# Homework Help: Standing Sound Waves

1. Apr 8, 2008

### dals2002

[SOLVED] Standing Sound Waves

What are the three longest wavelengths for standing sound waves in a 121 cm long tube that is (a) open at both ends and (b) open at one end, closed at the other?

the wavelength equation that i used for open-open was $$\lambda$$= 2L/m; where m is the number of modes (m=1,2,3,4.....)

and then for open-closed $$\lambda$$= 4L/m; where m is the number of modes (m=1,3,5,7......)

so i have the length, but the one question that i have about this problem is could i start with the lowest number of modes, but if that is true then why ask for the three longest wavelength, so i am kind of lost if anyone could give me a clue on what to do

2. Apr 8, 2008

### Snazzy

The three longest wavelengths correspond to the three lowest modes.

3. Apr 8, 2008

### dals2002

oh ok, that was exactly what i thought it was thanks