Resonance occurs for sound waves as for all other sorts of waves. Resonance of sound waves in pipe – open at one end or open at both ends is particularly interesting. When resonance occurs on a string it does so only for those frequencies for which a whole number of half wavelengths can be fitted onto the string. When resonance occurs in a pipe, it can do so differently depending on whether the pipe is closed at one end or open at both ends. In either case, the open end is not quite at an antinode, a point of maximum vibration. The antinode is actually slightly outside the pipe opening..
Open pipes exhibit resonance for frequencies for which the length of the pipe is just over a multiple of half wavelengths, so that there is an antinode at either end, while pipes closed at one end exhibit resonance for those frequencies for which the length of the pipe is just over an odd number of quarter wavelengths.
