The physics of playing guitar - Oscar Fernando Perez

432,071 views ใƒป 2015-08-13

TED-Ed


ืื ื ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ืœืžื˜ื” ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ.

ืชืจื’ื•ื: Ido Dekkers ืขืจื™ื›ื”: Tal Dekkers
00:07
Hendrix, Cobain and Page.
0
7014
3763
ื”ื ื“ืจื™ืงืก, ืงื•ื‘ื™ื™ืŸ ื•ืคื™ื™ื’'.
00:10
They can all shred,
1
10777
1577
ื›ื•ืœื ื™ื›ื•ืœื™ื ืœื˜ื—ื•ืŸ,
00:12
but how exactly do the iconic contraptions in their hands
2
12354
3881
ืื‘ืœ ืื™ืš ื‘ื“ื™ื•ืง ื”ืžืชืงื ื™ื ื”ืื™ืงื•ื ื™ื™ื ื‘ื™ื“ื™ื ืฉืœื”ื
00:16
produce notes, rhythm, melody and music.
3
16235
5459
ืžื™ื™ืฆืจื™ื ืชื•ื•ื™ื, ืžืงืฆื‘ื™ื, ืžืœื•ื“ื™ื•ืช ื•ืžื•ื–ื™ืงื”.
00:21
When you pluck a guitar string, you create a vibration called a standing wave.
4
21694
4909
ื›ืฉืืชื ืคื•ืจื˜ื™ื ืขืœ ื”ื’ื™ื˜ืจื”, ืืชื ื™ื•ืฆืจื™ื ืจื˜ื˜ ืฉื ืงืจื ื’ืœ ืขื•ืžื“.
00:26
Some points on the string, called nodes, don't move at all,
5
26603
3927
ื›ืžื” ื ืงื•ื“ื•ืช ืขืœ ื”ืžื™ืชืจ, ืฉื ืงืจืื•ืช ืฆืžืชื™ื, ืœื ื ืขื•ืช ื‘ื›ืœืœ,
00:30
while other points, anti-nodes, oscillate back and forth.
6
30530
4650
ื‘ืขื•ื“ ื ืงื•ื“ื•ืช ืื—ืจื•ืช, ืื ื˜ื™ ืฆืžืชื™ื, ืจื•ื˜ื˜ื•ืช ืงื“ื™ืžื” ื•ืื—ื•ืจื”.
00:35
The vibration translates through the neck and bridge to the guitar's body,
7
35180
4404
ื”ืจื˜ื˜ ืžืชื•ืจื’ื ื“ืจืš ื”ืฆื•ื•ืืจ ื•ื”ื’ืฉืจ ืœื’ื•ืฃ ื”ื’ื™ื˜ืจื”,
00:39
where the thin and flexible wood vibrates,
8
39584
2848
ืฉื ื”ืขืฅ ื”ื“ืง ื•ื”ื’ืžื™ืฉ ืจื•ื˜ื˜,
00:42
jostling the surrounding air molecules together and apart.
9
42432
4193
ืžืจืขื™ื“ ืืช ืžื•ืœืงื•ืœื•ืช ื”ืื•ื™ืจ ื”ืžืงื™ืคื•ืช ื™ื—ื“ ื•ืœื—ื•ื“.
00:46
These sequential compressions create sound waves,
10
46625
3105
ื”ื“ื—ื™ืกื•ืช ื”ืจืฆื•ืคื•ืช ื”ืืœื• ื™ื•ืฆืจื•ืช ื’ืœื™ ืงื•ืœ,
00:49
and the ones inside the guitar mostly escape through the hole.
11
49730
4202
ื•ืืœื” ืฉื‘ืชื•ืš ื”ื’ื™ื˜ืจื” ื‘ืขื™ืงืจ ื‘ื•ืจื—ื™ื ื”ื—ื•ืฆื” ื“ืจืš ื”ื—ื•ืจ.
