Ultrasonic investigations in shopping centres
High‑pitched and ultrasonic tones in shopping malls, streets, and other public spaces are increasingly being noticed as a source of discomfort, especially for younger people and those with sensitive hearing. Commenters explore likely sources ranging from anti‑loitering and pest‑deterrent devices to PA system test tones, parking sensors, and poorly filtered electronics, and share tools and methods for measuring these sounds with consumer audio gear and specialized recorders. The thread also raises concerns about the impact on animals and neurodivergent people, and notes that similar ultrasonic techniques are already used in areas like advertising, crowd tracking, and FM broadcasting.
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.