On-board Sound Intensity Research Articles

Assessment of Tire Noise on Concrete Pavement in California Highways

A 2-year initial study, recently completed in California, measured and compared tire–pavement noise levels with the onboard sound intensity method on existing concrete pavements. The study included 120 pavement subsections at 47 sites; most sections were measured twice in the 2 years. The surfaces encountered were classified into five texture categories: burlap drag, diamond ground, diamond grooved, longitudinally broomed, and longitudinally tined. The experiment was not balanced for age, traffic level, or climate region. The surfaces were further categorized as having new, aged, or worn-out texture. The differences within and between surface types were assessed for spectral content and overall sound intensity. The results revealed a large overlap in the onboard sound intensity levels between texture types. The quietest sections overall were measured on diamond ground surfaces. However, on the basis of the average noise level of the evaluated sections of each texture type, the longitudinally broomed surfaces as a group were the quietest, although they were represented by a small sample in the experiment. The study indicated that the sound intensity of concrete pavements in California ranged from about 99 to about 107 dB(A). The measured onboard sound intensity levels included the effects of joint slap, faulting, and sealant, if present, in addition to the texture.

Research and Application on the Crumb Rubber Modified Low-Noise Asphalt Pavement

In this paper, the research of Low-Noise Asphalt Pavement（LNAP）mix design with the crumb rubber has been studied, including materials selection, gradation selection, asphalt content selection, performance tests, and so on. To verify the high-temperature performance and the effect of noise reducing, the new test methods are studied in the lab. The On-board Sound Intensity (OBSI) is developed to measure the tire-pavement noise and evaluate the noise reducing effect of trial pavement. The QC and QA of LNAP is researched by the trial pavement and the tire-pavement noise is measured by the OBSI，the LNAP has not only the good performance but also low noise than the conventional asphalt pavement.

Research and Application on the Crumb Rubber Modified Low-Noise Asphalt Pavement

In this paper, the research of Low-Noise Asphalt Pavement（LNAP）mix design with the crumb rubber has been studied, including materials selection, gradation selection, asphalt content selection, performance tests, and so on. To verify the high-temperature performance and the effect of noise reducing, the new test methods are studied in the lab. The On-board Sound Intensity (OBSI) is developed to measure the tire-pavement noise and evaluate the noise reducing effect of trial pavement. The QC and QA of LNAP is researched by the trial pavement and the tire-pavement noise is measured by the OBSI，the LNAP has not only the good performance but also low noise than the conventional asphalt pavement.

Determining End Limits of Quieter Pavement Projects

Ongoing work in the area of tire pavement–acoustics has definitively determined that there can be a significant variation of noise levels between the loudest and quietest pavements. With the use of the onboard sound intensity (OBSI) measurement procedure, it has also been determined that tire–pavement noise is highly correlated to the overall traffic noise levels, especially when traffic is flowing at freeway speeds. OBSI presents road agencies with a potential new tool for lowering traffic noise levels by using quieter pavements. Changing from a loud or old and raveled pavement to a newer, smoother, lower noise pavement can yield acoustic benefits to roadside communities or “receivers.” The decrease in noise level depends on the difference between OBSI levels of the existing pavement and the selected quieter pavement, and the magnitude of this decrease may also be influenced by vehicle mix. After the decision to use a quieter pavement has been made, the end limits for the pavement must be determined. The problem is somewhat similar to deciding where to terminate a sound wall relative to the location of the roadside receivers. This analysis determined that the quiet pavement end limits were less sensitive to variation in typical roadway cross sections, somewhat sensitive to the distance between the receiver and the roadway and where the quiet pavement terminates, and very sensitive to the absolute differences between the noisier and quieter pavements.

