Theatrical Curtains and Acoustics

We frequently get inquiries regarding the possible use of theatrical curtains to control room acoustics.

First, a disclaimer: although we have fabricated and/or installed theatrical curtains in dozens of spaces ranging from multi-purpose rooms to state-of-the-art theatres, we are not acousticians. We are offering here some basic information combined with our own observations. For critical applications, we recommend that you consult a professional acoustical consultant.

Although stage curtain fabrics are typically not as effective as materials designed specifically for this purpose, they do offer some remediation and many users consider them a more attractive alternative. In addition, with the use of traveler tracks (or other rigging method), the amount and location of sound absorbing materials in a room, as well as the appearance of the room, may be altered quickly and conveniently.

Room acoustics are affected by numerous factors including the sound absorption characteristics of surfaces. We have compiled below, from several sources, absorption coefficients for various surface materials. (An absorption coefficient at a given frequency is a measure of how well a material absorbs sound at that frequency.)

PS - P.E. Sabine, VK - V.O. Knudsen, BR - Building Research Station, WS - Wallace Sabine; from Modern Recording Techniques, by David Miles Huber & Robert E. Runstein (Focal Press, 2001, see http://www.modrec.com) AS - from Acoustics 101, AcousticSurfaces, Inc. (http://www.acousticalsurfaces.com/acoustic_IOI/101home.htm)

Low pitched sounds have a low frequency and a long wavelength. High-pitched sounds have very short wavelengths. A piano can generate sounds ranging from 20Hz (cycles per second) to 4600Hz cycles per second (Hz).

In general, curtain fabrics are much more effective at absorbing high frequencies, than low frequencies.

The human voice ranges in frequency from 87 - 1174 Hz. Speaking voices for men range between 110 - 130Hz. Speaking voices for women range between 200 - 230Hz.

Adding fullness, will increase a curtain's ability to absorb low frequencies, however curtains are not likely to approximate the effect of materials specifically designed for sound absorption.

Here are some related resources on the web:

• http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html (click on Sound and Hearing)
• http://www.modrec.com (companion site to Modern Recording Techniques)
• http://www.acousticalsurfaces.com/
  acoustic_IOI/101home.htm (This is a commercial site with good resources)
• http://www.association-of-noise-consultants.co.uk (The Association of Noise Consultants (UK)
• http://www.caa-aca.ca (The Canadian Acoustical Association)
• http://asa.aip.org (The Acoustical Society of America)

Other Portable Alternatives

Although curtains may be the simplest way to install "adjustable" acoustics, there are many specialized products available that may be installed in ways that allow adjustment. Limelight Productions has the expertise and experience to address almost any rigging challenge.

(photo at right: Acoustical panels installed at Ozawa Hall, Tanglewood Music Fetival, Lenox, MA. Installation by Limelight Productions.)