✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Choosing a mic for a purpose

Which type for which use

It is tempting to make technical lists of microphone types like

method of sound pickup in the capsule (dynamic mic, condenser mic, ribbon mic)
design around it that (holes for phase cancelation, interference tube and other methods of getting directionality; shock mount, etc)

Yet probably the most important is the type of intended use (vocal mic, measurement mic, boom mic) because that's what you buy them for, and that's why you pick them out of the box when you need them.

Yes, it's worth understanding the ingredients, and how choice correlate with uses, but engineers can think about implementation details better than we can.

We just need to choose in the right direction.

So often, you care first about how will you actually use the mic, and only then about what options that gives you.

radio, podcasting - comfort for long term use, allow a a few of them next to each other

probably don't care about how it looks

streaming - comfort and mobility for something you do for a long time

e.g. putting whatever mic on a movable arm

may also care about how it looks

"close range mic" - tends to refer to things intended to be close to the mouth at all times, e.g. during presentations where you want to walk around

Frequently refers to head-worn mic, sometimes to lav/lapel mics.

especially when there is a camera pointed at you as well; if not, then headset mics, and technically stage dynamic mics, radio-station mics, CB mics etc. qualify as well

note that headset mics with a closed back will often be better than a headset mic that is effectively omnidirectional

also the choice depends a little on whether the room is quiet or not

also note that decent earbuds may work roughly on the same principle as a lapel

stage - isolation from the other loud things, and sturdiness
- handheld - held close, makes a lot of sense for stage vocalists
- stage, fixed - e.g. on drumkits, guitar cabs

studio / close micing - often fixed
- studio vocal mics might be more stubtle, and used at a little more distance

instrument mics - generally these are somewhat specific to the instrument - caring about the loudness, frequencies

for more mobile instruments these may need to be clip-on

Sometimes practical details are more important than specs

How much should I spend on a mic?

To introduce the technical names...

Contact microphones are those that pick up vibration that are delivered directly to them, and pick up little to no air vibrations.

As a product, they are often something you fixate to a specific surface, picking up primarily what we like to call contact sounds, via hard coupling.

Contact sound tends to be hard for us to hear, unless there is also a large-ish sounding board (e.g. side of a computer tower case) or resonance cavity (e.g. guitar).

The simplest contract microphone is a piezo disc, pretty much as-is, although those by nature have a very non-flat frequency response - even if you try to take away the main resonance that they also have.

There are also moving-coil microphones, often either

suspending a coil within magnetic field, or

suspending a magnet above a fixed coil

...where one of the two moves (but where neither will respond to air)

In a pinch, you might plug up a regular microphone, shield it from air, and lay it on the surface.

https://en.wikipedia.org/wiki/Contact_microphone

array microphones / microphone arrays

a set of microphones with known position (and thereby phase relation)

arrays allow processing that picks up and may isolate direction

By practical application (can be varied capsules)

Body-worn microphone / face-worm microphones are useful for large-stage presentations, in classrooms, and such
- on-face microphone - are basically headsets without listening, and often made small and flesh-colored so they are hard to see. Useful for presentations.
- lav mics, a.k.a. lavelier mics, lapel mics

useful for video recording where you want

relatively easy to hide

particularly where a boom mic (someone holding a mic on a stick just out of frame) is impractical

boom microphone are used in movie recording - especially where lav mics are impractical

the boom names the stick used to hold it, and it's held just out of frame when shooting video

this is preferable when lavs are unpredictable, and you can't have something else close

often contains a very directional (e.g. shotgun-style) mic, in more wind isolation

stage microphones are specific less in technical details and more in practical details:

you generally don't use anything fragile

lower handling noise is great

lower sensitivity can be a good choice because they deal with loud levels -- this is part of

if they are somewhat directional, they can be great at e.g. lowering the audience and monitors

studio recording mics are also not overly specific thing, also in that studios allow more variation than e.g. stages

but more easily condenser mics because those are more easily made a little more sensitive to sound, even if they are a little more fragile,

you often want something more directional - to avoid picking up other players

sometimes dynamic, sometimes ribbon, sometimes other

...so "vocal mics" are usually the more sensitive condenser mics when used for subtle vocals, and dynamics when shouty or used on stage

video conference mic

fancier versions may be microphone arrays that isolate sounds, even at a table's worth of distance

cheaper versions may just be boundary mics, which pick up everything

Measurement microphones

Measurement microphones are those used when it's less important to sound subjectively good, and more important to measurements that others can repeat - science stuff, that most of us won't deal with.

Tend to have a larger dynamic range (perhaps 130dB, whereas studio mics don't always try for more than 70dB)

May focus on more temperature stability

Often have their own sort of power supply

Tend to be higher impedance(verify)

May have a well defined, probably flat frequency response

Also goes into details like whether they are more free-field, pressure-field, random-incidence/diffuse-field.

Probe microphones - often used for scanning surfaces, possibly in tight spaces and/or industrial settings, so designed to deal with more temperature, airflow, cramped spaces, and such.

Intensity microphones - care more about getting intensity right, and they may be engineered to allow in in a wider intensity range (than mics that care about subtlety can)

-->

"I'm a..."

...podcaster, gamer, or streamer

"...why do various people use larger microphones on mic arms?"

"...is a lav/lapel mic useful?"

