Trying to Quieten the 110KVA Generator

[awemawson]

I’d intended to use U channel initially, indeed the fellow I got the panels from was going to bend some up from zintec for me as he has an 8 foot folder. But in the end I decided putting a single 6 meter long angle iron was simpler and easier.

Last night I cut a 3 x 3 inch infill from an old 5 x 4  fence post  to make the wall that I’m working off a simple vertical (upper feather boarding sticks out 3” from lower masonry) the plan is to fix a horizontal batten sticking out from this wall at an arbitrary height, and use it as a datum to take measurements up an down to transfer onto the panel for cutting..

[awemawson]

Depressingly little done today (cottage guests leaving, cleaners on holiday, cottage guests arriving - you get the jist !) But I did manage to fix the 3x3 timber wall packing piece in place. All of three 10 mm clearance holes in the timber and 10 mm into the masonry for the frame anchors, but it came at a cost . . .

My Bridgeport milling machine doubles up as a drill press, and drilling the first 10 mm hole in the timber resulted in a dramatic bang and flash of flame with a tripped main breaker  Holes had to be completed on the drill press in the woodwork shop, but that's another fault that needs tracking down. I had a very brief look in it's control box and I suspect the motor contactor as a bit of it's insulation is now missing, but that will have to wait until later to be properly looked at as I'm back 'on duty' 

[awemawson]

I LOVE it when our cottage guests actually ring up and say that they will be arriving late -  suddenly I have another 90 minutes of TIME 

So I devised a way of supporting a horizontal lath as a datum line, and took 'soundings' up and down from it having marked the widths of the two (different) panels on the lath. This allowed me to transfer the datum onto the one remaining 1 metre wide panel, mark off it's odd shape and that of the rafter and cut it to size.

Still with time in hand I decided to try and fit it - it fitted like a glove  Just clamped no time to screw it as they'll hove over the horizon any moment now - but that's the PENULTIMATE  panel in place - so definite progress.

[awemawson]

I finally got ALL the panels fitted this morning - no major dramas.

I nearly forgot that as the panel engages 50 mm into the one on the left I needed to leave an extra 50 mm on the rafter 'notch' for this to happen - just remembered it time.

Having won the auction last night for the PVC strip door parts on eBay then the door closing is now determined 

[awemawson]

At long last I managed to find a few minutes to hang the PVC strip curtains. Simple enough once I'd mounted a piece of wood up top to act as a transom.

As the strips have been roiled for quite some time the bottoms are very curly. Hopefully this will 'hang out' given time - if not I'll dunk them in a bucket of hot water to encourage them.

I'll eventually secure the two outer strips to the panels with strips of 2 x 1 to keep them close to the wall, but I can't do that until they uncurl.

[russ57]

So, does it work....

-russ

[awemawson]

Got 'cottage guests' sitting in their courtyard garden eating breakfast, so daren't try it yet !

[John Rudd]

Got 'cottage guests' sitting in their courtyard garden eating breakfast, so daren't try it yet !

Lol.....go for it!....

[awemawson]

Well I did . . but not until they all went out 

Seems that the curtains have reduced the noise by the cottages courtyard by about 3 dBa to 68/69 dBa. The background noise at that point (road / animals / etc is about 60/61 dBa.

But noise perception is a funny thing - it still sounds pretty loud to me !

[awemawson]

When I bought the job lot of PVC strip curtains for the generator enclosure I was aware that there might JUST be enough left over to span the eastern entrance to the stable.

At last yesterday I managed to get the 'curtain rail' up and today I hung the strips - they have an absolute minimal overlap of 'one hook' as I don't have enough for more overlap, but in the future if any more turn up it's just a case of hanging and cutting to length.

No doubt they will blow all over the place when it's windy, but there is a noticeable noise reduction over towards the tractor shed now that they are up.

With neither the floor nor the lintel being horizontal positioning the rail was fun - it IS horizontal but doesn't look it!

[Muzzerboy]

I'd be thinking about slapping some of that horrible rock wool insulation around the generator room itself. I hate handling it, as it seems to make me itchy before I've even touched it but the sound deadening is pretty good bang for buck.

[awemawson]

It’s not too bad To handle in ‘slab’ form intended for cavity walls, but with 25 square meters to cover it gets expensive . And that’s without doing the ceiling - another 21 sq m

Fair old breeze through the generator room when it’s running, and the ‘off the roll’ stuff would be blowing all over the place, and need a mesh to retain it.

[Muzzerboy]

Yes, that's a big old room. On the other hand, you probably don't need to completely cover every surface to absorb a lot of it.

I guess you can get an idea how good/bad it is from your feedback reviews!

[tom osselton]

I put rockwool in the garage walls covered with chipboard and you can barely hear the compressor running.

[awemawson]

Remember that the partition panels are themselves a 70 mm thick sandwich of foam core with 0.5 mm steel facings. Were the room hermetically sealed it would probably be acceptability quiet outside. But of course it needs airflow, lots of it !

[nrml]

Acoustic foam panels are fairly cheap on ebay and are less messy than rock wool. If you place a few on surfaces that reflect towards sound apertures, it could go a long way.

[Muzzerboy]

The point I was trying to make was that you can deaden a lot of noise with sound absorbent foam without needing to cover every surface and fill every hole. A good example is fitting a carpet or large curtain in an otherwise empty room. The relative silence can be deafening. The steel coverings over the foam will provide very little dampening of sound within the space. Similarly, painting a wall a dark colour can reduce the light levels in an otherwise well lit room. True, sound won't pass through the panels so well but that isn't going to be the dominant mechanism here.

[awemawson]

Yes I take your point entirely - just waiting for a job lot of something suitable to turn up 

[WeldingRod]

Compressed fiberglass duct board is excellent for this application...

Sent from my SM-G892A using Tapatalk

[awemawson]

Yes you mentioned that before as I recall, but it doesn’t seem to be available this side of the pond. I had a search when you previously recommended it. Domestic ducted heating systems went out of fashion here in the mid ‘70s so perhaps that explains it.

[nrml]

Some interesting experiments on sound absorption.

[awemawson]

Some interesting points raised in that video, thank you.

It reinforces my opinion that lining the walls and ceiling with rock wool cavity batts is the way forward if only I can find a job lot at an affordable price, they don’t need to be as thick as a standard 100 mm batt, probably 25 mm would quite adequate, but it’s not practical to split them. Rock wool by the roll is of course available but mounting it brings more issues.

[awemawson]

At last I've sourced a load of Rockwool Acoustic insulation in 25 mm thick slabs - supposedly 'semi-rigid'  - we'll see if it is or not when fixing!

Fixing to three different types of substrate:

Steel partition - self drilling screws

Timber cladding - 2" No 10 wood screws

Concrete Blocks - 50 mm x 5 mm 'hammer fixings'

All using 60 mm nylon washers. No doubt this is going to be one of those 'fun jubs' !

[awemawson]

I thought that I'd experiment fixing a slab to the partition wall, in the end it went so well I actually got nine fixed before I was called away to rescue the wife from the puppy

Initial marking out was a pain then I hit on the idea of making a jig - speeded things up considerably.

Then starting the self drilling screws wasn't easy - they wander as of course the point is the wrong side of 25 mm of soft insulation - they need centre punching, but you'll never find the centre pop through the insulation

Simple solution, clout the screw with a hammer and carry on screwing - went like a dream.

. . . so nine sheets done out of a total of 96 so about 10% - but it's the easy 10% I reckon.

Too early for noise tests as guests are present and anyway much more probably needs doing before the effect will be  noticeable though I can tell it's already less echo-y.

 

[tom osselton]

Looking good that will help out a fare bit.