Tire Noise Generation and Propagation over Porous and Nonporous Asphalt Pavements

Acoustic measurements were made on several asphalt test pavements at the National Center for Asphalt Technology test track, including five porous pavements. Onboard sound intensity (OBSI) measurements were taken to quantify the tire–pavement noise source strength as a function of pavement parameters. The OBSI results fell into three pavement groupings based on spectral shape. More than other parameters, these groupings were determined by whether the pavement was porous or not and whether it was new or older. The OBSI results also indicated that single-layer porous pavements were particularly effective at reducing tire–pavement noise source strength at frequencies above 1,250 Hz for designs 18 to 33 mm thick. For a thicker, double-layer porous pavement, source strength reductions extended down to 630 Hz. Porous pavements were also found to be effective in reducing the source strength of the tire–pavement interaction by reducing some tire noise mechanisms and by reducing the sound power level of the source through local sound absorption. Testing was also conducted to evaluate the additional attenuation for sound propagating over porous, sound-absorbing pavements compared with nonporous pavements. From the propagation measurements, all porous pavements produced additional sound attenuation over that produced by the nonporous pavements. The additional attenuation also increased with distance from the source.

Comparison of tire-pavement noise characteristics of rubberized and conventional asphalt concrete mixes

This study compares tire/pavement noise characteristics of flexible pavement sections in California using the On-Board Sound Intensity (OBSI) method. Two experiments are presented in this work. The first one compares noise properties of pavement sections of different ages constructed with open-graded rubberized asphalt concrete (RAC-O) and gap-graded rubberized asphalt concrete (RAC-G) versus sections with conventional open-graded asphalt concrete (OGAC) and dense-graded asphalt concrete (DGAC). The second experiment compares the performance of trial sections that used different modified rubberized asphalt mixes as surface course. The results show that, compared with conventional asphalt concrete surface course of the same age, rubberized asphalt concrete surface courses have lower tire-pavement noise levels. The reduction comes mainly from better durability of rubberized asphalt concrete mixes. Additional information analyzed in this quieter pavement research study includes the effect of mix design variables and pavement surface distresses on tire-pavement noise characteristics of rubberized and conventional asphalt concrete mixes.

Effects of Aging on Tire–Pavement Noise Generation for Concrete Pavements of Different Textures

Between 2003 and 2010, research on the changes in tire–pavement noise generation over time was conducted on 11 textures applied to portland cement concrete. The initial textures included longitudinal tining, burlap drag, and longitudinal broom. Additional texturing was applied to these surfaces in the form of longitudinal grooving of varying depth and spacing and diamond grinding with varying spacer dimensions, as well as a combination of the two. Since their application, these sections have been routinely monitored for tire noise performance with the onboard sound intensity method. As originally measured in June 2003, the range in level between the surfaces was relatively small at 2.7 dB. At 5 years, the range is slightly smaller at 2.3 dB. During the total 71/2 years of the study, the overall noise performance increased at an average rate of about 0.10 dB per year. The study has shown that for different frequency ranges the change in noise level has displayed some variation; the lower-frequency levels have decreased for some pavements with time, while the higher-frequency levels have increased at a rate higher than the overall levels for all pavements. For the higher frequencies, findings suggested that the increased noise was due to polishing of the surfaces. For the lower frequencies, the reduction in noise level was less pronounced with more variability between textures. For the ground surfaces, some evidence was found that indicated that the reduction might be linked to some loss of larger-scale texture as the surfaces were worn down.

Rapid deterioration of sound level benefits for quieter pavements in Washington state based on the on‐board sound intensity method.

This paper provides detailed descriptions of the three test sections of “quieter” pavement evaluated by the Washington State Department of Transportation (WSDOT) using the on‐board sound intensity (OBSI) method and the unique deterioration of those pavements. Within 6 months of installation, OBSI for the test sections were not audibly lower than the control sections. OBSI is the predominant metric used to evaluate the success of quieter pavements in Washington State. Monthly OBSI measurements describe the seasonal variability in measured sound levels and highlight more rapid general sound level increases in the test pavements relative to the control. Asphalt mix compositions and installation procedures used in Washington were similar, or identical, to those used in southern states where the same pavements have been successful. Challenges to the success of all pavements in Washington State include studded tires, frequent freeze‐thaw cycles, and cool summers that encourage lower surface temperatures during installation than in southern states. These challenges are particularly significant for open‐graded friction course OGFC pavements as evidenced by spikes in OBSI measurements following seasonal weather events. Parallels between OBSI measurements and structural durability measurements are described in detail.

