What happens as wavelengths of sound waves approach tens of micrometers?What happens to sound waves?Resonance in a 1 ft granite boxcan silence happens when 2 sound waves destroy each otherFrequency of Sound WavesTransmission of Sound WavesRefraction of Sound WavesDetect original sound wavesWhat happens to energy lost as soundSound Waves + Closed Box --> What happens under movement?Sound Waves concept problem
How does a Potion of Poison work?
Do you know your 'KVZ's?
Why do players in the past play much longer tournaments than today's top players?
Keep milk (or milk alternative) for a day without a fridge
Comparing two limsup's
How can one write good dialogue in a story without sounding wooden?
How to know whether a Tamron lens is compatible with Canon EOS 60D?
Why are Hobbits so fond of mushrooms?
Should disabled buttons give feedback when clicked?
Is there a word for a message that is intended to be intercepted by an adversary?
Is anyone advocating the promotion of homosexuality in UK schools?
How to achieve this rough borders and stippled illustration look?
What happens as wavelengths of sound waves approach tens of micrometers?
How might the United Kingdom become a republic?
Is Trump personally blocking people on Twitter?
How can I get a player to accept that they should stop trying to pull stunts without thinking them through first?
How is angular momentum conserved for the orbiting body if the centripetal force disappears?
Why isn't pressure filtration popular compared to vacuum filtration?
How did the hit man miss?
Who Can Help Retag This?
Was lunar module "pilot" Harrison Schmitt legally a "pilot" at the time?
What does "it kind of works out" mean?
As the Dungeon Master, how do I handle a player that insists on a specific class when I already know that choice will cause issues?
What explains 9 speed cassettes price differences?
What happens as wavelengths of sound waves approach tens of micrometers?
What happens to sound waves?Resonance in a 1 ft granite boxcan silence happens when 2 sound waves destroy each otherFrequency of Sound WavesTransmission of Sound WavesRefraction of Sound WavesDetect original sound wavesWhat happens to energy lost as soundSound Waves + Closed Box --> What happens under movement?Sound Waves concept problem
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;
$begingroup$
I was having an online conversation about Dungeons and Dragons, and my acquaintance abbreviated "Barbarian Level 17" as Bb17. I took the opportunity to make a joke about how that is similar to musical notation (i.e. B♭₁₇). Then I tried calculating the frequency and wavelength and got:
$$f=3.8 text GHz$$
$$λ=87.5 text μm$$
Can a compression wave (not sure you could even call it sound at that point) have such a high frequency? Does anything happen when it does?
acoustics
asked 8 hours ago
David CoffronDavid Coffron
1305 bronze badges
New contributor
David Coffron is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
I was having an online conversation about Dungeons and Dragons, and my acquaintance abbreviated "Barbarian Level 17" as Bb17. I took the opportunity to make a joke about how that is similar to musical notation (i.e. B♭₁₇). Then I tried calculating the frequency and wavelength and got:
$$f=3.8 text GHz$$
$$λ=87.5 text μm$$
Can a compression wave (not sure you could even call it sound at that point) have such a high frequency? Does anything happen when it does?
acoustics
asked 8 hours ago
David CoffronDavid Coffron
1305 bronze badges
New contributor
David Coffron is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
I was having an online conversation about Dungeons and Dragons, and my acquaintance abbreviated "Barbarian Level 17" as Bb17. I took the opportunity to make a joke about how that is similar to musical notation (i.e. B♭₁₇). Then I tried calculating the frequency and wavelength and got:
$$f=3.8 text GHz$$
$$λ=87.5 text μm$$
Can a compression wave (not sure you could even call it sound at that point) have such a high frequency? Does anything happen when it does?
acoustics
asked 8 hours ago
David CoffronDavid Coffron
1305 bronze badges
New contributor
David Coffron is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
I was having an online conversation about Dungeons and Dragons, and my acquaintance abbreviated "Barbarian Level 17" as Bb17. I took the opportunity to make a joke about how that is similar to musical notation (i.e. B♭₁₇). Then I tried calculating the frequency and wavelength and got:
$$f=3.8 text GHz$$
$$λ=87.5 text μm$$
Can a compression wave (not sure you could even call it sound at that point) have such a high frequency? Does anything happen when it does?
