 So we've learned that we can change the wavelength of our sound by Controlling the length of our strings. The reason we can do that so well is that we are forcing it to be at a node Wherever we sort of fix the string and when we have a woodwind instrument That's actually a lot harder because if I am going to be blowing to this supposing this is a Bad didgeridoo if I'm gonna blow into this then is this point here gonna be a node or an anti node How's that gonna work? And the actual answer is that that's quite a complicated issue and it depends on technique and skill So you should get someone to show that to you The speed of sound can't really be changed. So when we had a contrast ring We could use strings of different tension and different density and so forth and that would give us different speeds We don't really have that control over air the speed of sound in the air does depend on things like pressure and so forth But it's hard to change that dynamically when you're playing an instrument So really all you can do is try and adjust exactly where you're getting nodes and anti nodes by careful mouth placement and so forth But you can hear very clearly the difference between having open ends and closed ends. Supposing I close that end So I'm certainly not going to have an anti node the point where my hand is and if I make a sound You get a note and if I take that hand away and make the same sound Firstly, it's louder because I'm getting more airflow. Yes But you'll note that the frequency is different. It sounds different and in fact They're an octave apart Bum bum that octave means that we're having a doubling of the frequency Which means the two situations there where I have the hand over one end or not Somehow I'm getting twice the wavelength in one case So what's a good model for what the waves are doing inside that pipe?