Open the beat with the tempo you want to match in Sound Forge 9.
Click and drag on the section of the beat that you want to use as a loop to highlight that specific section. Try to pick complete bars to make some of the later steps easier.
Click on "Options" and a drop-menu will appear. Click on "Preferences."
Click on the "Toolbars" tab, click on "ACID Loop Creation Tools" and click on "OK" to open that toolbar in your main editing window.
Click on "Edit ACID properties ... " on the "ACID Loop Creation Tools" toolbar. It's the icon with the "A" on it.
Select "Loop" -- small highlighted section -- by clicking the check point next to it.
Click on the "Root Note for Transposing" drop-menu to select the key in which the beat that you want to match is made. If you don't know the exact key, click on "Don't Transpose."
Select the number of beats per bar in the beat. If you have a 4/4 beat -- four beats per measure -- then key in 4. If you have a 3/4 beat, key in 3.
Click on "OK" to save that information and close the window.
Click on "Edit Tempo" -- the button with "4/4" on it -- and the tempo-editing tool will open.
Enter the amount of beats your selected piece of music has in the "Selection length in beats" box. For instance, if the section you selected has four beats, enter 4 and if it has 12 beats, enter 12.
Once you enter the number of beats, the tempo of the section -- and, most times, the entire song -- will be indicated in the "Tempo in beats per minute" box.