How Sound Works (In Rooms)

How Sound Works (In Rooms)


Hi, I’m John Calder of Acoustic Geometry.
Let’s talk about Acoustics, which is basically how sound works in rooms.
It may seem complicated, so let’s make it simpler.
Most rooms have flat walls and flat ceilings and sound bounces off of these.
So how does that affect the sound? I’ll use these two Nerf guns to demonstrate.
I’ve got this one aimed so this disk goes directly to the ear.
That represents direct sound. I’ve got this one aimed so that disk bounces
off the wall and it represents reflected sound. I’ll shoot them both at the same time.
Reflected sound arrives at our ears later than direct sound, even though it started
out at the same time, because it’s traveling farther.
And this wall is only one flat surface. There are at least 6 in the average room and
that’s a lot of reflected sound. But why is reflected sound bad?
I’ll demonstrate using these two identical patterns.
The blue pattern represents direct sound waves. The red pattern represents reflected sound
waves. They start out together, but when I move the
red one backwards, like a delayed sound reflection, it creates destructive interference patterns
which changes the original sound wave. Here’s the problem.
Original sound waves are distorted by strong later-arriving reflections.
Also, sound travels really fast. About 1130 feet per second.
A sound wave will bounce back and forth between these two walls about 60 times in one second.
Sound travels so fast it fills a room almost instantly.
This is only one bounce angle, every room has thousands.
How can we make our rooms sound better? Remember our Nerf guns?
I’ll shoot these at the same time, again representing a sound wave bouncing off a wall.
Both discs bounce together in the same direction, which means the reflected sound is at full
strength. Now let’s use the first of our two acoustical
tools, an absorber, to reduce the strength of sound bounces.
To a sound wave, an absorber looks a little like a hole in the wall, so some of the energy
doesn’t come back. An absorber works by reducing the strength
of reflected sound that would otherwise cause more destructive interference.
But if we use only absorbers in a room it makes it sound dull and unnatural.
Historically, humans don’t like overly absorbent rooms.
So, let’s use the second of our two acoustical tools, the curved surface diffusor.
It also reduces the strength of sound bounces. A diffusor works by scattering the sound reflections
in different directions, smoothing out destructive interferences throughout the room.
Room acoustics are greatly improved using a combination of absorption and diffusion. It’s all about reducing those flat-surface reflections.
Use a combination of absorbers and diffusors and your room will sound a lot more natural.
Thanks for watching.

100 Comments

  • Oldestpunk Inargentina

    May 29, 2019

    Acoustics 101 for dummies; the simplest I've seen so far. Thanx !

    Reply
  • PPS076 Reviews

    June 20, 2019

    Very helpful

    Reply
  • Zam Suan Mung

    June 20, 2019

    Very Good

    Reply
  • YhelloWish

    June 23, 2019

    I come here by my own not youtube reccomedation.

    Reply
  • Christian Torma

    June 24, 2019

    Danke

    Reply
  • Harrison Haynes

    July 10, 2019

    High IQ

    Reply
  • Mumshad Mannambeth

    July 11, 2019

    Why does your audio sound so good when you are in a room without any absorbers or diffusors?

    Reply
  • Rom Bo

    July 11, 2019

    So direct sound is better?

    Reply
  • Fredrik Johansson

    July 12, 2019

    Awesome information

    Reply
  • Alexxx Dee

    July 16, 2019

    That is really simple and helpful! Thanks!

    Reply
  • iah se

    July 25, 2019

    Thanks

    Reply
  • 관점다른

    July 26, 2019

    greatly explained
    but when lot of you guys putting a reverb plug-in , what's the point of using a absorber

    Reply
  • william fitzpatrick

    July 30, 2019

    Checked your prices. Using the old .99 trick huh? How tacky.

    Reply
  • Wilson

    August 3, 2019

    I'm watching all these sound engineering videos as if I'm about to make a podcast, but I have nothing worth to say…

    Reply
  • Patrick Yore

    August 7, 2019

    What material can you use it a diffuser? and is it best that the diffuser is hollow i.e. its not packed with sound absorption material?

