ABSTRACT
The absorbers and diffusers discussed in previous chapters have difficulty altering low frequency sound. Low frequencies have long wavelengths, which means the absorbers and diffusers have to be large to perturb or absorb the wavefronts. This can be overcome to a certain extent by the use of resonant structures, most often used in bass absorber design, but in recent years there has been growing interest in the use of active control technologies to absorb or diffuse low frequency sound.
