Homework #6 Pitch
S702 D. Kewley-Port W. Su 3/5/02
Measuring the fundamental frequency (henseforth pitch) at the onsets and offsets of utterances is tricky. There are many methods of pitch extraction. The purpose of this homework is to compare some methods of pitch extraction including 'manual' measured pitch and one of the two Colea methods (Autocorrelation approach and Cepstrum apporach). We will use high quality recordings of 'Steve eats candy cane' for comparing pitch tracking at syllable boundaries.
Load the two .wav files from Oncourse or from Wen's Zip disk. Have Colea ready to go.
1) Try F0 tracking (Autocorrelation approach or cepstrum approach) for these two sentences in Colea. The update interval is 10 ms. If you see any areas with mistracking, try preprocessing with a low pass filter. A higher order for the LP filter allows for steeper filtering. To filter, go to "tool" on top of the window, then choose "filter tool" and the filter window will pop out. There are three filters, high pass, low pass and band pass . Choose the low pass filter and change the cutoff value (also try orders 4 or 8) and view filter first to see its shape. Then click on "apply filter". The filtered waveform will be displayed at the top of the window and the original waveform at the bottom of the window. Save the filtered waveform window by clicking on the selected window (observe yellow square) and save as the "filename.wav" (remember to put wav. after the filename).
2) Select pitch extraction by: Display -> Fo contour -> choose one of the approaches. You will get the F0 values in the pitch extraction window for the whole sentence. You can save values as text file: "filename.pit" from "save pitch values" on top of the window. To open and print the .pit file, bring up the wordperfect program first and then open the .pit file. Remember, sometimes, the "save pitch values" will not appear when the program itself is not happy...
3) Choose one sentence. Changing methods and filtering, select the one that tracks F0 the best. Print the waveform, the F0 track and pitch values for this method. (3 print outs in this section)
4) Now measure the sentence onset and offset manually. Put the cursor around the boundary of the first syllable and zoom in. Find the first four pitch pulses (about 20 ms). Measure and write down the beginning and ending time of the four pitch pulses (you will be able to see the time on the bottom of the left side window) using the cursor. Use the same procudure manually to measure F0 values of the four pitch pulses at the offset of the last syllable.
5) For this homework, turn in the 3 print outs. Write down the manual measured F0 values and the time for the onset and offset of the sentence on a print out. Calculate the average of the four F0 values at the boundaries for the first and last syllables. Compare the average values with the values that you got from Colea. Comment on the comparison between the values of Colea and the hand measured values.