A series of reverberating sounds observed in downtown Kyiv with no clear point of origin. The event was witnessed by the city's general public. Mental and physical symptoms were reported, including aphasia, sleep paralysis, and excess [REDACTED] in the reported individuals.
Due to the brief nature of the event, overseas Bureau agents were not able to respond while it was active. Immediately upon arrival, agents collected audio recordings taken by local witnesses. All Bureau monitoring stations located at global junctions of acoustic amplification were directed to monitor any auditory events of similar pitch, wavelength, and duration in an effort to trace echoes or epicenters. In the following weeks, similar cases were reported from both various amateur sources and Bureau stations in major cities across the globe. The subsequent events diminished in volume and frequency per each occurrence.
Event is believed to be generated by planar friction, though this is not confirmed (see file 71-849-062 for full hypothesis).