Is the operational noise very loud? Will the noise be multiplied by installing multiple units?

The noise level of the fan is approximately 70-75 decibels. Industrial noise typically exceeds 90 decibels, approaching the volume of general loud speech. Tolerance to noise levels varies among individuals, considering the background noise volume. Installing multiple fans does not result in a multiplicative increase in noise because their operating frequencies are the same, so there is no issue of noise increasing multiplicatively.