The lure of a cure-all is well known. No complicated diagnosis, no visit to a specialist, no "surgery". People prefer simple, quick and easy, and salespeople know that.
But in our view, the only simple "cure" is the one that is effective the first time.
Noise transmission isn't a single "disease", and can't be treated without a thorough investigation of the sound source, the characteristics of the sound and the building construction. And the "cure" most often involves common building materials, when "soundproofing" is needed at all. Sometimes the only effective course is to treat the noise source itself. But don't expect an online or over-the-phone "consultant" to recommend a new bearing for the exhaust fan on your roof.
No material or method is effective in all circumstances, and some of the "soundproofing products" sold on the Web are ineffective in all applications. Expensive too. But they promise a "painless" experience for the buyer and that's a powerful incentive. We would advise you to remember that you that nothing is as expensive, messy and time-consuming as doing a job twice. Get competent advice first, from an independent consultant.
An independent consultant has no products to sell and no workmen to keep occupied. His interest is the same as yours: the most effective and efficient solution. And he will have the necessary tools at his disposal: testing, inspection and experience.
Expertise and proper measurements can save time, trouble and money.
Read "A Case Study in Two Letters": A cautionary tale of a job done twice and a lawsuit as told in two letters of thanks from a client (finally) enjoying some quiet.
In another twist on "sales-consultation", we have recently heard of companies offering “Remote Sound Testing”; they send you a sound measuring device to allow them to “consult” without coming to you. They then offer solutions, featuring - not surprisingly - products they sell themselves. One company offers a credit for their multi-thousand dollar report, but read the fine print: it only applies to a purchase of at least $10,000 of their materials.
Anyone who claims that such a device can replace the need for an independent acoustic consultant is doing you a serious disservice. They have neither the infomation nor the independent perspective needed to make the proper recommendations.
By carefully investigating in person, I frequently find simple ways to solve problems. But I have to inspect under, over, around, in-between and inside of hidden cavities. They ask you to send a few pictures, none of which will show the compressor unit in the floor above with the faulty mounting.
I use a stethoscope, an accelerometer, a spectrum analyzer and my ears to track down the noise as I move around the room and adjoining spaces. They ask you to put their gadget in a handful of predetermined locations.
I calibrate my equipment at every job; Their gadget certainly will not be.
They sell a particular line of products; I can recommend the most efficient solution, whoever might sell it. That might new bearings for the fan motor rather than an "acoustic" material. Or it might be Sheetrock. Sound isolation is more about techniques than specific "special" materials.
One of these services claims to be “guaranteed”, but their literature says that they “can not control whether or not the end result will be well received”.
These types of errors make it clear that anyone who offers such a remote consulting service does not have the experience to properly "consult" for you.