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On Cuba, diplomats, ultrasound, and intermodulation distortion
Chen Yan1, Kevin Fu2, Wenyuan Xu1
1Department of Systems Science and Engineering, Zhejiang University, China.
Computers in Biology and Medicine
|December 12, 2018
Summary
Unintentional ultrasonic signals may have caused the metallic sounds heard by diplomats in Cuba. Acoustic interference, not malicious intent, could explain these audible sensations through intermodulation distortion.
Area of Science:
- Acoustics
- Signal Processing
- Biophysics
Background:
- Diplomats in Cuba reported experiencing unexplained metallic sounds.
- Previous investigations considered various causes for these anomalous auditory sensations.
Purpose of the Study:
- To investigate the potential role of ultrasound in generating the reported metallic sounds.
- To explore the mechanism of intermodulation distortion as a cause for audible byproducts.
Main Methods:
- Analysis of acoustic spectral plots from Associated Press (AP) news recordings.
- Reverse engineering of ultrasonic signals capable of producing observed spectral characteristics.
- Development of a proof-of-concept ultrasonic device demonstrating amplitude modulation and interference.
Main Results:
- Demonstrated that intermodulation distortion between ultrasonic signals can create audible tones.
- Identified spectral characteristics of synthesized tones matching AP news audio.
- Showcased a plausible mechanism for unintentional sound generation.
Conclusions:
- Intermodulation distortion of ultrasonic signals offers a plausible explanation for the metallic sounds heard by diplomats.
- Acoustic interference, without malicious intent, could be responsible for the audible sensations.
- Further research is warranted to confirm the role of ultrasound in such incidents.
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