Acoustics of straw bale structuresEdit
A report carried out in Denmark (Halmhuse - Udformning og materialeegenskaber Straw_Bale_Construction/Resources/Technical_Studies) measured the sound insulation performance of a wall in an existing home. The measurements were carried out in a wall with both horizontal strawbales (where the straws were perpendicular to the plane of the wall) and on a wall with vertical strawbales (where the straws were parallel with the plane of the wall). In both instances there were approximately 40 mm of clay rendering on each side of the wall. In the first instance the sound insulation (expressed with the sound reduction R’w) was found to be R’w=52 dB and in the second instance to be R’w=46 dB. The second result is affected considerably by bed-lofts in both rooms that were carried by a wooden framework in the wall. DELTA  estimates that an construction focusing on reducing the transmission due to openness in the construction (flank transmission), would be able to obtain values of 53-54 dB, regardless of the direction of the straws. For comparison it can be mentioned that the requirement of the Danish Building Regulations in 2004 for a wall that separates apartments in housing blocks is 52 dB, while the requirement for walls between non-detached houses built in accordance with the Danish Building Regulations for Small Houses is 55 dB. It should be mentioned that walls that only just satisfy these code requirements are not always perceived as satisfactory by the residents. For most other applications the strawbale-walls will have satisfactory sound insulation performance. Within a dwelling the sound reduction is particularly satisfactory and the actual sound insulation will most likely be determined by the doors.
A less formal study was made of a recording studio in Sydney by John Glassford of Huff 'n' Constructions. This has yet to be added.
These links are what I have for SB recording studio's