An investigation of low-frequency footfall noise in multifamily, wood-frame residential construction has led to the conclusion that, at present, there is no economically practical method of avoiding the perception of "thuds" and "thumps" in rooms beneath the walking surface. The IIC rating of a floor system is meaningless with respect to the perception of these low-frequency components of footfall noise, because the methodology ignores the frequency spectrum below 100 Hz; the peak energy in a footfall spectrum occurs at the fundamental natural frequency of the floor/ceiling system, which with typical light-weight structural framing is usually between 15 and 30 Hz. Although the construction of floated floors, or the addition of carpeting, is effective in attenuating mid-to high-frequency components of footfall noise, the data indicate that the amplitude of floor response at the natural frequency is actually increased. It is believed that this occurs because walking on a more resilient system results in a longer rise-time of the footfall waveform, which permits more low-frequency energy to be coupled into the system. The principal factor controlling the perception of low-frequency footfall noise is the point-stiffness of the structural floor system. In normal light-weight residential construction, the stiffness is usually much less than that required to avoid an audible disturbance. However, such problems are relatively rare in concrete structural floor systems, due to their substantially increased stiffness.

California law requires noise abatement for classrooms in which noise levels from a freeway exceed 50 dBA. In contrast, the Federal Highway Administration's criterion level is L10 = 55 dBA. This discrepancy reflects, in part, a lack of hard data regarding how noise from external sources affects the educational process. About 100 classrooms in 15 schools comparable with respect to certain socioeconomic variables but at different distances from freeways were studied. Noise levels inside the third and sixth grade classrooms with and without children were measured. In addition, teachers' voice levels and certain indications of classroom performance were obtained during three days of observation in each classroom. The Los Angeles Unified School District and the California Department of Education provided scores for each classroom on standardized tests of academic achievement in reading and mathematics. Preliminary analysis of the data indicates that achievement in reading and mathematics is poorer as noise levels increase, a finding consistent with previous studies. However, our data indicate that the coefficients of correlations between noise levels without children and achievement are higher if the levels are C-weighted rather than A-weighted, and that L1 and L5 are better predictors of achievement than are the other Lxs. [Work supported by F.H.W.A. and California Departments of Transportation and Health.]

This paper reviews the role of the California State Government in noise compatible lend use planning. Since the responsibility for land use planning in California lies almost entirely with local government, the State has provided, through various pieces of legislation, the means for insuring that noise is considered in the process. Among the approaches the State has adopted are (1) a requirement that cities and counties adopt a noise element as part of their general plan; (2) the establishment of an Office of Noise Control to provide assistance to local governments and coordinate efforts at the State level; (3) the establishment of airport land use commissions; (4) the use of the EIR/EIS review process; and (5) the adoption of noise insulation standards for multifamily dwellings. The effectiveness of these measures in achieving noise compatible land use is discussed. Examples of good and bad land use in the vicinity of various sources are presented and analyzed. Some alternative approaches are presented and pitfalls pointed out.

Since 1974 the California Building Standards Law has required that new multifamily housing, hotels, and motels be designed to prevent the intrusion of exterior noise above a community noise equivalent level of 45 dB. At about the same time, the State also adopted energy insulation standards which require low air infiltration rates for new dwellings. While these requirements seem to be complementary from the standpoint of noise insulation, the relatively mild climate of costal communities often obviates the need for air conditioning or even mechanical ventilation. This paper discusses some of the design, cost, and enforcement conflicts between adequate ventilation and noise insulation for areas with mild climates.