Noise, which is defined as unwanted sound, is present everywhere whether at home, in an office, or on the road. Highway noise is one such noise that has become a serious issue in many cities in the United States. In an effort to mitigate highway noise, local, state, and/or federal agencies typically construct noise barriers adjacent to the highway. These barriers effectively reduce the noise heard by those located behind the barrier, but this method of noise reduction can come at a cost of up to $290/m2 in some cases. In addition, some sound barriers are not aesthetically pleasing to the public. An alternative to constructing noise barriers is to address the highway noise problem at the source with the use of sound absorbing asphalt mixtures such as open graded friction courses. The use of crumb rubber modified (CRM) asphalt mixtures have also been identified as having the ability to reduce the noise from the tire/pavement interface. However, there has been limited research comparing the sound absorbing benefits of CRM asphalt to the same mixtures produced with conventional binders. Results of this study have the potential to add to the attractiveness of CRM asphalt as a paving material, which has already shown to be a more durable paving material. The scope of the project will include:

1. Conduct mix designs using CRM binders and the conventional alternatives (e.g., PG 64-22 or SBS modified PG 76-22) combined with aggregates from three different sources for the following mix design types (18 mix designs):
   1. 9.5 mm surface course
   2. 12.5 mm surface course
   3. 12.5 mm open graded friction course (OGFC)
2. Measure the sound absorbance of the above mixtures using laboratory methods.
3. Measure the following properties of the mixtures listed in Item 1 that potentially effect the sound absorption:
   1. Permeability
   2. Surface texture