"...what's the cheapest good mic?"

"...are USB mics any good?"

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tl;dr: There are some good options in there -- but it still fits a specific use, plus you still have to find them.

Mics with USB connections have existed as long as USB has - but for a long time were mostly there for convenience, not quality.

Good USB mics were a niche demand until recently. Streaming and vlogging has made for more options, including some decent-enough EUR50 and pretty good USB EUR100 to 150 options.

But the shit also still exists, and everything inbetween, and their marketing often looks the same.

USB mics can be seen as audio interface and microphone in one.

If you only ever need one mic - which includes most streamers - then you can e.g. spend something like 100 EUR/USD in total on audio, have it be smaller on your desk, less fuss, and there are some options in the "getting vaguely professional" range.

If your first choice is the one that makes you happy for years, great. ...this is a bigger if, though. For example, if the sound quality is great, but also it hears every bump and touch, then you have to replace all the things.

One reason pro-audio people tend to dislike all-in-ones solutions is that individual known quantities are easier to work with:

One good audio interface means you don't have to evaluate how good/bad every specific internal amp is.

One good mic for vocal work means you can plug it into whatever interface the person has

They'll also talk about upgrade paths (=upgrading one part, without needing to necessarily replace the entire thing) though arguably this is only really valid if you expect to change parts more than rarely.

...but this is as true for them as it may not be for you.

"...can I get an off-screen mic?"

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

tl;dr: Yes, but that's not necessarily worth it.

Putting a mic closer to your mouth is the easiest way to have your voice be be stronger than environment noise (including the noisy computer you're typing at, and other things in the room).

That's just physics - of things making sound. A pricy mic can't do much to change noise that is already sitting right beside you.

Also, a closer mic probably means you will strain your voice less.

Yet - a directional mic is one that (also due to physics) focuses more on picking up sound from one direction more than from another.

This too is physics, of the mic design, and it means that -- compared to an omnidirectional mic in exactly the same situation -- the thing you point the mic at (e.g. you) will be a few dB louder.

which direction varies

how much varies. Assume you're not getting more than 10dB, and that's optimistic.

So putting a directional mic just out of frame and pointing it at you can work fine. Overhead can make the most sense, for some subtle reasons like that any sensitivity at the back is best pointed at where ther eis nothing.

The above relates to

why decent quality vocal mic tend to be on screen.

why boom mics on movie sets (directional) are still specifically held as close as possible without being in frame.

why headphones with a built-in mic, even when cheap, can actually sound quite decent

they are close, meaning they can be cheap omnidirectional and still have your voice be stronger than environment noise (that said, other noise in the path is less predictable)

also, they are at a stable distance (consistent proximity effect), and can often be positioned to the side (don't have to think about pops and esses)

why you see a lot of lav mics (the things you pin to a shirt) in things like interviews - it's closeish and stable

their downside is the wire (nice-quality wireless means expensive), and you need to learn to place them, because rubbing against them is very audible.

If you insist on an out-of-shot mic:

consider doing facecam rather than room cam - it means "just out of shot" is closer.

a directional mic, probably a shotgun mics (e.g. those specific for camcorders)

...but you can't buy away physics, so it only goes so far, and don't expect very much spending under 100-200EUR/USD (and you can get a somewhat nicer vocal mic for that price).

above 200 you start taking pro mics, like NTG2, which may also be directional enough to reduce room characteristics

Also, if your goal is actually an unobtrusive mic, you might also consider a halfway-decent lav. But those are some work on positioning, thinking about movement noise, and are still wired (wireless lavs are a bunch more expensive).

...home recorder / amateur musician / student doing fieldwork

...youtuber / film student

"Can't I just use my phone?"

Using a mic well

Some simple/cheap quality-improving tips

Put it as close as is sensible

Typical use and gain / How to set reasonable levels for any given mic

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Handling noise / desk noise

Mic technique

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Note: A lot of this is going to repeat arguments - from different angles of givens, and needs.

Arguments from room noise

Arguments about distance

Arguments about direction

Basic mic positioning / mic technique: Just plain distance

Relevant for: everyone (from streamers to casual recorders to studios)

Too close: pops and proximity effect

Pops are sudden rushes of air from your mouth (from plosives - p and b sounds mostly). Those rushes disspiate quickly, but if you're basically eating the mic, they arrive at the capsure very efficiently. And if you're that close you also can't put anything inbetween that reduces this. You can maybe do it to the side, but would have to know about it.

The proximity effect basically points to a constructive effect that means bassy sounds work well when very close to a mic. Which you may like, for that deeper radio voice, yet it also means very little movement varies that bass, so you would have to know about it.

There is a simple and stupid way to avoid having to explain this to people: tell them to sit 10-20cm away. Or avoid having to, but putting a pop filter or something else in front. (I've seen radio stations use large foam windscreens, probably for this reason)

Too far: Consider the how intended signal strength, such as your voice, relates to environment noise.

If your environment is otherwise pretty quiet, and you want to pick up the environment (people, cats, dogs, whatnot), then you can sit at some distance so that everything is picked up.

You can absolutely amplify that, but you will necessarily be amplifying both you and that environment noise.

So consider your room being loud, or people or cars through an open window are, or the HVAC system has a low hum, your PC is loud and/or you'll be on your keyboard while recording, etc. If it's roughly as loud as you, you will hear it just as much, and there's no separating the two afterwards.

