A Few Curtains, a Little Physics, and We're Set

"How can I Make a Room Soundproof?"
wiseGEEK

"Even if one isn't building a recording studio, there are times when a home or business owner will want to reduce the amount of sound coming into, or out of, a room. While many methods are available, choosing one will depend on the room itself and the amount of money the owner is willing to spend.

"To understand how to soundproof a room, it is first necessary to understand a little about 'sound.' Sound is composed of waves that travel through a medium. Some mediums, or materials, are more resistant to sound than others. Air, for example, offers little resistance and is therefore a major contributor to unwanted noise in a room. To soundproof a room, however, more is needed than just blocking the flow of sound through air...."

So far, so good. Then came this:

"...Another source of unwanted noise in a room can come from vibrations. A vibration occurs when a sound wave travels back and forth from one object to another. This can happen, for example, when a sound wave strikes one wall in a room, bounces off that wall, and transfers its energy to the opposite wall. That vibration can create an annoying noise problem...."

The Lemming is pretty sure that the author meant "reverberation" instead of "vibrations" in that paragraph. ("Reverberation: the repetition of a sound resulting from reflection of the sound waves" (Princeton's WordNet))

Still, it's a pretty good introduction to how to deal with a room's accoustics.

More:

"Sound Dampening Curtains - Three Types Of Uses In Your House Or In A Music Studio"
Jason Stark, EzineArticles.com

"There must be a good reason for you to be looking for sound dampening curtains. Sound dampening curtains or soundproof drapes are basically just like the regular curtains, except they are made of thick and heavy, sound dampening fabric, or plastic. Are you a parent of a budding musician who is delighted that their offspring plays a musical instrument or sings, yet would like to get some more privacy in other parts of the house when the kid is practicing? Or perhaps, you are a musician and know that sound attenuating curtains can improve the way your voice sounds or the way your instrument projects its voice.

"Regardless of why you are looking for sound dampening curtains, in this article you will find three types of uses which are good reasons for anyone to purchase them. The types of uses are: Blocking the sound from the outside, Blocking the sound from the inside the room, and Sound absorption. Let's see how these play out with what you are trying to accomplish...."

This article focuses more on the practical aspects of making a room usable for singing or instrumental work. And, has two links near the end - which the Lemming appreciated.

The Lemming had a personal interesting while researching this post. I learned that my youngest daughter isn't satisfied with the acoustics in the room we've assigned as her music studio. Taking a look, I can see why. The six surfaces - walls, ceiling and floor - are hard and flat. Great for dust control, but not so hot for making - or teaching - music.

These two articles were the first resources the Lemming found that weren't geared for industrial applications. The foam-core high-density quilted vinyl sheets I'd found earlier might have contained the sound of a drill press: but the Lemming is nearly certain that his daughter would not have been happy with their aesthetic qualities.