Industrial silencers and mufflers absorb and attenuate noise levels from machinery and other sources for environmental amelioration and regulatory compliance. They use several basic designs. Absorptive silencers and mufflers incorporate sound-deadening materials, fabric and compounds to absorb the noise energy from the flow of gas or air. Reactive silencers and mufflers use complex passages and/or chambers to optimize noise attenuation while maintaining application requirements such as pressure drop, airflow and size. Hybrid designs use both absorptive and reactive design elements, combining airflow path management and acoustical materials to reduce noise. By contrast, active noise cancellation devices use sound sensors to characterize the sound profile and noise-canceling speakers to produce sound 180° out of phase with the airflow noise.