Helmholtz resonance powers miniature boats and ultrasonic flying robots

Executive Briefing & Key Highlights

When air is blown across the neck of a bottle, it doesn't just produce a pleasant tone: it also demonstrates a phenomenon called Helmholtz resonance. This occurs when airflow passing across an opening causes air trapped inside a cavity (like a glass bottle) to oscillate back and forth. At certain frequencies, these oscillations become much stronger, producing the familiar humming sound.