Fourier Analysis (and guitar jammin') - Sixty Symbols

[coolpop1234]

Looks like Professor Moriarty is a Jedi. 3:08 :D

[coldlogic1]

so how would you describe the 3 waves you drew on the paper?

also, we're looking at a 2d wave, waves are 3d right, is it just how we describe them that way because its easy to understand? or is it a true represenation containing all information in a 2d form?

[MrTanookiMario]

@coldlogic1 The actual sound wave is 3-d, of course, but we're really only interested in where the wave intersects our ear (or the microphone). It's how the air pressure at that (basically) one point varies over time, which results in a 2-d graph.

[pvolt]

"If I pluck this string here ... or if I pluck it over here ... " Pluck the damn string! The suspense is killing me!

[HaileISela]

my favourite sound does come from a traditional Swedish instrument called the Nyckelharpa (keyed fiddle). It's very closely related to the hurdy gurdy and sort of represents the trend of mechanic instruments in long gone times. in this case on the bowed instruments. it's got resonant strings that do not get touched by the bow but vibrate because of resonant frequencies. sounds like a natural reverb. or like angels to me. you should check that one out.

[Kafzilla]

@HaileISela That's a fun one! I once jammed all sorts of music with myself and another one on guitar and a lady with a nyckelharpa .. first and only time I've seen that instrument. It sounding interesting!

[affablegiraffable]

someone at my school used fourier analysis on "a hard day's night" by the beatles to figure out the beginning chord which was apparently a mystery.

it turns out theres a very quiet F (or F#, cant remember) played on piano.

[Kntrabssi]

So no one noticed that the note he called A was actually a concert G? Metalheads and their downtuning :P

[runnybabbit12]

Moriarty eh?

I'll alert the Yard to send Holmes after you.

[phuckingkunt]

Telekinesis @ 3:09 !!!

[wblakesx]

diez- I've bought several guitars to play with, switching necks, p'us etc. Most often it's the p/u's and partic the impedance that affect tone most and of course the amp. I have a 50 quid LP copy that is terrible in many respects but sounds great . I don't believe a 2000 pound Gibson is anywhere near worth the cash. Your copy is probably close enough.

[Neavris]

Professor Moriarty is playing Sherlock with Physics

[av733]

Maybe you could get some kind of high frequency bionic ears, 6:54. So you can hear the irritating noise.

[wblakesx]

100 quid, f n gibson for 2000

[Deizelcore]

@wblakesx

It's a cheap Les Paul copy guitar, that's why it sounds like crap.

[pwed546]

i think i want more of dr irish playing guitar

[ravishethwala]

can I have cords!

[Ignorantf00l]

METAL!!!

[mpdp85]

i liked the wahwah pedal

[nbachmann]

Just as an example of the usefulness of a Fourier transform, it can be used to pick out the multiple natural frequencies of a building, which will vibrate just like a guitar string, only at much lower frequencies (first fundamental freq of a building is ~ 1 Hz vs 440Hz for a typical "A string")

And knowing the natural frequencies of a building is key to understanding its behavior during an earthquake.

[ghgjftythnhcfghdty]

Interesting, instructive video, thanks Prof(s).

[MusicalDarkHorse]

Math and music are cousins. It is no surprise that many of the great mathematicians were obsessed with music. See Pythagorean tuning, for example

[ericwongty]

ok i'm doin fourier in my engineering course, and i hate them.

[colouredmirrorball]

@ericwongty I got them as well, and at first I was very excited because I could write any function as a sum of sines and cosines, until I arrived at my math exam...

[axelasdf]

ELECTRONICS!

[PanzarMetal]

I think Philip Moriarty is one the coolest professors out there!

[angelohsa1]

\m/

[csguy12]

hahahaha AWESOME intro

[haavardjenssen]

I like your taste in music prof.!

[panzarw]

Hell yea, physics and guitar jammin, nice!

[MarkArandjus]

Well the guitar riffage isn't really surprising, since this channel has always rocked :)

[heyandy889]

love it

That is a really neat piece of software on Prof. Moriarty's computer.

