Ultrasonic investigations in shopping centres

Everyday experiences with high‑frequency sound

• Many commenters report hearing piercing tones in shopping centers, Tokyo streets, US suburbs, cruise ships, garages, and department stores.
• Several note age-related differences: adults often can’t hear sounds that children or younger adults find unbearable.
• Some describe headaches or nausea in malls, and lifelong sensitivity to CRT “whine” and other ultrasonic-ish noise.

Suspected sources and purposes

• Anti‑loitering “mosquito” devices targeting youths are widely mentioned; some still exist and have been vandalized.
• Other hypothesized sources: pest/animal deterrents (rats, cats, birds, insects), ultrasonic parking sensors, building occupancy sensors, loss‑prevention systems, and PA system line‑integrity test tones.
• Alternative technical explanations include class‑D amplifier artifacts, subharmonics from ultrasonic sensors, and PA systems designed to send a continuous high‑frequency pilot tone to monitor speaker wiring.

Measurement and tooling

• Basic suggestion: any microphone plus laptop, or phone with a spectrogram app.
• Notes on limitations: common audio interfaces cut off near 20 kHz; higher‑end gear offers 96–192 kHz sampling.
• Mentions of specialized devices like Audiomoth recorders, omnidirectional reference mics, and pro apps (e.g., SMAART-style tools) that can calibrate to phone hardware.

Impacts on people and animals

• Concern that such tones likely affect dogs and other animals with higher hearing ranges, as well as autistic or otherwise sound‑sensitive people.
• LED bulbs, induction stoves, and other electronics are cited as additional, often inaudible but uncomfortable, sound sources.
• Some worry about pets trapped in constant ultrasonic noise without owners realizing.

High‑frequency tones in music and broadcast

• Reports of commercial music releases containing 15–19 kHz carriers for concert lightstick control or due to production errors.
• FM radio stereo pilot tones (19 kHz) and inadequate filtering are cited as another source of annoying inaudible‑to‑most whines.
• Discussion of modern pop mixing: heavy use of autotune, bright EQ, layered vocals, and how production choices can create harshness.

Surveillance, tracking, and ethics

• Ultrasonic audio has been used for cross‑device tracking in advertising; class actions have challenged this.
• Mention of emerging Wi‑Fi Doppler sensing for occupancy and movement, with both useful and “alarming” potential.
• Some view anti‑youth soundscapes as antisocial and harmful, especially when deployed in public spaces.