A method of forming a monolithically fabricated sound absorbing structural precast concrete noise barrier panel comprising a sound absorbing layer of specialized raw materials. The method includes providing a sound absorbing layer that is a blended mixture of an aggregate, granulated rubber, chemically treated wood particles, cement, pozzolans, water, air entraining admixture, and water reducing mixture; placing the sound absorptive layer ingredients in a form mold; compressing the ingredients to a preset density; backing the compressed ingredients with reinforced structural concrete; and curing the backed and compressed ingredients.