The Difference Between Sound Isolation and Insulation

There is a distinct difference between sound isolation and insulation, the same as the difference between water resistant and water proof.  Insulation absorbs frequencies, and isolation keeps them from getting into or out of your recording space.

Building a recording studio space in an existing structure limits the amount of sound isolation possible.  A wood framed house is difficult to isolate because the materials are light, and there is only one barrier between the sound and outside.

In order to effectively isolate your studio you would have to decouple the walls and ceiling.  This can be done by building another wall inside the existing wall, and another ceiling on top of that, essentially building a box inside of a box (this is called decoupling and will be covered in another segment). This method is horribly impractical in your home; it would reduce your space dramatically and cost a fortune.  And even after you build your room in a room, low frequencies can still get through.

Achieving isolation requires mass.  Sand filled concrete blocks, poured concrete, lead, and depleted uranium are all effective in isolation of sound.  Again, horribly impractical, and would cost a fortune.  And you would still need to build a room inside a room to achieve total sound isolation.

Considering the cost of total sound isolation, let’s talk about what you can do.  Fill your walls with insulation, the more dense the better.  The drywall is where you will gain as much mass as possible by layering your drywall sheets with MDF (Multi Density Fiberboard).  Layer your wall with Drywall, MDF, and then a last layer of drywall.  Secure each layer with screws and glue; the glue will reduce the amount of vibration between the layers.  Any more than that is overkill because it is still not isolated.

Now that you have a realistic idea of what works, let’s talk about the sound control.  You can have a studio, 1,000 feet underground, and it will still sound terrible if you do not control where your sound is going.
To treat acoustical problems in your studio space, you will first need to have an understanding of how sound travels and reacts to its environment.  Frequencies are measured in hertz, and one hert is one cycle per second

This is what a frequency cycle “looks” like.

Higher frequencies reflect off of objects, such as a wall, and lower frequencies go around and through objects.  High frequencies reflect because the sound wave is small, for example, 2,000hz is 6.75 inches in length.  This means it does not move much air, and is not strong enough to transfer its energy through the wall.  On the opposite end of the spectrum, low frequencies are larger and move more air.  A 20Hz wave is 56 feet long, which is longer than a semi trailer.  So when a 20Hz wave hits a wall, it will cause the wall to vibrate and transfer that wave’s energy.

Controlling all frequencies requires insulation and absorption to be placed in strategic areas around the room (This will be covered in another segment).