# lowest frequency of a water with drinking straw

#### ling233

the ans given here is 'using the opened pipe method'. but i solve it using closed pipe method. which i have sketched using the pencil on the right of the diagram. why cant i solve it using 'closed pipe method' , i just couldnt understand.

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#### topsquark

Forum Staff
the ans given here is 'using the opened pipe method'. but i solve it using closed pipe method. which i have sketched using the pencil on the right of the diagram. why cant i solve it using 'closed pipe method' , i just couldnt understand.
Unless I missed something reading the question, the open pipe method is used because both ends of the straw are open, not closed. I'm not sure what the difficulty is?

-Dan

#### MBW

I think you are indicating that the open pipe (with a stationary node at the middle) is equivalent to a closed pipe (stationary node at the closed end) of half the length of the open pipe.
Thus the open pipe will give the same lowest frequency as a closed pipe of half the length.