On‐board sound intensity measurements and results in Florida.

This paper describes an investigation of on‐board sound intensity (OBSI) and concurrent wayside sound levels along multiple roadway surfaces in the state of Florida. By conducting concurrent sampling of the OBSI and wayside noise not only were insights into the pavement texture noise generation at the tire/pavement interface possible but direct comparisons allowed findings on the propagation characteristics as well. Measurement values, pavement rankings, multiple findings, and preliminary statistical modeling will be shown.

Pavement characteristics affecting the frequency content of tire/pavement noise

Tire/pavement noise is a major contributor to traffic noise at highway speeds. Annoyance is more closely related to frequency content than to overall A-weighted noise levels, therefore spectral content analysis of tire/pavement noise is an important consideration. A study conducted in California measured the noise levels of different mix types and the pavement characteristics affecting noise levels as determined by on-board sound intensity (AASHTO TP 76-08). Data was collected on dense-graded asphalt concrete mixes (DGAC), conventional open-graded mixes (OGAC), open-graded rubberized asphalt concrete mixes (RAC-O), and gap-graded rubberized asphalt concrete mixes (RAC-G) with ages less than 8 years old. This paper evaluates the effects of pavement characteristics including the air-void content, gradation properties, rubber inclusion, roughness, texture, pavement surface condition, and age on one-third octave band noise levels. This research confirmed that macrotexture and IRI, which are associated with the impact and shock mechanisms, increase the noise levels at lower frequencies. Higher air-void content, associated with the air pumping mechanism, reduces the noise levels at higher frequencies.

Evaluation of Test Variables for Onboard Sound Intensity Measurements

As a portion of the overall research work for the NCHRP 1-44 project, an examination of test variables was conducted for the onboard sound intensity (OBSI) method of measuring tire–pavement noise at the source. The intent of this investigation was to provide guidance on test variables for users to determine the control limits needed to implement the OBSI procedure. An extensive review of literature about onboard tire noise measurement methods identified pertinent variables that could affect the repeatability and reproducibility of the measurements. The sensitivity of OBSI results to variations in pavement temperature, the configuration of the OBSI measurement fixture, tire inflation pressure, test vehicle type, test speed, and load were measured. The testing was done on both asphalt and cement concrete pavements with two different test tires: the ASTM standard reference test tire and the Dunlop SP Winter Sport M3 tire. This paper summarizes the evaluation and results of the test parameter investigation, the information obtained, and the implications for development of a rational test procedure.

Estimation of Vehicle Pass-By Noise Emission Levels from Onboard Sound Intensity Levels of Tire–Pavement Noise

As a portion of the overall research work for NCHRP Project 1-44, field tests were performed on in-service pavements to demonstrate the applicability of the onboard sound intensity (OBSI) method for quantifying the effect of different pavement types in relation to total vehicle noise emissions measured with the controlled pass-by (CPB) and statistical pass-by (SPB) methods. Testing included the simultaneous measurement of OBSI on two specific candidate test tires, CPB on test vehicles equipped with those tires, and SPB of both light and heavy-duty vehicles. With the SPB data, the relationship between OBSI tire–pavement noise and average vehicle noise emissions were examined for both light vehicles and heavy trucks. To account for site-to-site variation, pass-by results were normalized by using the measured relationships between OBSI and CPB levels for each site. On the basis of these results, it was found that SPB levels for both light vehicles and heavy trucks could be predicted accurately with a standard deviation of 0.8 dB for both vehicle categories for an average of sites that used OBSI data obtained from either of two candidate light-vehicle test tires.