acoustics
acoustics
asked 8 hours ago
David CoffronDavid Coffron
1305 bronze badges
New contributor
David Coffron is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 8 hours ago
David CoffronDavid Coffron
1305 bronze badges
New contributor
David Coffron is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 8 hours ago
David Coffron
asked 8 hours ago
David CoffronDavid Coffron
1305 bronze badges
New contributor
David Coffron is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 8 hours ago
David CoffronDavid Coffron
1305 bronze badges
asked 8 hours ago
David CoffronDavid Coffron
1305 bronze badges
1305 bronze badges
New contributor
David Coffron is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
David Coffron is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
When we think of air as a continuous medium that can support waves, we have to assume that the scale of spatial variation in macroscopic quantities (like pressure, density, etc.) is significantly higher than the mean free path of the molecules. To within an order of magnitude, the mean free path of air molecules is around 0.1 µm, which is still a few orders of magnitude smaller than the wavelengths you're looking at. So treating this as a sound wave is probably still fine.
It's also worth noting that acoustic microscopy uses sound waves with frequencies up to a few GHz, not too far off from what you're talking about. However, we're usually talking about waves in solids or liquids in this case; in air, waves of high frequencies like this are quickly attenuated as they propagate.
answered 8 hours ago
Michael SeifertMichael Seifert
17.3k2 gold badges33 silver badges60 bronze badges
$endgroup$
add a comment |
$begingroup$
Yes, no problem in principle.
The limit for wavelengths is the interatomic distance. The cut-off frequencies for phonons in solids are about $10^13$ Hz.
In gases, attenuation goes up a lot a short wavelengths. This paper says that attenuation in air is 80 000 dB/m (for $f = 20$ MHz): http://acoustics.ippt.pan.pl/index.php/aa/article/viewFile/555/486
answered 8 hours ago
PieterPieter
9,8003 gold badges18 silver badges39 bronze badges
$endgroup$
add a comment |
$begingroup$
It's called ultrasonic because most people cannot hear it (this particular frequency is way over the typical audible threshold of 20,000Hz). You could also call it an overtone in a more musical nomenclature. This sound would resolve smaller features than larger waves, so you can use it to generate higher resolution images as in ultrasound or with a hypothetical creature in D&D with ultrasonic echolocation (animals typical echolocate in the range 40-140kHz).
answered 6 hours ago
guitarphishguitarphish
111 bronze badge
New contributor
guitarphish is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
2
$begingroup$
This doesn't seem to address my question. Welcome to StackExchange; I'm not super familiar with the Physics stack, but their tour could shed some basic light on what kind of answers are expected here. My question isn't about what class of sound this would be, but on the physical implications of such an occurrence. In any case, it's a pleasure to meet you and I hope to see you around.
$endgroup$
– David Coffron
6 hours ago
$begingroup$
I can delete my answer if you don't like it. The other answers also do not talk about phonons, which are quantum quasi-particles of sound that are much smaller than the scales being talked about. en.wikipedia.org/wiki/Phonon
$endgroup$
– guitarphish
6 hours ago
add a comment |
Your Answer
StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "151"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);
else
createEditor();
);
function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);
);
David Coffron is a new contributor. Be nice, and check out our Code of Conduct.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f491084%2fwhat-happens-as-wavelengths-of-sound-waves-approach-tens-of-micrometers%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
When we think of air as a continuous medium that can support waves, we have to assume that the scale of spatial variation in macroscopic quantities (like pressure, density, etc.) is significantly higher than the mean free path of the molecules. To within an order of magnitude, the mean free path of air molecules is around 0.1 µm, which is still a few orders of magnitude smaller than the wavelengths you're looking at. So treating this as a sound wave is probably still fine.
