Low-frequency aircraft noise is most noticeable to the rear and side of aircraft that are taking off and are on or near to the ground. Recently concluded at Minneapolis–St. Paul International Airport (MSP), this study investigated levels and effects of low-frequency noise in residential areas. The study built on work conducted at other airports. It reached five significant findings: (1) the primary effect of low-frequency noise annoyance caused by noise-induced rattling of windows, doors and furnishings; (2) the best predictor of annoyance was the average of maximum levels in the 25–80-Hz bands (called the low-frequency sound level, LFSL); (3) the existing residential sound insulation program at MSP does not measurably change the low-frequency noise reduction (LFNR), but it reduces the annoyance as much as a 5-dB reduction in low-frequency noise level; (4) the maximum practical level of noise in new single-family residences is approximately 25 dB, about 10 dB higher than the LFNR found in the typical untreated residence, and (5) the maximum exterior LFSL compatible with residential use is 87 dB.