Passive Design

Interior sound-reducing construction should:

• have mass
• discontinue the structure between linings as much as possible
• have internal sound-absorbent material
• have all joints sealed.

Upgrading existing partitions

A standard 100 x 50 mm timber partition provides very little noise reduction. Normal conversation can be heard. Options for better sound stopping include:

• for reasonable noise reduction at low cost – a standard timber partition with additional 9 mm plasterboard on both sides
• for good noise reduction at moderate cost (loud conversation will still be audible) – a standard timber partition with lining removed on one side, sound-absorbing insulation, two layers of 9 mm plasterboard on one side, and an additional 9 mm plasterboard on the other side
• for very good noise reduction at high cost (conversations won’t be audible) – a standard timber partition with lining removed on one side, an additional partition built alongside, sound-absorbing insulation, two layers of 9 mm plasterboard on one side of the new partition, and an additional 9 mm plasterboard on the existing partition.

New partitions

Options include:

• for good noise reduction at low cost – a standard 100 mm x 50 mm timber partition with two layers of 9 mm plasterboard one side, sound absorbing insulation, and one or two layers of plasterboard on the other side
• for very good noise reduction at moderate cost – a staggered stud partition with 50 x 50mm bottom and top plates, 100 x 50 mm offset studs, sound-absorbing insulation, and 12.5 mm plasterboard on both sides.
• for excellent noise reduction at high cost  double wall construction with two 100 x 50 mm partitions with a 10 mm gap, sound-absorbing insulation, and two layers of 9 mm plasterboard both sides.

Heavy solid masonry construction can also be used to provide an acoustic barrier, with the possible advantage of providing thermal mass.

A key to acoustic design is ensuring that there are no gaps or paths in the completed construction through which noise can pass. This means:

• avoiding the need for service penetrations in the acoustic wall
• sealing around the perimeter of the wall.

Ceilings

On new and existing ceilings:

• for improved noise reduction at low cost  add an additional layer of 9 mm or 12.5 mm plasterboard.
• for much improved noise reduction at high cost – a battened ceiling with existing lining removed (for existing ceilings), sound-absorbing insulation, resilient batten fixings, proprietary steel battens, and two layers of 9 mm plasterboard.

Timber floors

Timber floors squeak and transmit footsteps and scraping chair sounds.

To minimise the risk of squeaking, specify that:

• sheet flooring is adhered as well as screw fixed to the joists
• framing is dry (less that 24% MC when the flooring is installed
• timber floor boards are securely cramped and nailed.

Regarding impact noise, standard floor/ceiling construction with particle board or plywood sheets and a 9 mm plasterboard ceiling is the lowest cost option but has low resistance to impact noise (IIC32). Other options include:

• for improved resistance to impact noise (IIC45) at moderate cost – standard floor construction with sound absorbing insulation, a ceiling system with proprietary resilient batten fixings and steel battens, and two layers of 9 mm plasterboard
• for good resistance to impact noise (IIC60) at moderate cost – standard floor/ceiling construction with carpet and rubber underlay
• for very good resistance to impact noise (IIC72) at the highest cost  standard floor construction with carpet and rubber underlay, sound-absorbing insulation, a ceiling system with proprietary resilient batten fixings and steel battens, two layers of 9 mm plasterboard, and carpet and rubber underlay.