Hi. I'm new and hope you can point me in the right direction. I'm not too sure how to write expressions here. Have to do some tests. So I've attached a *.doc file that outlines the problem and what I'm looking for. I'm too sure how this all works so I might have to try again. In short it's an expression to calculate the frequency of oscillation of a pipe with conical nozzle on the end. Thanks in advance. Graham. P.S. I have a degree in Physics with Maths, but that was 25years ago and I'm more than a bit rusty now.