00:53
They eventually propagate to your ear,
12
53932
2289
ื”ื ืœื‘ืกื•ืฃ ืžื’ื™ืขื™ื ืืœ ื”ืื•ื–ืŸ,
00:56
which translates them into electrical impulses
13
56221
2569
ืฉืžืชืจื’ืžืช ืื•ืชื ืœืื•ืชื•ืช ื—ืฉืžืœื™ื™ื
00:58
that your brain interprets as sound.
14
58790
3135
ืฉื”ืžื•ื— ืฉืœื›ื ืžืคืจืฉ ื›ืฆืœื™ืœื™ื.
01:01
The pitch of that sound depends on the frequency of the compressions.
15
61925
4557
ื”ื’ื•ื‘ื” ืฉืœ ื”ืฆืœื™ืœ ืชืœื•ื™ ื‘ืชื“ื™ืจื•ืช ืฉืœ ื”ื“ื—ื™ืกื•ืช.
01:06
A quickly vibrating string will cause a lot of compressions close together,
16
66482
4498
ืžื™ืชืจ ืฉืจื•ื˜ื˜ ื‘ืžื”ื™ืจื•ืช ื™ืฆื•ืจ ื”ืจื‘ื” ื“ื—ื™ืกื•ื™ื•ืช ืงืจื•ื‘ื•ืช,
01:10
making a high-pitched sound,
17
70980
1573
ืžื” ืฉื™ื’ืจื•ื ืœืฆืœื™ืœ ื’ื‘ื•ื” ื™ื•ืชืจ,
01:12
and a slow vibration produces a low-pitched sound.
18
72553
3865
ื•ืจืขื™ื“ื•ืช ืื™ื˜ื™ื•ืช ืžื™ื™ืฆืจื•ืช ืฆืœื™ืœ ื ืžื•ืš.
01:16
Four things affect the frequency of a vibrating string:
19
76418
3264
ืืจื‘ืขื” ื“ื‘ืจื™ื ืžืฉืคื™ืขื™ื ืขืœ ื”ืชื“ื™ืจื•ืช ืฉืœ ืžื™ืชืจื™ื ืจื•ื˜ื˜ื™ื:
01:19
the length, the tension, the density and the thickness.
20
79682
4528
ื”ืื•ืจืš, ื”ืžืชื—, ื”ื“ื—ื™ืกื•ืช ื•ื”ืขื•ื‘ื™.
01:24
Typical guitar strings are all the same length,
21
84210
2820
ืžื™ืชืจื™ ื’ื™ื˜ืจื” ื˜ื™ืคื•ืกื™ื™ื ื”ื ื‘ืื•ืชื• ืื•ืจืš,
01:27
and have similar tension, but vary in thickness and density.
22
87030
4494
ื•ื™ืฉ ืœื›ื ืžืชื— ื“ื•ืžื”, ืื‘ืœ ื”ื ืžืฉืชื ื™ื ื‘ืขื•ื‘ื™ ื•ื‘ื“ื—ื™ืกื•ืช.
01:31
Thicker strings vibrate more slowly, producing lower notes.
23
91524
4467
ืžื™ืชืจื™ื ืขื‘ื™ื ื™ื•ืชืจ ืจื•ื˜ื˜ื™ื ื‘ืžื”ื™ืจื•ืช ืื™ื˜ื™ืช ื™ื•ืชืจ, ื•ืžื™ื™ืฆืจื™ื ืฆืœื™ืœื™ื ื ืžื•ื›ื™ื ื™ื•ืชืจ.
01:35
Each time you pluck a string,
24
95991
2001
ื›ืœ ืคืขื ืฉืืชื ืคื•ืจื˜ื™ื ืขืœ ืžื™ืชืจ,
01:37
you actually create several standing waves.
25
97992
2755
ืืชื ืœืžืขืฉื” ื™ื•ืฆืจื™ื ื›ืžื” ื’ืœื™ื ืขื•ืžื“ื™ื.
