An assignment for Audio Visual Technology in Year 2. A concise PowerPoint presentation explaining how the acoustic guitar works.

1. Acoustic
Guitar
Oisín Deignan’s AV Tech Presentation
HOW DOES IT WORK?

2. Background
ACOUSTIC GUITAR: HOW DOES IT WORK?

3. Background to the Guitar
•The guitar is one of the most popular musical
instruments of all time.
•Known use since as early as the 1500s but
some sources suggest it has been around for
over 3000 years.
•Musicians in rock, country, and world music
use the same acoustic guitar but in different
ways to make wildly different sounds.
•Since the 1500s – huge effect on popular
music.

4. The Construction of
the Acoustic Guitar
ACOUSTIC GUITAR: HOW DOES IT WORK?

5. Guitar Parts
Hollow Body
Base of the guitar
Neck
Holds the frets
Head
Contains the
tuning pegs

6. Guitar Parts
Soundboard
The most important part of the body.
Job – to make the sound of the guitar loud
enough to hear.

7. Sound board
•Soundboard has a large hole called the sound hole.
•Bridge – attached to soundboard, anchors for one
end of the six strings.
•Saddle – hard piece that the strings rest on.
•Vibrating strings > saddle > bridge > soundboard.
•Soundboard vibrates – body of guitar forms a
hollow sound box that amplifies vibration of
soundboard.

8. Guitar Body
•Body of acoustic guitars have two widenings
(happens to be a leg rest).
•Two widenings – upper bout and lower bout.
•The tone of a guitar depends on the size and shape
of the bouts.
•Lower bout accentuates lower tones. Upper bout
accentuates higher tones. (Rattling a plectrum inside
demonstrates this).

9. Neck and Scale Length
•Fingerboard/Fretboard - Face of neck containing the frets.
•Pressing fingers onto a fret – changes length of string and the
tone it produces.
•Saddle and nut act as two ends of string.
•Scale length – distance between these 2 points.

10. How the Acoustic
Guitar works
ACOUSTIC GUITAR: HOW DOES IT WORK?

11. Sounds, Tones, and Notes
•Sound is any change in air pressure that our ears
are able to detect and process.
•For our ears to be able to perceive sound, a sound
has to occur in a certain frequency range.
•Human’s perceivable sound: 20-1500 Hz.

12. Sounds, Tones, and Notes
•A tone is a sound that repeats a certain frequency.
•A tone can be made up of one frequency or a small
number of related frequencies - usually a pleasant sound.
•Noise - combination of a number of random frequencies
– usually not a pleasant sound.

13. Sounds, Tones, and Notes
•A musical note – collection of tones that are pleasing to the human brain.
•Major sale – certain collection of tones that sound pleasing.
•There certain tones have been given letter names.
264 Hz - C, do (multiply by 9/8 to get:)
297 Hz - D, re (multiply by 10/9 to get:)
330 Hz - E, mi (multiply by 16/15 to get:)
352 Hz - F, fa (multiply by 9/8 to get:)
396 Hz - G, so (multiply by 10/9 to get:)
440 Hz - A, la (multiply by 9/8 to get:)
495 Hz - B, ti (multiply by 16/15 to get:)
528 Hz - C, do (multiply by 9/8 to get:)

14. Sounds, Tones, and Notes
•One thing to notice is that the two C notes
are separated by exactly a factor of two -- 264
is one half of 528.
•This is the basis of octaves. Any note's
frequency can be doubled to "go up an
octave," and any note's frequency can be
halved to "go down an octave."
264 Hz - C, do (multiply by 9/8 to get:)
297 Hz - D, re (multiply by 10/9 to get:)
330 Hz - E, mi (multiply by 16/15 to get:)
352 Hz - F, fa (multiply by 9/8 to get:)
396 Hz - G, so (multiply by 10/9 to get:)
440 Hz - A, la (multiply by 9/8 to get:)
495 Hz - B, ti (multiply by 16/15 to get:)
528 Hz - C, do (multiply by 9/8 to get:)

15. Tempered Scale
•After a long period of time, the
musical world came to agree on a scale
called the tempered scale.
•All of the notes are offset by the 12th
root of 2 (1.0595).
•So if you take any note’s frequency and
multiply it by 1.0595, you get the
frequency of the next note.
82.4 E - open 6th string
87.3 F
92.5 F#
98.0 G
103.8 G#
110.0 A - open 5th string
116.5 A#
123.5 B
130.8 C
138.6 C#
146.8 D - open 4th string
155.6 D#
164.8 E
174.6 F
185.0 F#
196.0 G - open 3rd string
207.6 G#
220.0 A
233.1 A#
246.9 B - open 2nd string
261.6 C - "middle C"
277.2 C#
293.6 D
311.1 D#
329.6 E - open 1st string
349.2 F
370.0 F#
392.0 G
415.3 G#
440.0 A - 5th fret on 1st string
466.1 A#
493.8 B
523.2 C
554.3 C#
587.3 D
622.2 D#
659.2 E - 12th fret on 1st string

16. Tempered Scale
•Here is the layout of the notes on the guitar.
•There are 72 fret positions here, but the tempered scale only
shows 37 unique notes.
•Therefore there are multiple ways to play identical notes on a
guitar.
•Example: Open 5th string tuned to A at 440 Hz = 5th fret on 6th
string tuned to E at 329.6 Hz.

17. Use of the
Acoustic Guitar
ACOUSTIC GUITAR: HOW DOES IT WORK?

18. Strings & Frets
•A guitar uses vibrating strings to generate tones.
•A string under tension will vibrate at a specific frequency
that is controlled by the:
• Length of the string.
• Amount of tension on the string.
• Weight of the string.
• Flexibility of the string’s material.
•The tension of the strings is controlled by the tuning pegs.
•The scale length is the distance from the nut to the saddle.
•When you press down on a fret, you change the length of the string and its frequency.

19. Acoustic Guitar’s Sound
An acoustic guitar generates its sound in the following way:
•Strings vibrate > vibrations transmit to saddle.
•Saddle vibrates > vibrations transmitted to soundboard.
•Soundboard and body amplify the sound.
•Sound comes out through the sound hole.

20. Harmonics & Envelope
Acoustic guitars add harmonics to tones.
•When one string is plucked, other strings pick up the
vibrations from the saddle.
•Therefore: the sound heard from a guitar note is a blend
of many related frequencies.
•The acoustic guitar also adds envelope to any note it plays.
•The sound builds and fades off.
•The amplitude (loudness) of the note changes.