If you want to pick up just you, then yes, you can look for directional mics, but there is an even simple method: sit closer.

The louder your are (in absolute terms), the less gain you need.

The closer you are to the mic, the louder you are. That environment noise did not change.

If you turn down the gain to keep your voice output the same, the net effect is that you are only really turning down that environment noise.

Or, from another view, that you are isolating yourself better from that noise.

(...also from other people in the room. This is one reason radio stations that have guests tend to sit close to mics. And have them sit at some distance, but there's only so much room for that)

In fact, the better you can do this, the more that even cheap mics will sound pretty decent. This is one reason even cheap headset mics sometimes work quite well - you even avoid the proximity effect variations by being in a constant position, and also pops if you put it a little to the side.

If you get to play with a decent mic (negligible other noise sources such as internal noise and lower amplification noise, so the effect is clearer):

Sit at half a meter, turn up the gain until you are at decent level.

You're clear, and so is you snapping your fingers behind you.

Sit at a few cm and turn down the gain accordingly

That same snap behind you is now barely there.

(Note: in the moment you won't hear the environment noise as much, because our brains have had a lifetime of experience at tuning that out, and you're hearing it through the headphones at the same time as you're in the room. Record it and play it back -- it's a lot more apparent.)

Now record both and listen to it later (because in the moment, you're good at thinking away the environment).

Listen to the difference in sound clutter and noise in the background, which probably includes your PC, and imagine a passing truck, neighbours shouting or walking down the hall, or even someone else on their own mic in the same room.

Notes:

This is one reason that a decent headset mic actually works quite well.

if your environment is louder than a mic's noise specs, those noise specs barely matter anymore

particularly for free-standing mics

in fact, if you're recording in your bedroom without sound isolation, this puts a serious limit on how much a fancy mic even can help

in some cases you may be just as well off with a EUR30 dynamic mic or decent headset mic (just because you'll use it closer) than a sensitive EUR200+ condenser

Beyond vocals:

Distance on acoustic instruments

again, closer makes for better isolation

for concurrent recording of live performances, this matters

also why pickups are nice

closer may catch some odd harmonic effects, more fingering sound, and such

further than necessary just loses volume (and isolation)

people point mics at guitar amps, rather than using the signal going to its speaker

arguments against micing an amp:

most of the internal tone and distortion processing is also present on the output

so using a DI is smaller, and not another another mic and stand to lug around.

you have to tend to gains to get decent on-stage isolation of sound

neutral arguments:

the physical driver is probably a little bassy, so it's not quite the same as the signal, though you can mostly EQ that

arguments for micing an amp:

it's an easy way to avoid ground loop noise (when you don't have enough DI boxes to do this properly)

the setup may introduce a little compression, because physics(verify) which is e.g. nice on bass guitars

Proximity effect

Notes specific to...

...lav mics

...head-worn mics

Accessories

Wind, shock, pop, reflection, and other noise protection

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Relevant for: vocals, outside recording, preventing some environment rumble anywhere

The issues

Wind as in weather.

Strong wind is a lot of physical movement streaming past, often turbulent around objects and cavities so if it reaches the capsule directly would often overpower most other sounds.

So when you can, you want to reduce wind getting close to the microphone, while reducing vibrations much less. This is relatively easy to do at all, though hard to do well.

Microphones tend to come with a little wind-style protection built in, because it's universally useful.

But they won't do it much because it will also reduce the amount of useful sound that arrives as well, so it's better as an option you can add only when you know you need it.

Whistling with the airstream directed into the microphone is the same sort of wind.

One vocal-specific issue is pop, the sudden ejection of wind from your mouth that you get from plosives like p, b, and others. When this easily reaches the capsule, it's the same as the wind problem, though a lot more instantaneous.

Another vocal problem is sibilance, the ess sounds (s, t, ch) that sound harsh - and easily louder than other parts of the vocals.

This one's harder than pop, in part because it's less directional. It's a good idea to record less of it to start with.

Shock refers to hitting whatever the mic is standing on / handing by (and anything hard-coupled enough, like your desk and keyboard, your floor and your foot-tapping and the passing truck and neighbours rumbling or walking down the hall). If the mic is mounted to avoids hard coupling, most of that sound won't make it in via this route.

Reflection here refers to the fact you probably have multiple walls nearby, meaning you record direct and reflected sound - effectively a little reverb on everything. For live use this isn't much of an issue (it just sounds like a person in a room, which we are used to hearing), yet lessening this reflection gives you more leeway and options when mixing later. (Note also that this can be less relevant when you're closer to the mic)

Solutions designs, and products

Pointing the mic at your mouth from the side

Helps: vocal pops

But: positioning of yourself now has a little more effect on frequency content (and volume, due to the pickup shape),

so it's often easier (and a little more controlled) to explain and use pop filters.

Pop filter are primarily for reducing pop in vocal use.

Helps: vocal pops

It's typically just any thin piece of fabric suspended in front of the mic.

One design is a few nylon layers to reduce wind speed - which is easy enough to DIY with some coathangers and pantyhose.

Foam windscreens

are a specific foam stuck over all the inlet of a microphone (which for many mic designs works out as blobs, though longer for e.g. shotgun mics).

