It is the most common form of noise we encounter on a daily basis and is generated by a variety of sources, including voices, music, machinery, vehicles, and other sources that produce air vibrations.

When a sound source generates vibrations, it alters the ambient air’s pressure. These pressure variations, known as sound waves, travel through the air and are detected as sound by our hearing or other receiving surfaces. This transmission of sound through the air is referred to as airborne noise.

Airborne noise can be further divided into two distinct classes:

Direct Sound: Direct sound is sound that travels from the noise source to the receiver without significant obstructions or reflections. For instance, when you hear a person speaking directly to you or a nearby musical instrument, you are perceiving direct airborne sound.

Reflected Sound: Reverberant/reflected sound is the sound that reaches the recipient after rebounding off of the environment’s surfaces. Sound waves can refract, diffract, or scatter when they encounter obstacles such as walls, ceilings, and floors. These reflections can cause the sound to arrive at the receiver via multiple paths and at various moments, resulting in a complex sound field. In enclosed spaces, where sound waves ricochet off surfaces and create echoes or reverberation, reflected sound is of particular importance.