01:40
There's the first fundamental wave, which determines the pitch of the note,
26
100747
4234
ื™ืฉ ืืช ื”ื’ืœ ื”ืจืืฉื•ื ื™ ื”ืขื™ืงืจื™, ืฉืงื•ื‘ืข ืืช ื”ื’ื•ื‘ื” ืฉืœ ื”ืชื•,
01:44
but there are also waves called overtones,
27
104981
2547
ืื‘ืœ ื™ืฉ ื’ื ื’ืœื™ื ืฉื ืงืจืื™ื ื”ืจืžื•ื ื™ื•ืช,
01:47
whose frequencies are multiples of the first one.
28
107528
3811
ืฉื”ืชื“ื™ืจื•ื™ื•ืช ืฉืœื”ื ื”ืŸ ื›ืคื•ืœื•ืช ืฉืœ ื”ืจืืฉื•ืŸ.
01:51
All these standing waves combine to form a complex wave with a rich sound.
29
111339
5716
ื›ืœ ื”ื’ืœื™ื ื”ืขื•ืžื“ื™ื ื”ืืœื” ืžืชื—ื‘ืจื™ื ืœื™ืฆื•ืจ ื’ืœ ืžื•ืจื›ื‘ ืขื ืฆืœื™ืœ ืขืฉื™ืจ.
01:57
Changing the way you pluck the string affects which overtones you get.
30
117055
4393
ืฉื™ื ื•ื™ ื”ื“ืจืš ื‘ื” ืืชื ืคื•ืจื˜ื™ื ืขืœ ืžื™ืชืจ ื”ื’ื™ื˜ืจื” ืžืฉืคื™ืข ืขืœ ืื™ื–ื” ื”ืจืžื•ื ื™ื•ืช ืืชื ืžืงื‘ืœื™ื.
02:01
If you pluck it near the middle,
31
121448
1737
ืื ืืชื ืคื•ืจื˜ื™ื ืงืจื•ื‘ ืœืžืจื›ื–,
02:03
you get mainly the fundamental and the odd multiple overtones,
32
123185
3918
ืืชื ืžืงื‘ืœื™ื ื‘ืขื™ืงืจ ืืช ื”ื”ืจืžื•ื ื™ื•ืช ื”ืขื™ืงืจื™ืช ื•ื”ืื™ ื–ื•ื’ื™ื•ืช,
02:07
which have anti-nodes in the middle of the string.
33
127103
2973
ืฉื™ืฉ ืœื”ื ืื ื˜ื™ ืฆืžืชื™ื ื‘ืืžืฆืข ื”ืžื™ืชืจ.
02:10
If you pluck it near the bridge, you get mainly even multiple overtones
34
130076
4282
ืื ืืชื ืคื•ืจื˜ื™ื ืงืจื•ื‘ ืœื’ืฉืจ, ืืชื ืžืงื‘ืœื™ื ื‘ืขื™ืงืจ ืืช ื”ื”ืจืžื•ื ื™ื•ืช ื”ื–ื•ื’ื™ื•ืช
02:14
and a twangier sound.
35
134358
2052
ื•ืฆืœื™ืœ ืžืื ืคืฃ ื™ื•ืชืจ.
02:16
The familiar Western scale is based on the overtone series of a vibrating string.
36
136410
5847
ื”ืกื•ืœื ื”ืžืขืจื‘ื™ ื”ืžื•ื›ืจ ืžื‘ื•ืกืก ืขืœ ืกื“ืจืช ื”ื”ืจืžื•ื ื™ื•ืช ืฉืœ ืžื™ืชืจ ืจื•ื˜ื˜.
02:22
When we hear one note played with another that has exactly twice its frequency,
37
142257
5004
ื›ืฉืื ื—ื ื• ืฉื•ืžืขื™ื ืชื• ืื—ื“ ืžื ื•ื’ืŸ ืขื ืื—ืจ ืฉื™ืฉ ืœื• ืชื“ื™ืจื•ืช ื›ืคื•ืœื” ื‘ื“ื™ื•ืง,
02:27
its first overtone,
38
147261
1934
ื”ื”ืจืžื•ื ื™ื” ื”ืจืืฉื•ื ื” ืฉืœื•,
02:29
they sound so harmonious that we assign them the same letter,
39
149195
4008
ื”ื ื ืฉืžืขื™ื ื”ืจืžื•ื ื™ื™ื ื›ืœ ื›ืš ืฉืื ื—ื ื• ื ื•ืชื ื™ื ืœื”ื ืื•ืชื• ืชื•,
02:33
and define the difference between them as an octave.