Helps: vocal pops, wind

These work against gentle wind, and also act as a pop filter.

They are not the best at either, but decent, cheap, and typically supplied with microphones.

Wind muffs (sometimes 'dead cat')

are furry variants of windscreens, that tend to be be a little better at reducing wind than just foam

Helps: wind, vocal pops

They cost a little more, and come with some practical details like fluff varying with air moisture, and that you may have to clean them more often.

Softies (initially a brand name, but later a much more generic one)

is a vaguer term but frequently refers to a larger synthetic-fur thing large enough you can stick various microphones's business end in them.

Helps: wind, vocal pops

Blimps and zeppelins

Helps: wind, vocal pops

similar to softies, but are larger, and will often contain the entire mic with a a bit more air between microphone and boundary, and usually use a mesh material (regularly with thin foam on the inside) to stop rushing air.

Seen e.g. on boom mics. They work better, but are heavier.

These may also have a removable synthetic fur cover. (This seems to be where the 'dead cat' name originated)

Shock mounts are elastic suspensions, which reduce physically coupled rumble.

Helps: shock, rumble

Basic versions are easy enough to improvise from, say, elastic bands. The characteristics of what frequencies they work best for varies, but halfway decent for no effort

Things like tension do matter matter to how well they work a little, and studios and other permanent setups will probably invest in something less fiddly and more durable.

Reflection filter is often a acoustic foam around half of the mic, opposing the sound source, creating a small stall.

The intent is to control and reduce reflections from hard surfaces in at least most of the direction, which can help isolate the source from other sources. Note that it does only half the job (at best) that e.g. a vocal booth would, but it reduces reverb to a good amount so can be an effective tool for e.g. vocal work.

Switches on microphones

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Are most commonly:

Low cut / roll-off (bent-line symbol) - removes low frequencies with a filter

when recording vocals, frequencies below 50 or 100Hz or so are likely to be nothing but rumble (also for home use; think passing trucks), and maybe some wind

knee frequency varies. Some mics have two positions for this, varying knee frequency

can't be changed, so doing this filter in an EQ down the line is sometimes more useful (and largely the same)

Pad switch - basically just lowers amount of signal - attenuation on the order of 5dB, 10dB or 20dB

useful when the input is structurally very loud, e.g. putting mics on a guitar cab.

when the output has a voltage maximum that can overload (consumer 3.5mm, +4dBu XLR), you want to do this before it hits the point it can overload. The mic is a perfectly sensible place to do that

You rarely want this for softer instruments, softer vocals

There are sometimes also pads down the line, which is more about gain staging - comparable levels and e.g. not forcing sliders/knobs down to their first 5%

(not directly related: pad is also sensible to have on DIs, for very hot signals)

Other mic tools

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Basic mic positioning

Fancier mic positioning

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Soundstage effects

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Relevant for: fancier serious instrument recording, and arguably any group of voices or instruments.

While in smaller untreated rooms there is value to individual micing, e.g. to reduce the amount of room acoustics and to isolate sources and to give you control of levels in mixing (and the source isolation you need for that), things like orchestras often play in spaces and placements that does consider the acoustics; individual micing would still give more choices later but also removes most of the spacious effect of the hall, of distance, of size, of ambiance, and that is hard to impossible to introduce later.

So there is good argument to record at least those cases in a way that reproduces that soundstage.

(Unrelatedly, it turns out that hand-held recorders with two mics in front tend to record in a way that, when produced later, lets us binaural humans better tell apart different speakers, making it easier to listen to and e.g. transcribe.)

XY pair

Two directional microphones, inlets/capsules very close, at a 90 degrees angle

proxmity means no time-of-arrival ambiguity, (so) stereo image comes mainly from directional pressure differences.

less impression of space/depth than most other setups, but more stable

no issues mixing down to mono

small amount of high frequency loss in the plane between the mics, which is why they are usually placed above each other (means this rejection is above/below, not left/right)

if the mics touch, this may ruin the effect (or the recording, if there's rattling)

AB pair

Two omnidirectional microphones in parallel, some space apart

tweaking the distance changes amount of directionality that is picked up (verify)

a little bassier, because omnidirectional mics tend to be (verify)

mixing to mono by adding the two is less than ideal, as that tends to show comb-filter-like effects. Yet often, using just one channel is perfectly fine.

Jecklin disk

AB style, at 36cm distance, and with a disk inbetween that increases the apparent separation

Easier to mix to mono because of side rejection (side tends to arrive more in one mic)

near coincident are setups with effects between XY and AB, usually decent ambient and decent directional, and most are named for institutions that thought up each specific setup, like ORTF (French television), NOS (Dutch television), DIN (German standardization)

ORTF: cardioid, pointed outwards, 110 degree angle between them, capsules 17cm apart (roughly a head's width)

https://en.wikipedia.org/wiki/ORTF_stereo_technique

NOS: cardioid, 90 degree, 30cm

https://en.wikipedia.org/wiki/NOS_stereo_technique

DIN: cardioid, 90 degree, 20cm

possibly more of a proposal and never used much?(verify)

more suitable for somewhat closer sources

Mid/Side

seems to refer to a two-mic setup, with a cardioid or omni facing the sound source, and a bidirectional mic acting pointed perpendicular

(...also sometimes imitated with three mics, one mid, and two imitating that figure-eight) (verify)

Those two microphones's output is not directly useful to listen to or use -- but in most cases, mid-side is only an internal thing, with some controls of the width, but outputting left and right like:

Left = Mid + Side

Right = Mid − Side

Note that if you want mono channel, you want mid -- and left+right is mid.

