Form Follows Function: The Basics of Acoustics for the NCIDQ Exam

The science of acoustics deals with sound in the built environment. Therefore, interior designers need to understand and be able to apply these basics for the NCIDQ Exam, on both the Practicum and for IDFX and IDPX.

Form follows function

Consider the function of a space first when planning concepts for the desired acoustic performance.

For example, are you seeking to reduce sound traveling between rooms in an office space?

A recent survey of millennial office workers found that 74% complained about noise in their workspace. On the flip side, can a little background noise actually help increase productivity instead — the same way that the ambient noise of a coffee shop helps you focus.

Or are you seeking to maximize the feeling of activity and excitement in a hip new restaurant by creating a “live” atmosphere?

How would the acoustic environment in a hospital facilitate healing while preserving patient privacy?

Some of the ways that interior designers can manipulate the sound in an environment include:

Designing walls and floors to minimize unwanted sound transmission between spaces
Specifying absorptive finish materials
Planning spaces with similar uses and noise levels adjacent to each other
Utilizing buffer spaces, such as closets and corridors, between noisy spaces
Staggering doorways in corridors
Minimizing furniture placement on shared walls if reduced sound transmission is desired
Use of sound masking or ambient noise

Don't just seek to memorize vocabulary terms. The key is to think about and understand how all these types of treatments actually work.

There are two parts of acoustics to understand for interiors —

How sound travels between spaces
How sound acts within a space

We created some images to help you visualize how this works, and download a copy here.

Absorption

Sound is energy. To stop this energy from spreading into areas where you don't want it, absorptive panels can convert energy into heat through friction.

The absorption coefficient of a product will determine the amount and quality of absorption. Absorption can be applied to fixed wall or ceiling elements, a common example is acoustic ceiling panels.

Diffusion

A sound that cannot be absorbed through acoustic treatments can be scattered evenly back into the room. This spreads the sound more evenly and maintains a live, vivid sound.

Diffusion can be achieved by alternating different depths and shapes of absorptive materials.

Attenuation

Like with the arrangement of partitions in space planning, other vertical elements can block the sound transfer between different spaces, “dampening” the sound.

This can include the use of sound blocks, vertical ceiling panels, room dividers, or desk screens.

Attenuation or sound dampening can also help to improve speech clarity.

There are some terms you need to brush up on, especially if you don't work with these in your job.

Here are a few of the rating systems you may come across on the exam. Understand the differences between the performance of different building materials and finishes at either end of the scale.

You can find more definitions for acoustics and other topics with visual examples in the NCIDQ Exam Glossary.

Important Acoustical Rating Systems

STC (sound transmission class) is a numerical rating that indicates the transmission of sound through construction materials. The higher the STC rating, the better the material is at stopping sound from transmitting through it.
Coefficient of absorption measures the amount of absorption or reflection of sound by a ratio system. A coefficient of 0.20 and higher is absorptive, while 0.19 and lower is considered reflective.
SAA (sound absorption average) is published in most product literature that offers acoustic ratings. The lower the SAA value, the more reflective the material is (0.0 = no absorption). Conversely, a higher SAA value indicates a more absorptive material (1.0 = total absorption).