Since you have already established a low opinion of the manager before he arrives, why don't you call back and request he bring a meter with him? No need for you to bad mouth anyone. I'm geting tired of society deteriorating to the point that bad manners has become the accepted norm. Learn how to address and resolve conflict or concerns without resorting to being confrontational and angry.
I have solved noise problems in museums, libraries, casinos, music studios and have not needed a db meter in over 22 years. A db meter will not give the tech any information as to the how or why there is a noise problem. Nice, maybe. Necessary, no. Noise issues are a failure in design, installation, or equipment. How much noise is acceptable varies and the amount of noise is usually proportional to the budget of the client, and residential is usually low budget. Let the company do their job and stop nit picking about how they should do it.
My point, that completely allude caslon, is that with a decibel meter I can usually prove positive that there is no problem with the sound level of an HVAC system even though there is clearly a problem that just does not equate to the decibel level. I have no further need to continue attempting to aid a person who is so arrogant and disrespectful of others. I do however wish caslon good luck with his problem. With such a defeatist attitude, luck is surely going to be needed.
We have customers that must be related to bats for hearing noises to complain about. So for us a db meter really won't help because they only here the noise when he's in bed alone and she is in the bathroom over the bidet.
As for as what tools the install manger shows up with; as a home owner I won't care if he used a Ougi board and a Voo Doo doll as long as the problem is corrected.
Except that damn short run 8" from the attic plenum to my living room duct.
Damn...that is such a short run an elbow. I can almost reach down the metal box to the plenum.
How about I have them keep all my ductwork as it is, but do something about that elbow to the plenum.
Like...put an elbow going the opposite direction and use 10 feet of flex duct to mosey on back to my living room duct box. To lenghten that previous "short" run from plenum to my LR.
That is what I am going to propose.
Okay, we get it.
You're disgusted with the short duct run to your living room. You're upset about noise. You're weary of your living room being a wind tunnel. You think the solution is to make a longer run of flex duct for the same supply register act as a sound attenuator.
We get it.
But...that's not the answer. If your HVAC guy is balking at selling you the correct solution, the one beenthere continues offering, find someone else. On average, residential techs/owners operate primarily by "hands-on" knowledge and training, which in itself is not bad. BUT...relied upon too heavily, situations like yours can throw the hands-on guy for a spin, whereas the guy that has a good balance between hands-on and theory will likely arrive at the correct solution. From that point it then becomes a matter of convincing the customer to pay for it. Then the tech has to switch gears and become a salesman.