1. Basic Spectrogram Lab 8

2. Spectrograms §Spectrograph: Produces visible patterns of acoustic energy called spectrograms §Spectrographic Analysis: l Acoustic signal changes rapidly & continuously l Need a dynamic analysis revealing spectral features l Short term running spectrum

3. Spectrographic Analysis §Time, Frequency & intensity l Time (horizontal axis): Phonetic elements will be from left to right l Frequency (Vertical axis): Increasing in upward direction l Intensity represented by a gray scale or as variations in darkness

4. Dimensions of Spectrograms A. Burst of noiseB. Vowel with 4 formants C. Noise with high frequency energy Time

5. Source/Filter §Resonator & Source Energy l Filter = Vocal tract Energy passed in a frequency selective manner Production of different vowels changes the filter shape l Source = Harmonic spectrum of voicing Fundamental frequency & its harmonics Source spectrum is the acoustic energy activating the formants §Source-filter theory of vowel production: l The energy form the source (vibrating vocal folds) is modified by the resonance characteristics of the filter (vocal tract)

6. Formants- Filter §Are formed through resonation of sound in the vocal tract (filter function) §Can only see through a wide band spectrogram F1 F2

7. Harmonics- Source Harmonics (Spectrum) Harmonics(Spectrogram)

8. Source-Filter Theory

9. Source-Filter

10. Wide Band vs. Narrow Band §Wide Band: analyzing filter wide, 300- 400 Hz l Good to show formants because they have a wide spread of acoustic energy §Narrow Band: analyzing filter is of higher resolution, 100 Hz l Good to show the harmonics of source spectrum

11. Bandwidth Narrow Bandwidth (Harmonics) Wide Bandwidth (Formants)

12. Continuous Spectrum Bandwidth

13. Vowel: Wide Band vs. Narrow Band

14. Fricative noise: Above 3 or 4 kHz Diphthong: Horizontal bands of energy Wide Band Spectrogram

15. Digital Signal Processing §Basic objective of digital signal processing: l Convert the analog acoustic signal (Panel A) to a digital form (series of #’s) l How do we get a waveform into a digital computer? Analog-Digital conversion (A-D): results in samples of time and amplitude l Correct sampling rate is important to reconstruct the wave form Sampling rate must be 2x the bandwidth of analysis: Nyquist Frequency –Ex. Sample speech with a bandwidth of 5000 Hz, than the sampling rate should be 10,000 Hz

16. Analog-Digital Conversion b. Time sampling intervals

17. Laboratory §Part I: Recording the sample- Sampling rate l Set sampling rate for shortest duration possible Sustain / a /: **open 3 views to print all samples on 1 screen Sample at 20,000 samples/sec; look at 5-6 cycles Sample at 5,000 samples/sec; look at 5-6 cycles Sample at 2,500 samples/sec; look at 5-6 cycles l What happens as sampling rate drops l Narrow band filter each sample (print each)

18. Laboratory §Part II: Filter bandwidth l Record “I am tall” Wide band and narrow band the statement –Find the following characteristics on one or both of the spectrograms: »Harmonic lines »Formant bands »Vertical striations »Acoustic indication of release of air pressure for /t/ –Which has better frequency resolution? Time resolution? Which can you determine formant bands?

19. Laboratory §Part II: Cont. l Make wide and narrow band spectrograms of the following, stressing the underlined word: “I am tall” “I am tall?” l Which spectrograms show the intonation contour? Mark the contour on one of your printouts

20. Laboratory §Part III: Changing the Filter l Say /i:u:i/ without changing intonation Prepare 2 spectrograms of this utterance –1st- 2x’s your fundamental frequency –2nd- no more than half your fundamental Answer questions: –Label each vowel on each spectrogram –Harmonics –Formants