Question about Corsair Carbide 678C

Good evening, It's true that this case is noisier than it's supposed to be. I used the fans supplied with the case in the following configuration: one SP140 PWM at the rear and two on the top. On the front I have 3 LL120 RGB also from Corsair. All these fans are supposed not to exceed 36dB at full load, which is no more than the Silent Wings 4 from BeQuiet! However, it seems to me that this threshold is exceeded, perhaps because of the design of the case? Should the fan curves be changed? Because they tend to increase in speed very quickly. How have you reduced the noise level of this case? With thanks.