There are a few different reasons to do this

one is flexibility: you can control the depth during recording, but if you record mid and side separately, you also have control over that later (something you can't do with most of the others)

mixing to mono is simple

Blumlein pair

XY pair using bidirectional microphones

tends to give a nicely realistic soundstage

Faulkner array / Faulkner pair

bi-directional, 20 cm apart, parallel and aimed at the source

not recommended when there is also audio in the other direction

Decca tree

three mics, at least 1.5m distance

seems to ask for moderately dictional mics, at least at higher frequencies (verify)

resembles AB with a center fill

wide stereo image, mostly used for orchestras and choirs and anything else large. Does not work so well for smaller areas(verify).

There seem to be variants with five (extra left, extra right, look for 'outrigger')

takes care to position, takes care to mix

https://en.wikipedia.org/wiki/Decca_tree

Mercury Triad

On Stereo

More on mid-side

Related tricks

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Relevant for: stage, studios

Differential microphone is a noice-canceling arrangement useful in live setups on smaller stages, where crowds and things like guitar amps are nearby:

use two identical microphones, one trained on the sound you want, the other not, and probably nearby each other

invert one (i.e. reverse phase) (fancier consoles tend to allow this in the mixer)

anything that shows up equally at both mics is likelier to cancel out

which is likely to include lowish frequency crowd noise, guitar amp bleed, drums, backline speakers, etc.

anything that shows up at one mic (e.g. the singer) barely so.

sometimes leads to some odd phasing effects, though(verify)

Not to be confused with differential microphone arrays, which use beamforming from multiple mics to isolate in a direction, thereby suppressing background noise and some reverb.

On active noise reduction

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

After-the-fact noise suppression may help with any mic.

...but not much, because doing so afterwards will not make the signal quality better, it primarily makes it less distracting within a mix of other sounds.

Noise, in this context, is primarily anything other than human talking.

This is e.g. great for streamers, and generally much less for music people.

🛈 For context, the classical options were:

gating - assumes you only need to hear loud sounds, and assumes anything low-level is always noise

sometimes this is hard gating, which basically toggles between full signal as-is, and basically-muted

but many implementations try to shift more smoothly between 'mute' and 'as-is', because that may sound less jarring

upsides:

when that threshold is well tuned

it's perfectly quiet when people are not talking

the noise is there when they are, but it's probably low enough to not bother communication

downsides:

when the threshold is set wrong

set too high and it removes to much, e.g. cutting off every first word

set too low and it removes no noise at all, or seems to cut in and out randomly

the noisier the mic is, the harder the threshold is to set - it can behave arbitrary enough it can be more distracting than not having it.

if input levels are not very consistent (e.g. varying distance to a stationary mic a lot), that threshold will be wrong over time

The later a gate sits in your audio chain, the harder it may be to tune (particularly if it's after a compressor(verify), because those by nature lessen the amount of variation in amplitude)

gating is potentially more annoying than leaving the noise in

Noise suppression based on an example of noise

Basic 'noise removal' features (e.g. try the one in audacity) often ask you to provide an example of noise without signal

typically what they do is

determine the frequency content in the noise, then later reduce those frequencies

often using an envelope detector to reduce it more strongly in weaker parts of the signal, so that it bothers actual signal less

upsides

great at removing anything constant - hum, AC rumble, whistle, microphone bias, steady device noise

downsides

as a moderately aggressive EQ (e.g. 12dB reduction in narrowish bands), so the more you remove frequencies, the more easily it introduces little artifacts.

The fancy new kid on the block broadly does two things:

The easy win in these could be considered 'gating, but triggered by the presence of voice, not of anything loud'

trying to be clever about what to suppress while you are talking

This is more fragile, but still typically a bunch better than nothing.

RTX was the known term, Krisp does something similar, and RNNoise is also something you've probably heard without realizing.

buzzword compliant, due to neural net training

what they do is typically mostly adaptive EQing

trained beforehand on what kinds of spectra to respond to(verify)

but adaptive, so unlike the previous, it it doesn't require an example of noise - and can deal with more varied noise and with changes in noise

upsides:

magically more selective - when it works, it works well.

limitations

magically more unpredictable - the training includes (and hides) a lot of assumptions, and you don't get to control them.

These seem to be trained for average vocals over typical noise,

so they do not deal well with singing, shouting, mumbling, less-usual noises

usually little to no way to tune or control any of that

...unless you know how to train neural networks and you chose something not proprietary (most are proprietary)

you still have to think about your audio chain, e.g. a compressor after probably works better than before(verify).

