These earth wool acoustic/thermal batts at bunnings are one of about 6 different density acoustic/thermal batts manufactured by Earthwool.
The claim is:
I would expect to get similar performance in wood stud construction with almost any kind of glass wool insulation of comparable density and thickness.
As far as sound absorbance goes it's all about the pore density and the pore size. To reduce thermal transfer you want enough density of cells to prevent convention and as high a total batt thickness as possible.
These have a density of 20kg/m3 which puts then in Earth Wools "High density " range, not sure what others Bunnings sell but its easy to calculate by working on the volume occupied by an expanded pack and dividing that into the pack weight.
Higher density is better since it means smaller pore sizes so lots of tiny little bubbles of of air inside the pack to bounce the sound waves around inside to absorb more sound.
Earthwool do make a 24 and 30kg/m3 batts but you may have to go to specialist places or maybe Bunnings can do a special order.
In comparison, Bunnings R4 ceiling batts
https://www.bunnings.com.au/earthwoo...-pack_p0810333 cost about $6 more for the same area coverage
These have around 1/2 the expanded density of the acoustical ones listed above - that's what generates their R4 versus R 2.5 thermal rating.
You could always pack the R4 batts into half the space and that will double the density and reduce the pore size so it should produce similar sound absorbance as the acoustical batts listed above - but you will lose thermal rating - well it certainly wont be 4 - it might well be 2.5! And pay $6 per pack more for the privilege
My guess is its all the same stuff with the glass fibres spun to different thickness and maybe the acoustic ones use an additive to increase the density of the glass. if you are are interested in heat control then just use the thermal ones - they will reduce a lot of sound anyway. If you are interested in noise reduction then us either acoustic ones as they will reduce heat ingress to some extent anyway.
The selection and use of acoustic batts are as you sound like you know by far the not the end of the noise story. The gaps are critical followed by the cladding and structure you use. If you use a high mass internal cladding with narrow studs spacings this should reflect most of the sound back into the shed so the batts will have to do very little work in absorbing the remaining transmitted sound. The thickness of Plaster board or MDF on narrow studs will then be the deciding factor. Inside the shed reflected sound can be reduced by scattering so the texture of the internal cladding makes a difference.