code: static float fromdBlook(float a) {
          int i = (int) (a * ((float) (-(1 << FROMdB2_SHIFT))));
          return (i < 0) ? 1.f : ((i >= (FROMdB_LOOKUP_SZ << FROMdB_SHIFT)) ? 0.f
                  : FROMdB_LOOKUP[i >>> FROMdB_SHIFT] * FROMdB2_LOOKUP[i & FROMdB2_MASK]);
      }
docs: /* interpolated lookup based fromdB function, domain -140dB to 0dB only