Here are three sounds to study. First listen to each of them without knowing what they are.
Can you distinguish two signal components? A high(er) frequency sinusoid and a slowly changing one which might sound like the signal is fading in and out.
beatcon.m is in the DSP Toolbox.
See Getting Started for details on downloading the DSP Toolbox and installing it.
Once the DSP Toolbox is installed correctly
beatcon should be on the
beatconat the Matlab prompt. A small control panel will appear on the screen with buttons and sliders that vary the different parameters for the
beatfunction (see the figure above with a screen shot of
beatcon). Experiment with the
beatconcontrol panel and use it to complete the following steps.
beatconGUI with the parameters:
dur=1secs. Plot the first 0.2 seconds of the resulting signal. Describe the waveform and look for periodic structure(s) in the plot. It should be possible to measure two periods: the period of the "envelope" and the period of the high frequency signal underneath the envelope.
delfwith different three values: 10, 4, 1 Hz. Send the resulting signals to the D-to-A converter and listen to the sounds (there is a button on
beatconthat will do this for you automatically). Observe the nature of the sound based on the waveform plotted in part (b) and on the theory developed in the textbook.
delfin an attempt to recreate the mystery sounds given above.