1.The jar file is the same as ZIP file. The only difference is the file extension.
So you can open it with UNZIP program. (Do not associate jar with UNZIP program, otherwise, you would not be able to run it by double click--UNZIP will open it instead.).

2. You will find a folder fkh inside the jar file when you open my soundGenerator.jar
And there is a file soundGenerator.class inside fkh folder,
and there is a function call SoundGenerator(frequence,amplitude) inside soundGenerator.class
That is why it is associated as fkh.soundGenerator function.

You will need to have source code or document in order to know what are the parameter for that function.

It is possible to de-compile the program if the program is not protected when it is compiled.
There exists some program to de-compile .class file back to .java
However, the best way is to find the original document or ask the programmer.

User need to find out how to use ConvolveFilter from the source code.
http://www.huxtable.com/ip/ConvolveFilter.java
You can call defined [b]public[/b] functions with required [u]parameters[/u].

However, user need to have basic information about java programming.
That is why EJS is called Easy Java Simulation, becauase it make java programming much easier than traditional programming.