Recap • In the first lecture we distinguished periodic sounds Spectral features of fricatives and stops (same patterns repeats every cycle) from aperiodic sounds (no regularity in the pattern of air perturbations). Cơ sở âm vị học và ngữ âm học 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 Lecture 14 Fricatives Fricatives • In a spectrogram, fricatives feature energy over a wide • Sound source: aperiodic noise → frequency range. random pattern in the waveform. ( không theo mô hình ) d ʒ ɔ n s n ̩ d ʒ ɔ n s n ̩ 6000 Frequency (Hz) Amplitude Time (s) 0 0 0.47 Time (s)
Voiceless fricatives Voiceless fricatives • The further back the constriction, the longer the front • For [f T] there is less filter → weaker energy cavity, and the lower the peak in spectral energy. From Ladefoged (2006), A Course in Phonetics From Ladefoged (2006), A Course in Phonetics Voiceless fricatives: overview Voiceless fricatives: overview • [s] and [S] have stronger energy because they are • For [f T] the constriction is in the front of the oral cavity, sibilants ( âm xuýt ) – the air encounters a sharp obstacle so there is hardly any vocal tract in front of the (e.g., edge of teeth) constriction to filter the sound! Location of energy maximum Energy strength Location of energy maximum độ năng lượng between 3 and 4 kHz weak [f] between 3 and 4 kHz weak [f] above 8 kHz weak above 8 kHz weak [T] [T] between 5 and 10 kHz strong between 5 and 10 kHz strong [s] [s] between 3 and 5 kHz strong between 3 and 5 kHz strong [S] [S]
Voiced fricatives Voiced fricatives • [v D z Z] are spectrally similar to [f T s S] , but with • Voiced fricatives (x-linguistically rare) are difficult to striations/voicing bar and weaker frication. produce, and are frequently voiceless or ‘partially voiced’ From Ladefoged (2006), A Course in Phonetics From Ladefoged (2006), A Course in Phonetics Other clues [h] • What (else) distinguishes these fricatives? • Listed as a fricative in the IPA chart, but actually... • The source of sound is not air being forced through a narrow opening, but instead caused by air rushing through the open vocal folds and vocal tract • This is the same sound source as whispered speech From Ladefoged (2006), A Course in Phonetics
[h] [h] • Listed as a fricative in the IPA chart, but actually... • Listed as a fricative in the IPA chart, but actually... • The source of sound is not air being forced through a • The source of sound is not air being forced through a narrow opening, but instead caused by air rushing narrow opening, but instead caused by air rushing through the open vocal folds and vocal tract through the open vocal folds and vocal tract • This is the same sound source as whispered speech • This is the same sound source as whispered speech ‘Stole my house’ he ha! who From http://home.cc.umanitoba.ca/$\sim$robh/howto.html#intro
Stops Stops • Stops consist of two parts: a closure and a noise burst. • Stops consist of two parts: a closure and a noise burst. 5000 5000 0 0 0 0.738 0 0.738 Time (s) Time (s) Stops Voiced stops • In voiced stops, we see a ‘voice bar’ during the closure • Stops consist of two parts: a closure and a noise burst. • these are weak striations at the low end of the frequency scale (because the mouth is still closed). 5000 5000 0 0 0.738 Time (s) 0 0 0.7848 Time (s)
Voiced stops Voiced stops [b d g] • In voiced stops, we see a ‘voice bar’ during the closure • these are weak striations at the low end of the frequency scale (because the mouth is still closed). • The burst of voiced stops often does not appear clearly in a spectrogram 5000 • If closure and burst are similar for all voiced stops, how do we distinguish e.g. [b] from [d]? 0 0 0.7848 Time (s) Voiced stops [b d g] Formant transitions • At the moment the stop constriction is released, the • The burst of voiced stops often does not appear clearly resonances of the vocal tract filter change very rapidly. in a spectrogram • These changes are called formant transitions . • If closure and burst are similar for all voiced stops, how do we distinguish e.g. [b] from [d]? • Formant transitions are extremely important perceptual cues to phonetic contrasts.
