Resonance will take place when the antinode is located at the open end of the tube. As a consequence the sound produced by the resonating column of air is louder than the sound produced by the sound source (tuning fork). The condition for resonance to occur is that the length of the air column L has to be odd multiples of one quarter wavelength ( 1 = 1, i, L; = 3_ j , L5 = 5_ :1 ,etc.) as described in general by: L z n '1 (2) n 4 where n =1, 3, 5, 7 (see also gure 2). Knowing the length of the air column when resonance occurs allows one to determine the wavelength of the sound wave. Using the known frequency of the incoming sound wave (produced by the tuning fork), one can determine the speed of sound from the following relation v5=fl (3)