The performance of double-glazed windows can be boosted even further where necessary by adding an extra heavy-glass or acrylic-sheet internal window (or even a secondary double-glazing system) with as large an air gap as possible between it and the original double-glazed window. Heavy curtains can help a little and will also provide some absorption to help with the room’s own acoustics, but they won’t be very effective at low frequencies. Small windows, or those comprising multiple separate panels, work best because large sheets of glass tend to be quite resonant, although if you can fit a separate internal window using a different thickness of glass from the original double-glazed unit, the severity of any resonances can be reduced.
Where you don’t need the daylight you can fill the window space with sandbags or high-density mineral wool slab and then board over it with a couple of layers of thick plasterboard or chipboard. Even in a rented room this is a practical
Adding an extra heavy-glass or acrylic-sheet internal window, with as large an air gap as possible, will boost the isolation performance of any window, even a double-glazed one.
Windows should be airtight and ideally either double-glazed or blocked off. Blocked off windows can be filled with sandbags to give much improved isolation.
temporary solution that will leave only a few screw holes to be filled when you move. Note that if the window you are boarding over isn’t airtight, but you don’t want to replace it, you can use some acrylic or silicone frame sealant applied from a mastic gun to seal around the edges first. In a rented property you can use gaffa tape to seal around the window frame.
Doors
While you can seal up unwanted windows, you’ll always need at least one working door! Domestic doors are often made from two very thin plywood or MDF panels separated by a lightweight
Wall
Double-Glazed Window
Extra Internal Window
Wall
Existing Window
Board
Sandbags
frame, so they don’t have the necessary mass to act as effective sound isolators – and they can also be very resonant.
They are not designed with airtight seals either as this would not usually be a domestic requirement, but when it comes to sound isolation the door must be airtight on all four sides.
To add mass to the door the simplest and cheapest solution is to fix a layer of 12 to 18mm chipboard, MDF or even drywall board to both sides, although replacing a lightweight door with a commercial ‘fire door’ is also worthwhile as these are necessarily heavy. Some form of sealing strip can then be applied around all four edges to form an airtight seal when the door is fully closed (see below).
Where space permits an even better solution, and one that is employed in many commercial studio designs, is to use a double-door entrance lobby with an air gap between the two doors. In a commercial studio this may take the form of a large ‘air lock’, often combined with storage space for unused gear, but in a home studio even a space of only the wall thickness between the two doors will make a big difference. It is possible to modify most door frames quite easily to take two doors, one flush with the inside of the wall and one flush with the outside.
When it comes to installing airtight seals around doors, consumer draught-proofing isn’t very effective for acoustic purposes, and we recommend using the kind of semi-circular, neoprene, sealing strip available from a studio-materials supply company instead. It is also best to fit the door (just one of the doors in a double-door system) with a compression latch that presses the door face firmly against the seals when closed. A typical domestic door latch won’t usually keep the door pulled tight against the seal.
Commercial studio doors often incorporate a sealing strip on their lower edge that is automatically raised and lowered as the door is opened and closed, as this avoids having to have a raised threshold strip on the floor. However, the only practical solution when using modified standard doors or fire doors in a domestic situation is to employ a raised threshold strip to give the lower edge of the door something to seal against.
Doors need to be heavy with airtight seals on all four sides. A heavy compression latch will keep the door closed tight. Double doors work even better, if you have the space to fit them.
T I P : Rather than fitting the wooden
‘closing strips’ to the door frame first, it is far better to glue your neo-prene seals to the wooden strips using contact adhesive, before pinning them in place. You can then precisely position the strips against the closed door so that the neoprene seal is just tight enough against the face of the door to hold a sheet of paper – any tighter and you may have problems closing the door. Ensure the corners are mitred neatly so there are no gaps in the seal and use a silicon sealer, if nec-essary, to ensure the corners are
Floors
Suspended concrete floors can offer a reasonable amount of sound isolation from airborne sound because of their significant mass, but sound energy coupled into the floor through direct physical contact will be transmitted with very little attenuation at all. Consequently, it is usually necessary to provide some additional means of isolating any direct source of vibration, such as footfall, kick drum pedals, guitar amps and so on. Suspended wooden floors generally offer poor isolation because of their lighter construction and also because most are not airtight. The airtight issue can be solved easily enough using flexible mastic filler, but to provide a good level of contact-sound isolation is for wooden or concrete floors to create a so-called ‘floating floor’ on top.
