The quieting of the Willgoos Turbine Laboratory, a jet engine development facility of the Pratt and Whitney Aircraft Company, presented very unusual acoustic design problems because there were residences within 200 feet of the proposed building. At the time of the design (early in 1948) there was little information available on the design goals, the expected noise levels in the operation areas, or practical methods of accomplishing the noise reduction. Altogether, 14 types of structures were designed to reduce various sources of noise emanating from this laboratory, including ventilation intake and exhaust ducts and atmospheric intake and exhaust systems for test cells, compressors, and exhaustors. The noise in control rooms and piping systems was also treated. The quantity of gases moved in some of these systems is nearly a million cubic feet per minute. A design goal was set at a sound level of 75 db in the 300–600 cps band in the immediate vicinity (approximately 50 feet) of the plant. The amount of sound reduction required for this band was 50 to 75 decibels. Various quieting constructions used on the project were baffle splitters, turns in the large acoustic ducts, lined plenums, and slotted exits. Some of the most important of these will be described in this paper. A limited number of measurements in the completed laboratory were made by using an air modulated horn driven by a broad-band noise source, from which a level up to 125 db could be obtained in the test areas. Measurements showed that, in all the installations except one, the attenuations obtained were within 5 db of those predicted before construction. The success of the project was such that none of the noisy operations inside the building can be heard at nearby residences.