vt.physics on Instagram: "In some parts of Japan, especially in cities, high-pitched noises come from devices like the Mosquito alarm, which emits a sound around 17–20 kHz - a frequency that most adults can’t hear but younger people (typically under 25) can. These devices are used near convenience stores, apartment entrances, and train stations to deter teenagers from loitering or gathering in groups, especially at night. While they’re intended to reduce noise, vandalism, and petty crime, their