Sound: Crash Course Physics #18

We learn a lot about our surroundings thanks to sound. But... what is it exactly? Sound, that is. What is sound? And how does it travel? And what is this doppler effect that we've heard so much about? In this episode of Crash Course Physics, Shini goes over some of the basics (and some of the not-so-basics) of the Physics of Sound.
--
Produced in collaboration with PBS Digital Studios: / pbsdigitalstudios
--
Want to find Crash Course elsewhere on the internet?
Facebook - / youtubecrashc. .
Twitter - / thecrashcourse
Tumblr - / thecrashcourse
Support CrashCourse on Patreon: / crashcourse
CC Kids: / crashcoursekids

[@crashcourse]

We made quiz questions to help you review the content in this episode! Find them on the free Crash Course App! Download it here for Apple Devices: apple.co/3d4eyZo Download it here for Android Devices: bit.ly/3TW06aP

[@g.f.w.parker5485]

Dr. Somara has some of the most intense eyes I've seen yet. I feel like she could stare down a goldfish and win.

[@hudamohyadeen8387]

Sound is a form of energy that produces sensation of hearing in our ears. Sound is produced when a body vibrates. Sound needs a medium to travel. It cannot travel in vacuum. Sound travels faster in solid medium (like wood) as compared to water and air. All musical instruments have vibrating parts/which produce sound. In human beings, sound is produced by the voice box or the larynx. We hear through the vibration of our eardrum, whenever sound reaches our ears. The number of oscillations per second is called the frequency of oscillation (f) and is expressed in hertz (Hz). A frquency of 1 Hz is one oscillation per second. The time needed to complete one oscillation is called time period (T). Hence, the number of oscillations per unit time is the frequency of wave f = 1 /T. The maximum displacement of the wave crest from the central position on either side is called its amplitude. We differentiate sounds on the basis of their amplitudes and frequencies. A human being can hear sound waves within a range of 20 Hz to 20,000 Hz. Some animals like dogs can hear sounds higher than 20,000 Hz. The larger the amplitude of vibration, the louder is the sound. Loudness of sound is proportional to the square of the amplitude of the vibration producing the sound. The loudness is expressed in a unit called decibel (dB). Shrillness or the pitch of a sound depends upon its frequency. Higher the frequency, higher is the pitch and vice-versa. Unwanted, unpleasant sound is noise. Loud noise produces noise pollution, which is harmful and may cause hearing impairment. The velocity of sound in air is approx.330ms−1 under standard temperature and pressure conditions. It varies with temperature, pressure, humidity and density of medium.

[@haleydavidson7693]

Huda Mohyadeen thanks

[@tryannchannel7784]

@@haleydavidson7693 why u say that

[@haleydavidson7693]

Tryann Tomlinson she gave me some extra notes to write down

[@t.o.m_is_a_writer]

Thanks thanks friend,I got a bad memory so this is good to look back at

[@emilychen2016]

omg i should've gone to the comment section sooner... just spent so long on learning these exact same points😂 *Thank you so much*

[@m.e44]

at 6:39 is where I have to see myself out of the door thank you

[@jns1253pnda]

My friends and I were walking through a high end bank looking for a bathroom when we were all in high school and when we reached the third floor, it sounded like a fire alarm was going off. We were looking around and none of the employees or customers were reacting in the slightest, and just kept going on with business. Thinking something was wrong, we left. Looking back, all of the employees and customers were 45-60 years old. After watching this video, I realize it was probably one of those security systems you were talking about, because the sound wasn't particularly urgent, but it was really high pitched. More than anything else, I'm kinda pissed that it worked. They got us to leave, bladders full, under the cloak of confusion at the sound. I feel so played.

[@pradeepjha362]

and free energy?PLEASE!!!!!!!!!!!!!!!!!!!!!!!

[@deadmanperipherals]

Crazy

[@Fenrick]

Good thing I was never able to hear frequencies above 5000 Hz.

