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For various reasons, I've been working nomadically in a city away from home, oftentimes videoconferencing from the laptop at public spaces. The background noise annoys meeting participants, and there's only so much that I can combat this by muting and unmuting.

I started looking at earbuds with mics. I need to travel light, so no battery powered Bluetooth sets, and to avoid 3rd party drivers on the laptop, no USB devices. Something that uses the traditional audio output and the mic input.

I was surprised to find on Amazon many options for earbuds+mic, but they only have one jack (at least in the images). How is it that an earbud/mic combination can use only one jack rather than both the headphone and mic ports of a laptop?

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  • 4
    oldtimemusic.com/…
    – Moab
    Oct 18, 2022 at 14:46
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    Note that wired earbuds with an in-line mic hanging down below your face won't be much better than the laptop's own mic. I assume as it's old enough to still be using two jacks for Headphones/mic it won't be new enough to be using an array mic, which can be almost silent in operation, even in noisy environments. If you opt for any device in which the mic & speakers have a fixed distance between or one with a boom mic, you may have better luck with the noise. You can specifically look for noise-reducing mics.
    – Tetsujin
    Oct 18, 2022 at 15:51
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    Mics, unless they have computational noise-cancelling, cannot differentiate between sounds. Sound, like light, works on an inverse square law - so if the mic's much closer to your mouth, the background gets correspondingly quieter, less overall gain, better SNR. Array mics get small enough to work in just one or both ears, no distinctly separate mic at all - look at Apple's earpods for instance - but they tend to all be bluetooth.
    – Tetsujin
    Oct 18, 2022 at 16:11
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    I’ve never had to download and install a 3rd party driver for a USB headset. I also don’t understand your aversion for Bluetooth.
    – Michael
    Oct 19, 2022 at 7:29
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    USB headphones don't necessarily use 3rd-party drivers. Most use the driver usbaudio.sys, which is included in Windows, and has been since Windows 98 (source). I verified it now on PolyBW3225T.
    – Jonathan
    Oct 20, 2022 at 13:58

3 Answers 3

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Audio jacks come in different versions. Some devices feature two separate jacks for speakers and microphone. The layout of these connectors is called TRS (tip-ring-sleeve).

For speakers the top (tip) of the connector is for the left audio signal. The middle (ring) of the connector between the two black insulation rings is for the right audio signal. Finally the bottom (sleeve) of the connector is used as ground:

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To connect another channel together with speakers via the same connector shape, an additional point of contact had to be created. This was done by adding another insulation ring to the connector, so there are now two contact points in the middle. The upper one of these is still being used for the right audio signal, but the lower one may be used for an additional signal. In the case of headphones it's being used for the microphone. The lower end of the connector remains the ground. This connector is called a TRRS (tip-ring-ring-sleeve) connector:

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The corresponding jack for the connector has to be designed differently for both layouts.

In case your laptop sports two jacks (one for speakers, one for microphone), it won't be compatible with a single connector headset.

Both pictures were released under the CC BY-SA 3.0 by Benedikt.Seidl.

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    @PasWei "Search engines do not care about capitalization" - maybe so, but the people who find things with search engines do.
    – MTCoster
    Oct 19, 2022 at 16:19
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    So you wrote it that way because you only intended that part of your answer to be meaningful to search engines, not to humans reading your answer. That's... not a good thing, and makes it more like a link-only answer, with less information in the answer itself. You could still edit this answer to at least fix that. As for answering cross-site duplicate questions with a link to the duplicate, often people just comment. But there is some limited justification for posting an answer that way. Oct 19, 2022 at 16:20
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    I updated my answer and attempted to realize your suggestions. I appreciate you all taking your time and telling me where to improve / what to avoid.
    – PasWei
    Oct 19, 2022 at 18:31
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    @287352 That's a good point, but it's not a good excuse. Anyway, this answer is now significantly improved and I'm happy to change my vote.
    – gronostaj
    Oct 19, 2022 at 18:36
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    Just wanted to point out that the second image in this answer isn't correct. There were a few devices that used that, but the standard today, for both laptop and cell phone audio jacks, is (from tip to sleeve) Left, Right, Ground, Mic. Also, I have seen laptops with two jacks that would also work with single-plug TRRS headsets. Oct 20, 2022 at 14:57
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Standard mono phone plugs have two separate electrical connections along the barrel, one at the end called the tip, for the audio signal, separated by a plastic ring from a second one called the sleeve, which is the ground reference. (The voltage difference between the signal and ground connections determines the amplitude of the audio signal.) Stereo connectors add another connector between those two, the ring; these TRS (tip-ring-sleeve) plugs by convention carry the left channel on the tip, the right channel on the ring and the ground on the sleeve.

To add a microphone signal to these you add a fourth connector in the same way, giving you a TRRS (tip-ring1-ring2-sleeve) plug: four metal rings separated by three plastic rings.

Here are examples of TRRS and TRS plugs:

alt text (Source: Wikimedia Commons.)