40
153203
3727
ื•ืžื’ื“ื™ืจื™ื ืืช ื”ื”ื‘ื“ืœ ื‘ื™ื ื”ื ื›ืื•ืงื˜ื‘ื”.
02:36
The rest of the scale is squeezed into that octave
41
156930
3185
ืฉืืจ ื”ืกื•ืœื ื ื“ื—ืก ืœืชื•ืš ื”ืื•ืงื˜ื‘ื” ื”ื”ื™ื
02:40
divided into twelve half steps
42
160115
1987
ืžื—ื•ืœืง ืœืฉื ื™ื™ื ืขืฉืจ ื—ืฆื™ ืฆืขื“ื™ื
02:42
whose frequency is each 2^(1/12) higher than the one before.
43
162102
5937
ืฉื”ืชื“ื™ืจื•ืช ืฉืœื”ื ื›ืœ ืื—ืช ื”ื™ื 2^(1/12) ื’ื‘ื•ื”ื” ื™ื•ืชืจ ืžื”ืงื•ื“ืžืช.
02:48
That factor determines the fret spacing.
44
168039
3251
ื”ืžืงื“ื ื”ื–ื” ืงื•ื‘ืข ืืช ืžืจื•ื•ื— ื”ืกืจื™ื’.
02:51
Each fret divides the string's remaining length by 2^(1/12),
45
171290
5825
ื›ืœ ืกืจื™ื’ ืžื—ืœืง ืืช ืื•ืจืš ื”ืžื™ืชืจ ื”ื ื•ืชืจ ื‘ 2^(1/12),
02:57
making the frequencies increase by half steps.
46
177115
3466
ืžื” ืฉื’ื•ืจื ืœืชื“ื™ืจื•ื™ื•ืช ืœืขืœื•ืช ื‘ื—ืฆื™ ืฆืขื“.
03:00
Fretless instruments, like violins,
47
180581
2020
ื›ืœื™ื ื ื˜ื•ืœื™ ืกืจื™ื’ ื›ืžื• ื›ื™ื ื•ืจื•ืช,
03:02
make it easier to produce the infinite frequencies between each note,
48
182601
4325
ื”ื•ืคื›ื™ื ืืช ื–ื” ืœืคืฉื•ื˜ ื™ื•ืชืจ ืœื™ื™ืฆืจ ืชื“ื™ืจื•ื™ื•ืช ืื™ืŸ ืกื•ืคื™ื•ืช ื‘ื™ืŸ ื›ืœ ืชื• ืœืชื•,
03:06
but add to the challenge of playing intune.
49
186926
3593
ืื‘ืœ ืžื•ืกื™ืคื™ื ืœืืชื’ืจ ืฉืœ ื ื™ื’ื•ืŸ ืœืคื™ ื”ืชื•ื™ื.
03:10
The number of strings and their tuning
50
190519
2062
ืžืกืคืจ ื”ืžื™ืชืจื™ื ื•ื”ื›ื•ื•ื ื•ืŸ ืฉืœื”ื
03:12
are custom tailored to the chords we like to play
51
192581
3212
ืžื•ืชืืžื™ื ืœืืงื•ืจื“ื™ื ืฉืื ื—ื ื• ืื•ื”ื‘ื™ื ืœื ื’ืŸ
03:15
and the physiology of our hands.
52
195793
2187
ื•ื”ืคื™ื–ื™ื•ืœื•ื’ื™ื” ืฉืœ ื”ื™ื“ื™ื™ื ืฉืœื ื•.
