What You Need to Know About Acoustics (Part 1)
Acoustical applications of fabrics
Main Curtain and Window Curtains at Baruch College Photo: Todd Kaplan
Rose Brand has partnered with our friends at Stages Consultants to create a blog series about the acoustical applications of fabrics. In this 3-part series, we’ll discuss some of the more common approaches for using fabrics in performance spaces and also the things to consider when choosing a fabric for your project.
Why Are Acoustics Important?
One of the basic goals of room acoustics is controlling reverberation, or the persistence of sound in a room after the source is silenced. While sometimes the goal is to create “live” spaces with longer reverberation times for a concert hall, more often you are looking for ways to make a room’s acoustics less reverberant, especially in theatre and studio spaces. Adding sound absorbing material to a room will reduce its reverberation time and the perceived loudness of sound. Shorter reverberation times enhance sound clarity, improve speech intelligibility, and reduce loudness. This allows better communication between performers and audiences at comfortable volumes. It also improves source localization, including surround sound effects.
Fabric is among the most versatile and effective sound absorption options available. Each fabric has different characteristics, such as type of fiber and weave that determine how much sound it absorbs and whether it provides even sound absorption from low (bass) to high (treble) frequencies, or whether it is only effective over a limited range. The way a fabric is used can also change its acoustic performance. A flat panel of fabric against a hard wall is different from a curtain with 50% or 100% fullness against the same wall. A fabric panel with backing, or one that’s set off from a surface with an airspace, will also perform differently.
Typical Use in Theatres
Typical fixed fabric elements in theatres include audience seating, wall panels, wall coverings, and a portion of draperies. Portions of draperies and dedicated acoustic elements are devices that may be extended in the room or removed depending on scenic needs and desired acoustical effect.
Acoustic Panels and Wall Coverings
When you think about acoustic wall panels, you may imagine a thick sound absorptive panel with an open-weave fabric covering like you see in many office conference rooms. Acousticians love these panels — low-cost, reliable performance, and most clients can find panels they like. However, in performance spaces you’re not always looking for maximum absorption or the same acoustic performance over every square foot of wall space. A larger variety of fabrics and in different applications is helpful in tuning a performance space.
Using fabric to cover walls is a great way to increase the absorption in a room or even cover a reflective panel. Attaching lightweight materials like a tulle or muslin will make walls more absorptive than paint at high frequencies, but have little impact on mid and low-frequencies. Heavier and thicker fabrics start to provide more substantial high frequency absorption and, depending on how they’re used, they can begin to affect mid and low frequencies, even without a porous backing.
Section of Upholstered Wall
Curtains and Banners
While we’ve occasionally motorized a set of acoustic wall panels to allow them to be extended or retracted within an auditorium, most often we use fabric as tracked curtains or vertical banners to provide a range of absorption in a room and vary reverberation and loudness. Velour and Wool Serge fabrics are most effective curtain and banner options, and can be doubled or combined with a backing fabric like Canvas or Commando Cloth to achieve the acoustic performance needed in a particular room.
Window Curtains at Baruch College Photo: Todd Kaplan
Fabrics with Acoustic Absorption Data Available from Rose Brand
In Part 2, we’ll take a more careful look at Rose Brand products and how they perform in different configurations.
Stages Consultants provides world class acoustics and theatre design consulting for performing arts buildings. We bring to every project the knowledge, creativity, design skills and leadership offered by only the most experienced members of our profession - with the individual client oriented service that a small firm can deliver best. You can learn more about them and their services at www.stagesconsultants.com.