Why does a piccolo sound shriller than a flute?

The piccolo sounds shriller than a standard concert flute primarily because it is pitched an octave higher.12

As a member of the woodwind family, the piccolo is a smaller instrument with a shorter air column compared to the flute. In acoustics, the pitch produced by a wind instrument is a function of its tube length; a shorter air column vibrates at a higher frequency, resulting in a higher fundamental pitch. Because the piccolo is designed to be significantly smaller than the flute, its range sits one octave above that of the ordinary concert flute, which contributes to its characteristic high-pitched, shrill quality.132