Which of the following wave properties is not taken advantage of in controlling noise?

Correct option is D

Introduction
· Noise control is the process of reducing sound pollution through various engineering and physical methods.
· Sound travels as a longitudinal mechanical wave, and its energy can be manipulated, dissipated, or redirected using the fundamental properties of wave behavior.
· Effective noise management typically involves addressing the source, the transmission path, or the receiver.

Information Booster
· Diffraction is the correct answer because it is a property that generally hinders noise control rather than being used to achieve it.
· Diffraction is the bending of waves around obstacles or through openings. In acoustics, this means sound waves can "bend" over a noise barrier or around a wall, reaching the listener even if there is no direct line of sight.
· Because lower frequency sounds (longer wavelengths) diffract more easily, noise barriers are often less effective at blocking low-pitched rumbles compared to high-pitched whistles.
· Engineers must account for diffraction by making barriers significantly taller or wider than the direct path, but the property itself is an obstacle to overcome, not a tool for reduction.

Additional Knowledge
· Absorption is widely used in noise control. Porous materials like foam or fiberglass convert sound energy into small amounts of heat as the wave vibrates the fibers of the material.
· Damping involves the use of materials (like rubber or specialized polymers) that reduce the "ringing" or vibration of a solid surface. This prevents the surface from radiating noise in the first place, effectively "soaking up" the mechanical energy.
· Interference is the principle behind Active Noise Cancellation (ANC). By generating a "counter-sound" wave that is $$180^\circ$$​out of phase with the noise (destructive interference), the two waves cancel each other out, resulting in silence.
· Reflection is another property used in noise control (as seen in solid masonry walls), where sound is bounced back toward the source rather than being allowed to pass through to a quiet zone.