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Chapter 30

Speech

Two lessons in Part XI, Applications. Read them in order, or start anywhere: a prerequisite is a link, never a gate.

Start with 30.1
0 of 2 readabout 34 minutes

Lessons in this chapter

Vowel /u/ at a pitch of 125 Hz. Waveform: five periods of 8 ms in 40 ms, scaled to a peak of 1. Spectrum: harmonics every 125 Hz under a dashed envelope whose peaks are the formants F1, F2 and F3, marked by dotted lines at 300 Hz, 870 Hz and 2240 Hz.Vowel /u/ at a pitch of 125 Hz. Waveform: five periods of 8 ms in 40 ms, scaled to a peak of 1. Spectrum: harmonics every 125 Hz under a dashed envelope whose peaks are the formants F1, F2 and F3, marked by dotted lines at 300 Hz, 870 Hz and 2240 Hz.

Lesson 118 minYou are hereRead

The source–filter model of speech

A vowel is a buzz through a tube: build one from a pulse train and three resonators, then recover the resonances by linear prediction.

Spectrum panel: the power spectrum of one 50 ms frame of the synthetic /a/ at 125 Hz, in dB re its peak, with harmonics every 125 Hz; the highest is at 750 Hz. Filters panel: all 26 mel triangles, equally spaced in mel from 0 to 4000 Hz, 106.0 Hz wide at the bottom and 618.3 Hz at the top. Log band power: all 26 bars, ln P for bands 1 to 26, from −4.36 (band 26) to 6.68 (band 10). MFCCs: all 13 stems, c for k = 0 to 12, from −12.49 (k = 2) to 5.57 (k = 1).Spectrum panel: the power spectrum of one 50 ms frame of the synthetic /a/ at 125 Hz, in dB re its peak, with harmonics every 125 Hz; the highest is at 750 Hz. Filters panel: all 26 mel triangles, equally spaced in mel from 0 to 4000 Hz, 106.0 Hz wide at the bottom and 618.3 Hz at the top. Log band power: all 26 bars, ln P for bands 1 to 26, from −4.36 (band 26) to 6.68 (band 10). MFCCs: all 13 stems, c for k = 0 to 12, from −12.49 (k = 2) to 5.57 (k = 1).

Lesson 216 minYou are hereRead

Speech features

Pool a speech frame into mel bands, take logs and a DCT, and see why these MFCCs follow the vowel more than the pitch.

After this chapter

Where to go next.

The chapters either side, and the rest of Part XI in the library.

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