Lloyd Herman

Surface Retexturing to Reduce Tire-Road Noise for Existing Concrete Pavements

A portion of 1-76 near Akron, Ohio, was reconstructed by the Ohio Department of Transportation with concrete pavement to replace the previous asphalt surface. During reconstruction, the concrete surface was textured with random transverse grooves. After construction, residents living in the project area as far as 800 m (2, 600 ft) from the roadway perceived an undesirable increase in noise level, which they attributed to the new concrete pavement in the reconstruction project. Therefore, another project was initiated to retexture the pavement surface by diamond grinding. The transverse grooves were replaced with longitudinal grooves. Traffic noise measurements were made before and after grinding at five sites in the project area, at distances of 7.5 m (24.6 ft) and 15 m (49.2 ft) from the center of the near travel lane. The average reduction in the A-frequency-weighted broadband noise levels at 7.5 m (24.6 ft) was 3.5 dB, and the average reduction at 15m (49.2 ft) was 3.1 dB. Spectrum analysis showed that...

Analysis of Strategies To Control Traffic Noise at the Source: Implications for Policy Makers

Traffic noise control strategies that reduce traffic noise at the source were identified. The strategies were grouped according to the vehicle noise sub-sources: engine, intake air, exhaust, cooling fan, transmission/driveline, and tire/pavement. Examples of the strategies and recent advancements in vehicle noise control are given. The analysis yielded a number of implications for policy makers. In the United States, market forces are currently fostering technological advancements to reduce most of the vehicle noise subsources. However, the reduction of tire/pavement noise, the dominant subsource at freeway speeds, is currently benefiting little from market forces and may be hindered in the future by trends in passenger car tires. Policies and regulations, where warranted, should be aimed at reducing tire/pavement noise through a concerted effort on the part of both tire and pavement industries as well as transportation agencies.

Perception of Traffic Noise Barrier Effectiveness: Public Opinion Survey of Residents Living near I-71

The completion of the largest Ohio Department of Transportation traffic noise abatement project in 1995 was met with public controversy over the effectiveness of the noise barriers. A public opinion survey was designed to obtain the perceptions of the residents in the project area. In a departure from most surveys of traffic noise barrier effectiveness, the coverage was not limited to the first or second row of houses, but was extended to 800 m on each side of the roadway. It was found that the larger survey area was needed to avoid misleading conclusions. Overall perceptions of noise barrier effectiveness were found to vary with distance from the roadway and with noise barrier configuration.

Analysis of noise barrier overlap gaps

Sound propagation through the gap produced by two parallel vertical barriers with overlapped ends is formulated for traffic noise sources. The analysis identifies both source and receiver regions according to the mechanisms that influence noise propagation in the vicinity of an overlap gap. A method to account for the contributions from the various source regions for a given receiver location is described. The derived method can be implemented using various equations for sound propagation. The results of using equations approved by the United States Federal Highway Administration for traffic noise propagation are given. Uncalibrated predictions are compared with field measurements for up to 30 receiver positions from each of four overlap gaps. The relative importance of contributions from reflected rays to the noise levels at receiver positions is given. The analysis confirms the initial hypothesis that a commonly used strategy of overlapping barriers by an amount equal to two or three times the overlap width is useful for controlling line-of-sight propagation but ignores the substantial effect of reflections.

Accuracy of a Traffic Noise Model Using Data from Machine Vision Technology

The FHWA Traffic Noise Model is used in a variety of applications to predict noise levels at locations of interest in the vicinity of streets and highways. The models traffic noise source characterization process requires the user to supply the volumes and speeds for each vehicle class for each lane of roadway to be modeled. Using these parameters, along with algorithms developed from typical vehicle pass-by data, the program calculates the vehicle noise emission levels for each vehicle class. The accuracy of the user-supplied traffic parameters, therefore, affects the final noise level prediction. Automated traffic data collection technologies offer an attractive alternative to manual data collection for high-volume roadways. The accuracy of noise model predictions was investigated for the machine vision technology, which uses video-based traffic detection with a procedure developed to determine the effect of video equipment setup parameters on traffic data acquisition accuracy, and the range of expecte...

Effect of Field Setup on Accuracy of Traffic Data Collection Using Machine Vision Technology

Video traffic data were collected in 24 combinations of four different camera position parameters. A machine vision processor was used to detect vehicle speeds and volumes from the videotapes. The machine vision results were then compared with the actual vehicle volumes and speeds to give the percentage errors in each case. The results of the study provide a procedure with which to establish camera position parameters with specific reference points to help machine vision users select suitable camera positions and develop appropriate measurement error expectations. The camera position parameters that were most likely to produce the least overall volume and speed errors, for the specific site and field setup with the parameter ranges used in this study, were the low height of approximately 7.6 m (25 ft), with an upstream orientation (traffic moving toward the camera), a 50-mm (midangle) focal length, and a 15° vertical angle.

Investigation of noise reflections using test signals

Repeatable test signals for use with a loudspeaker system were generated to investigate noise reflections from traffic noise barrier walls. Four classes of signals were considered: impulses, maximum‐length sequences, pseudorandom binary sequences, and linear frequency‐modulated sine waves or chirps. Overall, the chirps yielded the most information from initial experiments. The test system was applied to single and parallel barrier configurations to identify the number of significant reflections, to determine the level of the reflections relative to the direct signal and to quantify the contribution of the reflections to the overall sound level at receivers of interest. For receivers located on the community side of parallel barrier configurations the contribution of the reflections was found to increase with receiver distance from the barrier.

PLACEMENT OF SOUND-ABSORBING MATERIALS TO CONTROL TRAFFIC NOISE REFLECTIONS AT A HIGHWAY UNDERPASS

The effectiveness of the installation of sound-absorbing material on the vertical retaining walls of a highway underpass was evaluated. A multifaceted experimental approach, involving both the actual traffic noise source and an artificial source, was used. The experimental results indicated that only a minor reduction in noise levels had been achieved from the sound-absorbing material. A theoretical analysis of sound propagation near highway underpasses was made and implemented in a computer simulation model. The application of the model to the highway underpass supported the experimental results. In addition, the modeling results indicated that reflections from the bridge understructure were more significant than reflections from the vertical walls.

An evaluation of STAMINA 2.0 using the ORNAMENT ground attenuation algorithm

The United States Federal Highway Administration (FHWA) computer program STAMINA 2.0 was evaluated with the ground attenuation algorithm used in the Ontario Road Noise Analysis Method for Environment and Transportation (ORNAMENT). The goal: To determine this method’s potential to improve noise level predictions at receivers located near traffic roadways with barriers in the propagation path. The study of 41 sites indicated that this method reduced the mean overprediction of noise levels from 2.6 dB using STAMINA 2.0 alone, to 0.5 dB using STAMINA 2.0 with the ORNAMENT ground attenuation algorithm.

Determination of traffic noise barrier effectiveness.

This study evaluated the benefits of a noise control program involving construction of over