Noise evaluation of various pavement textures on new Portland cement concrete

Tire/pavement noise measurements were made on a newly constructed, unopened portion of California State Route 58 that bypasses the City of Mojave. Initially, three different Portland Cement Concrete surface textures were tested including longitudinally tined, burlap drag, and longitudinally broomed. Afterwards, eight test sections of the original pavements were ground and/or grooved to various surface texture geometries and the noise measurements repeated on all eleven pavement textures. Noise measurements were made near the tire/pavement interface using the on-board sound intensity (OBSI) method and at the wayside using limited, controlled vehicle pass-bys. Interior noise testing was also done for comparative purposes. Audible slaps from the concrete joints were also isolated in the OBSI recordings of the test surfaces. Noise from the slaps was also clearly apparent in the vehicle pass-by data. The effect of grooving/grinding operations on joint slap was also evaluated

Measuring and modeling tire-pavement noise on various concrete pavement textures

It is well accepted that pavement texture affects tire-pavement noise. Furthermore, there exist a large number of unique nominal concrete pavement textures to choose from, and with tire-pavement noise an important pavement surface characteristic, pressure now exists to select textures that are quieter but do not compromise safety and to some degree, durability. To assist in this optimization process, improvements are needed in the efficiency and accuracy of texture measurement, along with the means to characterize concrete pavement texture in such a way that is more relevant to the potential for tire-pavement noise. To illustrate improvements being made in measurement technology, an innovative robotic texture measurement system termed RoboTex is described herein. RoboTex consists of a line laser machine vision sensor fixed atop a remote-controlled robotic chassis. The system is capable of collecting three-dimensional macrotexture data with a spatial resolution of approximately 0.4 mm2 and a height resolution of 0.01 mm. For tire-pavement noise measurement, On-Board Sound Intensity (OBSI) has become the de facto measurement standard in the USA. While most measurements to date have been conducted at 60 mph using a Goodyear Aquatred III test tire, recent standardization is migrating towards the new ASTM F 2493 Standard Reference Test Tire (SRTT). Coupling texture and noise data, collected with RoboTex and OBSI, respectively, is serving to advance the state of the art. The ultimate goal is to identify the fundamental links between texture and noise. In the interim, more relevant phenomenological links are sought that have the potential to be expanded to more fundamental models as more is learned about these complex phenomena. This project utilized data collected on over 1000 unique concrete pavement test sections located throughout North America under sponsorship of the National Concrete Pavement Technology Center at Iowa State University, Federal Highway Administration, American Concrete Pavement Association, and now a consortium of State Departments of Transportation. The specifics of these measurement systems, and analysis techniques used to link the results, are described herein

On-board sound intensity testing of PFC pavements in Texas

This paper presents results of tire/pavement noise testing performed on Texas pavements during 2006 and 2007, by means of the on-board sound intensity (OBSI) procedure. Roadside measurements with sound pressure level (SPL) meters were also performed. The pavements tested were primarily of the New Generation Open-Graded Friction Course type, also known in Texas as Permeable Friction Course (PFC), a permeable asphalt design with air voids in the area of 18 percent. There were also some tests performed on dense-graded asphalt pavements, and on concrete pavements. Because of their relatively high air void content (which increases their acoustic absorption), and sometimes the inclusion of crumb rubber in the mix (which decreases its stiffness), PFC pavements also exhibit the fortuitous side effect of reducing noise, both inside the vehicle and at the roadside. Therefore, these pavements are increasingly being studied as �quieter� pavements to verify their feasibility as an alternative to the construction of noise barriers.

Long-term noise performance of open graded asphalt concrete (OGAC)—Results of 10-year long study

During June and July of 1998, an open grade asphalt concrete (OGAC) pavement overlay was applied to a 5.6-mile (9-kilometer) stretch of aged dense graded asphalt concrete (DGAC) along Interstate 80 to the east of Davis, California. Beginning in 1998, noise conditions have been monitored by Illingworth & Rodkin as part of an ongoing study conducted by the California Department of Transportation (Caltrans) to evaluate the long-term effects of highway pavement types on traffic noise. Noise evaluation of the OGAC pavement was conducted using the continuous flow traffic time integrated method (CTIM) of measuring traffic noise levels at locations adjacent to the roadway and the on-board sound intensity (OBSI) method of measuring tire-pavement noise close to the tire-pavement interface. Measurements were conducted on more than 70 days over the past 10 years, resulting in a total of more than 275 hours of noise measurements and generating an extensive data set. This paper focuses on the results of the OBSI and CTIM measurements. Results discussed in this paper include; 1) a comparison of the acoustical performance of the OGAC pavement to the baseline DGAC and other pavement types, 2) a description of the effects of aging of the OGAC pavement on acoustical performance, and 3) a description of seasonal trends in noise levels based on the data set. Based on the noise measurements, the OGAC pavement initially resulted in noise levels that were about 7 dB below those measured for the baseline DGAC pavement and maintained these quieter characteristics through 10 years, with only a slight increase in noise levels over time.

