代做LIN328 Lab: Creating sinewaves帮做R语言

LIN328                    Lab: Creating sinewaves

In this lab, you will:

- Create different types of sounds (simple and complex periodic sounds, aperiodic sounds) from formulas in Praat

- Compare waveforms, spectra, and perceptual properties of these sounds

You will need to have downloaded the free software Praat prior to beginning the lab: http://www.fon.hum.uva.nl/praat/.

This worksheet contains the instructions to guide you through the lab exercises. You do not need to turn in anything now, but the highlighted boxes are questions you may be asked to answer in the lab report to be submitted later in the term.

Tutorial: Creating sine waves in Praat

1. New → Sound → Create Sound from formula

2. Enter the relevant parameters in the formula (see below). You should also change the “Name” to something more descriptive than “sineWithNoise”. Leave the other boxes with the default settings.

3. This will create a new item in the “Objects” window with the name that you specified.

4. Looking at your sound: Select the sound, then click “View and Edit” to see the waveform. (and the spectrogram).

5. You can zoom in and out of sounds when viewing them by using the buttons on the bottom left corner or in the View menu (which also provides keyboard shortcuts). I recommend learning the keyboard shortcuts!

6. Listening to your sound:

a. In the Objects window, select the sound and press Play.

b. When viewing the sound, you can press Tab to play all or part of the sound.

1. Creating simple sine waves

Create simple sine waves (using a formula in Praat) with the following characteristics:

sineA: Frequency = 220 Hz, amplitude = 0.6

sineB: Frequency = 220 Hz, amplitude = 1

sineC: Frequency = 440 Hz, amplitude = 1

sineD: Frequency = 950 Hz, amplitude = 0.4

a. Write the formula you used to create each of the sounds.

	Formula
sineA
sineB
sineC
sineD

Look at the waveforms and listen to each sound. Think about the similarities and differences, both in terms of what you can see in the waveform. (acoustic properties) and what you hear (perceptual properties).

b. For each of the comparisons below, describe the acoustic and perceptual differences.

Comparison	Acoustic differences	Perceptual differences
A vs. B
B vs. C
A vs. D

c. Do the differences you heard match what you expected based on your knowledge of the properties of sine waves? Why or why not (make sure to discuss each expected difference, and give specific examples)?

2. Creating complex periodic sounds

Create a complex periodic sound (name it Complex1) that is the sum of the following three sine waves:

- freq = 200 Hz, amp = 1

- freq = 400 Hz, amp = 0.75

- freq = 600 Hz, amp = 0.5

a. What is the fundamental frequency (f0) of Complex1? You should be able to figure this out in two ways:

· mathematically from the information above, AND

· from looking at the resulting sound in Praat

Note: You can check whether your answer is correct by creating a pure sine wave with the same frequency!

f0 (Hz) of the sound
Mathematical explanation
Explanation from looking at sound

b. Draw a line spectrum of this sound (in any way you’d like).

c. View a spectral slice in Praat, using the following instructions:

· View the sound. Select a portion of the sound wave

· Spectrum → View Spectral Slice (or Ctrl-L). This will create a Spectrum in the Objects window that you can view. Note that you may need to zoom in to see the relevant portion of the sound.

Try selecting very long or very short portions the sound to create different spectra. What are the similarities and differences of the spectra when they have been created from a short portion vs. a long portion?

d. Create your own complex periodic sound, made up of 4 component waves that has a fundamental frequency of 350 Hz. Compare sounds with your neighbor (or if you are working by yourself, create two different complex sounds that both have a fundamental frequency of 350 Hz).

What are the two formulas for these sounds? What are the similarities and differences between the two sounds, from both an acoustic and perceptual point of view?

3. Creating an aperiodic sound

a. Create a 3-second sound of white noise (a formula for white noise is “randomGauss(0,0.1)”). Listen to the sound and look at the waveform. and the spectrum of the sound.

How does the waveform. and spectrum differ from the waveform. and spectra of the sounds you created above? Why is this the case?