Basic rules of thumb:

• Speakers form an equilateral triangle with listener's head
• Tweeter at or near ear height
• No speakers close to walls if at all possible

While there is a bit of questionable advice here (read: "get one of the entry-level Monster cables"), most of it is basically solid and generally applicable.

Wired How-To Wiki: How to Set Up Your Speakers

NOTE: The advice in this piece involves cracking open your computer and monkeying around.  This is a good way to break your computer and possibly lose data.  If you're not comfortable with this, please avoid doing anything described in this post! Proceed at your own risk.

First off, this post will assume you're using a desktop, not a laptop.  Although desktops are arguably becoming less common relative to laptops, the steps you can reasonably take to remedy noise from a laptop are quite different, and will be left for a future post.

Noise from desktop computers comes from two main sources: fans and hard drives.  Often fans are the louder of the two, but clicks from a hard disk can also easily ruin a good take.

To reduce noise from a hard disk, the best way is to isolate the hard disk from the case so that the sound dissipates inside the case, rather than efficiently traveling through the rigid metal frame of the case and out into the room.  Some computer cases have built-in rubber grommets that the hard disks rest on.  Of course, if you're reading this bit, your case doesn't, so let's look at a poor man's solution to this issue.

For the advanced DIYer, there is the bungee-cord approach. Although this technique is a bit tricky, it will virtually eliminate hard disk noise from your setup.  It comes to this blog from the incomparable Slient PC Review.  Basically, one builds a small rig inside the case to suspend your hard disk(s) from bungee cord.  Rather than shooting through the metal of the case, and out into the room, the vibrations from the disks dissipate in the flexible cord.   Admittedly, this is a bit involved, and involves modifying your computer case.  Not recommended unless you like that sort of thing.

If you're less ambitious, but still want to mitigate hard drive noise, there is still an effective, and cheap option.  Even if your case didn't come stock with rubber grommets for isolation of the hard disk, there's no reason you can't add some.  This is pretty straightforward.  Get a pack of flexible rubber grommets. The previous link has some for sale, but as a reviewer notes, you can undoubtedly get them cheaper at your local hardware store. Remove the hard drive from your case, and unscrew it from its mounting.  Reassemble it with rubber grommets between the hard disk and any rigid surface.  This should make a marked difference in the amount of hard disk noise you hear. (Editor's note: My case came with grommets and the hard disks are basically inaudible)

Now, we move on to the bigger issue of fan noise.

When computers compute, they generate heat.  As a rule, although not strictly, faster computers generate more heat. Also as a general rule, people working on audio require fast computers. To remove the heat from the CPU and other components, fans are the most cost-effective option.  The more heat, the more fans you need, and the faster you need to run them.  Most computers include at least 2-3 fans, if not more.

The cheapest way to reduce noise from fans is to just get rid of some fans.  Of course, to do this without breaking your computer, it requires a thoughtful analysis of airflow, heat propagation, and so forth.  The gist of it is that you rearrange things (mostly cables) inside the case in such a way that the fans cool more efficiently, allowing you to eliminate one or more superfluous fans. A more detailed discussion of case airflow is a bit out of scope for this blog, but again, we recommend further reading at Silent PC Review. This article in particular has some good information.

An equally cheap way to reduce fan noise is to block noise from propagating out of the case.  Some cases have decorative holes or superfluous vents, which can sometimes be blocked with tape or other material to keep noise in.  It's worth taking a close look at your case for such opportunities.

The second-cheapest way* to reduce noise from fans is to purchase some fan-speed controllers and hook them up to the power cords for the fans inside your computer.  Fan-speed controllers let you slow down your fans by reducing the voltage reaching the fan.  The correct procedure is to install the controller, then use temperature monitoring software to gradually optimize the balance between thermally safe and quiet operation.

*Note: your motherboard may have a feature that allows adjustment of fan speed either through the BIOS or through another utility.  Try this first! If it works, you've just saved yourself a few bucks.

The third cheapest way to reduce fan noise is to invest in new fans.  While not dirt-cheap, this method is effective. Again, a full discussion is beyond the scope of this blog, but basically, not all computer fans are created equal, and some fans are noticeably quieter than others for a given amount of air moved.  I defer to Silent PC Review's recommendations on fans, but caution the reader to shop around as well.   Unsurprisingly, high-quality fans carry a price premium, but for something like $25-75 you can make a dramatic difference in your noise level.