[@moe8885]

(515)

[@jean8991]

@@noname-ue7lb ur a weird guy. Are u the joker?

[@euchale]

One thing I missed in this episode is that even though we cannot hear sounds outside of our hearing spectrum, it doesn´t mean that they have no effect on us.

[@Julia-qp2hh]

+

[@Ahmadabdal_]

It's frequency is way too much so therefore the eardrums can't produce much amplitude in order for us to hear because the eardrum don't have enough time to go back and forth much distance look it's complicated just Google it

[@SheikhEddy]

This is such a sound video

[@noobnoobyify]

I hate hearing those types of puns. Get out orals I'll turn off the internet.

[@chowtom5174]

With these qualities, no wonder Crash Course Physics is such a resounding success.

[@InsideCellardoor]

+

[@sadik.oagile6779]

+Chow Tom 😂😂😂 Well done mate

[@plainmainaccount5554]

You deserve a like

[@MightyUnderdog]

5:06 gosh, I served in US air base where air planes and fighter jets frequently take off and land. That really did drive me round the bend. Miraculously, I managed to retain my hearing. Cheers for the instructive lecture and reminding me of that memory mate!

[@shreyanchetia5860]

4:05 did anyone realise the dogs brown patch shifts from right to left on his face ?

[@PattheBassist]

I'm teaching an introductory music technology course at university this fall. This is my saving grace for not having to dive into the physics!! This came out at the perfect moment in time.

[@henrybrown2004]

When she was on the doppler effect part an ambulance went by my open window. lol perfect timing.

[@Beahati]

Ah this was so good! I need to know the physics of something before I can understand it, so this helped my sound production studies so much. Thank you!

[@gustavouchida1]

first timer here. Your class is amazing! Thanks for being so clear.

[@Jartny]

I love crash course but I wish you'd guys would sloooow down a little itty bit, sometimes you guys (and gals) spew out information so fast it takes two times through for me to really soak it all in. I love this course though, thank you guys!

[@LowwestMember._]

Thank you for providing the information! Even if this video is 6 years old it still helps a lot! Thanks.

[@X-3K]

"It happens with light, too... but more on that much later" Aw man, but relativistic mechanics are my favorite! :(

[@SolarLiner]

Me wants some Lorentz contraction!

[@boumelhaadam3681]

the whole of my words can t even express how much i love this channel and how it helps me

[@shaahidfaiz2889]

someone get this channel nominated for nobel prize awards

[@daisyladyklg8538]

It's really quite fascinating to realize that the correlation between music & mathematics is literally off the charts. I didn't learn how to read music (other than strumming chords on a guitar) until I was almost 50... Or so I thought!! I really did try my best... well, actually what I thought was my best, to learn how to play musical notes on the guitar when I was in middle school as well. Honestly, I don't know if this is true for everyone but I was super surprised at what it took for me to understand fairly basic all-around music theory. What it took for things to click for me was to 1st apply it on a piano rather than a guitar. And to go even one stepfurther, if someone would have told me right off the bat how music theory is so dependant mathematics to the point of being inseperable, I would have looked at it from a completely different perspective. BUT in as much as I know this to be soooo completely true/irrefreputable, it's still really hard to wrap my head around the very idea that such a creative artform such as music depends so heavily on something as technical as mathematics. I guess that subconsciouly, I always felt like I had to hide one side of my brain or the other because having two dominant sides ofthe brain is an oxymoron 🤷 ✌️💞✌️

[@cianskid2116]

It's useful to describe sound waves as pressure waves, because we can build devices that detect those changes in pressure. I love CrashCourse Subscribed!

[@Boogabeega]

Her voice is angelic.

[@illblues1072]

I love how passionate she is! Love the videos 👍🏼

[@RealityHijacked]

This is the dopest educational show in the history of the world

[@seraphinabishop1586]

XD true

[@chandaowen6046]

False

[@chandaowen6046]

That one robot show is better

[@noodlenado7827]

Thank you so much! These videos are even better when I'm just curious about certain things

[@shamneo23]

have a hard time sleeping? put the decibel equation part on loop. it'll put u right out

[@iks_justice]

Lol!

