How much do accoustic tiles help?
Plasterboard is quite reflective, actually.

Armstrong states that their "High Noise Reduction Coefficent" tiles absorb 70% or more of sound energy striking the surface. One version claims a NRC of 0.90, which would appear to imply 90% of sound energy absorbed. That probably is within a specific frequency range - I rather doubt the effectiveness of acoustic tile for low bass energy (musical) for instance. However, that probably smiles upon your application as it's likely weighted for human voices, given the typical use of the product.

As such, yes, they absorb sound, but check the NRC before investing in cheap acoustic tile, as it may not be inexpensive, just cheap, if the NRC is too low...