Sound deadening in an A7...

[squeak]

Factory soundproofing in Austin 10s was to attach sundela board covered in hessian to the bulkhead.  Generally a bit tatty after 80 odd years absorbing oil!

I assume sundela board  is another name for the product we called Nelson board which was a shredded leather and bitumen composite. Black and flexible, a bit too flexible when damp as seen in old door trims. This was commonly used on the inside firewalls of vintage cars, in association with a layer of jute felt/carpet underlay, up against the metal.  It would be held in place by a few sort of, long, soft, bifurcated rivets and the tangs folded over on the engine side. 
This is the method I used in my 29 Dodge, and I extended the job with underlay only glued to all inside surfaces of the cowl back to the doors. Some say that a sound deadening mat is also useful on the underside of the bonnet.  cheers  Russell