[@gustavouchida1]

oh that was mean... but stil...lol

[@Necrapocalypse]

Pssh, speak for yourself. I make a career in this stuff.

[@shamneo23]

12Rman21 lol. so serious.. can't understand it was a joke? i wouldn't have watched this video if i wasn't interested in science. go go.. go troll somewhere else. you seem to be better than me. no need to look down at people. now arrogance.. that's the worst. blocked. no need to reply.. i know you have something witty back to say..

[@speedwagonbestwaifu5436]

+Sham Neo k

[@jasperscott5426]

Now I know more about sound energy and what it dose thank you I am your #1 fan

[@shuriken188]

That ambulance was moving down the street at nearly Mach 1, passing someone at that speed would produce a more interesting effect than a pitch change. Just kidding, great series, good visualization.

[@frogman3102]

human beings are amazing. i started looking up physics stuff because of a psychedelic experience in which i learned how particles and waves work, and now i see that everything i saw was just science. interesting stuff

[@c.crespo8196]

like tbh this is the best of all the crash courses she is an amazing teacher and even the graphics and intro are 1000 times better

[@jamesonthomas9583]

7:21 me when I stub my toe

[@HalimonAkhmedova]

Man thats sad

[@imranabduke7121]

Feel bad

[@obpico6346]

What do I do

[@amiaf]

Finally after several useless high view videos, I clearly understood the definition of decibel! Thanks a lot for great explanation

[@angeldude101]

Wow, PoGo Fever has even infected Crash Course!

[@crashcourse]

I know, right? -Nick J.

[@angeldude101]

CrashCourse CrashCourse responded to my comment! :O Unrelated: my first comment typed with bépo keyboard layout.

[@GuardianDiancie]

lol

[@PuffleBuns]

I have no idea what you are torquing about.

[@serene9532]

King PufflePuff 😆

[@Bob_Lob_Law]

4:50 I see you put h3h3 in there...

[@WOLFG4MIN]

It’s actually Sea get your punctuation write and it’s also they’re idoit dum arce

[@voicehead]

woah bro calm down just becuz he maed a hORIBAL spelign acksidint duzent meen u gotta be so meen 2 him

[@Rowdouble]

I'm going to start my sound engineering degree next month such an interesting topic.. as a musician it fascinates me, I think i'll be having fun. thank you for this video very well explained thank you =)

[@TheCabbageMan]

Did I just see when Ethan from H3H3 during to rock scene?!

[@Dooality]

Glad I'm not the only who noticed. I never thought I'd see Ethan In a Crash Course video. It's like two worlds that could never really mix.

[@TheCabbageMan]

+Dooality I know right I thought I was seeing things.

[@benaaronmusic]

I never would have thought I'd seen Ethan in his Pikachu outfit on Crash Course.

[@spenorr]

lmao I can't believe you put an h3h3 reference in here...

[@kirakat2516]

can u link the time plz

[@plog9572]

4:45 lol

[@ColtonPhillips]

That was mind blowing

[@ganaraminukshuk0]

Also note that the low end of safe hearing is 1 pikawatt per square meter.

[@mithrilld]

The smartest show I know made a reference to the stupidest show I know

[@NMalteC]

I love your videos, but why don't you make them a third longer while reducing your talking speed by one third?

[@playc.holder6432]

This is a hilariously great idea. +++++++++

[@rebdomine1]

You could mess with the speed if it's too quick for you. Time is bandwidth.

[@adilezy]

It's also money for them, so..

[@SuperVarunan]

Apatheism but it also warps the sound "chump"

[@mohamadi2651]

I slowed it down but it was STILL too fast

[@user-bq8gd1wj6t]

4:48 Was this a reference to H3H3s EDM concert video

[@0ne323]

Yea

[@jessy4637]

Lol it is

[@willdickinson2874]

I like the human being hosting this. She is good human.