Principal Components Regression of Onboard Sound Intensity Levels

Roadways paved with open graded asphalt mixes typically generate lower traffic noise levels as compared to other types of pavements. A program was initiated in 2005 in California to evaluate the effectiveness of noise reducing surfaces over time and the pavement characteristics affecting those noise levels. In this study, tire/pavement noise was measured using the onboard sound intensity method. Data were collected on four different types of mixes: conventional open graded asphalt concrete, rubberized asphalt concrete that are open graded, rubberized asphalt concrete that are gap graded, and dense graded asphalt concrete mixes. A total of 72 field pavement sections that were at that time less than 8 years old were included in the study. Various pavement characteristics were measured and their effects on noise levels were evaluated using principal components regression, in addition to ordinary least-squares regression. This research confirmed that open graded pavements exhibit reduced tire noise compared to dense and gap graded mixes and quantified this reduction for typical mixes in California.

Evaluation of the ASTM Standard Reference Test Tire for purposes of standardized measurement of on‐bound tire/pavement noise

Currently in the US, efforts are underway to develop standard methods for on‐board sound intensity (OBSI) measurement of tire/pavement noise. Up until recently, the default standard tire was the Goodyear Aquatred 3 tire originally selected due to its apparent similarity to Tire A specified in the ISO CPX procedure. Because of longer‐term availability, the ASTM Standard Reference Test Tire (SRTT) is the primary candidate for replacement of the Aquatred 3. Issues of concern for the SRTT include tire‐to‐tire variation, the relation of the SRTT to previously used reference tire, and the period required for stable test tires. To address tire‐to‐tire variability, six SRTT's were tested on variety of asphalt (AC) and Portland cement concrete (PCC) surfaces. These included four new tires and two that had been in use for some time. Two of the new tires were retested with increasing use to examine any break‐in period effect. For comparison, the older Aquatred 3 was also tested on these same surfaces using both OBSI and controlled pass‐by measurements. The results of these measurements are presented along with their implication to for reference tire selection.

Evaluation of effects of pavement characteristics on the OBSI levels using Principal Components Regression

Tire/pavement noise is a major contributor to traffic noise at highway speeds. Tire/pavement noise is affected by different pavement properties. A study conducted in California measured the noise levels of different mix types and the mix characteristics affecting noise levels. In this study, tire/pavement noise was measured using the on‐board sound intensity (OBSI) method. Data was collected on four different types of pavement mixes: conventional open graded asphalt concrete (OGAC), rubberized asphalt concrete that are open graded (RAC‐O), rubberized asphalt concrete that are gap graded (RAC‐G), and dense graded asphalt concrete mixes (DGAC). A total of 72 field pavement sections were included in the study, all of which were less than 8 years old at the time of the measurements. This paper evaluates the pavement characteristics affecting noise levels using principal components regression. This technique was used due to the multicollinearity found among the variables. Two principal components were extracted from the measured parameters such as air void content, gradation properties, pavement roughness, age, and pavement surface condition.

Acoustical Absorption of Porous Pavement

Acoustical absorption coefficients of more than 140 pavement cores were obtained by the impedance tube method with two microphones and cross-spectral analyses. The effectiveness of the impedance tube in predicting noise reduction for different mixes was evaluated by comparing the correlations between onboard sound intensity levels and absorption. Theoretical predictions of acoustical absorption due to friction between air and porous matrix and thermal relaxation were compared with measured results for an idealized porous structure. The model was used to infer porosity, tortuosity, and pore size from measured acoustical absorption spectra for manufactured porous asphalt and extrapolate test results to nonnormal angles of incidence, assuming isotropy of the porous structure. This model will help improve mix designs to increase the absorption of pavement surfaces and can be used to estimate porous pavement properties.