in the 1920s and 1930s, revolutionising the way that we could communicate. All of a sudden, people could talk to each other from one side of a country to another - from one country to the next!

Fast forward to the modern day and the technology used to manufacture microphones has come a long way. And, the ways in which a microphone works depend on its designed purpose. 

Microphone Types

Now, there are several types of microphones. Each type is built differently and as mentioned before, the way in which it works depends on what it is used for. 

Dynamic Microphones

Perhaps the most common type of microphone is the dynamic microphone. Dynamic microphones are an industry standard - and a great all-round microphone solution. They’re celebrated for their reliability and rugged build, which make them perfect for live events and generally being thrown around!

Inside, there is a microphone capsule that uses electrical energy to produce an audio signal. The capsule contains a small diaphragm that’s connected to a moving coil - this vibrates when sound waves hit it, causing the coil to move back and forth within the magnetic field, thus generating an electrical current.

Dynamic mics are generally less sensitive than other microphones, such as condenser mics, and therefore need to be positioned close to the intended subject. While this could be seen as a negative, the lower sensitivity actually results in effective sound isolation. For example, if you were using the dynamic microphone for gaming or streaming, the microphone would isolate the voice without picking up background noises like clicks, keyboards, mouse movements etc. 

Condenser Microphones

Another popular mic type is the condenser microphone. Condenser microphones are characterised by their sound sensitivity, accuracy, frequency response range and phantom power requirement (more on that later). Now, how these microphones work differs from dynamic microphones but with the unifying result of producing an electrical signal by the movement of a diaphragm.  

This type of microphone uses a capsule containing a diaphragm and an electrically charged backplate to form a capacitor. Soundwaves hit the diaphragm making it vibrate, and altering the distance between the diaphragm and the backplate. This fluctuating movement (matching the sound it’s picked up) produces an electrical signal that is amplified by an internal preamp. This feature requires the help of additional power - this can be provided by batteries, phantom power, an audio interface, or depending on the mic, a computer’s USB port. 

As mentioned, condensers are characterised by their sensitivity. This type is much more sensitive than the dynamic options and as such, does not need to be placed as close to the intended subject. This, as well as wide frequency response and their capacity to pick fine details, clarity and presence, make them popular choices for recording studios and podcasters. However, the caveat to this is that the increased sensitivity means they’re more likely to pick up unintentional, background noises if you're not in a soundproofed recording environment.

Ribbon Microphones

Ribbon Microphones are an interesting one. They’re actually a type of dynamic microphone but instead of soundwaves vibrating a diaphragm attached to a coil; a ribbon microphone is fitted with an extremely thin strip of conductive material suspended in a permanent magnetic field - we’re talking half the thickness of a human hair! Where traditional microphones respond to the pressure of air particles, ribbon microphones respond to variations in the velocity of air particulars. As sound waves hit the ribbon, it vibrates within the magnetic field, which in turn generates a voltage that corresponds to the changes in velocity.

Now, this may sound more confusing and/or stranger than it’s worth - and without added insult to injury - there’s more. Ribbon microphones are known for being fragile. A rogue plosive or accidental bump while moving your kit could easily damage or break the extremely delicate conductive material. And, as such, they must be handled with care. Furthermore, they take some getting used to when put into practice. Most ribbon microphones are passive i.e. they have no onboard preamps or active components. This means it is vital to accurately set the impedance of your preamp input e.g. if it’s set too low, you’ll get a weak output and the tone will suffer. Fortunately, though, you can't damage a ribbon mic by changing the input impedance - you’ll just be altering its tone and sensitivity.

So why would you want one? Well, ribbon microphones have a unique sound. The ribbon acts as a diaphragm and transducer itself which actually provides a similar level of sensitivity as you’d expect from a condenser, with the added bonus, they have a unique and different tone to the audio they can capture. And, many newer ribbon microphones are less fragile and prone to breaking, so you can enjoy the beautiful audio quality these microphones can capture with less risk.

Different forms

Lavalier Microphones

Most commonly used in film, television, broadcasting or theatre - this type of microphone is designed for discretion without compromising on audio quality. Also known as a lav, lapel mic or body mic, a lavalier mic is small and often clipped to the user’s collar, hidden from view. Not only this, but this type of microphone also offers hand-free use. Both of these factors are ideal for situations where another type of microphone could be an eye sore and/or distract a viewer e.g. theatre actors. 

