A BEGINNER'S GUIDE TO ACOUSTICS
In the enthusiasm that often accompanies the idea of owning a Home Theater, the lack of experience of the people involved might lead to a counterproductive design and execution. In our experience as AV integrators, witnessing a 5.1 Dolby system where all the speakers are seated on a credenza underneath the TV is not uncommon. Simply moving the same set of speakers and positioning them in their intended way, elevates your movie experience to a level that was previously unachievable. This example should serve to place emphasis on the importance of being aware of the right approach.There is more to building a home theater than merely aggregating and integrating Audio & Visual Equipment. The general tendency nowadays is to think of equipment first and equipment only. With the right approach, even modest home theater systems can deliver satisfactory results. That said, the right approach in conceiving an ideal design & setup of your Home Theater begins with addressing the weakest link in the chain, Room Acoustics.
The aim of this article is not to overwhelm the reader with math heavy technicalities of Acoustics but to educate the reader of the problems that acoustics intends to solve. The article will also clarify common misconceptions along the way.
SOUNDPROOFING AND ACOUSTICS - Are they the same?
The objective of a Home Theater is to infuse Cinema Hall experience within a dedicated space at your residence. If it is not already apparent, discussing this idea with your neighbours and old chaps should duly inform you of an alarming concern both the categories of people will experience : Loud Sounds and their leakage. Viola! We have our first obstacle to tackle.
The process of soundproofing ensures loud sounds from within your room don’t escape and adversely affect the neighbouring environment and its inhabitants. An added advantage is that soundproofing is not a unidirectional solution. Soundproofing also safeguards the room against undesirable noises in the vicinity and makes sure they don’t creep in, thereby eliminating any distractions that might hamper a pleasant experience.
And then there is Acoustics!
As stated earlier, soundproofing defends your room of any external interference and restricts sound leakage. Now that we have tamed the problematic behaviour of sound waves leaking in and out, it is time to deal with problematic behavior of sound waves within the theater room, and that’s where Acoustics comes in to play.
The problems that acoustics aspires to solve are generally a function of unruly reflections. This is an observable phenomena ; excessive reflections in an empty room reduces intelligibility and requires louder volumes to convey conversational speech. If that’s the case with speech, it’s up to the reader’s imagination to grasp the detrimental effect of reflections imposed upon audio emanating from five or more speakers.
At this point, we feel the need to clarify that not all reflections are detrimental in nature. Reflections are critical to our brains in processing the spaciousness of an enclosure. Our brains perceive essential details such as height and depth information with the aid of reflections. Hence, a treatment plan that proposes dressing up the entire space with absorptive materials will render the space unfit and invokes a feeling of discomfort amongst its occupants.
While an in-depth elaboration on the types of reflections and methods of treatment are beyond the scope of this article, we shall make efforts in highlighting the most common one and its methods of treatment.
When two traveling sound waves are propagating in opposite directions, as a result of reflections inside a room, the interference of these waves combine to create a resultant wave that appears to stand still at certain resonant frequencies called modes. The result is they unduly enhance or suppress certain frequencies at different spots in the room. Room modes are a function of the Room’s dimension. Acoustically unsuitable dimensions can aggravate the peaks and nulls across the room. Consult an acoustician to infer the best orientation of the room to minimize the effects of room modes. Since room modes are a consequence of interference between direct sound and it’s reflection from a boundary, ensuring that your boundary is made absorptive will eliminate this issue.