[填空题]
A person hears a pure tone in the 500–1000-Hz range coming fre y-/e xgi4mx7xwq0; mom t(w( i 6xctdj/xob:.uv wo sources. The sound is loudest at points equidistant from the two sources. To determine exactly what the frequency is, the person moves about and finds that the sound level is minimal at a point 0.34 m farther ow biuv.x/d c6(:(t jxfrom one source than the other. What is the frequency of the sound? Hz