Professional floating floors can be extremely complex, some comprising thick concrete structures suspended on springs, but fortunately you don’t need to worry about that kind of expense for home use! A simple DIY technique that we’ve tried – both for complete floors and for sound-isolating drum
Typical consumer draught-proofing isn’t very effective for acoustic purposes – we recommend using semi-circular, neoprene sealing strip, available from all good studio-materials supply companies.
Door Frame
Half Round Neoprene Seal
Note: Door must have seals on all four sides
Door Door
plinths – is build a simple structure comprising two layers of 16mm chipboard glued and screwed together, resting on a bed of 30mm or 60mm thick mineral wool cavity wall insulation laid upon the original floor surface. The mineral wool should have a density of around 60kg per cubic metre or higher in order to provide sufficient stiffness to take the weight of the new flooring. Using two layers of board not only adds mass but also ensures the structure is rigid if one set of boards is arranged lengthways and the layer above orientated widthways (i.e. at 90 degrees to the first layer). If you aren’t planning on carpeting the floating floor, then plywood may make a more durable and attractive upper surface. Alternatively you could fit standard laminate flooring on top of the chipboard.
Of course, this arrangement will result in a small step up into the room, and it will be necessary to modify the doors (and possibly the skirting boards) to fit above the new floor level.
It is essential to avoid vibrations from the floor coupling into the surrounding structure, so if installing a floating floor across the entire room, strips of felt or neoprene should be fitted around the walls to prevent the new floor from touching them.
If the new floor was allowed to touch the existing walls sound would be transmitted via direct mechanical contact, essentially
‘shorting out’ the new resilient floor completely! Similarly, if you fit a skirting board you must leave a small gap below it so it doesn’t touch the new floating floor layer.
If the room has a wooden floor and sound transmission to the room below is a problem, you may get a worthwhile improvement by laying 20kg per square metre barrier mat,
A basic DIY floating floor can be built with two layers of 16mm chipboard, glued and screwed together, resting on a bed of high-density, 30mm- or 60mm-thick
mineral-wool cavity wall insulation.
Wall
Felt Two Layers of Board
Floor High Density Mineral Wool Slab
sometimes called dead-sheet, on the floor before putting down the mineral wool. Barrier mat is a flexible vinyl material loaded with clay particles, and in this application it adds mass, seals gaps between the floorboards, and absorbs a useful amount of energy due to its ‘lossy’ structure. Most studio-materials suppliers have various types in their catalogues.
However, while the improvement in sound attenuation should be significant if you install a floating floor, it’s still unlikely that you will be able to use an acoustic drum kit in a wooden-floored room without some of the sound still being audible in the room below. And even if you use an electronic kit, the thump from the mechanical pedal action still tends to come through, so a separate floating drum plinth, using the construction just described, is still a worthwhile addition.
Ceilings
Ceilings are more difficult to treat, as to bring about any serious improvement you need to construct a suspended ceiling below the original ceiling leaving as big an air gap as possible – and even then the results may not be as good as might be hoped for. Few DIY enthusiasts will want to tackle this job, and this is one area where you might want to think about calling in the professionals. However, if the room above is part of your own building, installing a layer of barrier mat (or other specialist noise absorbing underlay material) on the floor above, between the floor surface and the normal floor covering, will certainly help. In more extreme cases, building a floating floor in the room above might do the trick, so long as you don’t mind the slight step up into the room and having to modify the doors and skirting to fit above the new floor level. Where the budget allows, there are also commercial systems for improving ceilings, some of which rely on sound-deadening panels fixed to flexible metal channel, similar to that used for walls.