About: http://webisa.webdatacommons.org/116117657

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	I think that sound is a beat frequency because the DC-9's engines are turning at a slightly different number of revolutions per second.
http://www.w3.org/ns/prov#wasQuotedFrom	dsprelated.com