Transmission Loss of Single, Solid Walls

The transmission loss (TL) curve of a typical single, solid wall is characterized by (1) a 6-db per octave slope at low frequencies, (2) a “plateau” of nearly constant TL extending over two or more octaves of frequency, and (3) a 6-db or more per octave slope beginning above the plateau. The height in decibels of the plateau is determined by the modulus, density, and to a lesser extent, the loss tangent of the wall material. Thus, the plateau height, in decibels, may be thought of as a material constant and is independent of the wall thickness. In many practical instances (e.g., speech privacy between typical office spaces) the plateau TL is crucial. In such instances, small changes in the wall thickness (e.g., plus or minus a factor of two) may not have practical significance.