Articulatory-Acoustic-Auditory Phonetics

Transcription

1 Articulatory-Acoustic-Auditory Phonetics when we look at speech (sounds) we look at how it is (1) produced, (2) transmitted, and (3) perceived (1) articulatory phonetics looks at the production side (how speech sounds are, for example, articulated) (2) acoustic phonetics looks at the transmission of these sounds (what are the acoustic properties of speech(duration, frequency, energy (all physical properties)) (3) auditory phonetics looks at how humans perceive theses speech sounds (what happens in the ear)

2 acoustic phonetics auditory phonetics fundemental frequency (Hz) intensity (db) duration (t) pitch (how high or low do we perceive a sound) loudness (how loud or soft do we perceive a sound) speech tempo (how fast or slow we perceive a speech signal)

3 Amplitude The amplitude is simply a displacement of the vibrating medium from its rest position

4 The amplitude of a wave refers to the maximum amount of displacement of a a particle on the medium from its rest position. In a sense, the amplitude is the distance from rest to crest (positives Maximum). Similarly, the amplitude can be measured from the rest position to the trough (negatives Maximum) position. Amplitude

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8 Fundamental Frequency The term fundamental frequency stands for the course of the lowest frequency in a harmonic vibration, therefore it is also called F0. Frequency is a technical term for an acoustic property of a sound namely the number of complete repetitions (cycles) of variations in air pressure occuring in a second (Ladefoged 1975, 162)

9 the fundamental frequency is the lowest frequency of all other sinus components in a spectrum therefore it is called F0 its whole-numbered multiples (2x, 3x, 4x,...) are the so-called harmonics

10 For example if F0 has 100 Hz, its harmonics are: 200 Hz 300 Hz 400 Hz... if F0 has 150 Hz, its harmonics are: 300 Hz 450 Hz 600 Hz... if F0 has 90 Hz, its harmonics are: 180 Hz 270 Hz 360 Hz...

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12 Where are all the other frequencies produced? all frequencies that you find a speech signal come from the larynx

13 Formants when we look at the vocal tract as a cylindric pipe which is closed at one end (glottis) and open at the other end (mouth) its wavelength is four times its length a female vocal tract is about 15 cm long, which means that its wavelength is 60 cm at about 35 C sound travels at about 352 m/sec 352 m/s : (4 * 0,15m) = 352 m/s * 0,6 m = 587 * 1/s = 600 Hz the resonance frequency of a simplified female vocal tract lies at about 600 Hz aside from this fundamental frequency there are resonance frequencies; in this case 1800, 3000, 4200,... Hz (1:3:5:7:...)

14 Schematic Vocal Tract

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17 acoustically the vocal tract is not a very good pipe energy is dampened in every frequency of the source signal (coming from the larynx) what is not dampened so much are the resonance frequencies, which show as dark shadings in the spectrogram

18 the laryngeal signal has many higher harmonics which means that energy can also be found in higher frequencies than simply the fundamental frequency as said before, the vocal tract dampens certain frequencies more and others less (depending on the formation of the articulators) these resonance frequencies are called formants

19 formants are a property of the vocal tract and completely independent from any source signal (it does not matter whether there is a source signal or not!!!) try this: whisper the following: heed, hid, head, had, hod, hawed, hood, who d

20 Formants

21 Formants The first two formants F1 and F2 are important for the intelligibility of vowels Their position characterizes the spoken vowel. In order to understand each other, it is important that these formants are similar in every speaker

22 Formants J. Clark und C.Yallop: "The tract resonances themselves are sometimes referred to as formants, but this is technically imprecise. Formants are a consequence of resonance, not resonance itself." (An Introduction to Phonetics and Phonology, 2nd ed.,1995, S.246)

23 Petursson & Neppert Cochlea

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25 Cochlea

26 Organ of Corti

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28 Ear