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Sabine's equation gives the time for sound to decay by 60 dB: T60 = 0.161V/A, where A is surface area times average absorption. A 250 m3 room with 240 m2 of surface at 0.25 absorption reverberates for 0.67 s - good for speech. Adding absorption is the only way to shorten it, since volume is usually fixed.
Sabine's equation
T60 = 0.161 V / (S x alpha)
Absorption
A = surface area x average absorption coefficient
About 0.4-0.6 s for speech and studios, 1.0-1.4 s for a multipurpose hall, and 1.8-2.2 s for orchestral concert halls.
Absorption coefficients fall at low frequency, so T60 rises there. Bass traps and thick porous absorbers are needed rather than thin panels.