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attenuation at·ten·u·a·tion (ə-těn'yōō-ā'shən)
A dilution, thinning, or weakening of a substance, especially a reduction in the virulence of a pathogen through repeated inoculation, growth in a different culture medium, or exposure to heat, light, air or other weakening agents.
The energy loss of an ultrasonic beam as it passes through a material.