RTX Voice

only runs on Nvidia cards, specific RTX and some GTX, and gamers may note a small framerate drop

proprietary(verify), free

can present a noise-filtered device based on another (practical to use it for voice chat without requiring plugin style integration)

RNNoiseRNNoise

Used by: OBS (its "Noise Suppression" audio filter)

open, free

https://github.com/xiph/rnnoise

Krisp

Used by: Discord

also a standalone, proprietary, paid-for thing (free version is time-limited)

can present a noise-filtered device based on another device (practical to use it for voice chat without requiring plugin style integration)

reported to sound more muffled

https://krisp.ai/

More technical

Microphone cabling

Directional behaviour

Sensitivity, noise performance, and some further stuff that influences quality (specs)

Acoustic Overload Point (AOP), "Maximum SPL"

Self-noise / equivalent input noise / equivalent noise

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

A mic and its preamp

Sensitivity

Sensitivity for analog microphones

That 94dB-referenced thing you see in mic specs

Okaaaay, more practically, what do the figures mean?

The audio world world be itself without dancing about the definitions

Sensitivity for digital microphones

Sensitivity and noise combined

SNR in theory, and in practice

Signal path can add noise

Environment noise can add noise

Distance and directionality

Mic dynamic range

Between specs and uses

Handling noise

Cable noise

On preamps

Powering mics

Note that

Of the microphones in common use, it is primarily condensers that need power.

it is fairly unusual for dynamic mics to use power.

Batteries

Pros:

Simple, avoids need for all of the below details

Cons:

Batteries can be empty, which is awkward to deal with.
(Forgotten) batteries can leak, which can cause damage

For real shows on stage, people tend to swap them out a lot faster than necessary just to be sure, because troubleshooting in the middle of an event looks really unprofessional.

AB powering / T-powering / T12 / 12T / Tonaderspeisung / Tonader 12V / DIN 45595

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Relevant to plugs: XLR, kleintuchel, grosstuchel?

⚠ Note: This is not phantom, is not compatible with phantom, and mistaking one for the other can damage some microphones

It seems that(verify)

T-power microphones will ignore Phantom power supplies, (verify)

but some phantom-power mics (and some non-powered ones(verify)) may damaged by T-power supplies?(verify)

T12 supplies power to a mic via the XLR/tuchel cable that also carries audio

by putting 12V DC between XLR pins 2 and 3 (the differential pair -- and note that the XLR pin numbering differs from the DIN numbering(verify)), with 180 Ohm series resistors

So yes, the microphone sees 12V across it.

Because 12V DC is easier to supply from batteries (than 48v for phantom), T-power was more popular around film work (and still is seen there, e.g. wireless mics), and why it may seem somewhat correlated with shotgun mics (and, apparently, Sennheiser).

Upsides:

Avoids shield, so avoids shield-related issues

easy to implement, also on batteries

Downsides:

accidentally mixing this with now-typical Phantom can damage things

more attention should be paid when supplying the power

any power impurity is on the same wires as the audio signal (and not equally present on both)

...and therefore audible (but you'll probably be DIYing neither this or Phantom, so...)

Phantom is easier easier for many-mic setups - they can draw from the same bus, whereas with tonader the best implementation is a simply power supply for each (verify)

Phantom power / P48 / IEC 61938 / DIN 45596

Relevant to plugs: XLR

Phantom power can supply power to a mic via the XLR cable that also carries audio.

by putting a voltage equally on pins 2 and 3

...and using shield (pin 1) as ground for this circuit

which is a bad idea for interconnects, which is why phantom should only be used/enabled for mics (and other phantom-powered things) and it is good habit to turn it off until you need it

Audio interfaces with XLR inputs often supply phantom on it.

Mixer panels can regularly let you enable phantom power on all their inputs.

Many active DI boxes can be powered by phantom, often as one of the options (Passive DI boxes do not need power).

Anything non-XLR does not do phantom power.

Upsides:

Lets you supply power to the mics that need it (mostly condensers) without needing extra wiring, replacing batteries, etc.

mics that need it send a stronger signal, so the net effect is that you can use longer cables before noise is relevant.

should not affect signal quality

Keep in mind:

mics that require phantom power will probably barely work without it, or not work at all

most notably condenser mics

For mics that don't support it, it makes no difference

There are a few reasons to keep phantom power supply turned off until you know you need it, roughly:

the pin 1 problem in interconnects (probably the largest reason)

Earth lift, sometimes necessary to work around the pin 1 problem, will also disconnect phantom power

applying this power on some unbalanced microphone designs (most aren't) can be trouble

and some other details, see e.g. [1]

Generally none of these are an issue, since you'll generally only plug balanced mics (or mics via DI boxes) into XLR-with-phantom sockets - but there is the odd case where you can introduce noise or even damage (mostly in stage settings), so it's something you want to eventually know

Technical side:

Phantom power is

a voltage placed equally on pins 2 and 3 (both signal pins)

which means that the receiving side (the differential amplifier on the audio lines) shouldn't see it on the signal at all (hence 'Phantom'), as as power should flow equally through both balanced-pair wires.

...and using shield (pin 1) is now used ground for this circuit.

Using shield as ground is not advisable in general -- primarily because it is a bad idea when using XLR for interconnects (see also the Pin 1 problem - and you want to turn phantom off on any XLR inputs used as interconnects)

yet is fine on inputs that are a single microphone (by nature isolated).

On DI boxes there are some extra footnotes (mostly to internal their design(verify)).