    Reply
  • Jezzriq Kismilardy

    August 19, 2019

    Why this video doesn’t appear the first thing I search for..? The best explanation ever. Thank you!

    Reply
  • Josh Oxion

    August 24, 2019

    Twist ending: It's a nuff commercial

    Reply
  • erol kaloglu

    August 27, 2019

    SUPEEEER ERKLÄRT.. KANN LEIDER KEIN ENGLISH..

    Reply
  • Doug Grinbergs

    September 2, 2019

    Wishing highway departments thought to use these principles for crazy-loud underpasses.

    Reply
  • bonanzatime

    September 2, 2019

    Superb Teaching.

    Reply
  • UtwoBed

    September 2, 2019

    I get the idea but it looks like your diffusers and absorbers are made from the same material, wouldn't the diffuser still act as an absorber even though it's curved?

    Reply
  • Rocky Beck

    September 2, 2019

    Great information – really well demonstrated – thank you!

    Reply
  • David Philips

    September 2, 2019

    "Looks cool, sounds bad" – A comment on the state of modern music?

    Reply
  • P. Hamilton

    September 2, 2019

    I have a deaf friend…he finds the concept of "sound"….very difficult to grasp.

    Reply
  • Song Whisperer

    September 2, 2019

    Great video, there's some really helpful information in this video for anyone interested in building recording rooms.

    Thanks.

    Reply
  • Shahar Yabo

    September 2, 2019

    Beautifully explained

    Reply
  • Timmy Spencer

    September 2, 2019

    Clap in, clap out, the absorber-diffuser.

    Thanks for pointing out the obvious. It's what science is here for. 🙂

    Reply
  • MP Rathnayaka

    September 2, 2019

    thanks

    Reply
  • Peter Yianilos

    September 2, 2019

    Direct is good, reflected is bad? That is not only fundamentally incorrect but a gross oversimplification. I know you aim to simplify but the fact is, even your voice, in making this misleading statement, is being supplemented by reflections in a highly beneficial way. We never, ever hear solely direct sound, and if we did we’d find it very disorienting. What matters, and it can be quantified as well as controlled, is the ratio of direct to reflected sound, the times of those reflections and the relative tone of those reflections, which we call reverberation. Real acoustical engineering designs for those three basic elements of reverberation to provide a sound field that is most conducive to the human mind’s expectations, which are very different for speech and music.

    Reply
  • Marcus Alexander

    September 2, 2019

    Sound travels 4.3 times faster in water , your body is 80% water, you hear through your whole body , which synthesises sound , sort your body out first, olive oil & vinegar in ears does the trick

    Reply
  • Cedar and Sound Studios

    September 2, 2019

    Kevin Nealon is looking old

    Reply
  • nomi udo

    September 3, 2019

    How are absorbers and diffusers place in a room to get the best sound?

    Reply
  • 6noteblues

    September 3, 2019

    As a poor man's solution, I hung corduroy fabric on parts of the walls using small diameter wood poles, hooks and brackets – like wall tapestry hangings. It improved the sound immensely. Thanks for the great video.

    Reply
  • MrBimster

    September 3, 2019

    Great demonstration 👌

    Reply
  • Kurt D.

    September 3, 2019

    I'm going to stack my walls with a couple hundred pillows now. Thanks for the idea!

    Reply
  • Manish Moktan

    September 3, 2019

    This video changed my thoughts… Really helpful

    Reply
  • Patrick Thibaut

    September 3, 2019

    Good explanation. I think our brain accepts the totally distorted sound of a stereo in a room because it 'knows' it is in a room, but that's psysiological.
    I once stood in a room completely covered in sound dampening foam. I clapped my hands so hard it hurt but all I heard was a dull thud, like two tennis balls colliding. Unreal.

    Reply
  • Sherloid Bai

    September 4, 2019

    John : "Reflected sound is bad"
    Ohm Walsh Speakers: "Am I a joke to you?"

    Reply
  • Zore Zmith

    September 4, 2019

    when you listen to a speaker, you also listen to the room.

    Reply
  • Video 17

    September 4, 2019

    USA USA USA – explainging with guns, what else?

    Reply
  • Ay Ay Reezy

    September 5, 2019

    This is borderline meme-able.

