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Acoustics Testing

In today's competitive environment, ETS-Lindgren Acoustic Systems offers acoustic testing services by our NVLAP accredited laboratory (NVLAP lab code 100286-0).

two men working in a labThe ETS-Lindgren Acoustic Research Laboratory (ARL), located within our Cedar Park, Texas, facility offers acoustic testing services in accordance with a wide range of standardized test methods. The ETS-Lindgren ARL is accredited by the National Voluntary Laboratory Accreditation Program (NVLAP lab code 100286-0) administered through the National Institute of Standards and Technology (NIST), United States Department of Commerce.

In addition to standardized testing, ARL also conducts customized test programs to answer client-specific product research and development needs, to develop trustworthy independently proven product marketing information, or ensure product compliance requirements.

The ETS-Lindgren ARL is comprised of: multiple acoustic test chambers, state-of-the-art measurement equipment and customized software, and expert staff. The entire laboratory operates under a quality system that meets the strict requirements of ISO 17025:2005, General requirements for the competence of testing and calibration laboratories.

Hemi-Anechoic Chamber

Acoustic Lab Photo The ETS-Lindgren ARL includes a precision-grade, double-walled hemi-anechoic chamber for product noise emission testing and other acoustic research/testing requiring an acoustic free-field over a reflecting plane isolated from background noise. Equipment available for use in chamber includes a multiple-channel simultaneous data acquisition system, automated microphone and specimen positioning systems, signal generators, and sound sources. The chamber is qualified for testing as meeting or exceeding requirements of accredited test standards.

Types of testing commonly performed in the hemi-anechoic chamber include: product noise emission testing (including sound power determinations, operator/bystander sound pressure level measurements, prominent tone evaluation, loudness calculations, and advanced sound quality analysis), waveform recording from microphones, or binaural recording/analysis. The extremely low-noise and free-field environment also allows for testing audio component frequency response, directionality response, and signal fidelity. Aural non-detectability of military devices (per MIL-STD-1474D) is also available. The hemi-anechoic chamber is easily configured for client testing requirements, including data lines, electric power, air supply/exhaust, etc. A large acoustically-isolated control area adjacent to the chamber allows incorporation of any client-supplied equipment into the test program if needed.

Accredited test standards conducted using the ARL Hemi-anechoic Chamber:

  • ANSI S12.10 / ISO 7779 / ECMA 74, Measurement and Designation of Noise Emitted by Computer and Business Equipment. Results include one-third octave band sound power levels and overall and A-weighted sound power levels, operator and/or bystander one-third octave band sound pressure levels and overall and A-weighted sound pressure levels, and identification of prominent discrete tones.
  • ANSI S12.54 / ISO 3744, Determination of Sound Power Levels of Noise Sources - Engineering Methods for Free-Field Conditions Over a Reflecting Plane. Results include one-third octave band sound power levels and overall and A-weighted sound power levels.
  • ISO 11201, Noise Emitted by Machinery and Equipment - Measurement of Emission Sound Pressure Levels at a Work Station and at Other Specified Positions - Engineering Method in an Essentially Free Field Over a Reflecting Plane. Results include one-third octave band sound pressure levels and overall and A-weighted sound pressure levels at specified operator and/or bystander positions around a piece of equipment.
  • ISO 9296 / ECMA 109, Declared Noise Emission Values of Information Technology and Telecommunications Equipment. Results include declared sound power levels in A-weighted bells, and A-weighted sound pressure levels in decibels for a given product / operating mode. Results used for compliance and product specifications.

Reverberation Chambers and Transmission Loss Test System

For building materials testing, as well other acoustic testing requiring use of reverberation chambers, the ETS-Lindgren ARL includes two reverberation chambers with a transmission-loss test system. The reverberation chambers are equipped with microphone positioning systems, data acquisition systems, diffusing elements, a 5-ton bridge crane system for specimen handling, and an acoustically isolated control area. The chambers are qualified as meeting or exceeding requirements in all accredited test standards.

Types of testing commonly performed in the reverberation chambers include: sound transmission loss testing of walls, windows, doors, and other partitions; highway noise barriers; random-incident sound absorption testing of materials and architectural elements; noise reduction testing of enclosures such as audiometric booths, broadcast studios, test cells, or other enclosures; and, sound power determinations of large equipment.

Accredited test standards conducted using the ARL Reverberation Chambers:

  • ASTM C423, Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method. Results include one-third-octave band random-incidence sound absorption coefficients, and single-number ratings Noise Reduction Coefficient (NRC) and Sound Absorption Average (SAA).
  • ASTM E596, Laboratory Measurement of Noise Reduction of Sound-Isolating Enclosures. Results include one-third octave band Noise Reduction values (in dB), and single number rating Noise Isolation Class (NIC, per ASTM E413).
  • ASTM E90, Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions. Results include one-third octave band Transmission Loss (TL) values (in dB), and single number ratings Sound Transmission Class (STC, per ASTM E413), Outdoor-Indoor Transmission Class (OITC, per ASTM E1332), and Sound Reduction Index (Rw, per ISO 717).
  • ANSI S12.51 / ISO 3741, Determination of Sound Power Levels of Noise Sources - Precision Methods for Broad-Band Sources in Reverberation Rooms. Results include one-third octave band sound power levels and overall and A-weighted sound power levels. 

Impedance Tubes

To critically evaluate acoustic properties of materials, the ETS-Lindgren ARL includes four impedance tubes (of different cross-sectional dimensions to cover a broad frequency range) with associated data acquisition systems and control software. Evaluation of the absorption properties of materials or barrier systems is conducted for use in design and specification of wide variety of product applications.

Test standards using impedance tubes:

  • ASTM E1050, Standard Test Method for Impedance and Absorption of Acoustical Materials Using A Tube, Two Microphones and A Digital Frequency Analysis System. Results include narrowband spectral results of the following acoustical properties of the specimen under test: complex reflection coefficients, normal-incident sound absorption coefficients, normal specific acoustic impedance ratios, normal specific acoustic resistance ratios, normal specific acoustic reactance ratios, normal specific acoustic admittance ratios, normal specific acoustic conductance ratios, and normal specific acoustic susceptance ratios.

Field Testing Services

ETS-Lindgren also provides acoustic field testing services at client sites globally. Acoustic field testing services include qualification of anechoic and hemi-anechoic chambers (in accordance with ISO 3744 or ISO 3745), qualification of reverberation chambers (in accordance with ISO 3741, ASTM C423, and other reverberation chamber-based test standards), environmental noise surveys, and in-situ testing of sound barriers or sound isolating enclosures. Portable microphone positioning systems, sound sources, and laptop-based data acquisition systems allow for precision testing at your location./p>


In 2002, ETS-Lindgren acquired Acoustic Systems of Austin, Texas, and in doing so, expanded their test and measurement capabilities to include the Acoustic Systems Acoustical Research Facility on Saint Elmo Road in South Austin. ASARF had existed to serve and outside clients and as a research and development branch for Acoustic Systems for most of its 30-year history.

From 2002 through 2007, ASARF maintained operations as part of ETS-Lindgren, and expanded testing capabilities with test equipment upgrades and continued laboratory development.

In 2008, the acoustic testing facility in South Austin was closed and existing ETS-Lindgren Test and Measurement facilities in Cedar Park were expanded to include new world-class acoustic test chambers. Testing equipment, procedures, software, and quality systems of the old laboratory were all upgraded and implemented at the new Acoustic Research Laboratory. Re-accreditation from NVLAP in all test methods was completed in October 2008.

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Information presented is subject to change as product enhancements are made. Contact ETS-Lindgren Sales Department for current specification.