There are unfortunately several different designs for TRRS, and this can cause compatibility problems.

  1. Left and right audio output are invariably on the tip and first ring, just as with TRS jacks. But the ground can be on the second ring or on the sleeve, with the mic signal on the other one. Mic-on-sleeve (CTIA/AHJ standard) is the more common arrangement nowadays; it's used on iPhones (back when they had phone jacks) and the majority of Android phones and many computers, including MacBooks and my Lenovo T510 Thinkpad laptop. The older OMTP standard puts mic on the second ring and ground on the sleeve; this is mostly found on older devices dating from around 2010-2012, including Nokia and Sony/Ericsson phones, Samsung Chromebooks and the PlayStation Vita.

  2. For compatibility with TRS jacks, TRRS jacks detect whether the second ring and sleeve are shorted together (i.e., both contacts are touching the continuous sleeve of a TRS connector), in which case they will do audio output only, or whether there are two separate connections there, one with a microphone on it. Simplifying somewhat, getting your mic detected involves putting a resistance between the device and the microphone: the resistor value varies but many microphones will be considered "unplugged" if just connected directly. Further, connecting the microphone connection to ground, sometimes through various levels of resistance, is also used to signal button presses on the headset for those that have one or more buttons.

That should be enough to give you some sense of how this works and understand the various compatibility problems that can arise with TRRS audio/microphone connections. If you need a few notes on connecting traditional devices (such as tape players and old computers) via TRRS, I have some here in the section "Smartphone Connections"; that also has some links to further information. If you need a deeper look at how any of the above works, the Electrical Engineering Stack Exchange is probably the place you want to ask. (What an electrical engineer would call "beginner" questions are welcomed there.)

It may also be worth noting that stereo audio + microphone is not the only purpose to which TRRS jacks have been put. I've also seen them used to carry mono or stereo audio + video, for example, and even for a computer serial data connection. So don't assume that anything with a TRRS jack is always designed for headphones or a headset.

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  • IDK if it's worth mentioning but as an aside the 4-pole connector can alternatively carry stereo audio and a baseband SDTV video signal. At one point Raspberry PI used this format, and I think some Apple device did too, but not with the same pinout.
    – Rodney
    Oct 19, 2022 at 10:40
  • @Rodney These plugs have been used for a whole lot of different purposes. Samsung Omnia 2/Pro phones had a TV out over a TRS jack (video on the ring IIRC). iPod Shuffle used a TRRS to USB cable to connect to a computer. Not only is the connector poorly designed, but it's also been used for a lot of sketchy stuff.
    – gronostaj
    Oct 19, 2022 at 12:35
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    Huh, so that's why these plugs change channels as you plug or unplug them (or if they're partially plugged in). Also why my one phone would register a "click to start Google Assistant" every time I plugged one set of cheap Dollar Store headphones into it. Oct 19, 2022 at 13:50
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    Excellent answer. It would be nice to explicitly state that TRS stands for Tip-Ring-Sleeve and TRRS stands for Tip-Ring-Ring-Sleeve but I got that from the answer by gronostaj superuser.com/a/1748277/115517
    – Caltor
    Oct 19, 2022 at 14:53
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    Just to add to the confusion, some modern high end audio gear also uses TRRS or TRRRS to output a balanced signal. Especially on portable equipment.
    – Chuu
    Oct 21, 2022 at 15:14
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They use a different plug.

These are the headphones plug (left) and microphone plug (right). The one on the left is called a "TRS" plug because of the Tip-Ring-Sleeve arrangement. The other one would technically be "TS" for its lack of a ring, but I haven't seen this term actually used anywhere. The terms "stereo jack" and "mono jack" are also used.

Drawings of two 3.5 mm jack plugs side by side. The plug on the left consists of three metal segments separated with pieces of plastic, labeled "tip", "ring", "sleeve". The other plug consists of two segments labeled "tip" and "sleeve". The second plastic separator is missing, effectively merging the ring into sleeve.

(Image adapted from this one)

In regular stereo headphones without a mic, the tip and ring are used for left and right audio channel respectively, and the sleeve is a common ground. Meanwhile a regular microphone is using a mono jack, with the tip carrying the sole audio channel and a ground on the sleeve.

On a headset a TRRS plug (Tip-Ring-Ring-Sleeve) is used, with tip and the first ring carrying stereo headphones audio, the second ring being a common ground and mono mic signal on the sleeve (usually - see cjs's answer for nuances). This type of plug requires a compatible TRRS socket. When plugged into a regular socket, it will behave like regular TRS headphones.

A drawing of a TRRS jack. Plug looks very similar to a TRS jack, but there's an second same-sized ring cut off from the sleeve after the first one.

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    "...the second ring being a common ground and mono mic signal on the sleeve..." Not always. See my answer for details on the two standards, CTIA/AHJ and OMTP.
    – cjs
    Oct 19, 2022 at 8:35

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