[wayner]

Dead ended resonators look like the same technique used to stop banging water pipes in a house (water hammer).

Essentially a capacitor.

On one of my vintage race bikes we simply inserted a wider diameter pipe mid way down the header pipes to reduce resonance that was causing backflow through the carbs.

(Head pipes exited small, got fat and then went back to small before hitting the collector).

These dead ended resonators remind me of that but later in the exhaust path.