Spectrogram & its reading

by Tae-Yeoub Jang

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What is spectrogram? Begin to be used since 1940s Another representation of frequency

domain analysis The most popular way of representing

spectral information 3 dimensional representation

X-axis: Time Y-axis: Frequency Darkness (or color): Energy

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Spectrogram example (color resolution of word “compute”)

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Spectrogram example (grayscale of word “compute”)

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Wideband vs. Narrowbandspectrograms of the question "Is Pat sad, or mad?" The 5th, 10th and 15th harmonics have been marked by white squares in two of the vowels

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Types of spectrogram Wideband spectrogram

better time resolution eg) 15 msec window, 1 msec shift, 125

Hz bandwidth Narrowband spectrogram

better frequency resolution eg) 50 msec window, 1 msec shift, 40 H

z bandwidth

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Advantages & Disadvantages Advantages

Time alignment

Disadvantages Less reliable than waveform

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Vowel Spectrogram Formant frequencies are critical cues fo

r vowel distinction F1: Height

high vowels: low F1 F2: Backness

back vowels: low F2

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Example formant frequencies of English monophthongs

F3F3 290

0255

0249

0249

0264

0238

0230

0250

0239

0

F2F2 2250

1900

1770

1660

1100

1030

870 1500

1190

F1F1 280 400 550 690 710 450 310 900 640

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"heed, hid, head, had, hod, hawed, hood, who'd" (a male speaker, American English)

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Consonant Spectrogram General

Acoustic structure more complicated than vowels

Adjacent sounds (especially vowels) convey important information locus

High frequency characteristics especially for fricatives and affricates

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What is LOCUS Information of formant transition from vowels

into obstruents or from obstruents into vowels

The target frequency that each formant transition is heading toward as an obstruction is made, or the frequency the transition comes as the obstruction is released

The characteristic of the consonantal place and manner roughly the same in different vowel contexts

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Stops General

Fairly distinct locus for each place Burst Silence during the closure (only at

syllable onset position) Virtually no difference during the

closure

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Stops (cntd.) Voicing distinction

voiced: vertical striations for voiced sounds, less abrupt burst, frequently weakened to be like fricatives or approximants

voiceless: generally abrupt burst at higher frequency area

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Stops (cntd.) Place distinction

bilabial relatively low F2, F3 locus rising into and

falling out of vowel weak and spread vertical lines

alveolar F2 locus about 1800 Hz Strong vertical lines

velar Velar pinch: vowels F2, F3 merging often double burst long formant transitions

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Stops (cntd.) Manner distinction

Silence duration, VOT, vowel F0

silence VOT F0

aspirated

short long high

tense long short high

lax med med low

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Examples -- “a bab, a dad, a gag”

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Place dependent loci

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Fricatives General

Random noise pattern especially in high frequency regions

Place distinction Labiodental [f, v]: rising locus into the following vowel Dental [, ð]: major energy above 6000Hz Alveolar [s, z]: major energy above 4000Hz Alveopalatal [š, ž ]: major energy above 6000Hz Glottal [h]: the trace of formant frequencies of neighbou

ring vowels

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Fricatives (cntd.) Weak vs. strong

Strong [s, z, š, ž ]: darker bands Weak [f, v, , ð ]: spread and fainter

Voiced [v, ð ]: often so weak and confused with nasals or approximants

Cues to tell [] from [f]: higher formants of [] fall into adjacent vowels

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Example – “fie, thigh, sigh, shy”

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Example – “ever, weather, fizzer, pleasure”

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Nasals General

Formants similar to vowels but fainter Very low F1 (about 250Hz), F2 (about

2500Hz), and F3 (about 3250Hz) Place distinction

bilabial [m]: downward F2, F3 locus alveolar [n]: less amount of F2 transition velar [ŋ ]: velar pinch

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Examples -- “a Pam, a tan, a kang”

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Liquies & Approximants General

Formants similar to vowels but fainter (especially at high frequency regions)

Approximately F1(250Hz), F2(1200Hz), F3(2400Hz)

Change in formant structure

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Liquids & Approximants(cntd.) Phone specific properties

Labial glide [w]: very low F1, F2 (600-1000Hz|) and gets

too close to each relatively low F3 rapid falloff of spectral amplitude

Palatal glide [y]: extremely low F1 extremely high F2, F3

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Liquids & Approximants(cntd.) Phone specific properties (cntd.)

Flap [ ]: soft burst, short durationՐ Retroflex [r]:

F3 dipping down close to F2 General lowering of F3, F4

Lateral [l]: Low F1, F2 (approx. F1 250Hz, F2 1200Hz) usually substantial energy in the high F region

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Example – “led, red, wed, yell”

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Final remarks Spectrogram is not the only cue

for acoustic distinction of speech sounds

Very often, the waveform is more reliable

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References & Links http://cslu.cse.ogi.edu/tutordemos/SpectrogramReadin

g/spectrogram_reading.html http://hctv.humnet.ucla.edu/departments/linguistics/Vo

welsandConsonants/course http://www.cs.indiana.edu/~port/teach/306/speech.aco

ustics.html http://www.phon.ucl.ac.uk/courses/spsci/b203/week2-5.

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