03:17
Guitar shapes and materials can also vary,
53
197980
2883
ืฆื•ืจื•ืช ื”ื’ื™ื˜ืจื•ืช ื•ื—ื•ืžืจื™ื ื™ื›ื•ืœื™ื ื’ื ื”ื ืœื”ืฉืชื ื•ืช,
03:20
and both change the nature and sound of the vibrations.
54
200863
3664
ืื‘ืœ ืฉื ื™ื™ื”ื ืžืฉื ื™ื ืืช ื”ื˜ื‘ืข ื•ื”ืฆืœื™ืœ ืฉืœ ื”ืจื˜ื™ื˜ื•ืช.
03:24
Playing two or more strings at the same time
55
204527
2679
ื ื™ื’ื•ืŸ ื‘ืฉื ื™ื™ื ืื• ื™ื•ืชืจ ืžื™ืชืจื™ื ื‘ืื•ืชื• ื–ืžืŸ
03:27
allows you to create new wave patterns like chords and other sound effects.
56
207206
4999
ืžืืคืฉืจ ืœื›ื ืœื™ืฆื•ืจ ืฆื•ืจื•ืช ื’ืœื™ื ื—ื“ืฉื•ืช ื›ืžื• ืืงื•ืจื“ื™ื ื•ืืคืงื˜ื™ื ืื—ืจื™ื ื‘ืฆืœื™ืœ.
03:32
For example, when you play two notes whose frequencies are close together,
57
212205
4074
ืœื“ื•ื’ืžื”, ื›ืฉืืชื ืžื ื’ื ื™ื ืฉื ื™ ืชื•ื™ื ืฉื”ืชื“ื™ืจื•ื™ื•ืช ืฉืœื”ื ืงืจื•ื‘ื•ืช,
03:36
they add together to create a sound wave whose amplitude rises and falls,
58
216279
5326
ื”ื ืžืชื—ื‘ืจื™ื ืœื™ืฆื•ืจ ื’ืœ ืงื•ืœ ืฉื”ืžืฉืจืขืช ืฉืœื• ืขื•ืœื” ื•ื™ื•ืจื“ืช,
03:41
producing a throbbing effect, which guitarists call the beats.
59
221605
4895
ืžื” ืฉืžื™ื™ืฆืจ ืืคืงื˜ ืคื•ืขื, ืฉื’ื™ื˜ืจื™ืกื˜ื™ื ืงื•ืจืื™ื ืœื• ื‘ื™ื˜ืก.
03:46
And electric guitars give you even more to play with.
60
226500
3006
ื•ื’ื™ื˜ืจื•ืช ื—ืฉืžืœื™ื•ืช ื ื•ืชื ื•ืช ืœื›ื ืืคื™ืœื• ื™ื•ืชืจ ืืคืฉืจื•ื™ื•ืช ืžืฉื—ืง.
03:49
The vibrations still start in the strings,
61
229506
2186
ื”ืจื˜ื™ื˜ื•ืช ืขื“ื™ื™ืŸ ืžืชื—ื™ืœื•ืช ื‘ืžื™ืชืจื™ื,
03:51
but then they're translated into electrical signals by pickups
62
231692
4239
ืื‘ืœ ืื– ื”ืŸ ืžืชื•ืจื’ืžื•ืช ืœืื•ืชื•ืช ื—ืฉืžืœื™ื™ื ืขืœ ื™ื“ื™ ืคื™ืงืืคื™ื
03:55
and transmitted to speakers that create the sound waves.
63
235931
3153
ื•ืžื•ืขื‘ืจื™ื ืœืจืžืงื•ืœื™ื ืฉื™ื•ืฆืจื™ื ืืช ื”ื’ืœื™ ื”ืงื•ืœ.
03:59
Between the pickups and speakers,
64
239084
1825
ื‘ื™ืŸ ื”ืคื™ืงืืคื™ื ื•ื”ืจืžืงื•ืœื™ื,
04:00
it's possible to process the wave in various ways,
65
240909
3766
ืืคืฉืจื™ ืœืขื‘ื“ ืืช ื”ื’ืœื™ื ื‘ื“ืจื›ื™ื ืฉื•ื ื•ืช,
04:04
to create effects like distortion, overdrive, wah-wah, delay and flanger.