    Reply
  • paul lawson

    September 5, 2019

    off to the store for Nerf gun…

    Reply
  • thafunktapus

    September 5, 2019

    thanks so much for this video. as a hobbyist trying to make improvements to my recording space this video definitely changed my ideas on how to go about it. fuggit. add some absorbent and diffusive pieces and then move stuff around til' you like how it sounds? use a few built-for-the-purpose items and then the indigenous contents of the room?
    aside from acoustic panels, etc , think i'm going to put up some shelves with old paperbacks? maybe add an overstuffed chair? how bout stuffed animals? worth a try anyway.

    Reply
  • Robert Dowler

    September 5, 2019

    This is how Satellites work.

    Reply
  • Johann Bogason

    September 6, 2019

    I am going to fill my room with diffusers and absobers and cry out loud!

    Reply
  • Jack the Rabbit

    September 6, 2019

    you could use that clip of the wood clappers for an 80's inspired music video…reminds me of some of back when MTV used to play music videos. Kinda funny.

    Reply
  • Ojb 1959

    September 6, 2019

    So the question is how can one do this inexpensively if it’s really that simple.

    Reply
  • Ima Wiseguy

    September 7, 2019

    well I too studied for many years the acoustical problem and if what this channel says is the absolute truth then Bose would be out of business because that's what made them the empire they have become today _Direct Reflecting Technology, their flagship the 901

    Reply
  • Janjão Jonata

    September 7, 2019

    AND bass traps

    Reply
  • Michael

    September 7, 2019

    Imagine your living room filled with these ugly diffusors lol

    Reply
  • Erick Cardenas

    September 7, 2019

    Wow, so informational, thanks! 😀

    Reply
  • calvintrainer1212

    September 8, 2019

    Is reflective sound also called ambient sound?

    Reply
  • Got Rice?

    September 8, 2019

    This is what I figured after playing instruments for so long. Simply having a fan set to low messes with sound frequencies too. It's interesting how it causes them to sound. Thanks for the video!

    Reply
  • sailaab

    September 8, 2019

    Mr. Calder seems like, AND IS, such a dedicated, industrious (20th centuryisque) genius who simply loves his craft.
    wish youtube would have more of THESE instead of the over animated 'fake' exuberant ones whose charade is all about fame, name and being up on the game.

    youtube, please have more of the likes of Acoustic Geometry, the Engineering Guy http://youtube.com/user/engineerguyvideo , Grand Illusions http://youtube.com/user/henders007 and the likes.

    Reply
  • Marty Jewell

    September 8, 2019

    Interesting and somewhat helpful. You should have mentioned Standing Waves and Room Modes and their effect on the sound. I find that my irregular shaped room is best for music reproduction. You do want some reflected sound to make it more natural. Also avoid "exact" distances between speakers and boundaries. The old equilateral triangle position is another fallacy for good sound. Just place your speakers where they sound best, but not the middle of the room. Fuhgeddaboudit!

    Reply
  • Studi Locker

    September 8, 2019

    Great!

    Reply
  • kosmaslemo

    September 8, 2019

    I ve been looking so lonf for something like that!! Great video.
    Instant subscribe :p

    Reply
  • Duco Darling

    September 8, 2019

    3:18 – "More natural" – That's funny to hear.
    Sound is supposed to bounce. It must be living inside of a box that isn't natural.

    Reply
  • evolunter

    September 8, 2019

    Therefore make a party with 50 people in a room and you will hear no reflections.

    Reply
  • Aero360Aviation

    September 8, 2019

    Fascinating and informative! We are currently in the middle of recording at our home studio and trying to get our sounds right and this puts a wonderful visual on WHY things happen the way they do.

    Reply
  • Carl Dupnt

    September 9, 2019

    So if I hear you right soft furniture, carpet and window treatment work just fine.

    Reply
  • Gerardo Paredes

    September 9, 2019

    What a great video. Thanks for sharing your knowledge.

