Second lab


To run the experiments you need the following:
1) Download the following files:
experiment1.fig
experiment1.m
beat.m

experiment2.fig
experiment2.m
masking.m

experiment3.fig
experiment3.m
maskingn.m
woodenv.m
2) run matlab from the command line (with the GUI)

First experiment: beating and roughness

When we hear two pure tones of slightly different frequencies, our ears usually perceive a single fused tone at the average frequency of (f1 + f2)/2 with beating (or amplitude modulation) at a rate of the difference frequency f2-f1. As the difference frequency increases, the amplitude modulation is heard less as a pulsation in loudness and more as a ``roughness'' in tone. When the separation in frequency is large enough, 2 separate tones are heard, and the roughness decreases. In this experiment, we will keep the frequency of the first oscillator stationary and vary the frequency of the second oscillator. You should play the two tones together at the same frequency and then keep incrementing the second oscillator's frequency by 1 Hz until two separate tones are clearly heard.

To run the experiment: -download the files from the web site
Type: >experiment1
in matlab
Click on the button PLAY to hear the 2 seconds sinusoids

Second experiment: Masking

When the ear is exposed to two or more different tones, one of the sounds may mask, or obscure, the others. The ``stronger'' sound, or masker, effectively raises our threshold of hearing so that the ``weaker'' sound must have a higher intensity in order for us to hear it. Here we will derive masking curves for two maskers. In the matlab GUI, select a masker frequency and change the frequency separation between the masker and the second tone (the maskee). Gradually decrease the volume level of the second tone until you can't hear its presence anymore. Copy down the dB level of the second tone when it ``disappears''. We will sample more frequency points of the second tone where it is within the critical band of the masker frequency, and fewer frequency points elsewhere.
To run the experiment:
Type: >experiment2
in matlab

Third experiment: masking of a pure tone using noise

In this experiment you will use a filtered noise burst to find the masker and the maskee.
To run the experiment:
Type: >experiment3
in matlab