The fourth cheapest way to reduce fan noise is to buy huge heat sinks in order to eliminate fans that are otherwise considered necessary.  This method is actually sort of expensive, but in some cases might be worthwhile.  For example, an audio workstation rarely needs a high-end video card.  However, most discrete video cards have fans that make a huge racket.  For $30+ you can replace your video card with a semi-respectable fanless model that relies on a big heatsink instead.  You also get a fanless cooler for the CPU, but it's not recommended.  Not only would the required heatsink cost quite a bit (probably $80+), you generally need to under-clock the CPU to keep heat under control, which is an unpleasant tradeoff for the typical person working with audio - this makes the computer slower.

For those that are serious about acoustics, a noisy PC is a serious concern.  With a few free or inexpensive steps, this scourge can be mitigated.  While perfect silence is usually difficult and expensive to attain, relative quiet is pretty cheap and easy.  If you're taking the time to improve your room's acoustics, the PC is worth a look as well.

It's also possible to punt and put the computer in an isolation box.  Rather than reduce the noise, you just trap it.  It's an appealing idea, but totally inappropriate for the Poor Man's Acoustic Treatment series - since most commercial isolation boxes will run you 4 figures.  However, hope!  There are some DIY solutions, which we may go into in the future.  Thanks for reading!

In general, you could say that acoustic treatment is about minimizing the influence of sound that isn't coming straight out of your loudspeakers and going directly into your ears. There are two main functions of acoustic material that help accomplish this. Absorption, and diffusion. Absorptive materials stop the sound from bouncing off surfaces, and make sure that it never makes it back to your ear. Diffusive materials scatter the sound in random directions, making sure that the sound has to take a longer and more multifarious path back to your ear.

Books are good for diffusion. Basically, the idea is that the irregular profile of books on a shelf acts as a pretty effective diffuser for sound waves. Look at the shape of a commercial diffuser panel compared to a bookshelf.

(Imagine the bookshelf is full of books.)

So, books are a good acoustic treatment, but to cover any significant portion of your walls, you're going to need a crapload of books. Let's assume we need about 10-20 average-sized books to cover each square foot of wall.  Where are you going to get the hundreds or even thousands of books needed to get some good diffusion going? (I'm going to assume you're not actually planning on reading most of them, so I won't worry about literary merit here.)

There are a few possibilities. Sites like Craigslist.com or Freecycle.org often feature individuals trying to get rid of books.Yard or estate sales might be a good place to find them on the cheap. Church rummage sales invariably have cardboard boxes full of old Tom Clancy hardbacks, and thrift stores might cut you a deal on a quantity of water-damaged romance novels.

Second, ask the local library for their discards. They may already have plans for them, but libraries are routinely forced to dispose of significant numbers of books to make space for more popular or useful titles.

Third, it's a little known fact that bookstores also routinely dispose of mass-market books that don't sell. It's often more expensive to ship unsold books back than throw them out. Instead, they remove the covers and send only those back, as proof that the book in question was not sold, and then dispose of the remainder. If you have a friend that works at a bookstore, it might be possible to get your hands on some of these.

Wait, we're not done.  This is Poor Man's Acoustic Treatment! What is the Poor Man supposed to do about shelving?   You might be able to scrounge up a bunch of free books, but what about the shelves? Bookshelves ain't cheap!

Oh wait, yes they are. The cheapest and most effective mass book-storage method I've seen was the old cinder block-and-board setup. Just  stack boards on cinder blocks until you have the space you need. If you go up higher than about 3 or 4 feet, it's recommended that you attach the top shelves to the wall with brackets. This is particularly suited to this project, because you can customize the sizes of your shelves to treat the exact amount of wall area needed. Shelving isn't free, but it can be done cheaply.

Shelves full of books probably aren't the only acoustic treatment your room needs, but if you cover 20-50% of your walls with books, they'll make a positive and noticeable difference, meaning any further treatment with absorptive material will get you that much closer to the ideal listening environment.

(Sonic Homework LLC is not responsible for anything or anyone that gets wrecked, injured or killed if you build an improper shelving system and are crushed under an avalanche of paperback thrillers.)

Photo by Question Everything @ Flickr