looking at sound
DESCRIPTION
Looking at sound. Sound can be made visible by waveforms and spectrograms Speech sounds are created by vibrations of the vocal cords, which produce a wave Variation in air pressure The air pressure can be plotted into a graph to produce a waveform How did we get this wave?. Pressure . - PowerPoint PPT PresentationTRANSCRIPT
Looking at sound• Sound can be made visible by waveforms and
spectrograms• Speech sounds are created by vibrations of the vocal
cords, which produce a wave– Variation in air pressure
• The air pressure canbe plotted into a graphto produce a waveform
• How did we get thiswave?
Time (s)0 0.8359
-0.6292
0.6185
0
0.417959184articulated
Time
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Production of sound waves by a loudspeaker
• Sound waves are like waves in a coil (like a Slinky)
The individual air molecules only vibrate back and forth locally, they do not travel from the source to the receiver
The red line is
like your vocal cords
Measuring the wave (pressure)
Loudness depends primarily on the amplitude
Time (s)
0 0.8359-0.6292
0.6185
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0.246385070.298629968articulated
Time (s)0.2464 0.2986
-0.6292
0.6185
0
articulated
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The sound wave of articulated
Complex waves
• The sound wave of speech is much more complex than the waves we’ve seen so far– The wave of a speech sound is always a
combination of multiple other waves with different frequencies and different loudness
– These waves are ‘added up’
Adding waves
Adding waves
This is how a synthesizer
works
Frequencies
• To see which sound is produced, we can’t just look at the waveform itself– We need to find the different waves in the waveform– More specifically, we need the frequencies of those
waves
• Frequency is the number of times one wavelength comes by in one second– If it comes by 10 times per second, its frequency is 10
Hertz (Hz)
• Humans can hear 20 to 20,000 Hz.• Most phonetic information is below 8,000 Hz.
Which wave has a higher frequency?
0 sec 1 sec 2 sec 3 sec 4 sec
Spectrograms
• The waveform can be analyzed into its frequencies• Frequencies can be made visible with spectrograms
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Fre
quen
cy (
Hz)
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articulated
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Freq
uenc
y (H
z)0
articulated
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ency
Dark areas indicate louder
frequencies
Voiced sounds have three or
four major frequencies
F1
articulated
F0
F2
F3
ə dɑr th ɪ k ɾyu l ey
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Freq
uenc
y (H
z)0
articulated ə dɑr
Time
Fre
qu
ency
You can recognize vowels
th ɪ k ɾ
articulated
yu l ey
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5000
Freq
uenc
y (H
z)0
articulated
Time
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qu
ency
You can recognize
stops:/p, t, k, b, d, g, ɾ/ articulated
ə dɑr th ɪ k ɾyu l ey
Time (s)0 0.8359
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Freq
uenc
y (H
z)0
articulated də
Time
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qu
ency
You can recognize aspiration
Little puff of airBig puff of air
articulated
ɑr th ɪ k ɾyu l ey
Time (s)0 0.8359
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Freq
uenc
y (H
z)0
articulated
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Pit
ch (
Hz)
75
5000
articulated
Time
Fre
qu
ency
articulated
You can recognize
pitch
ə dɑr th ɪ k yu ley
ɾyu l ey
Which word is this? a. whoseb. pseudonymc. judgmentd. dessert
How did you know?
What would you do?
• Your students consistently pronounce this as /dɪs/.• Your students consistently pronounce back as /bɑk/.• Your students have a tendency to insert /ə/ between
words in phrases like cold, drink, wet towel, and gas station.
• A student asks you for advice, saying: “People can’t tell whether I’m saying thirteen or thirty. What should I do?”
• One of your ESL students has many young American peers who regularly use rising intonation with statements. This student asks you about the conflict between this observation and what has been taught in the class.
Next week
• Submit or hand in midterm assignment– On BB or in class– March 18, at beginning of class
• Lab session in PH212 at 6:45pm