Soundman2020 - Studio Design Forum

my room absorbs a lot of the medium-low from 200 to 400 hz although I have not treated excessively. My room is 5x4 meters, has a ceiling completely treated with 20 cm of rock wool and a wall treated with only 3 cm of rock wool, all other walls are reflective, how is it possible that the decay time has dropped a lot on those frequencies? two of the walls are in 2 cm plasterboard spaced 4 cm from the original wall, even if it acts as a resonator it should absorb below 200 hz, but how is it possible that there is excessive absorption from 200 to 400 hz? I am attaching the decay time of my vocal booth

Have you moved your listening position to see if it's only canceling at that point?

the absorption you described would target 100hz and up, although how you took the measurements would be helpful.

As Glenn and Dave have pointed out, the dip might simply be due to the location where/how you are making those measurements. It would help if you could describe where you had the mic when you did that measurement, and how you did the measurement.

On the other hand, you said:

a ceiling completely treated with 20 cm of rock wool

. A 20cm thickness of insulation is able to absorb down at least a bit to around 60 Hz, and quite well from 100 Hz up. The entire ceiling is also a large area. So it is quite possible that the dip in decay time you are seeing is partly due to that. But also likely that it is related to the location where you measured it.

- Stuart -