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

Pre

ssu

re

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

0

0.246385070.298629968articulated

Time (s)0.2464 0.2986

-0.6292

0.6185

0

articulated

Time

Pre

ssu

re

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

Time (s)0 0.8359

0

5000

Fre

quen

cy (

Hz)

0articulated

Time

Fre

qu

ency

articulated

Time (s)0 0.8359

0

5000

Freq

uenc

y (H

z)0

articulated

Time

Fre

qu

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

Time (s)0 0.8359

0

5000

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

Time (s)0 0.8359

0

5000

Freq

uenc

y (H

z)0

articulated

Time

Fre

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

0

5000

Freq

uenc

y (H

z)0

articulated də

Time

Fre

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

0

5000

Freq

uenc

y (H

z)0

articulated

Time (s)0 0.8359

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