0

I have a room where very loud sounds (140-160dB) are going to be produced on an occasional basis. I am trying to acoustically insulate the ceiling with the materials I have in my regional warehouse. I know I can't stop some sound from escaping to the outside where the neighborhood is, but the idea is to insulate it adequately so it won't be so annoying.

I have made a schematic with the configuration and materials used. Also, on the right I add three types of membranes and multi-layer sheets that I could get.

The roof is wood (and has onduline and shingles on top), with longitudinal rafters. Between the gaps in the rafters I have filled them with mineral wool, extruded polystyrene and polyurethane foam. I suppose that the wooden beams are the weakest link in terms of acoustic insulation, compared to all the filling between them.

The final layer is going to be a tongue-and-groove pine wood decking. My question is, what do I put in the gap? (see diagram, empty space to be filled). I have a 4mm thick MAD-4 high density bituminous sheet, which I had thought to put on top of the wooden platform, but I could put more materials in between, such as:

  1. 3-5cm of mineral wool
  2. One more layer of high-density bituminous, perhaps varying with other models (2mm or 4mm; see the right margin of the sketch).
  3. A layer of multilayer sheeting (textile felt+high density bituminous).

In any case, everything that is placed there, in addition to the wood decking and the MAD-4, will be fastened by lag screws against the joists.

I have noted in the diagram the properties of each element, although in the MAD-4 technical sheet there is an error as I do not understand how it can be only 6-9dB compared to other bituminous.

What would be an appropriate solution to increase the acoustic absorption and make that little sound goes outside?

ceiling scheme

user3819881
  • 131
  • 1
  • 1
    160dB??? You can probably forget anything short of 2ft of concrete… & I'm not even sure that would be enough. If you're serious about those sound levels, you ought to start with airport construction, 160dB is louder than an aircraft take-off from 25m. It is immediate & permanent hearing loss territory. – Tetsujin Jan 29 '21 at 11:57
  • I know, but it is like that, although only for 0.5-1 second each time (20-30 times a day). Don't worry about myself, just about the neighbors. That's why I opened this post. – user3819881 Jan 29 '21 at 12:50
  • Then I'd suggest investigating how indoor firing ranges handle it. Ultimately, the way to prevent sound transmission is *mass*. None of your suggestions have anywhere near the mass required for such high volumes. – Tetsujin Jan 29 '21 at 12:52
  • Not even adding another layer of high density membrane? (MAD-4, FIeltex-65, Viscolam-35, etc)? It has low mass but really high density.

    Remember, I will be happy if it decreases to 120dB, it is not necessary to reduce to 80dB. My purpose is to find the best combination for that space (mineral wool? membrane 4mm? a combination?) to reduce the sound propagation to outside.

     – user3819881 Jan 29 '21 at 12:53
  • You will be expensively disappointed. I once built an entire room within a room of similar components. The attenuation below 100Hz wasn't enough to suppress a drum kit to tolerable levels, let alone a gun. – Tetsujin Jan 29 '21 at 13:55
  • I think your best bet is around 60db reduction... with a lot of work and money – frcake Jan 29 '21 at 17:48
  • 60dB will be perfect, but you don't specify the configuration with the materials. Can you elaborate?

    For example, the "Multilayer sheet" has one side with a MLV 4mm and the other with a 16mm textile felt. I was thinking to put in the hole: multilayer with the MLV part towards the ceiling, the textile felt towards the bottom. Next layer below, the MAD-4 (MLV 4mm), then the last layer the pine wood decking. That would be the best configuration with these materials?

     – user3819881 Jan 30 '21 at 22:50
  • I believe that even 60 dB is way over the possible values. Once I took part (did some evaluation measurements not the design or the construction) in a project trying to minimise the sound transmission of a night club to the neighbours living above. They had to build a 2.5 metres thick concrete (with other layers in between) ceiling (along with the auxiliary constructions to hold it) to achieve a 58 dB noise reduction, in the low frequency bands of interest (which was 63 Hz octave if I recall correctly) – ZaellixA Dec 15 '21 at 00:20

0 Answers0