Page 55 - Fall 2011

Instrumentation Dick Stern 1150 Linden Hall Road Boalsburg, Pennsylvania 16827 Acoustics Today welcomes contributions for “Instrumentation.” There is no charge for this service. Submissions of about 250 words that may be edited in MSWord or plain text files should be e-mailed to <acousticstoday@aip.org>. Graphics must be at least 300 dpi. Please send the text and graphics in separate files. G.R.A.S. Sound & Vibration, a globally renowned designer and manufacturer of precision acoustic measurement solutions, has announced the North American market introduction of the G.R.A.S. 45CB Acoustic Test Fixture According to ANSI S12.42. Offering high-reliability performance over a wide dynamic range, the 45CB is expressly designed to meet a growing industry need for commercially available acoustic test fixtures (ATF) that can help meet or exceed the ANSI/ASA S12.42 stan- dard, “Methods for the Measurement of Insertion Loss of Hearing Protection Devices in Continuous or Impulsive Noise Using Microphone-in-Real Ear or Acoustic Test Fixture Procedures.” The 45CB provides sufficient acoustic damping for objective measurements of both high-level continuous impulsive noise and the attenua- tion-related insertion loss encountered with active and passive hearing protection devices such as earplugs, earmuffs and safe- ty helmets. The sturdy, high-temperature and humidity resist- ant construction of the 45CB is ideally suited for outdoor measurement environments, as well as simulated real-life con- ditions of test sites, vehicle interiors, aircraft and other areas. In addition, Ear Simulators with built-in 1⁄4˝ pressure micro- phones ensure a measurement system that can rapidly and cor- rectly account for impulse peaks produced by heavy industrial and agricultural equipment and guns. They can therefore be used with any type of test signal or real-life noise source, including environments where use of human test subjects is simply not possible, due to high noise levels or expressed requirements for objective statistical data. The 45CB fulfills requirements for real-life objective hear- ing protection measurements over a wide dynamic range, including self-insertion loss measurements of greater than 70 dB over a wide frequency range. A peak dynamic level of 174 dB allows for real- istic testing levels. Levels of up to 190 dB can be measured and calculated accurately based on closed ear measurements, combined with measurement of the transfer function of the open ear (TFOE). Ear canal extension dimen- sions, rubber coating and appropriate shore hardness make it possible to further measure the insertion loss of insertion plugs and other elastomeric materials at actual human body temperatures. When testing calls for the use of continuous noise, broadband ran- dom noise is recommended, as out- lined in ANSI S12.42. Measurements can also be conducted using recorded signals of the actual usage environment for intended hearing protection devices, such as vehicle noise and similar sources. When measuring with continuous noise, a variety of G.R.A.S. free-field and random incidence measurement microphones may be used for reference. All G.R.A.S. products are made of high-quality materi- als that will ensure life-long stability and robustness over their useful service life. The G.R.A.S. 45CB Acoustic Test Fixture According to ANSI S12.42 is delivered fully assem- bled. An individual test certificate is included with each 45CB. All G.R.A.S. products are calibrated in a controlled laboratory environment using traceable calibration equip- ment, with subsequent annual calibrations recommended. In addition, the G.R.A.S. 45CB Acoustic Test Fixture According to ANSI S12.42 is offered with a two-year com- prehensive product warranty. For more information, visit www.ansihead.com. Editor’s Note—The items printed in “Instrumentation” are reported for informational purposes only and are not necessar- ily endorsements by the Editor, Acoustics Today, or the Acoustical Society of America. 54 Acoustics Today, October 2011