Practical Acoustics – facts, not marketing, by Ultrafonic.

We get asked over and over about how to design soundproof walls. The reason varies from recording studios to noisy neighbours. Sadly, there are a lot of myths surrounding soundproofing, most of which are aimed at making manufacturers more money rather than giving customers more soundproofing.

Lets start with “sound” insulation batts. There's no such thing. They are batts. Choose any of the manufacturer's technical manuals and find the acoustics section. They will all show similar data because it is simple physics that has been lab tested and calculated to death.

An empty cavity is bad. However, much more than a simple wall insulation batt only yields a very small increase in soundproofing (typically 1dB) but the cost is much higher. For example, in the table below, a 10mm plasterboard cavity wall on a 70mm stud gets Rw 39 with a Gold Batt but only 1dB more with a Soundscreen Batt.

Have a look at the price difference below that! And these are just examples from public websites selling insulation. There is no real difference between manufacturers. If anyone has other data and prices to contribute, please do. We'll work on adding more over time.

So instead of spending lots of money on very little gain in performance, perhaps we could find other soundproofing materials or techniques that give us more “bang for buck”?

Look at the last graph to see what a huge difference sealing gaps makes. Sealant is cheap and quick to apply. Making the wall airtight by sealing all of the edges and penetrations is likely to give much bigger soundproofing increases than cavity insulation other than a simple batt.

To see how to seal the wall properly, click here

Out of interest, you can also compare how little extra soundproofing you get on bigger studs. In this case you spend more on wider studs and lose floor space.

R2.0 Insulation Batts 430mm - wall & floor pack 22 

cover per pack 9.0m2

- $5.85 per square metre for Rw39

$52.69 

R2.0 Soundscreen Batts 1160x430mm 8 batt pack 

Each pack covers approx 4.43m2 when installed
- $11.40 per square metre for Rw40

$50.52 

Nearly double the price to go from Rw39 to Rw40

Effect of sealing on level of soundproofing