ECE303L Signals and Systems Lab 2

Objectives

  1. Learn how to acquire samples of audio signals.
  2. Learn now to mathematically generate audio signals.
  3. Capture some audio impulse responses.
  4. Investigate dual tone signals
  5. Learn how to use the ARB programming features of the function generator.

Background

Download lab2 materials

Both Windows and MATLAB provide a variety of functions and utility programs to record audio, edit and manipulate audio signals, and generate sound from audio files. See audio overview. As part of this lab you should experiment with a variety of tools for handling audio data.

Other courses, like ECE 203, will allow you to experiment with digital processing of audio signals. In this lab you will split a audio signal into two pieces. See splitname example.

There is some information about beat signals produced from the sum of two sinusoidal waveforms with slightly different frequency.

There is also an example of programming the ARB feature of the function generator and an example of the difference of two gaussians (dog).

Requirements

  1. Record your voice pronouncing your name as a Microsoft WAV file. There are a number of ways of doing this. Create a MATLAB script that displays a picture of you (using imshow) and plays your wav file (using wavplay). Publish this script and submit the resulting html, MATLAB source, and media files.

  2. Use MATLAB to separate the previous file into two parts, one for your first name and one for your last name.

  3. Modify the analog output demo code (daqsong.m) to play the wave sound of your voice.

  4. Find a sound/music sample of stereo audio. Plot the two channels in subplots, one above the other.

  5. Record one or more impulse sounds using your sound card and using the powered microphone, connected to an oscilloscope. Generate plots of the resulting waveform from the two devices. Try for the highest time resolution possible.

  6. Use MATLAB to generate a few seconds of a mixture of two sinusoids such that the base frequency is 300 Hz and the beat frequency is 5 Hz with 80% modulation. Save your results as a WAV file, generate MATLAB plots and oscilloscope images of the output. How does the sound change if you vary the modulation from 80% to 5%?

  7. Use MATLAB to generate a few seconds of the following mixtures of two sinusoidal components. Identify the resulting sounds. Save your results as WAV files and generate MATLAB figures and oscilloscope images showing two cycles of the resulting sound (when on).

    #Description
    1350 Hz / 440 Hz continuous
    2440 Hz / 480 Hz , 2 seconds on/ 4 seconds off
    3480 Hz / 620 Hz, on/off every 0.5 seconds

  8. Generate a difference of Gaussian waveform and upload it to the ARB volatile memory of the function generator. Use 500 points/waveform, 200 points/waveform, 100 points/waveform, and 50 points/waveform. Capture oscilloscope output for each case. Discuss any observed differences among the various outputs.

Maintained by John Loomis, last updated 9 September 2010