Shotgun Microphones

Shotgun microphones are named for the long tube in front of the microphone capsule that resembles a shotgun. They’re highly directional and thanks to the interference tube, which helps reduce incoming sound from the sides, this type is perfect for isolating and capturing audio from subjects that are far away. They’re commonly used in film productions, music recording and any situations where there is a lot of distracting ambient noise that would otherwise, distract from the intended subject.  

Handheld Audio Recorders

You might think you could just use your phone to record audio when you’re in the field. But a dedicated handheld recorder is going to provide a much higher level of audio quality. It’ll have better microphones, stereo imaging and compression, all of which provide that vastly superior audio recording. There are several types of handheld recorders including those with multiple mics and XLR inputs for direct instrument recording, but generally, this type of microphone is ideal for field recording, interviews, recording live music or even just the sound of nature itself.

Headset Microphones

Headsets are designed for hands-free operation. You’ll see this type of microphone in a range of applications from gaming, call centres, sportscasters, pilots, singers and the list goes on! Generally, this type of microphone will feature a cardioid polar pattern to capture the user’s voice and ignore surrounding voices or noises. 

Wireless Microphones

Wireless microphones are used for live music performances, filmmaking, journalism, business, making speeches, education and more. They’re an essential part of modern audio recording and audio capture. But that’s not to say that wireless is better than wired! 

Sure, wireless makes some recording environments easier, but some would say that you can’t beat a wired microphone. Furthermore, for wireless mics, you have to consider your transmitter, receiver, maximum range and the issue of latency. So, which is better?

As usual, it’s all based on your situation. Wired mics offer a direct connection, they’re simple and generally more reliable than wireless. But, wires can break, and cables can be a trip hazard. They simply add more or different elements to consider. Likewise, with wireless options, batteries can fun out, latency can be an issue and connectivity can become a problem. But if it were a question of audio quality, in the modern day, we’re lucky enough that there are options from both that provide exceptional audio quality.  

USB Microphone

With the rise of streaming and home recording, USB microphones have certainly seen some improvements from early models. USB mics differ from standard microphones in that they have an analogue-to-digital converter and a dedicated preamp. They also come with a built-in audio interface that allows you to directly connect to your device via the USB port, without having to invest in expensive audio equipment. USB mics are generally cheaper than other options out there but still offer excellent audio quality.

Other factors

Polar Patterns

In basic terms, a polar pattern describes a microphone's directionality. There are different types of polar patterns that can be attributed to a microphone's sensitivity to sound waves coming in from different angles to the central axis. There are five patterns and each type has its advantages and disadvantages, but it’s important to know what pattern is so you can get the right tool for the job

Directional polar pattern

The most common type of directional pattern is the cardioid polar pattern (named due to its heart shape). This type is used when you need to focus on one sound source while reducing pick-up from the sides and rear. An example of this would be a singer on stage. This pattern would pick up the vocalist's voice while limiting sounds from other performers or monitor foldback.

Hyper-cardioid and super-cardioid polar patterns

These two types are similar and variations of a standard cardioid pattern, but with a narrower pickup range at the front. Both also have less sensitivity on the sides - something to note if you use a microphone with either of these patterns. You’ll often find these patterns on shotgun microphones that are designed to pick up sound from a specific area/distance away from the mic. The longer the shotgun mic, the narrower the fontal pick-up area and the less side sound will be picked up. 

Bidirectional polar pattern

Also known as a figure-of-eight pattern, this pattern will pick up an equal level of sound from both the front and rear of the microphone, while blocking sound from the sides. This is often used to record ambient sounds alongside the main sound source in your environment. Another example could be if you were to record a guitar and vocals from a single player - you’d augment the microphone so it separately picks up the guitar sound and vocals. 

Omnidirectional polar pattern

This pattern is designed to be sensitive from all angles, equally picking up sound from a 360-degree radius. This type is often used to pick up multiple instruments or sounds from different people simultaneously e.g. live performances or an interview setting. Of course, due to its sensitivity to sound from all angles - with no null points - this microphone is not ideal if you’re wanting to isolate a specific sound source.

Frequency Response

Not exclusive to microphones, frequency response illustrates how that device responds to audio frequencies, and it is the most important factor in determining a microphone’s characteristics. 

You’ll come across specifications like 20 Hz - 20 kHz, but this doesn't paint a useful picture and this is partly why we use a frequency response diagram to illustrate a microphone's sound balance and characteristics. These diagrams allow us to see how well a microphone reproduces all audible frequencies and if it makes any changes to the signal along the way.

