Sound reduction on living room floor (re-visited)

red_imps_2003

Thank you both for your further comments and observations. Norman, the sound reduction company we had round were going to fit a dense rubber matting called 'Acoustilay' which sounds like what you describe. We prefer the sound of Phonestar, though, because it [apparently] feels less 'spongey' under foot and because it is easy to install (the sound company were charging over £1k just to fit the matting and wool; that's after the cost of the materials had been accounted for).

Furts, I certainly agree that minimising the activity generating the noise is a partial solution and one we try to enforce. We encourage the rugrats to calm down after 7pm, not jump off the sofas like Ninja Turtles, and try not to drop their heavy toys from too great a height. However, I don't want to be a 24x7 party pooper and ruin their childhood (plus I have stuff to do when home besides restrain those two all the time, and shouting at them just substitutes one irritating noise for another). We try to be considerate for the neighbours. We can hear their dog farting next door so god knows how intrusive the thuds and rumblings from our side must be. They say it doesn't bother them but I'm sure they must find it irritating. They are not in the best of health and I know one of them tries to sleep a lot during the day on Sundays.

wrightk

Hi there, Ive looked at your post with interest. I've trained in sound engineering and acoustics in the past so can give a little help

The boom you are describing in your posts is likely to be 'standing waves'. You can insulate and 'soundproof' all you like with the floor but the walls are likely to be the culprit. You mention about the echo or 'smack' compared with outside. Think about it. When you make a sound in the outdoors there is very little 'bounceback' ie there isn't very many solid surfaces to bounce that soundwave back to your ears. In a home environment most rooms are square. You make a sound or bang, this is reflected off the walls, bounced back in an almost identical way in which it approached the wall (because of the dimensions of the room), this creates a standing wave which makes the original noise sound twice as loud.

Have a look around, particuarly at pictures of control rooms in recording studios. Thousands are spent on making each surface break up the soundwaves as much as possible and as varied as possible so there is no opportunity for reflection of soundwaves.

In simple terms, look at your room.An octagon is the perfect room shape,although not many will have this! Try to break up each surface that is flat with something, pay attention to corners.Try to find out what sort of sounds are the most resonant ie high frequencies or low. Low frequencies will need dense, heavy items to absorb and reflect the frequencies.Bookshelves with heavy dense books are a good idea.

And finally know your limits. A wood floor with wood joists will always make noise. It is never going to be possible to reduce all sound especially from above. Look into every company carefully and remember db works on a logarithmic scale not linear so any company or figures you read remember that a difference of just 10db equates to almost double the sound pressure/perceived noise

phil24_7

I've not read the whole thread but further supporting of the floor joists would be the best way to go.

How much space is there below the joists and is there any access to the sub floor other than taking up floor boards?

If you could remove enough boards to get access and get materials down and then work from underneath any works would become a lot easier.

I would look at supporting the joists mid-span, failing this then you could glue and screw ply wood to the sides of each joist or even bolt steel plate to the sides. These would all decrease deflection as well as vibrations.

While you are down there you could insulate the sub-floor (taking care to allow an air gap just below the floor boards).

Regards
Phil

red_imps_2003

Thank you both for your excellent follow ups and observations. I appreciate it.

wrightk, you are, of course, correct that a lot of any noise generated is deflected about the room via hard surfaces like walls and ceilings. This is certainly something we will be mindful of but we are hoping to try and minimise the generation of noise in the first place where possible.

phil24_7, I am certainly coming around to the idea of supporting the joist in the middle of the room (or two of them dividing each third of the room) if possible. However, I am fairly sure we only have a handful of inches under each joist to play with so will probably be limited in what we can do. I will ask our friendly neighbourhood builder what can realistically be achieved in that respect. Certainly access is only available from above and there is no space to accommodate a person. It is actually the practicality of insulating the sub-floor (as you describe at the end) that my original enquiry was about. Every sound-proofing company I have contacted suggests it (in conjunction with a dense matting above the deck) but I am becoming increasingly sceptical about the additional benefit it will bring for the considerable effort involved. I can see it working well between one room and the one above or below it, which is the more conventional use, but less so at ground floor level.

red_imps_2003

In the end I just installed the Phonestar soundboards. I couldn't be bothered with the disruption and expense of lifting the floorboards and trying to secure insulation in the correct place. The soundboards do seem to have reduced the vibrations and shaking, but I would say the actual 'noise' has not been reduced that significantly. I suspect fitting the insulation wool underneath probably would have muted the airborne noise a bit more. I am hoping that once we have a proper carpet fitted with decent underlay the overall noise levels will be tolerable. At the moment we have a patchwork of unfitted carpet from another room, a rug, and carpet tiles covering the floor to protect the soundboards. Proper fitted carpet and underlay should reduce the impact sounds a little better. Overall I am moderately pleased with the reduction in vibration for a cost of about £740.

Ainsley1

I am not going to disagree with some of the things written by wrightk but having also worked in acoustics it would be wrong to think that just stopping reflections would cure the problem. Tackle the source first! Unfortunately most dampening will have worked at frequencies higher than the very low ones of the flexing floor as your little darlings pound them! Those low frequencies are the most difficult to reduce (size matters here) and making the floor more rigid and the length of unsupported floor smaller would have been the best starting point compared to expensive (in my mind) dampening material.
It could be that the figures quoted for phone star are weighted against frequency (almost certainly are but I do not have the ISO standard to hand to be specific) so the 20db is significant but perhaps not so great a reduction at the low impact frequencies you experience. A bit of support might have worked better or in combination to get your floor mass and rigidity closer to that of concrete! Extra support has worked wonders in our kitchen, but then access underneath was relatively easy......

red_imps_2003

I think you are right, Ainsley1. I think the soundboards are primarily intended to dampen vibrations a little and impede the transmission of airborne sounds. They do feel as though they have made some difference, particularly when the boys drop their toys on the floor. However, I realise that one is never going to eliminate the sounds generated by whacking a hollow surface with force entirely. Insulation beneath the floor boards may have deadened it a little further but was too risky in this instance. As you say, the most effective option would likely be to add more vertical supports to the structure so it doesn't shake as much.