This picture illustrates the Eckel metal wedge system. The chamber pictured above has interior dimensions of 168" long by 156" wide by 133" high. The exterior dimensions of the panel room are 244" long by 232" wide by 176" high to the top of the panel roof. The overall acoustic performance of the anechoic treatment met ANSI standards for a cut-off frequency down to 63 Hz. Ambient noise levels within the chamber with the HVAC system operating was less than ND-15. The chamber is used to test hydraulic pumps and there is a serarated room for the dynamometer that is connected to the pump under test through the wall of the chamber. A shaft silencer was provided for the dynamometer shaft. The anechoic wedge peaks were formed with perforated metal which in turn contained fiberglass of the proper density and flow resistance to provide the desired performance.