Bass & bother: Why traffic hums in your 12th floor highrise flat but kanwar truck boomboxes rattle windows

Each year, as the Kanwar yatra season arrives, a wave of noise begins to build up before the trucks even come into view. In high-rise buildings in Noida and Gurugram, the sound seeps through double-glazed windows, rattling frames and causing doors to flex. While the windows and doors may comply with legal noise limits, the low-frequency bass from the trucks penetrates through, shaking structures and affecting people's bodies in ways that standard sound meters cannot detect.

India's noise rules treat all sound as equal, regardless of frequency. However, bass waves, which have longer wavelengths, are not stopped by obstacles as easily as higher-frequency sounds. They bend around objects and pass through materials that would block shorter waves. Sound-absorbing insulation is not effective against bass, as it is too thin to vibrate at those frequencies.

Resonance also plays a role, as many parts of a house naturally vibrate at frequencies between 5 and 50 hertz, the same range as truck-mounted subwoofers. When the sound wave aligns with the object's natural frequency, it amplifies the vibration, causing the rattling noise. The distance at which bass is still audible is also longer than that of higher-frequency sounds, making the impact of truck traffic more noticeable even from a distance.

Bass can also travel through the human body, creating a mechanical thump felt in the chest. This physical vibration can occur even at low sound levels, disturbing sleep and affecting cortisol levels. Cortisol, a stress hormone, remains elevated after noise exposure, potentially leading to health issues such as cardiovascular problems. The World Health Organization has recognized environmental noise, particularly low-frequency noise, as a significant contributor to ill health, ranking it second only to air pollution.