Hoarseness is caused either by condensation or droplet formation in the wind tunnel, or by a too swollen block
In the case of hoarseness by droplet formation, anticondens can be dripped into the wind tunnel and distributed over the block and channel superlattice
Here it reduces the surface tension of the condensed water: it does not form any disturbing droplets, but flows off as a smooth film
The "hoarseness" of your flute can be effectively prevented