66
244675
7083
ื›ื“ื™ ืœื™ืฆื•ืจ ืืคืงื˜ื™ื ื›ืžื• ื“ื™ืกื˜ื•ืจืฉืŸ, ืื•ื‘ืจื“ืจื™ื™ื‘, ื•ื•ืื”-ื•ื•ืื”, ื“ื™ืœื™ื™ ื•ืคืœืื ื’ืจ.
04:11
And lest you think that the physics of music is only useful for entertainment,
67
251758
4381
ื•ืื ืืชื ื—ื•ืฉื‘ื™ื ืฉื”ืคื™ื–ื™ืงื” ืฉืœ ืžื•ื–ื™ืงื” ื™ืขื™ืœื” ืจืง ืœื‘ื™ื“ื•ืจ,
04:16
consider this.
68
256139
1920
ื—ืฉื‘ื• ืขืœ ื–ื”.
04:18
Some physicists think that everything in the universe
69
258059
2763
ื›ืžื” ืคื™ื–ื™ืงืื™ื ื—ื•ืฉื‘ื™ื ืฉื”ื›ืœ ื‘ื™ืงื•ื
04:20
is created by the harmonic series of very tiny, very tense strings.
70
260822
6070
ื ื•ืฆืจ ืขืœ ื™ื“ื™ ืกื“ืจื•ืช ื”ืจืžื•ื ื™ื•ืช ืฉืœ ืžื™ืชืจื™ื ืžืžืฉ ื–ืขื™ืจื™ื ื•ืžืชื•ื—ื™ื.
04:26
So might our entire reality
71
266892
2576
ืื– ืื•ืœื™ ื›ืœ ื”ืžืฆื™ืื•ืช ืฉืœื ื•
04:29
be the extended solo of some cosmic Jimi Hendrix?
72
269468
4302
ืžื•ืจื—ื‘ืช ืœืกื•ืœื• ืฉืœ ื’'ื™ืžื™ ื”ื ื“ืจื™ืงืก ืงื•ืกืžื™?
04:33
Clearly, there's a lot more to strings than meets the ear.
73
273770
5355
ื‘ื‘ืจื•ืจ, ื™ืฉ ื”ืจื‘ื” ื™ื•ืชืจ ืœืžื™ืชืจื™ื ืžืฉื ืฉืžืข ืœืื•ื–ืŸ.
ืขืœ ืืชืจ ื–ื”

ืืชืจ ื–ื” ื™ืฆื™ื’ ื‘ืคื ื™ื›ื ืกืจื˜ื•ื ื™ YouTube ื”ืžื•ืขื™ืœื™ื ืœืœื™ืžื•ื“ ืื ื’ืœื™ืช. ืชื•ื›ืœื• ืœืจืื•ืช ืฉื™ืขื•ืจื™ ืื ื’ืœื™ืช ื”ืžื•ืขื‘ืจื™ื ืขืœ ื™ื“ื™ ืžื•ืจื™ื ืžื”ืฉื•ืจื” ื”ืจืืฉื•ื ื” ืžืจื—ื‘ื™ ื”ืขื•ืœื. ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ื”ืžื•ืฆื’ื•ืช ื‘ื›ืœ ื“ืฃ ื•ื™ื“ืื• ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ ืžืฉื. ื”ื›ืชื•ื‘ื™ื•ืช ื’ื•ืœืœื•ืช ื‘ืกื ื›ืจื•ืŸ ืขื ื”ืคืขืœืช ื”ื•ื•ื™ื“ืื•. ืื ื™ืฉ ืœืš ื”ืขืจื•ืช ืื• ื‘ืงืฉื•ืช, ืื ื ืฆื•ืจ ืื™ืชื ื• ืงืฉืจ ื‘ืืžืฆืขื•ืช ื˜ื•ืคืก ื™ืฆื™ืจืช ืงืฉืจ ื–ื”.

https://forms.gle/WvT1wiN1qDtmnspy7