Assertion: wind instrument's type | /r/HasProperty | one of the order of 20 hz
Facets:
Source sentences:
text: John W. Coltman, in a detailed analysis of flute acoustics, describes two types of warbles in Native American flutes: One "of the order of 20 Hz" caused by a "nonlinearity in the jet current", and a second type "in which amplitude modulation occurs in all partials but with different phases".