EEL6586: HW#1

Due Friday, Feb 11, 1999 in class. Late homework will lose $e^{\char93 ~of~days~late} -1$ percentage points. To see the current late penalty, click on
http://www.cnel.ufl.edu/analog/harris/latepoints.html

In this assignment you will be recording some phonemes and trying to match these phonemes using the synthesis techniques discussed in class. The ideal method for handing in this assignment is through a webpage where you email the link to Dr. Harris by the due date. Instead you can also email a word file, pdf file, framemaker file or an html file if you are not able to set up a webpage properly. As a last resort, you may hand in a report on paper with a 3.5 inch floppy disk containing the sound files.

Make sure that you properly answer all of the questions and describe your solution technique for each problem. You may talk to other students, in fact you are strongly encouraged to do so. However, the final work and matlab code you turn in MUST be your own. Some parts of this assignment are open-ended where there are many possible solution methods.

You writeup should contain an appendix that includes all of the matlab code that you wrote for this assignment. You do not need to include any of the code in Parts A, B, or C but you should describe your solution technique in these parts.

PART A: Recording Speech

A1

Record yourself on a computer saying the two phonemes /i/ and /schwa/ for about 0.5 seconds each. Remember the /i/ is the vowel in heed and the /schwa/ sound is the first vowel in the word ``ago.'' Hand in the two sound files. The usual format will be an 8KHz .wav file.

A2

Hand in a portion of the time domain plots of each phoneme. Clearly indicate the pitch period and its note its numerical value for both phonemes.

A3

Plot the magnitude spectrum of the two sounds. Clearly indicate the values of F₁, F₂ and F₃ on the graphs for each vowel.

A4

Estimate the bandwidth of each formant using whichever definition you like. However, be sure to explain your calculation.

A5

Plot the spectrogram of each vowel. Show results from using both short and long windowing functions.

PART B: Formant Synthesis

B1

Write a matlab program that can filter a signal using the sum of three bandpass filters. Each bandpass filter will be specified by a center frequency and a bandwidth. This is an open-ended question, use your best judgment in the filter design but explain your reasoning.

B2

Use the code in [B1] to filter a train of impulses of appropriate pitch to produce the two vowel sounds from part A. Hand in a 1/2 second sound file for each vowel (8KHz .wav file).

B3

Filter an impulse train of Rosenberg pulses-assume a duty cycle of about 50%. Feel free to tweak other parameters in order to improve the quality of the sound.

B4

Plot time and frequency domain representations of the two vowels (don't use spectrograms). Compare your synthetic sound results to the recorded sounds. Do they seem reasonably close?

B5

Listen to the real and synthetic sounds. Do they sound reasonably close?

PART C: Articulatory Synthesis

C1

Implement the discrete-time vocal tract model discussed in class. Discretize the length $\ell$ vocal tract into N stages.

C2

Produce the schwa vowel sound by filter an appropriate train of Rosenberg pulses through a uniform vocal tract. Using appropriate lip and glottis models, produce a segment of speech for this vowel. Adjust the vocal tract length $\ell$ and do anything else to improve the quality of the sound. Remember that this method produces a signal that could be sampled much higher than is reasonable. We only trust frequencies up to 4KHz. Also, the model does not provide for losses in the vocal tract so some of the higher frequencies are not attenuated as much as they should be.

C3

Use the area function for the vowel /i/ given at
http://www.cnel.ufl.edu/analog/courses/EEL6586/areafunctions.html. Adjust the vocal tract length $\ell$ and feel free to do anything else to improve the quality of the sound.

C4

Plot time and frequency domain representations of the two vowels (don't use spectrograms). Compare your synthetic sound results to the recorded sounds. Do they seem reasonably close?

C5

Listen to the real and synthetic sounds. Do they sound reasonably close?