Sound transmission is measured by Weighted Sound Reduction Index (Rw) – the number used to rate the effectiveness of a soundproofing system or material. In conjunction with the Rw value, the Ctr is an adjustment factor used to account for low frequency noise. The higher the Rw+Ctr value, the less chance you have of hearing the noise.
Acoustic effectiveness is measured through AAAC star ratings. The higher the rating the more the sound is reduced.
Between Floors
Hebel Powerfloor
Budget: 15k to 30k+
Powerfloors are generally considered the best product (other than a concrete poured floor) for sound insulation. There is however mixed reviews online about their effectiveness and my advice would be to do some research on this through other forums as well as Facebook groups. The Powerfloors also help with different types of noise transfers but not all.
Details extracted from Hebel data sheets
| Composition | Rw | Rw + Ctr |
|---|---|---|
| Panel only | 36dB | 33dB |
| Commercial Floor Carpet Ground Floor Enclosed | 33dB | 30dB |
| Commercial Floor Carpet 2nd Storey Gyprock Ceiling (CSR 822) | 57dB | 50dB |
| Commercial Floor Timber Floating Ground Floor Enclosed | 37dB | 33dB |
| Commercial Floor Timber Floating 2nd Storey Gyprock Ceiling (CSR 822) | 57dB | 48dB |
Underlay
| Product | AAAC Rating | Thickness | Price |
|---|---|---|---|
| AngelStep Gold 4 | 5 | 4mm | $13 p/m2 |
| AngelStep Gold 8 | 6 | 8mm | $64 p/m2 |
| AngelStep 48P | 6 | 8mm | $99 p/m2 |
| AngelStep 250 | 6 | 4mm | $21 p/m2 |
| Regupol 5512 | 5mm | $17.5 p/m2 | |
| Airstep | |||
| Pro-Insul Foam Matting | 5 | 2mm | $6.60 p/m2 |
| 2mm Green | 4 | 2mm | $3.85 p/m2 |
| 3mm Silver Foam | 4 | 3mm | $2.2 p/m2 |
Insulation
A common mistake people make when deciding on sound insulation between floors is to look at the R values. R values are used for thermal measurements. For sound density is the key measurement to use which is measured by a number of properties like density per kg and STC ratings (how much noise travels through the material)
Bradford SoundScreen is a common product used for sound insulation.
Resilient/Furring Channel and Sound Isolation Clips
Budget: Sound Isolation clips: $6 per clip and roughly 3 p/m2 or $18 p/m2
These are used to help with impact noise as they help decouple the drywall from the structure. The resilient channel aka. furring channel, will absorb some of the impact and the sound isolation clips improve this further.
The isolation clips are the most important part of the construction as the do the work of isolating the drywall from the timber frame. You will likely need 2 isolation clips per m2 but theres a few factors that go into this. You can get a rough idea through the IsoStore Calculator
Comparison of noise reduction from different materials
As you can see from the table below the different in noise reduction between Bradford SoundScreen and Bradford Gold Batts can be negligible. Bradford have confirmed this however the way Soundscreen is manufactured it has a woven composition. Depending on your stud/joist thickness you may decide to save costs by choosing the Gold Batts instead.
| Area | Material (Density) | Thickness | Lining | Rw / Rw+Ctr | Bare Floor Ln,w | Carpet + Underlay Ln,w |
|---|---|---|---|---|---|---|
| Ceiling | Soundscreen 2.0 (25.7kg/m3) | 70mm | Gyprock 10mm | 40/32 | 75 – 80 | 60 – 65 |
| Ceiling | Gold Batts 2.0 (24kg/m3) | 90mm | Gyprock 10mm | 40/32 | 75 – 80 | 60 – 65 |
| Wall | Soundscreen 2.0 (25.7kg/m3) | 70mm | Gyprock 10mm | 34/25 | – | – |
| Wall | Gold Batts 1.5 (24kg/m3) | 70mm | Gyprock 10mm | 33/24 | – | – |
| Party Wall | Soundscreen 2.5 (24kg/m3) | 88mm | Superchek 10mm | 66/54 | – | – |
| Party Wall | Gold Batts 2.0 (24kg/m3) | 90mm | Superchek 10mm | 65/53 | – | – |
| Party Wall | Gold Batts 2.7 (24kg/m3) | 90mm | Superchek 10mm | 63/51 | – | – |
| – | Soundscreen 3.1 (24kg/m3) | 110mm | – | – | – | – |
Joists with 10mm Gyprock
Joists with furring channels (10mm Gyprock)
Joists with resilient mounted furring channels
Joists with furring channels (13mm Fyrchek)
Walls
For airborne noise dense insulation can be used in the wall cavity. The R rating is often confused with sound insulation, you should just consider the density of the material used instead and if they have Rw ratings then this is what should be used to compare.
Walls can use sound isolation clips and resilient mounts too.
Windows
To minimise sound from going in or out of a room thicker laminated glass is more effective than double glazing. For double glazing to be effective you require a space of over 100mm which isnt possible for most standard residential homes. To reduce sound from a subwoofer in a theatre room for instance you would need more density ie. thicker windows.
Common Materials
Plasterboard (Gyprock)
There are different thicknesses available which can help with sound insulation and can be used in walls and ceilings. Check the STC ratings to find out how important this is.
Theres a few different options with plasterboard used in a home.
| Type | Thickness | Density |
|---|---|---|
| Standard Core Plus | 10mm | 5.7 kg/m2 |
| Soundchek | 10mm | 9.7 kg/m2 |
| Soundchek | 13mm | 13 kg/m2 |
| Supercheck | 10mm | 10.4 kg/m2 |
| Fyrchek | 13mm | 10.5 kg/m2 |
| Fyrchek | 16mm | 12 kg/m2 |
Another option thats effective is the use acoustic green glue where you can glue two plasterboards together.
Technical Details
Theres a few different factors to consider with soundproofing a home. An opinionated view of this is that you probably dont want to hear footsteps above (structure-borne/impact noise) and people speaking/tv (airborne noise).
Structure-borne noise
Structure-borne noise includes footsteps on hard floors, scraping chairs and dropping objects. For this type of noise, Australia uses a standard measurement called the weighted standardised impact sound pressure level LnT,w.
Airborne noise
Airborne noise includes sounds that travel through the air like a TV and people speaking/shouting. Different methods of soundproofing are required to reduce this.
Rw
The Weighted Sound Reduction Index (Rw) is used to rate the effectiveness of a soundproofing system or material. Increasing the Rw by one translates to a reduction of approximately 1db in noise level. Therefore, the higher the Rw number, the better a sound insulator it will be.
Rw+Ctr
Ctr is an adjustment factor which is used to account for low frequency noise – typically the biggest problem with sound insulation. Ctr is always a negative number, so the Rw+Ctr will always be less than the Rw value. Many sound insulation types will represent how effective they are by displaying the Rw/Rw+Ctr values together.
Related Articles
CSR Red Book – This is a great resource with technical information about the different combination of their materials including insulation
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