inaudible frequency

My father wondered whether the minute silken filaments spun by spiders, strung from twig to twig in the apple trees, and hammocked between blades of grass in the lawns, were like tiny aeolian harps, each vibrating  to a frequency beyond human register. Now, every time I see a spider's web quivering in the wind, I recall his words, and imagine the entire garden resonating in a symphony of sound that I shall forever be unable to hear.