Reverb HF and LF decay:
The types of surfaces in a space also affect the sound. Carpet and soft furnishings will absorb more high-frequency waves, thereby reducing the high-frequency decay time, while hard surfaces such as tile or stone reflect sound extremely well, resulting in a “brighter” ambience.
Similarly, the high-frequency (HF) and low-frequency (LF) decay time allow you to adjust the “brightness” or “darkness” of the reverb, enabling you to better emulate these environmental factors.