CGSC433 Lab 1

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Apr 3, 2024

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CGSC 433 Spring 2024 Lab 1: Measuring F0 Goals:  practice measuring F0 from an acoustic waveform  practice measuring F0 from a spectrum  practice converting between period and frequency  become familiar with thinking on a millisecond timescale  learn the relation between F0 and the frequencies of harmonics The hypotheses that we are exploring in this lab relate to the expectation that the various ways (as enumerated below) of calculating fundamental frequency should result in similar values. You’ll need to expand this in your lab report to make the hypothesis (or hypotheses) very clear to the reader. Preparation: Before you begin, you will need to make a series of recordings that you will analyze in this assignment. For each recording, you can use a sampling rate of 44,100 Hz and you should make sure that your microphone levels are adjusted to give adequate signal amplitude without risk of clipping (if possible). TIP: It is recommended to unplug your laptop while you are recording on it, as the power adapter usually introduces unwanted noise into the recording. Each recording should be short in duration, around 1-2 sec (1000-2000 ms), and in all cases you should attempt to use a “neutral” configuration of your supralaryngeal vocal tract, i.e. an unstressed schwa [ə]. Below is a list of recordings that you should make: 1. Natural pitch schwa: produce a schwa with the most natural F0 (pitch) for you. 2. Higher pitch schwa: produce a schwa with a higher-than-normal F0 (but not your highest) 3. Highest pitch schwa: produce a schwa with the highest F0 you can make 4. a creaky schwa with very slow vocal fold vibration 5. produce a schwa as long as you can, trying to maintain vocal fold vibration for as long as possible (this recording will necessarily be longer than 1-2 s).

CGSC 433 Spring 2024 Analysis procedure: For each recording: 1. View & edit sound. 2. Somewhere in the middle of the sound (you will need to zoom in), select 1 cycle in the waveform. Make sure you start your selection at a zero crossing and end the selection at a zero crossing at equivalent points in the cycle (hint: you can use the “Select” or “Sound” option from the menu to “move start of selection to nearest zero crossing” and “move end of selection to nearest zero crossing”). Determine the duration of that cycle (You can select “Query” or “Time” and then “Get selection length”). You should put it in ms. This value goes in the 1 st row of the table below. 3. Compute the fundamental frequency of the sound based on the period determined in step 2. Use the formula f=1/T and remember to convert from ms to s before using the formula. This value goes in the 2 nd row . 4. Next, from the same sound, select a sample of 10 adjacent cycles in the waveform (make sure the selection is done at zero crossings), and again note the duration. This value will go in the 3 rd row . 5. Compute the fundamental frequency of the sound based on these 10 cycles (Hint: you’ll need to divide the duration of the 10 cycles by 10 and convert to s before determining the frequency). This value will go in the 4 th row . 6. With the 10 adjacent cycles in the waveform still highlighted, choose Spectrum (or Spectrogram) >> View spectral slice (or Ctrl-L or Command-L as shortcuts). This will pop up a new window showing the spectrum. 7. Zoom in significantly to view the first 10 harmonics clearly. Take a screenshot and paste it in your lab report. 8. Find the frequency of H1 and H2 (the 1 st and 2 nd harmonics) by clicking where the peaks are and noting the values that Praat shows you. These values will go in the 5 th and 6 th rows , respectively. 9. Compute the period based on the frequency value you found in the 5 th row. This period value will go in the 7 th row . 10. The value in the 8 th row involves subtracting the value in the 5 th row from the 6 th . 11. The value in the 9 th row is the frequency of the 10 th harmonic (or if it’s hard to see exactly where H10 is, use one that’s nearby, maybe H8, H9, or H11). 12. For the value in the 10 th row , you will need to compute the fundamental frequency based on the 10 th harmonic. Hint: remember that harmonics are multiples of the fundamental frequency. Note: If you used a different number harmonic in step 11, you’ll need to be consistent with that when calculating the frequency value here.  Fill out the table on the next page with these values and include it in your results section.  Be sure to replace the example values in the first column with your own actual values (1 decimal place is sufficient).  For the prolonged schwa, you will want to make one measurement early in the recording and a second near the end. Be sure to report exactly at which time points you took these measurements from in your methods section.

