Microphones – Why you need them

Dec 4, 2020 | Science


Lot’s of EVPs have been recorded using inexpensive recording equipment, even old-fashioned tape recorders – but if you want to up your game and get crisp, clear voice recordings, you will want to invest in a decent microphone. But as anyone who has ever shopped for recording equipment can attest, there are so many choices available you could easily spend months learning about different microphones and which one is the best for you and your budget.

I will begin by stating something very important. Generally speaking, with electronics, you get what you pay for. There are a lot of non-name brands on the market promising a lot of cool-sounding features, but they tend to be made with cheap materials and flawed design. It doesn’t make sense to shell out money for a low-priced mic if you’ll have to replace it with something marginally more expensive in a month, so hopefully I can save you the time, money, and frustration by explaining your options.

The Nutshell Version: Get a dynamic omnidirectional microphone with a large or medium diaphragm. Married to Kanye West? You can afford a condenser mic.

What does a microphone do?

Pressure variations, whether in the air, the water, or another medium the human ear can detect, are considered sounds. The human eardrum transfers pressure oscillations, or sound, into electrical signals that our brains interpret as music, speech, noise, and so on. Microphones are designed to do the same thing.

Microphones are a type of transducer – a device which converts energy from one form to another. Microphones convert acoustical energy (sound waves) into electrical energy (electronic audio signals).

Different types of microphones have different ways of converting energy but they all share one thing in common: The diaphragm. The diaphragm is a thin material that vibrates when it comes into contact with a sound wave. This vibration converts sonic energy into electrical energy.

The first question you must answer is “How will I be using this, and what am I recording?”. As you can imagine, a ghost investigator in a creaky old house trying to capture whispers from unknown direction will have very different needs than a singer in a recording studio. Among your considerations, you have to take into account the directionality of the sound, the acoustics, background noise, the amplitude of the sound (how loud will it be).

Specification of the intensity of a sound implies a comparison of the intensity of the sound with that of a sound just perceptible to the human ear. For example, a 60-dB, or 6-bel, sound, such as normal speech, is six powers of 10 (i.e., 106, or 1,000,000) times more intense than a barely detectable sound, such as a faint whisper, of 1 dB.

Of course a lot of this is difficult to anticipate, but you actually do know a few things. You know that you don’t know the direction of the sound, that it is likely to be very low volume, that the acoustics may be very bad, and (especially if you are in a group) that there will be a fair amount of background noise to contend with.

First Consideration – Microphone Polar Patterns

Polar patterns describe how microphones pick up sound, showing specifically where mics ‘listen’ spatially and which positions are blocked. Having a good grasp of these polar patterns will help you select the right mics that capture the sound that you need while minimizing unwanted noise.

1) Cardioid Microphones

Cardioid mics capture everything in front and block everything else. This front-focused pattern will let you point the mic to a sound source and isolate it from unwanted ambient sound, making it ideal for live performance and other situations where noise reduction and feedback suppression are needed.

2) Super/Hyper Cardioid Microphones

These mics have the same front directionality, but have a narrower area of sensitivity compared to cardioids. This results in improved isolation and higher resistance to feedback. Because of their enhanced ability to reject noise, you can use these for loud sound sources, noisy stage environments or even for untreated recording rooms. On the flip side, back rejection is a bit compromised, so you will have to position unwanted sounds on the dead spot sides.

3) Omnidirectional Microphones – (top pick for investigations)

These are microphones that capture sound from all angles. Because of their non-directional design and zero rejection, these mics capture nuances better, resulting in a more natural sound. Use these in studios and for live recording of multiple instruments, as long as the noise level is low. The obvious downside is that they lack background noise rejection.

4) Figure-8 Microphones (2nd top pick)

The name of this pattern is derived from its graphical representation, which looks like the number 8. The long and short of it is that Figure-8 mics capture the sound of both the front and back, while rejecting the two sides. This front and back sensitivity makes them idea for stereo recording and for capturing two or more instruments.

5) Shotgun Microphones

Shotgun mics, also called Line and Gradient, feature a tube like design that make their polar pattern even more directional than hyper cardioids. The capsule is placed at the end of an interference tube, which eliminates sound from the sides. This design is commonly used for film and theatr.

6) Switchable/Multi-Pattern Microphones

These are microphones that can change between different polar patterns, allowing for versatile placement. Many of today’s USB condenser microphones have this feature, letting you switch between multiple patterns by simply flicking a switch. Others provide the same flexibility through changing the mic head. The advantage that these mics offer is obvious, more positioning possibilities and more usage. But extra moving parts = more chance to lose or damage the mic.

Second Consideration – Diaphragms

Well, not a lot of jargon in this category. There are small, medium, and large diaphragms. But there is no standard, so you’ll do best to look at the overall size of the mic.

1) Small Diaphragm (not recommended)

Mics with small diaphragms are commonly called pencil mics because of their thin cylindrical shapes.

Pros: Their compact design makes them lighter and easier to position, and interestingly, they are designed to be stiffer, to handle higher sound pressure levels and have wider dynamic range.

Cons: Known limitations of this particular diaphragm type are increased internal noise, and low sensitivity. If you can get a mic with a medium or large diaphragm instead, you will be happier with the results.

2) Large Diaphragm

The bigger the diaphragm, the more it can sense air vibrations.

Pros: As more vibrations are captured, more of the sonic details are faithfully reproduced. These move easily, allowing them to detect even faint differences in sound pressure levels which result in a more transparent and natural sound. Also the most common configuration on modern USB mics.

Cons: just make sure that you keep the volume in check because they can distort when the sound pressure level is increased. Probably not an issue for ghost investigations.

3) Medium Diaphragm

Medium Diaphragm mics are sometimes called hybrid because they combine the characteristics of small and large diaphragms.

Pros: They tend to have a slightly fuller and warm sound similar to large diaphragms while retaining some of the high frequency content that small diaphragms could.

Cons: A large diaphragm is better able to pick up ambient sound, which you actually want. But between a medium and a small, definitely go with the medium.

Even more considerations?

There are several other options, but these are generally geared towards live and recorded music, theater, and film. If you are a musician, you would want to choose for your instrument, and for your particular venue.

For example, dynamic, condenser, or ribbon microphone each have different designs reflecting how the diaphragm is positioned. A dynamic mic should suffice, but if you can afford it, a condenser microphone will pick up more nuanced sound and changes in sound waves.

* Do you want a tube (vacuum tube) or valve power supply? A vacuum tube may give a “warmer” sound.

* What is the maximum SPL (sound pressure limit) it can absorb without distortion? The higher the better.

* What is its level of self-noise (usually 5 decibels and up). This is the noise the microphone itself gives off, so you want it to be as low as possible.

* Is it a well-known brand? Trusted brands include Sennheiser, Blue, Shure, Audio Technica, Primo, Warm Audio, Neumann, Electro-voice.



Studio Microphone Buying Guide


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