It's also worth noting that acoustic microscopy uses sound waves with frequencies up to a few GHz, not too far off from what you're talking about. However, we're usually talking about waves in solids or liquids in this case; in air, waves of high frequencies like this are quickly attenuated as they propagate.
answered 8 hours ago
Michael SeifertMichael Seifert
17.3k2 gold badges33 silver badges60 bronze badges
$endgroup$
add a comment |
$begingroup$
When we think of air as a continuous medium that can support waves, we have to assume that the scale of spatial variation in macroscopic quantities (like pressure, density, etc.) is significantly higher than the mean free path of the molecules. To within an order of magnitude, the mean free path of air molecules is around 0.1 µm, which is still a few orders of magnitude smaller than the wavelengths you're looking at. So treating this as a sound wave is probably still fine.
It's also worth noting that acoustic microscopy uses sound waves with frequencies up to a few GHz, not too far off from what you're talking about. However, we're usually talking about waves in solids or liquids in this case; in air, waves of high frequencies like this are quickly attenuated as they propagate.
answered 8 hours ago
Michael SeifertMichael Seifert
17.3k2 gold badges33 silver badges60 bronze badges
$endgroup$
add a comment |
$begingroup$
When we think of air as a continuous medium that can support waves, we have to assume that the scale of spatial variation in macroscopic quantities (like pressure, density, etc.) is significantly higher than the mean free path of the molecules. To within an order of magnitude, the mean free path of air molecules is around 0.1 µm, which is still a few orders of magnitude smaller than the wavelengths you're looking at. So treating this as a sound wave is probably still fine.
It's also worth noting that acoustic microscopy uses sound waves with frequencies up to a few GHz, not too far off from what you're talking about. However, we're usually talking about waves in solids or liquids in this case; in air, waves of high frequencies like this are quickly attenuated as they propagate.
answered 8 hours ago
Michael SeifertMichael Seifert
17.3k2 gold badges33 silver badges60 bronze badges
$endgroup$
When we think of air as a continuous medium that can support waves, we have to assume that the scale of spatial variation in macroscopic quantities (like pressure, density, etc.) is significantly higher than the mean free path of the molecules. To within an order of magnitude, the mean free path of air molecules is around 0.1 µm, which is still a few orders of magnitude smaller than the wavelengths you're looking at. So treating this as a sound wave is probably still fine.
It's also worth noting that acoustic microscopy uses sound waves with frequencies up to a few GHz, not too far off from what you're talking about. However, we're usually talking about waves in solids or liquids in this case; in air, waves of high frequencies like this are quickly attenuated as they propagate.
answered 8 hours ago
Michael SeifertMichael Seifert
17.3k2 gold badges33 silver badges60 bronze badges
answered 8 hours ago
Michael SeifertMichael Seifert
17.3k2 gold badges33 silver badges60 bronze badges
answered 8 hours ago
Michael SeifertMichael Seifert
17.3k2 gold badges33 silver badges60 bronze badges
answered 8 hours ago
Michael SeifertMichael Seifert
17.3k2 gold badges33 silver badges60 bronze badges
17.3k2 gold badges33 silver badges60 bronze badges
add a comment |
add a comment |
$begingroup$
Yes, no problem in principle.
The limit for wavelengths is the interatomic distance. The cut-off frequencies for phonons in solids are about $10^13$ Hz.
In gases, attenuation goes up a lot a short wavelengths. This paper says that attenuation in air is 80 000 dB/m (for $f = 20$ MHz): http://acoustics.ippt.pan.pl/index.php/aa/article/viewFile/555/486
answered 8 hours ago
PieterPieter
9,8003 gold badges18 silver badges39 bronze badges
$endgroup$
add a comment |
$begingroup$
Yes, no problem in principle.
The limit for wavelengths is the interatomic distance. The cut-off frequencies for phonons in solids are about $10^13$ Hz.
In gases, attenuation goes up a lot a short wavelengths. This paper says that attenuation in air is 80 000 dB/m (for $f = 20$ MHz): http://acoustics.ippt.pan.pl/index.php/aa/article/viewFile/555/486
answered 8 hours ago
PieterPieter
9,8003 gold badges18 silver badges39 bronze badges
$endgroup$
add a comment |
$begingroup$
Yes, no problem in principle.