CGSC 433 Spring 2024 Most natural F0 Higher- than- normal F0 Highest F0 Creaky schwa Prolonged schwa (beg.) Prolonged schwa (end) 1. Duration (i.e. period) of 1 cycle (ms.) 6.547 ms 5.13 ms 4.565 ms 4.467 ms 3.815 ms 1.181 ms 2. Freq. (Hz) based on 1 period 152.74 Hz 194.93 Hz 219.058 Hz 223.86 Hz 262.123 Hz 846.74 Hz 3. Duration of 10 periods (ms.) 62.766 ms 50.9 ms 46.909 ms 46.824 ms 51.959 ms 51.954 ms 4. Freq. based on 10 periods 159.322 Hz 196.464 Hz 213.179 Hz 215.567 Hz 193.459 Hz 192.478 Hz 5. Freq. of H1 156.36 Hz 186.07 Hz 211.39 Hz 219.83 Hz 177.44 Hz 181.66 Hz 6. Freq. of H2 318.68 Hz 388.65 Hz 430.85 Hz 439.29 Hz 354.70 Hz 363.14 Hz 7. Period (ms.) corresp. to H1 freq. 6.243 ms 5.374 ms 4.731 ms 4.549 ms 5.636 ms 5.505 ms 8. Freq. of H2 – Freq. of H1 158.49 Hz 202.58 Hz 219.46 Hz 219.46 ms 177.26 Hz 181.48 Hz 9. Freq. of H10 1545.25 Hz 1840.44 Hz 2118.98 Hz 2220.27 Hz 1709.24 Hz 1878.23 Hz 10. F0 based on H10 (see step 12 for notes) 154.525 Hz 184.044 Hz 211.898 Hz 222.027 Hz 170.924 Hz 187.823 Hz

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CGSC 433 Spring 2024 Notes:  The values for the first 4 rows of the chart you should compute based on the waveforms. The last 6 rows will have values based on the spectra of the samples that you extract.  As you can notice in the sample values given in the chart in the 1 st column, we should expect the calculations from Row 2, 4, 5, 8, & 10 to be similar to one another, as they are all different ways of essentially obtaining the fundamental frequency.  In your Results section, in addition to the values requested above in the chart, you should include the screenshot images (6 total) of the spectrum for each of your schwas (i.e. for most natural schwa, higher-than-normal schwa, highest schwa, creaky schwa, prolonged schwa (from beginning) and prolonged schwa (from end)). Label harmonics H1-H10: you can label by writing them in if you don’t know how to add this on the computer. Natural

CGSC 433 Spring 2024 High Highest

CGSC 433 Spring 2024 Creaky Prolonged (1.666 s= 1666 ms to 2.247 s= 2247 ms)

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CGSC 433 Spring 2024 Prolonged (4.196 s= 4196 ms to 5.007 s= 5007 ms) Guidelines for lab write-ups (for this and following labs) Describe the procedure and findings from your lab in a brief scientific report. It should be concise but not schematic: don’t use bullet points and dashes, but full-fledged sentences and paragraphs to discuss your ideas. The information that I ask for within each section is information you should include in some way in that section, but you shouldn’t answer it point-by-point . Instead, work it all into paragraph form . Use the guidelines below. Your lab reports should contain the following sections, labeled with the headings “Introduction”, “Methods”, etc. 1. Introduction a. What question(s) is/are being explored in the lab, or what are the goals of the lab? b. If you have a particular hypothesis about the questions being explored, what is it?

CGSC 433 Spring 2024 2. Methods a. A brief summary of your methodology. b. List materials (this includes recordings) used in the lab. c. Explain the measurement techniques employed. 3. Results a. What values did you get for your measurements? (Note: this can be in the form of charts/tables, but you should also summarize what we’re seeing) b. Organize the collected data in a clear readable manner (use tables and charts whenever possible) and introduce this data briefly. Note: It is important to explain what we are seeing in any charts or graphs you provide. You shouldn’t leave it up to the reader to interpret it. c. How precise were your measurements? (That is, what are the sources of error and imprecision inherent in the method?) d. What kinds of variation do you see in the data? 4. Discussion and Conclusions a. Do the results line up with your initial hypothesis? Why or why not? That is, are you surprised by any of the results? b. Are there any generalizations you can make? c. Given your results, what can you conclude about the phenomena studied in this lab? d. Are there any new questions raised by your results?