Formant transitions Formant transitions • In fact, work from speech synthesis shows you can’t • In fact, work from speech synthesis shows you can’t understand speech without the formant transitions – understand speech without the formant transitions – even though they only average about 50ms in duration. even though they only average about 50ms in duration. • What does this mean for the conception of words as • What does this mean for the conception of words as strings of phone[mes]? strings of phone[mes]? Formant transitions Formant transitions • The direction of F2 and F3 formant transitions depend • F1 always rises after a stop. on the particular constriction producing the stop (lips, tongue tip, tongue body). http://www.cns.nyu.edu/ david/courses/perception/lecturenotes/speech/speech.html http://www.cns.nyu.edu/ david/courses/perception/lecturenotes/speech/speech.html
Formant transitions Formant transitions • Formant transitions at the start of the vowel following a • Formant transitions at the start of the vowel following a voiced stop (reverse for vowels preceding voiced stop): voiced stop (reverse for vowels preceding voiced stop): F2 F3 rises rises [b] [d] ∼ level falls falls rises [g] From Ladefoged (2001) ebb vs. egg Velar stops [k] [g] ebb egg • Velars are relatively easy to spot due to the ‘velar pinch’ 5000 5000 of F2 and F3. 4000 4000 3000 3000 2000 2000 1000 1000 0 0 release release vowel stop vowel stop closure closure
Velar stops [k] [g] Velar stops [k] [g] • Formant transitions for [g] tend to be longer for other • The place of constriction for velar stops can vary – why? stops – tongue body is also involved in vowel formation. Voiceless stops [p] [t] [k] Voiceless stops [p] [t] [k] • In voiceless stops, the movement of lips and tongue take • In voiceless stops, the movement of lips and tongue take place during the burst, prior to the onset of voicing. place during the burst, prior to the onset of voicing. • Therefore these movements are not as clearly reflected • Therefore these movements are not as clearly reflected in formant transitions/spectrograms in formant transitions/spectrograms • A more reliable cue to the place feature for voiceless • A more reliable cue to the place feature for voiceless stops is the noise burst. stops is the noise burst.
Voiceless stops [p] [t] [k] Voiceless stops [p] [t] [k] • The closure is devoid of voicing bar activity... • In voiceless stops, the movement of lips and tongue take place during the burst, prior to the onset of voicing. 5000 • Therefore these movements are not as clearly reflected in formant transitions/spectrograms • A more reliable cue to the place feature for voiceless stops is the noise burst. 0 0 0.738 Time (s) Voiceless stops [p] [t] [k] Voiceless stops [p] [t] [k] • ...and the burst can be clearly seen in the spectrogram. • However, not all bursts are created equal. 5000 5000 0 0 0 0.738 0 0.738 Time (s) Time (s)
Voiced vs. voiceless stops Energy location Energy strength Length of burst [p] wide range faint short [t] mostly > 4 kHz strong long aba mostly < 4 kHz strong longest [k] k p t Frequency From Kent & Read (1992), The Acoustic Analysis of Speech Voiced vs. voiceless stops Voiced vs. voiceless stops ap h a ap h a aba
Voiced vs. voiceless stops Other cues / g ʌ k / [k h AA] ‘donkey’ 5000 [kAA] ‘neck’ Frequency (Hz) Frequency (Hz) • closure duration Frequency (Hz) 0 / g ʌ g / • voicing during closure 5000 5000 Frequency (Hz) Frequency (Hz) 5000 • duration of preceding vowel 0 0 0 0.4504 0 0.4566 Time (s) Time (s) 0 0 Time (ms) Other cues Other cues / g ʌ k / / g ʌ k / 5000 5000 • closure duration • closure duration Frequency (Hz) Frequency (Hz) 0 0 / g ʌ g / / g ʌ g / • voicing during closure • voicing during closure 5000 5000 • duration of preceding vowel • duration of preceding vowel 0 0 0 0 Time (ms) Time (ms)
Other cues Spectrogram practice / g ʌ k / 5000 • Ladefoged course website: • closure duration http: Frequency (Hz) 0 //www.phonetics.ucla.edu/course/chapter8/figure8.html / g ʌ g / • voicing during closure • More spectrograms: 5000 • duration of preceding vowel http://home.cc.umanitoba.ca/~robh/howto.html 0 0 Time (ms) Spectrogram practice • Ladefoged course website: http: //www.phonetics.ucla.edu/course/chapter8/figure8.html • More spectrograms: http://home.cc.umanitoba.ca/~robh/howto.html
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