A camera muzzle is a muffler, also known as a ‘blimp’, designed to reduce noise generated by film advance and shutter click. They can be soft (sewn) or hard (plastic). Sound suppression is necessary where noise is considered an interruption, such as golf events, court room proceedings or symphonies.
A hard muffler/blimp was designed in the 1960s. These hard case designs use a plastic case cut to accommodate the camera, fit with foam and silicon to baffle the sound. Hard case blimps are very expensive and usually operate remotely. The camera muzzle, made as a sewn item, was designed to be more cost effective and to be used by the photographer (vs. remote operation).