Also, I sympathize with him about playing music. I became a Computer Science major to pay the bills. Now, I can only play guitar in my free time.

[puncheex]

@heyandy889: The software is a graphical implementation of a Fast Fourier algorithm. Fourier analysis is the breaking down of a complex waveform into it's component sinusoid frequencies. You can get the same display anymore on any audio software, like Audigy or Goldwave, and even on various sound playbacks, such as Winamp or MS Media. Of note only to weird EEs, the similar LaPlace transform breaks down waveforms into their component exponential series. Ummmmm... Just thot I'd mention that...

[Furiouslyfappin]

The way that different frequencies get played is very cool with musical instruments as well. Different instruments have different tones because of of the overtones that they play when the strings or notes are played. For example if you play on a piano a C with an unmuted 8ve higher C and G and yell into the piano the piano will take your yell and turn it into that highest frequency. The way these frequencies work is very cool. Love the video. (BTW get rid of that MG)

[majambl]

I'm math professor, but I'm in love with physics now :)!

perfect man this professor Philip :)!

kisses from bosnia :)!

[someguyoketcetc]

Interesting how one responds to this as a guitar player with some interest in science, it's like sciencesciencesciencescience..­.Ooh! Science with guitars! It all makes sense now!

[micol018]

VooDoo Child

[insme]

I misread this as "Fournier's gangrene"

[betadrum1]

professor moriarty is an opeth fan!

[Moriarty2112]

@betadrum1 Delighted that you recognised the opening riff to "Deliverance"! Possibly the best use of flattened fifths in metal (apart from the riff to "Black Sabbath", of course!)

I'm a huge Opeth fan - "Ghost Reveries" is in my top ten, possibly top five, albums of all time...

All the best,

Philip

[betadrum1]

@Moriarty2112 good man! - the end section to that song blows me away!

you heard porcupine tree? its the guy who produced "blackwater park" 's band. (forgive the clumsyness!) - it's much more pop but some of the musicianship is fantastic! (although they can go heavy when they need to!) - and the drummer is insanely/annoyingly good.

Rich

[Moriarty2112]

@betadrum1 Ah, yes, the last four minutes of "Deliverance" - goosebumps every time!

Porcupine Tree are another favourite. "Deadwing" is probably my favourite album - "Arriving Somewhere But Not Here" has that blend of progressive and metal elements I love. Steve Wilson is an exceptionally talented bloke. He even had Alex Lifeson (Rush) guest on "Fear of a Blank Planet".

Best not get me onto the subject of Rush, though - I've been hooked ever since I heard "All The World's A Stage"....

Philip

[hadr0n]

Physics rocks!

[rovusss]

shit that copy looks nice, the only reason i realized was because of the headstock

[smeghead666]

I was hoping we were about to hear Voodoo child then :P

[pbtwentythree]

OMG?! Is this guy named Professor Moriarty?!

[nulev]

and i needed 3 years of studies to understand this thing that explained here in 7:26 min?

[champignones]

i loved fourier in my engineering carrer, and is very usefull to understand it even thou you wont use it for your carreer. i took both fourier series and fourier transform and isnt quite difficult it just require practice as everything in life.

[jimmyshitbags]

fourier analysis is one of my most favourite things ive learnt about in my physics course, it's such an awesome realization that complicated waveforms can be built from the simplest sine waves. i love stuff like that.

[ogatobranco]

We can think of video compression and image compression computation as well ;)

[Komojo]

What amazed me the most learning about Fourier transforms is that you can do it with any shape. You could trace the profile of George Washington's face or something, convert the points into numerical inputs, and then express that graph as a sum of sine waves, no matter what the input is. (The number of waves necessary depends on the number of inputs.) That's just crazy.

[puncheex]

@Komojo: One of the neat things is that the analysis that converts a waveform in the time domain into the equivalent in the frequency domain can be reversed. Nothing is lost in the transform. (At least that's true if I remember it right. Phase?)

[Kowzorz]

1:50 I thought someone cussed for a second!