[@josephweiss3931]

crash course music theory for the love of jebus

[@davisdavis468]

They could have that Adam Neely guy do them

[@Ikkarson]

@6:50 the number of which you need to take the log is not "a trillion Watt per metre-square". it has no dimension since you divided a quantity by another quantity of the same dimension or unit. So it's just "a trillion", period. This why (deci)bels are so confusing: to compute them, you need to take some reference point (noted I_0 in the video); this is why there are actually several (and possibly, infinitely many) decibel scales depending on the reference chosen for a particular application. Oh, and there actually is an absolute maximum to that scale: when the sound wave becomes so intense that the depressed phase of the wave basically becomes a vacuum or "cavitates".

[@Belmont_14]

That unsolved Rubik’s cube is making me sad I just wanna get in there solve it and tell them to leave it alone

[@dorraineahearn7158]

You coulndt even solve it

[@alexh.8575]

The best sounding video ever

[@NarekAvetisyan]

Descpribing sound as pressure waves makes sense why a jet flying in supersonic speeds near buildings will do some serious damage. Since it creates a difference in pressure in the air.

[@EvilNeonETC]

This is a good video to teach deaf people how sound works, even if they can't hear them. Thanks!

[@TraderTravels]

My eyes glaze over when the math starts LOL

[@TonecrafteLuthiery]

Hey Crash Course, I really like this channel. The diversity of topics and depth of insight is something that is, in my opinion, unrivaled by most other KZbin channels. The idea of this channel alone, that being videos of moderate length explaining a range of topics in detail, is priceless. Now more than ever it is vitally important to the American economy that our citizens be intellectually literate, especially in fields such as science and technology. Come to think of it, it may be a good idea for you guys to make a STEM (Science, Technology, Engineering, and Mathematics) playlist. Just a thought. On another note, what would you guys/girls (meaning whoever is reading this) of an interview series on Crash Course? It would be really interesting to see Crash Course collaborate with scientists, artists, authors, poets... etc. Couple that with longer interviews with the guest and I think it would have the potential to really grow the channel and even further diversify the content, appealing to a different breed of knowledge junkie. I can only hope that some high profile names in the various fields of expertise would be willing to collaborate. Richard Dawkins for biology, Lawrence Krauss for particle physics, Bill Nye for climate change and engineering, Cornell West for social and political reformation and history, and so on and so forth. I believe that and do of those names have collaborated with the channel Big Think (which is another channel that I love), and they have only have about 1/3rd of the amount of subscribers that Crash Course has. Not to mention their connection to PBS, which may hold some sway. I believe that Crash Course is connected to a few other large channels as well, like SciShow, which could also host those sort of interviews and collaborations.

[@stephaniegonewild5857]

As far as sound this takes effect. Light can measure distance in the universe. There is a difference. Sound can travel very far but can be blocked at anytime therefore cannot be used as measure instrument. But this great vid and great information.

[@erikziak1249]

Wait, measure the distance of stars? I would say the relative speed the star is moving to earth. Also I highly recommend that everybody build at least one set of hifi speakers, measuring the impedance and characteristics, running simulations, applying Thiele/Small theory in the design of passive crossovers. I learned a lot by doing that three years ago just for fun. Buying a calibrated microphone is not that expensive and a nice DIY project can be made, learning A LOT about sound. Hmm. Now that I think of it, I forgot most of it. :-)

[@orkideailona]

WOW you are just excellent, why might the note c6 have a dark colour istead of bright? Ihave downloaded a pitch app and used my voice to draw this conclusion.

[@Ravenwest19]

Why sound waves traveling in all directions ?? Recently I've read about sound wave propagation. Let's look on loudspeaker. If it creates sound waves by pushing and pulling the air in front of it , how we can hear sound when we are behind the loudspeaker or above or under?

[@HexerPsy]

Episode 24 "Light" confirmed.... damn, still have to wait so long...

