Check if you have any leakage in the toilet pan. Most likely the noise is related to the toilet cistern or the plumbing system. If there is any leakage please contact your Plumber and fix the leakage as a first step. In case the noise persist, we can then check again the connections to the bidet.

Remember:
The only other component that we provide, that can actually make noise, is the Dual Check Valve.

You can offer to the customer to buy one and try to replace that to fix the noise.