I suspect that the filter material absorbs a little noise too.  Don't know
why these were designed in, prolly the government........
Randy Bergum

Steve Hoge wrote:

> John C. Iseman wrote:
>
> > It also appears that they  get clogged with dust etc.,
> >which may inhibit their functioning.
> Mine were so dried out, crumbly and clogged that I pulled them out
> entirely, hoping to get better air flow-thru.  Marginal improvement, if
> any.
>
> -Steve Hoge
> '89 Syncro
> '89 Syncro Westy Woemobile