[@iamsuccessful2241]

"Light" is the episode 24 of Crash Course Astronomy and not Crash Course Physics........ so basically, you don't need to wait cause it's already there....go to the previous episodes of Crash Course Astronomy.. :)

[@SuperAngryPacman]

"Light" is episode 24 of Crash Course Astronomy'

[@HexerPsy]

Oh... seen it already. But here's to hoping there will come a physics episode on light!

[@chrismarklowitz1001]

Now, I think I have a good idea. Since energy is Force times the distance the force is applied. Think of a pulse. You oscilate once which means you apply a force up and down on a rope. The part of the rope you pulled up and then pulled down. You only pulled down on that part of the rope. That part of the rope pulls down on the next part of the rope just as the part you pulled down goes down. And then it continually is replaced. (i.e think of a wave at a stadium. The people to your left moving up pulled you up and then as they went down their movement pulled you down as well as you pull down the people to your right.)

[@flamedragon07]

Dear, Crash Course, I am wondering what is the name of the song they used for the H3 Ethan reference. I want to get that sound file for my mp3 player. It sounds nice even in this episode. Keep up the wonderful work crash course.

[@Nedu.99]

Excellent video 😃 hopefully I can pass this final tomorrow

[@joaquingarcia3106]

Incredibly smart, incredibly gorgeous and love the accent also! Thank you! X10 to the 25! #belle : )

[@MirellaBellido]

First video ever I had to slow down

[@Miller4731]

Wooow such a great video, I love this chanel!

[@DannoCrutch]

Talk about standing waves!

[@komalupadhya4551]

what is difference between Isolation and Separation in Biophysics??? n pls upload vdo on electrophoresis.

[@dr_spankz]

I have a theory that she could be lying about those frequent text

[@eucalyptus9411]

i have to make 5 questions about it

[@hussientharwat2037]

this channel is the best on youtube.....

[@DaneGilCabrales]

Objection! The apparent frequency is changing as the source moves. Meaning the perception that the pitch is changing is false, its the amplitude that is changing

[@NS-xr8qy]

Incredibly informative! It's okay to be smart. :)

[@yourbuddyunit]

I wish there was a crash course music! But, this is definitely a start 😊

[@neerajmahto8406]

Eardrum in our ear is also called tympanum

[@anaselfellah6243]

First video on this channel, and I did not expect at all to see Ethan down here! Really useful video btw papa bless.

[@rohitjain79]

It’s been a while since I’ve been following your videos, and I must say, they are amazing! By any chance, is there a scope for business collaboration?

[@Ph03n1X87]

In Science we were learning about Sound vs Light. I may know what's the difference to them or what's similar to them. I'll tell ya something. What I know is sound can go through any sort of objects that are opaque. Light shines through any object that are transparent or translucent. Ive learned it since in high school and even I'm in Year 7

[@Miller4731]

This is just what I nees to speed up my understanding before getting into the math used to describe the physics, btw nice Feynman books I have the spanish-english version, really nice book (I'm a native spanish speaker)

[@CarlosMendoza-zw2gw]

Crash course on music theory please :)

[@shlomostrauss7229]

Great video, thank you very much ❤

[@jamyocstap8709]

Sounds great😂thank you for the lesson

[@VishalGupta07]

That Pikachu while describing about picowatts was amazing.

[@chrismarklowitz1001]

Waves transmit energy and not matter. My question was what causes this? to solve the problem of waht is a wave anyways? Do we call it energy? If so what qualities of energy can be revealed in a wave that also translates into how to measure it. How to understand it.

[@duna1174]

this is just amazing, i watched like 100 videos with green, and now crash course has a girl. thats crazy, i thought this channel was just biology

[@arbb7751]

Me too

[@shreyasriram8674]

me too

[@minh.nguyen12]

Pokemon Go!!! Walk on the street and sticking your eyes on the Phone playing Pokemon Go and there you go, "Crash" course XD. And Ash Ketchum's cap in the Doppler effect too XD

[@feitocomfruta]

This is the physics I had to learn for my degree in Communication Disorders

[@honey4xi]

Light & sound separations: White light can be separated into different color lights by prism (science). Can a song be separated (mp3, AIFF, Wave) into each different instrument track and vocal track by the computer software (art)?

