Which one of the following is correct? A concrete wall generally,

When a sound wave strikes a material like a concrete wall, three primary processes occur: reflection, transmission, and absorption [t8]. Standard dense concrete is highly reflective, often returning up to 99% of sound energy due to its high density and minimal particle movement [t2][t4]. However, it is not a perfect reflector; it also transmits sound through the material, a property measured by its Sound Transmission Class (STC) [t5][t6]. Furthermore, while ordinary concrete is a weak absorber, it still possesses a sound absorption coefficient (typically around 0.1), meaning a small portion of sound energy is converted into thermal energy within the material [t4][t8]. Modern engineering can further enhance these properties using porous aggregates or 'Acoustic Insulation Concrete' to increase absorption [t3]. Therefore, a concrete wall generally performs multiple acoustic functions, primarily reflecting sound while also absorbing and transmitting a portion of it.