You mean to tell me that you think it's not possible to localize a saxophone or a trumpet? How about a flute? 700Hz is right around F5 on the musical scale; near the upper registers of the former two, and right in the middle of the latter.
There is far more that goes into acoustic localization than merely wavelength. One of the biggest factors is timing, which the human ear is extremely sensitive to. Let's not forget how reflections and reverberation contribute to that element of auditory perception. The body is also extremely sensitive to pressure acting upon it, and acoustic sound is nothing more than cycles of pressure changes around us. Let's not forget harmonics, because pure tones don't exist oustide of an electrical/digital environment...including after they go through transduction to be turned into acoustic waves.
While it's true that localization becomes more difficult as the frequency of a sound is lowered, you need to get WAY down there for there to be an appreciable effect. Maybe this would be true in an anechoic chamber, but this question is a little too narrow minded in it's consideration.
I don't mean to sound condescending in this response, but, practically speaking...without supplying a specific context...this is a silly idea.
yes, i edited that last line...stupid omission on my part.