Voltage:

Technically three variants: 48V, 12V, and later 24V

in practice often 48V (though is apparently allowed to be 10..52V(verify)

the 48V is purely for historical reasons, and actually somewhat impractical now (9..12V is enough for almost all circuits, and microphones have to step it down to that)

Current:

early phantom supplies might only guarantee suppling around 2mA, enough for a single FET

modern phantom supplies should be capable of 10mA-15mA, and modern mics usually use something like ~5mA

Other specifics

Plug-in power / Bias voltage

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Relevant to plugs: 3.5mm plugs (and some custom ones)

In practice, bias voltage is a mostly a thing on mics connected via 3.5mm TRS, like PCs, video cameras, DSLR, phones, voice recorders, minidisc.

Can be but don't expect it to be more than 2V. (Used to be 5V, now often 3.3 or 2.5V, whatever Vcc is, and we've seen iPhones deliver too little)

Can be but don't expect it to have to supply more than 1mA or so.

(The actual voltage has varied with designs and over time - on specific/custom equipment might actually between 1.5V and 10V - but anything you connect to consumer hardware (e.g. sound card, hand held recorders) is likely to be around 2 or 3V (DC))

This bias power is specifically for electret mics with a FET amplifier inside it.

...it just happens that most desktop mics with a 3.5mm connector are exactly that. Note that not all mics with 3.5mm need (or can use) bias voltage, including e.g.

lav mics with an inline battery-powered amplifier
dynamic mics (but this is rare)

Mics that don't need it are often designed to ignore it, so it should be hard to damage a mic with bias voltage.

The voltage, and low current capacity, means there is a quick and dirty test for the presence of DC bias on a mic input with a plain LED (probably even without the resistor), preferably a red one because those have a lower forward voltage.

Wiring microphones

Things to keep in mind:

On impedance

See Music_-_studio_and_stage_notes#Analog_audio_stuff

But basically: most pro, XLR-connected mics are order of 200 ohm (often within 150..250 but it's not a fixed range), because they are designed to impedance-bridge with approximately 1.2kOhm on the other side - mixer, interface, or other mic input.

This is typical enough that for the most part, you plug it in and it works.

Higher and lower mic impedance exists.

Higher and lower amp impedance exists.

Most of them are special cases - which you'll typically intuit are unusual, even if you don't understand the details yet.

If either side's impedance is switchable, that mostly changes the amount of load, which mostly just bends the frequency response a little.

The effect is mostly about EQ -- unless you're connecting a rather unusual mic, or a very old one (from the era when studios were new, and only two steps removed from how phone systems used to work).

Offset or rectify

Amplification

Isolation, DC removal

Types of microphone - workings

Dynamic microphone

Condenser

Pre-polarized versus externally polarized

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

This is often often about condenser mics (not always?(verify)).

It's about where the backplate's energy comes from.

externally polarized means something external to the mic applies voltage to the backplate

e.g. phantom-powered qualifies (typical on XLR)

though the term seems to come up mostly around measurement microphones, apparently then often 200V,

and you see connectors like e.g. 7-pin LEMO seems used around some measurement microphones

Pre-polarized

e.g. electrets by definition have a magnet as the energy source

seems to effectively refer to electrets

note that these may still need power for amplification, just not for the capsule

e.g. an XLR "phantom to pre-polarized microphones adapter" is probably an adapter for electret (likely for some lav or maybe head-worn mics), and to do that conversion close to the mic for quality reasons.

It is a little unfortunate that these terms refers only to the backplate design -- most real-world electrets have a FET integrated that does still need external bias power, but this detail is left up to context.

Electret microphone

Circuit use

Related hacking

MEMS

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

More widely, microelectromechanical systems (MEMS) refers to microscopic devices that have both electronic and moving parts, particularly where the processes to make the electronics can also be used to make said moving parts, so it's not just two things in the same package, it can e.g. be part of the same silicon.

For microphones, MEMS e.g. means smaller than electrets, and MEMS is now quite typical in smartphones. While electret can be made just as small, MEMS have other properties that makes them a practical choice.

So basically, a tiny condenser-style design etched into an IC, usually alongside a preamplifier and possibly ADC.

Many speak PDM (at MHz rates), or possibly things like I2S. PDM also makes them a less sensitive to electronic noise than analog (...when consumed as high speed digital signals, often by an audio codec), and because it's PDM you could choose to use their output as an analog signal.

Piezo microphone

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Piezo microphones, a.k.a. crystal microphones.

Piezo elements are more general type of sensor, usable to sense stress, vibration. They are ceramic capacitors that are designed to be bent a little. This bending creates the voltage. (due to the piezoelectric effect: stress on a crystal leads to voltage across it).

They are often discs, presumably because it's an easy design and it makes it easier to couple to a larger surface. There are other designs, e.g. the flat ones in piezo guitar bridge pickups -magnetic.

Reacting to being bent means they are good at picking up sound that carries through a solid material, and quite poor at picking up airwave sound directly.

This "it hears only what it's pressed onto' is a feature in applications like as in vibration sensors, impact sensors (you can DIY a drumkit with these), instrument pickups. Contact microphones are often piezo elements plus a little amplification (often fairly closeby because the high output impedance is less than ideal).

One limitation of piezos is relatively narrow frequency response, which also comes in part due to the physical size - each disc design has a significant physical resonance frequency and its sensitivity falls off beyond it.

Acoustic-guitar pickups are often piezos under the bridge so that string vibration makes it to the piezo fairly directly. (There may also be a body pickup as well, piezo or electret, to get the soundbox's sound).

