Multiple compound words [duplicate]

Possible Duplicate:
How to connect a word and a phrase with a dash?

Hello, I'm a non-native English speaker and I'm writing a scientific paper about biometric identification based on heart sounds.

In this context, is the following phrase correct?

Comparison of recent articles on heart sounds-based biometrics.

I am using it as a caption for a table.

Solution 1:

The correct form would require another hyphen:

Comparison of recent articles on heart-sound(s)-based biometrics

However, such long compound adjectives are a bit ugly. Instead you could write this:

Comparison of recent articles about biometrics based on heart sounds.

Or perhaps this:

Comparison of recent articles on heart-sound biometrics

It seems clear that these biometrics are based on whatever word you use to specify them, which is why I suspect the word "based" isn't really necessary; or is it?