The limit for wavelengths is the interatomic distance. The cut-off frequencies for phonons in solids are about $10^13$ Hz.
In gases, attenuation goes up a lot a short wavelengths. This paper says that attenuation in air is 80 000 dB/m (for $f = 20$ MHz): http://acoustics.ippt.pan.pl/index.php/aa/article/viewFile/555/486
answered 8 hours ago
PieterPieter
9,8003 gold badges18 silver badges39 bronze badges
$endgroup$
Yes, no problem in principle.
The limit for wavelengths is the interatomic distance. The cut-off frequencies for phonons in solids are about $10^13$ Hz.
In gases, attenuation goes up a lot a short wavelengths. This paper says that attenuation in air is 80 000 dB/m (for $f = 20$ MHz): http://acoustics.ippt.pan.pl/index.php/aa/article/viewFile/555/486
answered 8 hours ago
PieterPieter
9,8003 gold badges18 silver badges39 bronze badges
answered 8 hours ago
PieterPieter
9,8003 gold badges18 silver badges39 bronze badges
answered 8 hours ago
PieterPieter
9,8003 gold badges18 silver badges39 bronze badges
answered 8 hours ago
PieterPieter
9,8003 gold badges18 silver badges39 bronze badges
9,8003 gold badges18 silver badges39 bronze badges
add a comment |
add a comment |
$begingroup$
It's called ultrasonic because most people cannot hear it (this particular frequency is way over the typical audible threshold of 20,000Hz). You could also call it an overtone in a more musical nomenclature. This sound would resolve smaller features than larger waves, so you can use it to generate higher resolution images as in ultrasound or with a hypothetical creature in D&D with ultrasonic echolocation (animals typical echolocate in the range 40-140kHz).
answered 6 hours ago
guitarphishguitarphish
111 bronze badge
New contributor
guitarphish is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
2
$begingroup$
This doesn't seem to address my question. Welcome to StackExchange; I'm not super familiar with the Physics stack, but their tour could shed some basic light on what kind of answers are expected here. My question isn't about what class of sound this would be, but on the physical implications of such an occurrence. In any case, it's a pleasure to meet you and I hope to see you around.
$endgroup$
– David Coffron
6 hours ago
$begingroup$
I can delete my answer if you don't like it. The other answers also do not talk about phonons, which are quantum quasi-particles of sound that are much smaller than the scales being talked about. en.wikipedia.org/wiki/Phonon
$endgroup$
– guitarphish
6 hours ago
add a comment |
$begingroup$
It's called ultrasonic because most people cannot hear it (this particular frequency is way over the typical audible threshold of 20,000Hz). You could also call it an overtone in a more musical nomenclature. This sound would resolve smaller features than larger waves, so you can use it to generate higher resolution images as in ultrasound or with a hypothetical creature in D&D with ultrasonic echolocation (animals typical echolocate in the range 40-140kHz).
answered 6 hours ago
guitarphishguitarphish
111 bronze badge
New contributor
guitarphish is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
2
$begingroup$
This doesn't seem to address my question. Welcome to StackExchange; I'm not super familiar with the Physics stack, but their tour could shed some basic light on what kind of answers are expected here. My question isn't about what class of sound this would be, but on the physical implications of such an occurrence. In any case, it's a pleasure to meet you and I hope to see you around.
$endgroup$
– David Coffron
6 hours ago
$begingroup$
I can delete my answer if you don't like it. The other answers also do not talk about phonons, which are quantum quasi-particles of sound that are much smaller than the scales being talked about. en.wikipedia.org/wiki/Phonon
$endgroup$
– guitarphish
6 hours ago
add a comment |
$begingroup$
It's called ultrasonic because most people cannot hear it (this particular frequency is way over the typical audible threshold of 20,000Hz). You could also call it an overtone in a more musical nomenclature. This sound would resolve smaller features than larger waves, so you can use it to generate higher resolution images as in ultrasound or with a hypothetical creature in D&D with ultrasonic echolocation (animals typical echolocate in the range 40-140kHz).
