Eurekalert  March 15, 2018 An international team of researchers (USA – University of Michigan, China) analysed a video sent by AP in which they heard a piercing, metallic sound. The spectral plot of the recording revealed a spectral peak near 7 kilohertz and a dozen other less-intense tones that formed a regular pattern with peaks separated by approximately 180 hertz. Based on their prior research the researchers hypothesized that intermodulation distortion can produce several by-products at other frequencies when multiple tones of different frequencies travel through air. Their math leads them to believe that intermodulation distortion is a likely culprit […]