The PhysioBank Archives are a a set of databases of physiological data like heart recordings (ECG's) and brain recordings (EEG's). Use the link above to browse what's available. Their advice is to use "Chart-O-Matic" to see small subsets of what is there. Try it out.
A little further down the page you can click on "rdsamp-O-Matic", which allows you to download data in digital form. You will see the digitized data displayed: then use "Save As" in the browser's File menu to save it. Once you have the data locally, you can make it Matlab-readable by deleting text headers on the columns (save the resulting altered file under a slightly different name, so that the original information is not lost). Then using the Matlab command "load [filename]" you can bring it into the Matlab work area. You can even use SOUNDER to graph it or see its power spectrum. (These traces are not sound signals, but you could also play them through the speaker as if they were. I will not be responsible for how it sounds.)