Exhaust Catalyst

The catalytic converter for cleaning up exhaust gas was invented by Eugene Houdry (1956), probably best known for inventing a process for cracking crude oil.

A catalytic converter is known to have two distinct acoustic effects:

Reactive Effect Acoustic wave reflections caused by cross-sectional area changes within the catalyst can and the catalyst brick.

Resistive Effect Acoustic wave dissipation caused by viscous losses. The resistive effect is frequency-dependent, that is, the catalytic converter acoustic transmission loss due to the resistive effect would increase with increasing frequency. It emanates from the multi-tubular brick of catalyst material. Other engine exhaust system components have resistive elements, such as the absorptive packing in a muffler.

See also: Exhaust.