Piezos are not used on electric guitars, which typically use magnetic pickups. Magnetic pickups work only with metal strings, which isolates to pick up just the string movement, and will e.g. ignore slapping and some other things you might do playing acoustic guitar (except whatever movement that makes it to the strings).

See more notes at Electronic music - pickups

Ribbon mic

Historic or exotic

Carbon

Liquid

Ribbon

Fiber optic

Laser

Some more glossary

Response field

Wireless microphones

Frequencies for wireless microphones

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Classical systems are analog RF systems, often FM modulated(verify).

The frequencies,

whether you are allowed to use them at all,
or only with a license,
or only with notice,
and/or only under certain conditions (e.g. bodypacks with low transmit power)

...will vary by country, and often additionally per local jurisdiction (even in smaller countries).

So products tend to focus on ranges with fewer problems. Preferably license-free ranges - but those are often full of random use already (and also vary per country),

But license-exempt frequencies change over time, particularly as markets like the mobile one demand more of that spectrum.

So it's an ongoing game, products are more easily sold only for specific areas (europe, US, Japan, australia), and part of this is still effectively left up to the consumer to figure out.

Many wireless mics fall within UHF, but have also used VHF.

A lot of devices target a specific ~50MHz band within that to put a bunch of channels in (often bands that are free in specific regions). Within UHF it's mostly between 470 and 868MHz , and these ranges may also be called things like 'the 700MHz range', 'the 800MHz range'. Not precise, but people will know what you mean.

For example, I have a device that

has a few variants, each aimed at a different part of the world

this variant sends between 786-822Mhz, which was aimed at most of the EU,

but e.g. in the Netherlands you should no longer use almost all of that (791..862MHz) since 2016 [2][3] and would already have trouble since around 2013, when mobile devices started using it.

It hard to find detailed information about frequency bands, partly because they are partly specific to a country (see e.g. this document), and partly because few people want to commit to something that may change next week.

Things like Sennheiser's SIFA might be more up to date, but I'm not gonna promise that.

"true diversity"

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

In radio communication in general, when using multiple antennas to receive, it frequently happens that one antenna receives a specifically positioned sender slightly better, e.g. caused by interference of the signal with reflections of that same signal.

So, if we could, why not use only the better antenna?

In this context,

non-diversity receiving means connecting an antenna directly to the tuner.

You can't have multiple antennas (or at least, they would just act as one, and sort of do an average)

dual antenna diversity receiving often refers to a small processor and switching the best antenna (which might also be doing some prediction) to a single tuner.

true diversity runs a tuner and receiver per antenna, and (roughly speaking) decides which demodulated signal is best.

True diversity makes somewhat better choices in a few more situations.

...those situations are best avoided anyway - because it's often "when the signal is borderline"

...but in the everyday sense, true diversity works a little better in the same situations

Unsorted

Clipping

Can I use my phone as a wireless microphone?

"Gradient microphone"

Electronics project notes/Audio notes - microphones

Choosing a mic for a purpose

Which type for which use

Sometimes practical details are more important than specs

How much should I spend on a mic?

To introduce the technical names...

"I'm a..."

...podcaster, gamer, or streamer

"...why do various people use larger microphones on mic arms?"

"...is a lav/lapel mic useful?"

"...what's the cheapest good mic?"

"...are USB mics any good?"

"...can I get an off-screen mic?"

...home recorder / amateur musician / student doing fieldwork

...youtuber / film student

"Can't I just use my phone?"

Using a mic well

Some simple/cheap quality-improving tips

Put it as close as is sensible

Typical use and gain / How to set reasonable levels for any given mic

Handling noise / desk noise

Mic technique

Arguments from room noise

Arguments about distance

Arguments about direction

Basic mic positioning / mic technique: Just plain distance

Proximity effect

Notes specific to...

...lav mics

...head-worn mics

Accessories

Wind, shock, pop, reflection, and other noise protection

Switches on microphones

Other mic tools

Basic mic positioning

Fancier mic positioning

Soundstage effects

On Stereo

More on mid-side

Related tricks

On active noise reduction

More technical

Microphone cabling

Directional behaviour

Sensitivity, noise performance, and some further stuff that influences quality (specs)

Acoustic Overload Point (AOP), "Maximum SPL"

Self-noise / equivalent input noise / equivalent noise

A mic and its preamp

Sensitivity

Sensitivity for analog microphones

That 94dB-referenced thing you see in mic specs

Okaaaay, more practically, what do the figures mean?

The audio world world be itself without dancing about the definitions

Sensitivity for digital microphones

Sensitivity and noise combined

SNR in theory, and in practice

Signal path can add noise

Environment noise can add noise

Distance and directionality

Mic dynamic range

Between specs and uses

Handling noise

Cable noise

On preamps

Powering mics

Batteries

AB powering / T-powering / T12 / 12T / Tonaderspeisung / Tonader 12V / DIN 45595

Phantom power / P48 / IEC 61938 / DIN 45596

Other specifics

Plug-in power / Bias voltage

Wiring microphones

On impedance

Offset or rectify

Amplification

Isolation, DC removal

Types of microphone - workings

Dynamic microphone

Condenser

Pre-polarized versus externally polarized

Electret microphone