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This paper provides an overview of a custom software developed to obtain measurement data in a self-contained acoustic test facility system used for conducting random incidence sound absorption tests and sound transmission loss tests on small samples in accordance with SAE J2883 and J1400 standards, respectively. Special features have been incorporated in the software for the user to identify anomalies due to extraneous noise intrusion and thereby to obtain good data. The paper discusses the thoughts behind developing user-friendly algorithms and graphical user interfaces (GUI) for the sound generation, control, data acquisition, signal processing, and identifying anomalies.

A large reverberation room of approximately 310 m3 (11,000 ft3) used in the air conditioning, heating and refrigeration industry, was in need of improvements to meet the updated requirements of the American Heating and Refrigeration Institute (AHRI) Standard 220. In addition, it was desired to extend the measurement qualification of the room down to the 63 Hz octave band. The initial qualification test results showed that the room did not qualify for the extended low frequency range and also had some irregularities in the 100 Hz third octave band. This paper reports the results of a three-part investigation to correct reverberation room response irregularities in the 100 Hz third octave band, to establish performance that qualifies relative to the most recent standard, and to determine and integrate the means by which its qualification could be extended down to the frequency bands of 50, 63, and 80Hz.

This paper presents the results of a study to reduce the background noise level within a large Quiet Room located adjacent to other laboratory testing environments and below a mechanical mezzanine which houses an extensive array of mechanical and electrical equipment including banks of low-temperature chiller compressors, air handling units, and electrical switchgear that serves the entire building complex. This equipment was installed atop the concrete mezzanine floor deck without provisions for isolating vibration. As a result, structure-borne noise from that equipment travels through the floor, radiates from the underside of the floor deck, and intrudes into the Quiet Room below. This causes the background noise level within the Quiet Room to be too high for conducting low sound level measurements and studies on vehicles brought into the Quiet Room.

This paper presents the upgrades and improvements needed to bring an old and seldom used reverberation room test suite up to current standards. The upgrades and improvements included eliminating a below-floor pit that was open to the reverberation room, improving the acoustical diffusion within the room, enlarging the opening between the reverberation room and an adjacent anechoic chamber, renovating the anechoic receiving chamber, constructing an innovative sound transmission loss test fixture, and installing of a high power reverberation room sound system.

This paper presents the design, construction, and implementation of a novel sound transmission loss (STL) testing fixture that is unique to the automotive industry. This fixture was built within a large 1.68 m high × 2.74 wide (5′6″ × 9′0″) opening in the wall between a 497 m3 (17,591 ft3) reverberation room and an adjacent anechoic chamber. The fixture was designed and built to accommodate interchangeable plugs that allow STL measurements on an automotive ‘buck’ as well as on flat sample materials. It features a removable sample holding frame system that simply and quickly clamps in place and acoustically seals with a pneumatically inflated seal.

This paper presents an overview of the acoustical design of a small volume self-contained acoustical testing facility (SCATF). The design focuses on a small volume (25 m₃) reverberation room for testing the random incidence sound absorption performance of small samples of acoustical materials and automotive parts. This reverberation room also couples to a small volume hemi-anechoic room and serves as the random incidence source room for sound transmission loss testing. These testing approaches respectively target the SAE J2883 (pending) and J1400 test standards.

High levels of broadband sound are generally required for sound transmission loss and sound absorption tests conducted within reverberation rooms. However, the sound system components such as loudspeakers are often selected with little consideration or knowledge of the audio engineering principles that govern system operation. This paper will address the selection of a loudspeaker system for producing the required sound level in a reverberation room, starting with the sound level requirements in a test room, and a brief review of the fundamental concepts of loudspeakers, including horn loading and compression drivers, radiation efficiency, directivity, power ratings and limits, thermal compression, crossovers, equalization, and spectral balancing resistors. Loudspeaker manufacturer's specification data, such as 1 watt/meter sensitivity, directivity index Q, and power ratings will then be discussed.

High levels of broadband random noise are generally required for conducting sound transmission loss and sound absorption tests within reverberation rooms. However, the sound system components such as loudspeakers, amplifiers, and other elements are often selected with little consideration of the audio engineering principles that govern device as well as system operation. This paper will explore some of the requirements for reverberation room sound systems starting with the acoustical power spectrum needed to overcome the transmission loss of high performance barrier assemblies, the background noise in the receiving room, the background noise floor of measuring instruments, and air absorption within the reverberation room.

The GM Noise and Vibration Analysis Laboratory (NVAL) was conceived in response to GM's need for a state-of-the-art noise, vibration and harshness (NVH) testing and development facility. This paper examines the construction of the NVAL to help illustrate the process of converting NVH facility design documents into a functioning facility. It features a summary of items learned through the course of the construction effort and outlines issues a technical building owner should consider when embarking on a new facility project. NVH facility construction is unique. The traditional construction approach, emphasizing time and cost reduction, must be buffered with an equal or greater emphasis on performance and the proper sequencing of tasks to allow these integrated facilities to meet their operational objectives.

This paper examines the critical design elements and issues associated with converting facility goals and business objectives into a functional facility. The design of the General Motors Noise and Vibration Analysis Laboratory (NVAL) will be discussed to help clarify key points. A team-oriented design approach is essential to meet the stringent safety, flexibility and operational requirements associated with noise, vibration and harshness (NVH) facilities. The first step is establishing the design team and their respective roles in the process. The challenge of “how to build a facility that meets the specified objectives” is addressed in the programming phase. Operational and financial objectives are reviewed and validated. Upon completion of the programming effort, the team attacks the special technical challenges borne out of that process.

Acoustical laboratories for vehicle testing have specialized requirements which differ from those for most conventional buildings and facilities. As a result, the normal design and building process takes on added dimensions which need to be carefully considered and addressed. This paper presents an overview of the process that starts with conceptualization of the laboratory and ends with the validation and qualification of the laboratory, and includes particular emphasis on the inherent peculiarities. Case studies are provided of several potential perils and pitfalls that may be encountered in the process which can adversely affect the usability of the laboratory as well as the validity and repeatability of test results obtained by that laboratory. The paper concludes with suggested courses of action which will help either to avoid or minimize the compromises that imperil the functional effectiveness of a laboratory.