[TheLockdawg]

i ask my physics teacher how sound waves applied to my guitar his explanation was sup par compared to this

[doubledown187]

No way - Prof. Moriarty. Way too cool man!

[gyshalom]

ok,i understand the basic idea... the oscillating string will wiggle wildly and displace the air molecules at diffrent rates...creating different regions of pressure...its easy for me to picture the logingtudal wave in the air molecules effected by a simple sinusodial wave...but how will this longitudal wave look when effected by a complex wave such as comming from a guitar string??

[puncheex]

@gyshalom: The complexity of a guitar string will still analyze out. For example, if you could generate a square waveform on a guitar, it will analyze out as the sinusoid of the basic frequency plus declining amplitudes of even harmonics of the basic frequency. A triangular waveform analyzes out as the base plus declining amplitudes of odd harmonics. These are the easy ones; the real waveforms of a guitar string are complex and involve all sorts of harmonics, and even forced non-harmonics.

[TheCynicalAtheist]

Music i get, some of the physics in the other videos i get, this video i follow totally, i just find the mathemathics involved incredibly difficult.

Took me months just to understand chi squared in statistics, id love to learn physics at undergrad and possibly post grad, i just fear my maths will never be good enough to be a physicist.

Youtube channels like this are of imense importance to me, it allows me to try teach myself something i dont think i could learn academically.

Thanks guys!

[adamthecg]

some of the most famous physicists of all time didn't do their own maths.

i think Faraday was one

[drokles]

You, sir, should check out MIT's channel on youtube. Look for professor's Gilbert Strang (for mathematics) and Walter Lewin (for physics). I'd especially recommend some of Lewins lectures on Waves and oscillations.

And don't worry, you don't need to understand math like that when you start your undergrad. You will get courses in calculus and linear algebra. In Denmark where I'm from you recieve math education for the first one and a half year.

I think you should go for it :).

[TheCynicalAtheist]

Thanks for the encouragement, trying to get into the life sciences at undergraduate level at the moment, well at least for 2010. I am passionate about all the sciences equally, but i find the advanced maths involved in some of the physics hard, however the harder i find a subject the more i involve myself.

Thank you for the recomendations, i already had MIT subbed on my channel, but the help was appreciated, i am familiar with Walter Lewin, but not the other guy, will check them out! TY!

[puncheex]

@drokles: However, if you do understand the math, the beauty of it all is overwhelming. Fourier analysis for simple waveforms can actually be computed by hand (the only way to do it before about 1965); complex forms are hugely difficult. But the calculus of infinite series converges with this. When you absorb all that and suddenly you see how it all fits together. It's a moment of beauty.

[hiyabuddy69]

"that allows us to distinguish an A note on guitar"

the note he played was a G haa

[Moriarty2112]

I'm impressed! I tune down by a tone (or a tone and a half) so when I pluck an open "A", as you say, it's indeed a G.

Did you compare it against a known note or have you got ...gasp... perfect pitch?!

Philip (person in video playing guitar)

[hiyabuddy69]

haa no i havent got perfect pitch yet

i could hear it wasnt a G and i was holding my guitar and played that note

by the way these are very interesting videos cheers for them mate

[AtomosNucleous]

i cant check it right now if it is realy g :), but it could be as many videos in youtube are a semitone or two off

[bng44270]

In your newer video on antenna's, you mention wavelengths. if you didn't know the frequency the rubber wire was oscillating at, you could measure the wavelength and figure it out with the following equation:

frequency = speed of light / wavelength

[Quantum024]

Hey,

I'm fairly sure that the equation you mentioned only works for photons - ie electromagnetic waves. You need to take into account the speed of the wave through the rubber in this case.

I'm pretty sure. (!)

[minus00]

frequency is also equal to the speed of sound divided by the wavelength... different scale really. lol

[cagedkiller360]

That equation is for electromagnetic waves.

Sadly, you couldn't calculate the wavelength anyway because the speed of the wave in the rubber wire is zero, which is why they call it a standing wave.

