The Role of the Acoustician
The art and science of understanding sound transmission, absorption, interference, reflection and refraction is a highly specialized field. From acoustical engineering and architectural acoustics to advanced technology dealing with the practical application of sound, an acoustical consultant has a specifically defined role in the field of architecture and construction. To gain insight and understanding into this highly specialized field, we examine its educational requirements, the phases of construction that acousticians become involved with and the specifications and details these experts are responsible for.

To ensure accuracy, we lean on the knowledge and expertise of Jim Good, an Acoustical Consultant with over 38 years experience and a principal at Veneklasen Associates. Jim Good graduated with a degree in architecture from the University of Southern California, Los Angeles. Veneklasen, an acoustical consultancy established in 1947, provides a full range of professional acoustical consulting, from audio-visual design and noise control, to in-house acoustical lab testing.

"The typical background of an acoustical consultant is rooted in physics, architecture, engineering or music," explains Good. Generally, a four-year bachelor's degree or a master's degree is obtained before practice in the field commences and experience is gained by becoming part of a team in a reputable consulting firm. Additional life long learning is continued via memberships in professional organizations such as the Acoustical Society of America, the Audio Engineering Society or the National council of Acoustical Consultants.

Representing all fields of acoustics, these organizations offer specialized programs geared towards furthering an acoustician's knowledge and helping them stay abreast of the latest advancements. Plus, the exchange of views these organizations foster serves the widespread interests of the entire acoustics community in all branches, both theoretical and applied. Because these professional acoustical organizations generally provide listings of member firms and consultants, they also serve as referral starting points for architects and builders searching for acoustical consultants. "The best referrals of course are still word-of-mouth from other clients who have worked with a consultant or firm on a previous project and had a positive and professional experience," explains Jim Good. But when word of mouth is not an option, a professional organization's list of members serves the need, especially when combined with follow up research into what projects the firm or consultant has been involved with in the past and a request for current list of client references.

So when is the best time to bring in the consultant? "An acoustician prefers to be involved in the very early stages of project planning", offers Jim Good. Knowing the type of project to be built provides more advantageous starting points for designing good acoustics. Helping determine not only space dimensions and geometry early on, an acoustician can address any structural limitations and restrictions that may exist. Rather than having to repair a list of defects after the fact, being on hand even before the blueprints leave the drawing table, even before the site for the project is selected, is where the acoustical consultant's involvement is most beneficial.

Because sound travels structurally, via columns and beams in the very skeleton of a building, it is important that proper materials are used throughout. The construction of exterior walls and windows is the most important factor in determining the level of acoustical performance. In the presence of abundant environmental noise, the acoustician will recommend that exterior walls be constructed of materials with a heavier mass, such as concrete or masonry. The more external noise, the more massive the walls the acoustician will recommend. The same goes for glass and windows. The more abundant the noise, the more likely the acoustician will recommend combinations of heavier glass and multiple layers for optimal performance. This is of course common sense for any type of venue, whether it be a performance hall or a condominium complex.

Once the walls and windows have been addressed, the acoustician will move to design the space layout and geometry. The size and height of the space will be determined to ensure optimal reverberation time, the time it takes for sound to decay as it travels. Mechanical utility rooms will be placed so as to eliminate acoustical interference. Also, if the site and space requirements present specific restrictions, those will be addressed too.

While there are no set specifications for optimal acoustics, consultants typically prefer certain shapes and layouts for certain needs. A performance hall, for instance, is commonly designed in the classic fan shape, 180-degree fan shape, circular shape or the shoebox shape. But the number of seats, whether there is a balcony or not, the sightlines and the size of the hall will effect how sound travels from surface to surface, and will ultimately determine an acoustician's use of specific shape, height, size and materials.

Once the space layout is finalized, an acoustician will begin specifying the various products and materials needed to manipulate the acoustical character of the space. As sound travels, it changes each time it hits a wall, floor or any other surface. How much it changes depends on the nature of the materials it encounters. Examining the shapes and surfaces of the walls, floors, doors, windows and ceilings, an acoustician will recommend various products to achieve a desired effect by specifying either sound-absorbing or sound-reflecting materials.

Sound-absorbing materials such as carpet, mineral fiberboard and fiberglass will be specified where sound absorption is desired. Sound-reflecting materials such as plaster, drywall, wood, vinyl, concrete, gypsum board, and stone will be specified where sound must be reflected back into the audience. "Simply using common sense and just thinking about what you're doing is the best bet", offers Good, "It is important not to over-specify products and materials and realize that at some point there are limitations on what can be achieved based on building design."

When evaluating and choosing a product manufacturer, an acoustician will rely not only on the quality of the products made, but on the manufacturer's reputation and reliability in the industry. Acousticians look at laboratory and onsite testing as a place to start the product evaluation process. Both lab and onsite acoustical tests are done with a loud speaker on one side, and a sound level meter on the other. Although the ASTM standards differ slightly from lab to onsite testing, both are looked at in the same respect.

Because field testing cannot take place until construction is completed, acousticians rely on laboratory test reports and ratings to start with. Acoustically tested and certified doors and windows are given a Sound Transmission Class rating (STC rating) which signifies a products ability to block sound at a given frequency, or the number of decibels that sound of a given frequency is reduced in passing through. Measuring transmission loss over a range of 16 different frequencies between 125-4000 Hz, is the basis for determining Sound Transmission Class. The higher the STC rating the better the performance of the product. Other acoustical products and materials such as wall partitions are given a 3rd Octave Band Performance rating, which signifies transmission loss in specific full-octave frequency bands. These test results are reported in third-octave bands. The higher the rating, the better the performance of the product.

Ratings and test results, among other data, make it possible for acousticians to find manufacturers with the type of products the project requires. "We prefer a single manufacturer to provide all the pieces of a product or assembly", adds Good, "When more manufacturers are involved in the creation of the product or assembly and something goes wrong, no one is responsible." When it is not possible to get an entire product or assembly from one manufacturer, Good highly recommends onsite acoustical testing of the final installed components i.e.: the door, the wall and the partitions, to assure the parts are working together to perform to the desired rating.

Because construction and acoustics are both a science and an art form, deficiencies are to be expected. The ability to effectively correct these deficiencies is the hallmark of what truly exceptional acousticians do. When deficiencies occur, an acoustician may recommend that additional seals be installed in doors and windows or acoustical curtains or panels be added to the interior walls. Unavoidable deficiencies such as structural blocks and incorrect geometry of a space can be corrected with "electronic architecture", a means of simulating sound reflection patterns with the use of critically placed microphones and loudspeakers supported by carefully tuned electronics and digital processing.

Whether it is noise reduction or sound enhancement, every construction project has a set of acoustical needs. Because there is not such thing as perfect acoustics, just optimal acoustics for the situation, it is the role of the acoustician to understand the situation and find not only the most optimal space layout and design, but to specify the materials and products that will achieve the desired outcome. When the project is completed, it is the acoustician's role to identify deficiencies and provide effective solutions for correcting the problem and supervise onsite testing to confirm that desired outcomes were in fact achieved.
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