Room Acoustics (Part II of II)

As mentioned in the part I of this topic acoustical treatment is a major part of the theater construction. I don't claim to know the subject, but from what I gather, here is why you should care to consider acoustical treatment of the room. Put in layman's terms.. Some of the sound waves reflecting (bouncing) off of the room walls that intersect with a listener position may cause sound distortion or echo. Also, sound reflecting off a surface suffers timber shift. So, it helps to tame those early reflections by applying acoustical treatment to those positions of the wall that cause these early reflections.

So, simply stated, acoustic treatment involves strategically applying sound absorption material to the wall surfaces. There is complex theory behind and generally you need professional help in finding exactly how and what to treat.

In general, for a multi-channel home theater experience (different from a 2-channel music listening), general practice is to treat the entire screen wall behind the front speakers (see the pic on the right). This helps control the back reflections from overlaying on to the surround field. Depending on the speaker placement, this treatment is brought along to the side walls (upto a certain height, not to the entire wall). Bottom of the soffits are also treated for similar different reasons.

A good material for sound insulation is what generally known as Owens Corning Fiberglass 703 series "Duct Insulation". There are several other choices like Johns Manville Insul-Shield or Knauf Duct liner/board.

In my case, finding one of these materials proved to be a difficult challenge. Despite trying very hard, I could not locate any of them. After months of trying and calling numerous people, I finally found a local supplier who luckily had a roll of (see pic) Johns Manville Insul-Shield.

These materials are typically made from fiberglass and if left uncovered is not only unsafe but also a nightmare for the interior designers and has zero WAF (wife approval facto). It just looks plain and ugly if left uncovered. So, it is customary to cover this material with 'special' kind of fabric that is acoustically transparent and "fire retartdant". So be carfeful, all the materials have to be fire safe and hence "any cloth" will not cut it. Most theaters use fabric from Guilford Of Maine .

Beyond treating the walls, it is upto your (and your designer) personal taste to define the look of the room. In my case, instead of putting the insulation on the walls and covering plainly with the fabric, I went with a painful process of builidng individual small wooden frames and installing one by one on the wall. End result is a great looking room. But, during construction, there was not a single day that I did not regret my painful decision to build these farbic frames. In the end, it not only costed me a lot of money but we all at home ended up working like hell to get these frames finished and installed. But I must admit, all that agony is vanished once after looking at the end result though.