answered 6 hours ago
guitarphishguitarphish
111 bronze badge
New contributor
guitarphish is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
It's called ultrasonic because most people cannot hear it (this particular frequency is way over the typical audible threshold of 20,000Hz). You could also call it an overtone in a more musical nomenclature. This sound would resolve smaller features than larger waves, so you can use it to generate higher resolution images as in ultrasound or with a hypothetical creature in D&D with ultrasonic echolocation (animals typical echolocate in the range 40-140kHz).
answered 6 hours ago
guitarphishguitarphish
111 bronze badge
New contributor
guitarphish is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered 6 hours ago
guitarphishguitarphish
111 bronze badge
New contributor
guitarphish is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered 6 hours ago
guitarphishguitarphish
111 bronze badge
answered 6 hours ago
guitarphishguitarphish
111 bronze badge
111 bronze badge
New contributor
guitarphish is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
guitarphish is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
2
$begingroup$
This doesn't seem to address my question. Welcome to StackExchange; I'm not super familiar with the Physics stack, but their tour could shed some basic light on what kind of answers are expected here. My question isn't about what class of sound this would be, but on the physical implications of such an occurrence. In any case, it's a pleasure to meet you and I hope to see you around.
$endgroup$
– David Coffron
6 hours ago
$begingroup$
I can delete my answer if you don't like it. The other answers also do not talk about phonons, which are quantum quasi-particles of sound that are much smaller than the scales being talked about. en.wikipedia.org/wiki/Phonon
$endgroup$
– guitarphish
6 hours ago
add a comment |
2
$begingroup$
This doesn't seem to address my question. Welcome to StackExchange; I'm not super familiar with the Physics stack, but their tour could shed some basic light on what kind of answers are expected here. My question isn't about what class of sound this would be, but on the physical implications of such an occurrence. In any case, it's a pleasure to meet you and I hope to see you around.
$endgroup$
– David Coffron
6 hours ago
$begingroup$
I can delete my answer if you don't like it. The other answers also do not talk about phonons, which are quantum quasi-particles of sound that are much smaller than the scales being talked about. en.wikipedia.org/wiki/Phonon
$endgroup$
– guitarphish
6 hours ago
2
2
$begingroup$
This doesn't seem to address my question. Welcome to StackExchange; I'm not super familiar with the Physics stack, but their tour could shed some basic light on what kind of answers are expected here. My question isn't about what class of sound this would be, but on the physical implications of such an occurrence. In any case, it's a pleasure to meet you and I hope to see you around.
$endgroup$
– David Coffron
6 hours ago
$begingroup$
This doesn't seem to address my question. Welcome to StackExchange; I'm not super familiar with the Physics stack, but their tour could shed some basic light on what kind of answers are expected here. My question isn't about what class of sound this would be, but on the physical implications of such an occurrence. In any case, it's a pleasure to meet you and I hope to see you around.
$endgroup$
– David Coffron
6 hours ago
$begingroup$
I can delete my answer if you don't like it. The other answers also do not talk about phonons, which are quantum quasi-particles of sound that are much smaller than the scales being talked about. en.wikipedia.org/wiki/Phonon
$endgroup$
– guitarphish
6 hours ago
$begingroup$
I can delete my answer if you don't like it. The other answers also do not talk about phonons, which are quantum quasi-particles of sound that are much smaller than the scales being talked about. en.wikipedia.org/wiki/Phonon
$endgroup$
– guitarphish
6 hours ago
add a comment |
David Coffron is a new contributor. Be nice, and check out our Code of Conduct.
David Coffron is a new contributor. Be nice, and check out our Code of Conduct.
David Coffron is a new contributor. Be nice, and check out our Code of Conduct.
David Coffron is a new contributor. Be nice, and check out our Code of Conduct.
Thanks for contributing an answer to Physics Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f491084%2fwhat-happens-as-wavelengths-of-sound-waves-approach-tens-of-micrometers%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