[JonNebula11]

THE WATCHTOWER LOL

[gamesbok]

The Fourier Hypothisis states that any wave is a sum of sin and cosin waves. While it remains an hypothisis it's used everywhere today, mostly in the form of FFTs (Fast Fourier Transforms) in the Levenson algorithm. The product is a power spectrum showing the energy in the different sin and cosin components, (the lower graph on the computer display).

[culwin]

Am I the only one who finds it hilarious that his name is Professor Moriarty? He probably gets that all the time.

[stieg003]

The older prof mentioned that by plucking on the string at different places you get different pitches on the guitar! Oops, that's not right -- I think he misspoke. In fact, if the string doesn't change length (by pushing on a fret), the pitch is the same no matter where you pluck it! There might be some differences in overtones briefly so the timbre of the note may vary slightly but the pitch is the same no matter where you pluck it. Right?

[kirkmax]

I agree.

[soaper4]

I thought it made a slight difference how far away from the pickup(s) you pluck/strum the string(s).

[puncheex]

@stieg003: what you get is different waveforms based on the basic frequency of the string. If you pluck it 1/4 the way from one end, you get a base note rich in odd harmonics. If you move and pluck it elsewhere, you get the same base note with different timbre (harmonic mix).

[TableWolfMusic]

It's quite fitting how he gets so excited about fourier analysis that he is compelled to break into blue movie wah wah music.

[toterer]

how much is his guitar? 100 'quits'?how much is that?

[toxik2005]

he said "100 quid"

thats £100

=]

[soaper4]

How much USD is that?

[toxik2005]

Roughly $165

[SearchingAbsolute]

Such a "complex" phenomenon (which has some much of practical implications in our daily life), explained in such a simple "cool" way .... !

Thanks.

[t0nybaker]

boom chicka wah wah.

I know that music ;o)

[xmaker1]

Sounded like slayer

[companyofthefallen]

you definately have to do a video with the prof playing more guitar.

[brilliantfranz]

absolutely brilliant

this just gets better and better,

Cheers from Venezuela

[darrenc12pdg123]

Are you From Northern Ireland? i couldnt happen to notice your accent

[Moriarty2112]

Not quite Northern Ireland but pretty close. I was brought up in Co. Monaghan (Castleblaney). I then spent about eight years in Dublin before moving to Nottingham. Good to hear that you can detect the Monaghan accent!

[BuggttiVeyronW16]

Wish he can play more Guitar ...-_-

[Envergure]

Waves are my favourite part of physics, they make me happy :) I'm a synthesist, that's why.

[Moriarty2112]

@Chentiangemalc: It was your comment on the Frequency (nu) video (elsewhere on the Sixty Smbols channel) that prompted a lengthier discussion of Fourier analysis, so thank *you*. We could, of course, have made an hour long video on Fourier analysis and still have only scratched the surface...

Best wishes, Philip

[yared94]

It's too bad that theirs the 10 min limit. I'm sure they could make better ones without it.

[Acid113377]

stop complaining...

[CaptainSpaktastic]

They explain what Fourier analysis is and does. If they went into any detail it would be beyond what the average youtube viewer could understand.

[MichaelERutherford]

Great Video. I love physics but god I hate his accent lol

[celeph]

I have some fond memories of fourier & wavelets in my study days... but what path did I take...what have I done that led me to here so far away from the interesting things I once learned about!?

Your videos make me want to return to university *now*! Great work! I'm looking forward to your next videos -- I hope you will continue producing more material, even when all 60 symbols are complete.

[JimPrower]

Lord. Fourier...I studied that. It's not as easy as you'd think...

[grnlfe01]

I definatly feel there need to be more guitars in physics. I wonder how many physics students have a professor they can jam with. Great video

[MichaelERutherford]

I study Chemical Physics and play guitar but don't know any riffing profs yet lol. Maybe one day:P

[bb0ss]

great vid

and you have a cool les paul prof

[CaptainSpaktastic]

Did Roger Bowley borrow that shirt from Nelson Mandela?

[wongsmokesbong]

you should have miked the amp! (actually if it was solid state it probably wouldn't sound too good anyway)