A brief message from your TAs • Tine Gulbrandsen • Wahab Hanif
Transcript
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A brief message from your TAs Tine Gulbrandsen Wahab Hanif
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Pure Tones are Very Rare in Nature! What are real sounds
composed of?
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Pure Tones are Very Rare in Nature! What are real sounds
composed of? Virtually all sounds are composed of several (or many)
frequencies all going at once
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Pure Tones are Very Rare in Nature! What are real sounds
composed of? Virtually all sounds are composed of several (or many)
frequencies all going at once Extra frequencies are called
harmonics
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What are harmonics? position up down imagine a guitar
string:
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What are harmonics? position up down imagine a guitar
string:
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What are harmonics? time -> position up down But more than
one frequency can fit between the end points
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What are harmonics? time -> position up down f0f0 f1f1 f2f2
In fact many frequencies can be superposed.
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Properties of a Sound Wave A 1 second, 1 Hz sound wave:
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Properties of a Sound Wave A 1 second, 2 Hz sound wave:
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Properties of a Sound Wave A 1 second, 3 Hz sound wave:
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Properties of a Sound Wave What would happen if two or more
sound waves were happening at the same time?
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Properties of a Sound Wave Sounds superpose (they add
together)
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Properties of a Sound Wave Sounds superpose (they add
together)
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Properties of a Sound Wave If most sounds are made of several
frequencies, then which sound determines the pitch that you
hear?
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Properties of a Sound Wave If most sounds are made of several
frequencies, then which sound determines the pitch that you hear?
Typically you hear the lowest frequency component as the pitch of a
complex wave
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Properties of a Sound Wave The lowest frequency is called the
fundamental
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The Missing Fundamental Your brain so likes to track the
fundamental of a set of harmonics that it will perceptually fill it
in even when it is absent missing fundamental
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Timbre (pronounced like: Tamber) pure tones are very rare a
single note on a musical instrument is a superposition (i.e.
several things one on top of the other) of many related frequencies
called harmonics Pronounciation of timbre
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Timbre the characteristic of a particular set of harmonics is
called timbre e.g. the set of harmonics generated when a particular
key is pressed on a piano timbre is one reason why we can tell the
difference between the same notes played on difference
instruments
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Timbre Although any musical note is a superposition of
harmonics, you still hear it as a single pitch (you hear its tone
height) The pitch that you hear is (usually) the fundamental
frequency (except in the artificial case of the missing
fundamental)
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Musical Intervals in music, notes are played together or in
quick succession pairs of notes share a relationship called an
interval
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Musical Intervals Within each pair, the higher pitch (f2) is
some multiple of the lower pitch (f1): e.g. 200 hz and 400 hz -- f2
is two times f1
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Musical Intervals f 1 = 400 f 2 = 800 (f 2 = 2 x f 1 )octave f
1 = 400 f 2 = 600 (f 2 = 3/2 x f 1 )perfect 5th f 1 = 500 f 2 = 800
(f 2 = 8/5 x f 1 )minor 6th f 1 = 400 f 2 = 550 (f 2 = 11/8 x f 1 )
octave perfect 5th minor 6th not quite a perfect fourth?!
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Consonance and Dissonance Consonance is the degree to which two
tones played together sound good Dissonance is the opposite
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Consonance and Disonance Dissonance seems to increase with
increasing complexity of the ratio of the tones
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Seeing Sound with Spectrograms A spectrogram is a 3D plot of
sound Time Frequency
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Seeing Sound with Spectrograms A spectrogram is a 3D plot of
sound Time Frequency Intensity Intensity is often coded by colour
such that red is high and blue is low