Submitted by Jennifer Cooper, Jordan Schleif, Adaleena Mookerjee,Tyler Flynn, O.H. Ott-Pietrak, Shane Lani
In the past years there have been reports of embassies being the subject of sonic attacks. News articles suggest that diplomats have suffered illness, allegedly caused by attacks with ultrasonic weapons. The symptoms suffered include serious nausea, headaches and dizziness. This is known as the Havana Syndrome, named after an alleged ultrasonic attack on the U.S. embassy in Havana, Cuba. An ultrasonic device plays sounds at or above 20 kHz, outside the audible range for most adults, and smartphones are not able to observe them properly, as they register sounds of up to ~20 kHz, but not far above that. At present, there is no readily available open source solution for quantifying exposure to ultrasonic sound.
For the submission to the ASA 2021 Design Challenge, the research team used the TYMPAN platform to develop and test a prototype ultrasonic dosimeter. This dosimeter works like a sound pressure level (SPL) meter, with the inclusion of the ultrasonic 1/3 octave bands. The algorithm determines the ratio between the ultrasonic frequencies and the lower frequencies. If sound energy occurs only in the ultrasonic frequency bands an audible alarm goes off. So basically, the device is not calibrated to absolute SPL levels of ultrasound, but the relative levels should give an accurate image of the presence of exceedingly high levels of ultrasound.
The Tympan can process the ultrasonic signal in real time, shifting it down in frequency to the audible range to make it audible. Listening to the frequency shifted ultrasound the ultrasonic dosimeter can provide valuable information about the spatial and temporal distribution of the ultrasound.The smartphone app that comes with the Tympan allows the user to adjust the amount of frequency shifting on the fly and record both the shifted and raw audio to .wav file on the SD card for later analysis. When listening and recording, the left channel is used for the ultrasound shifted down to audible and the right channel for the raw audio (with a low pass filter for listening).
Graphs showing the raw ultrasound signal (left) and the signal shifted down to the audible frequency range (right).
For this ASA design challenge, a first prototype for an ultrasound dosimeter was made. Next steps in the development include:
- Improving the threshold for questionable ultrasound levels
- If possible, test the device with something that resembles the "ultrasonic weapons"
- Calibrate the built-in mic at ultrasound frequencies or use an external mic that is calibrated for ultrasound
- Improving the responsiveness
- Include other areas of interest: are cats disturbed by high frequency sound coming from the TV? Why does he run away? Can we hear bats in the neighborhood (work in progress). Can a readily available open source solution for quantifying exposure to ultrasound be useful in the field of ultrasonic devices for pest and pet repellent and crowd control?
About the TYMPAN ASA2021 Design Challenge
During the ASA (Acoustical Society of America) conference in June 2021, Tympan hosted a design challenge: What is possible with the Tympan?
10 exciting new applications were submitted and presented at the following ASA conference: Enhancements of hearing aids, spatial acoustic processing and smart earphones and much more. Stay tuned if you want to learn what is possible and to keep track of future developments.