Ideally, a frequency response curve should be a fairly smooth line. Sudden and abrupt peaks and valleys result in unnatural sound reproduction and may cause discrepancies like feedback. Although, some microphones enable you to change the frequency response to suit different applications. Most commonly, you’ll see low-frequency roll-off control to reduce pickup of low rumbles and an upper mid-range boost that enhances voice intelligibility.

Sound Pressure Level

Sound pressure level, or SPL, is an important factor in choosing a microphone. A microphone’s maximum SPL level is the level at which it can withstand without distorting the signal. This is important because, for example, if you require a microphone for live music performances, you need to use a microphone that can handle high volumes to reproduce a clean and crisp signal. 

Microphone Switches

Many microphones feature switchable options that enable you to alter the way your microphone works. The obvious one that needs no explanation is the on/off switch. Easy, simple, we can move on! Other switches include EQ boosts/cuts, high-pass filters, attenuation pads and polar pattern switches. 

Attenuation Pad

Passive Attenuation Device. Active mics contain circuitry that can overload if the incoming signal from the capsule is too strong. When this happens, your audio signal can become distorted. Attenuation pads reduce incoming signal levels before the microphone’s active amplification process to avoid overloading. This may be used if you know the incoming audio source is going to be very loud.

High-Pass Filter 

High-pass filters, or roll-off switches, are used to cut out low frequencies from an audio source. By cutting these lower frequencies, you remove those unwanted low-level rumbles, that would otherwise degrade or interfere with your audio source. Using this type of filter can also reduce the proximity effect and distracting plosives within directional microphones.

Accessories

Pop shield

A pop shield, also known as a pop filter or screen, is designed to reduce or eliminate plosives, and mechanical noises when recording singing or speech. This is an inexpensive and highly useful studio accessory for increasing the production value of your recordings. 

Shock mount

A shock mount/cradle is designed to suspend a microphone, helping to avoid the microphone from picking up low-frequency rumbles that can be caused by bumps, shocks or hand movements. 

Dead cat

Made from faux fur, a “dead cat” is a soft, fluffy accessory that can be put over a microphone, like a sock. Designed for outdoor use, this accessory adds an extra layer of protection from wind noises and plosive sounds while retaining acoustic transparency. 

Stands

A mic stand is used for hands-free operation when using a microphone. There are various types of stands that suit different purposes such as stand arms, desktop stands, straight stands and gooseneck stands. Which is more suitable comes down to personal preference and/or the intended use. 

Boom Pole

Boom poles are an essential tool for television production and other industry use. This simple tool allows you to mount your microphone securely and easily follow your sound source without being in the shot of a camera. These are used when handheld or lav mics etc. are not appropriate e.g. filmmaking.

Glossary

Amplification - Amplification is a process of increasing the strength of an electrical signal with an amplifier. Amplification is needed for mic signals so those signals can be recognised by mixing consoles and DAWs. Additional amplification is needed when sending these signals to loudspeakers.

Attenuation - Attenuation is a process of decreasing the amplitude of a signal. For microphones, attenuation is needed to decrease strong signals that could overload active circuitry. 

DAW - DAW stands for  “digital audio workstation”. This is an electronic device or application software used for recording, editing and producing audio files

Decibel (dB) - A decibel (dB) is a unit of measurement used to display the intensity of sound waves or the power level of an electrical microphone signal.

Diaphragm  - A microphone diaphragm is located inside the mic capsule. When sound waves hit it, it moves, causing transduction which produces an electrical signal. 

Distortion  - Distortion is where a waveform is altered. Analog microphone distortion is caused when active circuitry is overloaded. Digital distortion happens when an audio signal exceeds 0 dBFS within a DAW.

Impedance - Measured in ohms, impedance is a way of expressing a circuit’s resistance and reactance to a signal.

Frequency  - Measured in Hertz (Hz), frequency refers to the number of vibrations per second of a soundwave. Humans typically have an audible frequency range between 20-20,000 Hz and as such, microphones will generally have a frequency response within this range. 

Phantom Power - Many microphones require external DC power to drive the circuitry inside. This is called phantom power. 

Transducer - A transducer transforms energy from one form to another. In microphones, a transducer converts acoustic pressure into an electrical signal.

About the Author

Leo White has been a member of the Wex Photo Video team since 2018, working in a variety of roles ranging from the contact centre to the product setup team. With both a photography BA and MA, Leo has a wealth of knowledge he's ready to share.