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Looking at sound

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 can be plotted into a graph to produce a waveform How did we get this wave?. Pressure .

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Looking at sound

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  1. 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 can be plotted into a graph to produce a waveform • How did we get this wave? Pressure  Time 

  2. Production of sound waves by a loudspeaker • Sound waves are like waves in a coil (like a Slinky)

  3. The red line is like your vocal cords The individual air molecules only vibrate back and forth locally, they do not travel from the source to the receiver

  4. Measuring the wave (pressure) Loudness depends primarily on the amplitude

  5. The sound wave of articulated Pressure  Time 

  6. 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’

  7. Adding waves

  8. Adding waves

  9. This is how a synthesizer works

  10. 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.

  11. Which wave has a higher frequency? 0 sec 1 sec 2 sec 3 sec 4 sec

  12. Spectrograms • The waveform can be analyzed into its frequencies • Frequencies can be made visible with spectrograms Frequency  articulated Time 

  13. ɑr th ɪ k yu l ey ɾ ə d Voiced sounds have three or four major frequencies Dark areas indicate louder frequencies F3 Frequency  F2 F1 F0 Time  articulated

  14. ɑr th ɪ k yu l ey ɾ ə d Frequency  Time  You can recognize vowels articulated

  15. ɑr th ɪ k yu l ey ɾ ə d Frequency  You can recognize stops: /p, t, k, b, d, g, ɾ/ Time  articulated

  16. ɑr th ɪ k yu l ey ɾ ə d Big puff of air Little puff of air Frequency  You can recognize aspiration Time  articulated

  17. ɑr th ɪ k yu l yu ley ey ɾ ə d Frequency  You can recognize pitch Time  articulated

  18. Which word is this? • whose • pseudonym • judgment • dessert How did you know?

  19. 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.

  20. 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

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