Rattles and vibrations in your room could be ruining your favourite movies - we show you how to find and cure them for even better cinema sound.
Everything vibrates to some extent, so it really pays dividends to ensure your cinema room is carefully checked to ensure everything is damped and muted. We only want to hear the sound from your loudspeakers - nothing else ! Even low level vibrations in your room can mask or blur key sounds coming from your loudspeakers so it's important when designing and building a home cinema room that vibration is considered from the outset and killed at source. It's often the case that these noises can go unnoticed if they are very low in level - but they are still a source of unwanted distortion. Let's see how we can get rid of them !
We start first during the design process of a bespoke cinema room, where we will consider the materials we are using and how we can use best practice to damp any vibrations at source during the build. An assessment of the bare room is done first, looking at the structural elements of the room, such as the doors, floors, wall, ceilings and other elements (such as windows. pipes and radiators).
To carry out all of our own tests we use a small 10" active subwoofer and an audio frequency generator app running on our iPhone. Connecting to the subwoofer with a phono cable we can now run sweep tests from 20Hz up to 200Hz and listen to each part of the room to see where we are getting issues. By moving the subwoofer around the room we can run the sweep tests at reasonably high volumes and listen out for unwanted noises - they will show up pretty easily with this test. Sometimes we sit the subwoofer directly onto the floor to "couple" the vibrations to the room and this is the best test usually for showing up problems with flooring and doors and sometimes we sit it on a cushion to isolate it from the floor which shows up other vibration problems.
- Doors & Handles - if your door rattles, either replace with a heavier door and try using foam strip around the door frame. Fit a better handle if yours rattles or tighten up the fitting screws. In a professional installation we may install heavier double doors with an acoustic seal around the frames.
- Radiators and Pipes - Check the mounting brackets for your radiators are tight and add extra pipe clips to stop rattling pipework.
- Windows - Check seals on all the windows and add foam strip where necessary. Some windows may be boarded over completely if they are not required in the room for light.
- Floorboards - These can be screwed down as a cheap fix but better still would be an acoustic floating floor which can be installed quite cheaply.
- Walls & Ceilings - Harder to fix, but consider adding a second layer of acoustic plasterboard, glued to the original wall with a viscous glue, or better still a professionally installed "floating" acoustic wall that is installed using rubber isolation grommets.
Once completed, we can now start building the cinema room elements, such as the wooden framing for the screen and front speakers, ceiling panels and rebates and any structural wall elements for cupboards or sound isolating walls. A lot of typical stud-work is employed and here we will ensure all joints are very well screwed and a little more framing than necessary is often employed to add rigidity and strength. Where wooden joist work interfaces with other surfaces, such as floors and walls we will install a neoprene cushion. Lengths of wood that need to run together will be fixed with silicon based sealants and extra screws to give some self damping. Before attaching plasterboard or mdf facing panels we will apply damping strips to all of the mating surfaces to ensure proper acoustic damping.
Throughout the process there is a constant testing process and we will typically "over engineer" the build to ensure we get the desired level of damping. Sometimes it is necessary to mount loudspeakers into these parts of the build (eg. overhead or surround Dolby Atmos speakers). We ensure the surrounding wooden/plasterboard structure is given extra damping, often with heavy weight nitrile rubber sheets glued to the internal surfaces at the build stage.
Behind the main screen we will either try and mount the front loudspeakers directly to a brick/structural wall, or if a concrete floor is available we would use loudspeaker stands. On a wooden floor or stud wall we need to provide some isolation interface between the loudspeaker and the mounting wall/floor to stop vibrations from the loudspeaker travelling and spreading through these interfaces. Sometimes thick carpet foam underlay can be enough but experimentation is key and each individual installation is unique.
Once the main room build is completed we will install the seating and hardware as well as any acoustic room treatments. We want a reasonably well damped sounding room so acoustic wall panels that absorb and scatter sound will give us the reduction in wall reflections and standing waves that will seriously enhance our cinema experience. But other elements in the room can now cause us issues and we'll deal with them one by one here -
- Equipment and AV racks - Your DVD player, AV Receiver and any other equipment you have in the room needs to be checked. Often their top panels are made of flimsy metal so add some weighted dampers (but avoid blocking ventilation holes). AV rack doors can benefit from foam strip around the edges of the doors.
- Artwork & Pictures - Your favourite movie posters can look great, but ensure the frames aren't rattling against the wall with a strip of foam door insulation and some BluTak around the back of the frame where it might be loose.
- Cinema Seats - Your reclining seats contain lots of metal parts underneath - carefully inspect the mechanism on each seat to ensure it is rattle free, but watch your fingers in the process!
- Ornaments and nic nacs - If you must have that ornament on the shelf, try putting something underneath it to make sure its not rattling away.
- Light fittings - Same as above. avoid large metal lampshades that can ring and resonate. Damp with masking tape if necessary.
Now that your room is free of spurious rattles and vibrations you should hear a real benefit from your work and efforts. Sounds will be clearer and you should be able to hear deeper into the mix with fewer distractions. You should find that you can now play louder than normal without it becoming uncomfortable or putting you on edge (assuming your loudspeakers and amp are up to the task!). Being able to play your cinema room at "reference" volume levels is exactly how the director and sound engineer designed your favourite movies to be heard and your cinema room will be all the better for it.
Here at AVEX Technology, we offer professional cinema room design and installation services. Our team of experienced builders understand whats needed to ensure you get the cinema room of your dreams. We design, build, install and commission and you can find out more by calling us today on 01455 234857 or 07932 793231.