Soundproofing between floors in wooden house

Hi All.
We live in between two noisy streets in Perth but our main issue is noise transfer from upper to lower floor. The house is solid jarrah hardwood and it was built in 1907. We are restoring they lower floor area I need some advice about the best type of sound insulation to keep the noise from upstairs transmitting to downstairs.
We are creating a Airbnb out of the downstairs part and we are living directly above this new guest area. We have removed the old horse hair ceiling.
The dimensions of the large room downstairs is 6m x 8m and the ibeams which support the joists are 2.2m above the newly poured concrete floor. Obviously there is a lot of street noise but we can't do much about that as we have used single pane glass windows and old doors etc. . You can ignore the walls in this equation also as I will be able to soundproof them sufficiently.

Currently we can hear every footstep that is made upstairs. The only thing that separates the two floors is Jarrah floorboards and 100mm joists. There is no wall to wall carpet upstairs – only rugs.
I did some research via the CSR Gprock RED book and their rep proposed resilient mounts and soundcheck plasterboard and insulation. However, whilst we realise it is the best method, it interferes with the aesthetic of the exposed I beams. By using resilient mounts and furring channels this lowers the ceiling so that almost half the I beams are covered. My wife is a designer and wants these rusty I-beams left exposed.
So the question is if we only use 1 layer of 13 mm sound check plasterboard below the joists then what is the most effective way of filling in the 100mm gap between I beam and floor above so that it attenuates the sound as much as possible? Can we tack or glue another layer of 13mm soundcheck or other material directly to the underside of the Jarrah boards, in between the joists?

The csr gyprock expert recommends R3 gold batts 165mm thick but he is only considering his own products and there must be many more options out there which I don t know about.
Any help would be greatly appreciated.

You should probably consider checking out Green Glue solution with 2-3 layers of 16 mm plasterboard

Thanks Alex

Sounds interesting. Looks like it would work well for walls. Have you used it on a ceiling?

It can be used for both walls and ceiling, pretty much a glue you put between plasterboard sheets.

For footsteps the resilient mounts are needed or you float a new floor upstairs. The height is the real issue it seems.

Thanks Guys Unfortunately, I cant get the resilient mounts happening because of the loss of the aesthetic of the exposed I beams

To reduce noise transfer without compromising the aesthetic of your exposed I beams, consider filling the 100mm gap between the I beams and the floor above with dense, sound-absorbing insulation like rock wool or fiberglass. Add a 13mm soundcheck plasterboard layer directly beneath the Jarrah boards, between the joists, for further sound reduction. Explore alternatives to R3 gold batts, such as higher density insulation or acoustic foam, to find the best fit for your needs.