Microphone jargon explained: Glossary of mic terms
An external microphone is an essential purchase if you're serious about getting quality sound recordings on your videos, but which type should you choose? To help you become more au fait with the world of sound recording, here's the lowdown on the audio jargon you can't avoid running into...
What is a polar pattern?
The direction from which a mic can pick up sound cleanly is known as its polar pattern, and this varies according to its design and intended use. In many ways, a mic's polar pattern is a bit like the audio equivalent of a lens's focal length, as it tells you how wide or narrow the pickup angle will be.
What is an omnidirectional mic?
Omnidirectional mics pick up sound from all around the capsule, and this polar pattern is popular on lavalier mics clipped to a presenter's clothing, as the wearer is likely to look up and down and turn their head from side to side while speaking. With omni lavs, it's also common to mount them upside down. This shields the capsule's top from plosives and nasal exhales, with only a small decline in high frequency response and sound level.
What is a cardioid mic?
Cardioid (heart-shaped) polar patterns are common on many types of mics. These pick up sound from the front and sides of the mic, and it falls off at the rear. Cardioid patterns are usually seen on handheld vocal and instrument mics, where the lack of rear response makes them less susceptible to feedback.
What is a supercardioid mic?
Supercardioid polar patterns offer a narrower pickup zone than regular cardioids, so they reject sound coming in from the sides much more. They are more sensitive to sounds from the rear than a cardioid though, so you need silence behind the mic when using them.
What is a hypercardioid mic?
Hypercardioid mics reject even more side-on sounds and are more focused on sounds directly in front. As they're very directional, and have a barrel shape, they're often called 'shotgun' mics, but they're also sensitive to sounds from the rear, so as with a supercardioid, you need to ensure all is quiet behind the mic to get a clean recording of the source you're targetting.
What is a bicardioid mic?
The figure-of-eight or bidirectional mic is the last popular polar pattern. This picks up sounds equally well from the front and rear, but strongly rejects anything coming in from either side. In essence, a figure-of-eight is used like a double-headed mic, so two sources 180 degrees apart can be cleanly recorded.
What is frequency response?
Sound waves are carried through the air, and are measured in cycles per second (also known as Hertz). This is essentially how many times the wave vibrates air molecules in a second to produce a 'note'. Soundwaves stretch from very low frequencies (think of a very low tone) to high frequencies (a very high, shrill note) and someone young with perfect ears may hear from as low as 20 cycles per second (20Hz) to a very high 20,000 cycles (20KHz).
This 20Hz-20KHz is the maximum frequency range of human hearing, though falloff occurs - especially at the upper limit - with age. By the time we pass 25, we're unlikely to hear beyond 15KHz, and this drops down to about 12KHz at 50 years.
To get natural-sounding audio, a mic needs to capture the frequencies we hear, and its frequency response reveals the lowest and highest-pitched sounds it is capable of recording. Professional mics often also have a frequency response chart, so the user can see how the mic may 'colour' the sound with an increase or reduction in sensitivity at particular frequency groups. If the frequency response is relatively flat across the range of human speech (about 100Hz to 8KHz), then the mic will produce a natural-sounding recording.
Phantom and Plug-in Power
Unlike 'passive' dynamic mics, condenser mics require power to run, and mixing desks, field recorders and video cameras in the pro sector offer XLR mic inputs with switchable phantom power. This is sent down the mic lead to fuel the mic's electronics, so no additional power supplies are needed. Enthusiast condenser mics also need power, but either take a battery or use a different standard with a low voltage, called Plug-in Power (PiP). This is sent through the mic lead from the device via its 3.5mm jack socket. Many audio recorders, camcorders and DSLRs offer this, so you can use PiP mics, but check your camera's manual. If your DSLR only offers a passive (unpowered) 3.5mm jack socket for external mics, you'll need a mic that offers its own power source in the form of a battery.
Types of microphones
What is a shotgun mic?
A shotgun microphone is a 'barrel' shaped mic with a hypercardioid pickup pattern that's used extensively in film and TV production to isolate the sound coming from a specific direction. Shotguns may be mounted on the camera, so they target the sound that the lens is pointing at, or attached to a telescopic boom pole. The boom allows them to be placed as close to the source as possible, while keeping the mic itself just out of frame. The mic is suspended on a shock-absorbing mount, so the boom can be moved and the mic directed at the sound source without creating any handling noise.
What is a lavalier mic?
A lavalier microphone is a very small condenser mic that can be clipped to a lapel to remain in close proximity to the mouth of the speaker. It is also often called a tie-clip mic. Because they are visually unobtrusive and give great audio quality, lavs are now the default choice for TV presenters and interview subjects. A subset of the lav is the headworn mic, which is either hidden in the performer's hair or on a small boom that's clipped around the ears. This ensures the mic stays close to the mouth even if the head is turned.
Large diaphragm condenser microphones
A large diaphragm condenser is the most common mic for studio voice recordings, such as voice-over for programmes or vocals for music. Because it's a powered condenser mic, it's able to record crisp, high frequencies much better than unpowered dynamic mics, and the large diaphragm within the capsule does a wonderful job of recording voices really cleanly. Although budget studio condensers are available, and are often sold as 'podcast' mics that plug in to a computer via USB, top pro-quality models are very expensive, costing several thousand pounds.
A handheld microphone is a medium-sized mic designed to be held by the performer or clipped to a stand. They're mainly used for work like speeches and live vocals over a PA system, but examples like Shure's SM58 is sometimes seen on screen as a general purpose interview mic or used as a general purpose post-production tool for voice-overs. Handheld mics are normally very robust, dynamic mics, so they'll withstand loads of abuse and require no independent power source for them to work.
What is a boundary microphone?
A boundary micrphone is an omnidirectional condenser mic that can be placed on a surface like a table. Sometimes called a plate mic owing to its flat shape, they're often used to record meetings or conferences, where speech could be coming from any direction. In a studio, they may be used to capture the live sound of the room.
What is a parabolic microphone?
A parabolic mic is a highly directional mic that works like a satellite dish to focus the sound waves onto a central point, where the mic is situated. They're sometimes used to isolate distant sounds in wildlife recording, but low frequency response is very poor on portable dishes, so they are more common in surveillance use.
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