[@RussianSevereWeatherVideos]

First time I discovered the Doppler effect? DooM I and running forwards, or backwards with a rocket launcher, as a kid :D

[@vladislavbogorov9922]

Sound travels faster and farther in denser mediums like steel. Yet it is stopped by heavier materials which is just another way to say by denser materials and this suggests that steal must be good at stopping it. Isn't there a contradiction here? I am confused.

[@Fquh]

Just trying to make my room soundproof so I can have some fun if you know what I mean

[@peter75]

Omg you added Ethan!!!!!

[@zimaelohey1524]

Thanks Dr. Somara!

[@christianpinto5671]

There should be a CrashCourse section on Linguistics :'( Greetings from Chile, South America.

[@jade02824]

thank god for this channel

[@doomermode7829]

I really want to be a regular viewer of this series because it seems interesting, but I am just too dumb to keep up with understanding all this stuff ;~;

[@sxmmii_gxchaa774]

Thank you

[@wurble]

I often wonder if sound is affected by weather. I always notice on nice and clear hot days during summer months that outside every day noise sounds different. It seems to have more clarity, like the treble has been slightly turned up. Whenever I mention this to people they always look at me blankly. Does anyone else notice this?

[@pranavmahapatra]

Now I actually understood the Intro....It shows up animations, in association with all chapters....

[@Donimations]

Ok, I need an answer, how do I make it so speakers have an uneven ratio between the compressions and expansions (aka making a net force)

[@Lotus49b]

Hey guys, I have a genuine and frustrating problem I'm trying to figure out so I can start to model. ---How is just the exhaust sound from a car come from? (Yes, i know feom the individual explosions that are happening inside the combustion chamber, but its more complex). Also, why if your not in the right gear going up hill, and even tho your RPM hasn't changed, as you give it more gas, the engine note changes. ( besides the obvious answer because you're giving it more gas there's a more complex answer). And finally, what makes a Ferrari V8 sound SO different that a Chevy or Ford V8, excluding size and exhaust layout. I have an hypothesis. We will focus on one cylinder of an Engine of your choosing. Engine takes in air and fuel, its compressed to around 120psi, ignition, rise and heat are produced and the piston gets pushed down, ( (very simple introduction). However , as the piston is at bottom dead center and before the exhaust valve opens, there still remains a calculatable pressure that remains. Due to a volume of air now hotter than originally, there is still pressure inside the chamber. When the exhaust valve opens, rapidly even at idle and the piston is thruster upward, thoes hot exhaust gases, as hot as 50psi, are forced into the exhaust system and out the tailpipe. Now 50psi being forces out a narrow tube in ,even as low as .06 sec, is bound to "carry a tone" what do u think

[@beaubunny4]

do a video on ultrasound! specifically diagnostic medical sonography

[@googledev566]

*_Awesome crashcourse keep creating such crucial videos_*

[@sallyhabib626]

The Jokes: "Learning about physics is not Bohr" Me: I isn't it supposed to be BORING not Bohr? Who the heck is Bohr?

[@AtenaHena]

man i'd ruther not be that guy

[@pradeepjha362]

please show us something about free electricity?PLEASE!!!!!!!

[@Anurag_Saxena]

I just feel this diagram is talking of amplitude whereas speaker is replacing the word with frequency... Now I'm confused to understand if frequency corresponds to amplitude or amplitude corresponds to frequency or vice versa or they are synonymous in use! Some expert, Help me

[@jimsagubigula7337]

No, frequency and amplitude are different things.

[@mixbagchannel4557]

Interesting. Simple and compact infos

[@namham8885]

No ones gonna talk about the dog from Pets?

[@muhammadimrankhaliq7191]

Dear crash course can you guide how these fantastic animations are designed?