    Reply
  • NATIVE INDIAN

    September 9, 2019

    AT 1:02
    LEFT-RED=440HZ RIGHT-BLUE=432HZ

    Reply
  • Tiny Ford

    September 9, 2019

    This is what bugs me most:
    fArther = fUrther
    Eleven hundred and thirthy = One Thousand one hundred and thirty

    Why do Americans make everything sound stupider with their slang

    Reply
  • Alex

    September 9, 2019

    The bare room feels more representative of the environment, so it makes sense if you'd want to lose that

    Reply
  • GREATEST SaWes

    September 9, 2019

    Very instructive video Sir.
    Please, what would your sound reflective surface be made of?
    Thanks alot!

    Reply
  • Firhan Rizani

    September 9, 2019

    Reverb pedal

    Reply
  • Marcel Lenormand

    September 9, 2019

    Sound advice.

    Reply
  • David Scott

    September 9, 2019

    Top tier editing!

    Reply
  • D Mc

    September 9, 2019

    Damn what a great and informative video, thanks for this.

    Reply
  • Travis Cooper

    September 10, 2019

    Very cool.

    Now someone with video editing equipment, do the Clapper part on a loop.

    Reply
  • BreadCasket

    September 10, 2019

    The irony of this video having subtitles

    Reply
  • SeFu2006

    September 10, 2019

    Is this the guy that voices how it’s made?

    Reply
  • Ross Ozarka

    September 10, 2019

    You're saying all this about flat walls causing bad sound, but you're in a room with flat walls and the sound on the video is perfect

    Reply
  • waverleyrocker

    September 10, 2019

    It creates interference patterns which have both constructive and destructive elements.

    Reply
  • Worst Producer

    September 10, 2019

    2:56 AMAZING

    Reply
  • Woodythehobo

    September 10, 2019

    Why am I here

    Reply
  • GEFFI

    September 10, 2019

    Finally a video that is easy to understand and concise

    Reply
  • Vicente Gutierrez

    September 10, 2019

    How the fuck did I end up here

    Reply
  • Edward

    September 11, 2019

    Wow! never seen a more simple explanation. Excellent video sir! I learned something today…Thumbs up

    Reply
  • Netiye 27

    September 11, 2019

    Awesome video.

    Reply
  • Dan Myself

    September 11, 2019

    now that's an explanation !

    Reply
  • Candy Pixel

    September 11, 2019

    Or just use a carpet

    Reply
  • Joe Harrison

    September 11, 2019

    What do magnets sound like?

    Reply
  • irlrp

    September 11, 2019

    In Eastern Eu it's super common to place carpets on the walls, it lowers the resonnance by a lot, and also makes it feel warmer

    Reply
  • Risk Romer

    September 11, 2019

    so how to know where to place a reducer and when an absorber?

    Reply
  • HORATIO MONROE

    September 11, 2019

    Does this work for reducing fart volume as well?

    Reply
  • Corky-Butchek

    September 11, 2019

    Thanks! Great Video 🙂

    Reply
  • خفايا الكون

    September 11, 2019

    dead bodies on the walls worked for me well

    Reply
  • fronkus

    September 12, 2019

    I always wondered why there were curved and flat thing on the walls of band rooms. I knew it was for sound, but this really helps. Thanks!

    Reply
  • Aberinkulas

    September 12, 2019

    awesome video. this is what youtube is for

    Reply
  • Mochure Al-Ghamdi

    September 12, 2019

    Holy fuck I learned something today!

    Reply
  • Derek Plymesser

    September 12, 2019

    Yo fuck that, echos aren't even real. That's the globalists lying to you.

    Reply
  • kirjian

    September 12, 2019

    Recommended

    Reply
  • sneakyfox

    September 12, 2019

    Fuck I just watched an ad

    Reply
  • Angel Wilson

    September 12, 2019

    3:06 I was waiting for some jump scare to pop out

    Reply
  • Alysson Drumond

    September 12, 2019

    What a simple yet fantastic video!

    Reply
  • Enzonic Gaming

    September 12, 2019

    When YouTube recommends you something to watch that's actually helpful while you sit on the toilet.

    Reply
  • Dawid Wolnik

    September 12, 2019

    So best thing is to open the doors and windows

    Reply
  • Bradley Frank

    September 12, 2019

    Trump would hate these. How is he going to hear the sweet echoes of his voice now?

    Reply

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