Noise Criteria Research Articles

Investigations of indoor noise criteria systems based on human perception and task performance

Several noise criteria methods commonly used in architectural acoustics have been quantitatively related to noise perception and task performance under a variety of ventilation systems-induced background noise conditions. Noise criteria, balanced noise criteria, room criteria, room criteria mark II, and A-weighted equivalent sound pressure level were examined. The first phase of the project included noise conditions controlled to be non-time-varying and nontonal, with neutral, rumbly, roaring, or hissy characteristics. An intermediate study examined exposure time length and types of performance tasks used. The final phase included noise conditions containing various levels of discrete tones from 120 to 595 Hz. Under each noise, subjects completed performance tasks and perception questionnaires. Results indicate task performance was significantly affected by perception of noise, but this relationship was not fully demonstrated by the criteria systems analyzed. The five criteria were generally well suited in describing subjective loudness perception, but some discrepancies in criteria spectral quality ratings and subjective perception existed. Finally, perception of annoyance changed based on the frequency and prominence of tones in noise, but these changes were not reflected in the criteria level or spectral quality ratings. Modifications to the existing criteria are recommended.

Analysis of parameter effects on sound energy decay in coupled volume systems

Several noise criteria methods commonly used in architectural acoustics have been quantitatively related to noise perception and task performance under a variety of ventilation systems-induced background noise conditions. Noise criteria, balanced noise criteria, room criteria, room criteria mark II, and A-weighted equivalent sound pressure level were examined. The first phase of the project included noise conditions controlled to be non-time-varying and nontonal, with neutral, rumbly, roaring, or hissy characteristics. An intermediate study examined exposure time length and types of performance tasks used. The final phase included noise conditions containing various levels of discrete tones from 120 to 595 Hz. Under each noise, subjects completed performance tasks and perception questionnaires. Results indicate task performance was significantly affected by perception of noise, but this relationship was not fully demonstrated by the criteria systems analyzed. The five criteria were generally well suited in describing subjective loudness perception, but some discrepancies in criteria spectral quality ratings and subjective perception existed. Finally, perception of annoyance changed based on the frequency and prominence of tones in noise, but these changes were not reflected in the criteria level or spectral quality ratings. Modifications to the existing criteria are recommended.

Sound Field Systems on the Rise in Schools

Sound Field Systems on the Rise in Schools

Acoustical Standards for Classroom Design Comparison of International Standards and Low Frequency Criteria

Many countries have acoustical standards or regulations for educational facility design and construction. They are based on speaking and hearing abilities of teachers and learners. Criteria are often stipulated for reverberation decay time, sound isolation and allowable background noise. The standards may use single number A-weighted overall level descriptors (dBA), or octave band spectrum criteria (NC, RC, NR, etc.). A-weighted overall level criteria control mid- to high frequencies better than lower frequencies. Very few, if any countries specify low frequency noise standards, although limitations are implicit in spectrum criteria curves, such as (North American) Noise Criteria (NC) or Room Criteria (RC) or (European) Noise Rating (NR). Many educators focus on mid- to high-frequency effects on speech intelligibility, but low frequency noise (LFN) may cause some (upward) masking of speech with reduction of intelligibility. In addition, LFN may affect student attitudes, behaviour, performance and/or fatigue. This paper compares acoustical criteria from several countries with respect to spectrum. Frequency spans or reverberation, sound isolation and background noise are contrasted with hearing and speech characteristics of children and adult learners. Principal findings of some LFN research by others are introduced, such as annoyance, speech intelligibility and fatigue. Tabular comparisons of acoustical criteria and graphic charts of representative criteria will be presented. General recommendations are made, based on findings inferred from review and comparison of standards.

공기조화 취출구 소음의 평가요인에 관한 연구

There are various types of noise around us such as road traffic noise, aircraft noise and floor impact sound, equipment noise, etc. Researches on the noise criteria and the evaluation method for the diffuser noise of HVAC are insufficient. dB(A) and NC values represented in ASHRAE guide book are applied as a noise criteria for diffuser noise, which have some problems like that the values between dB(A) and NC have deviation even if the sound is same one. Therefore, the evaluation method should be considered and proposed based on the subjective responses. From these reasons, this study aimed to analyze the evaluation factors for the diffuser noise of HVAC reflected on the subjective responses by surveying vocabularies and grouping them with factor analysis.

Finding Connections Among Indoor Noise Criteria, Human Perception, and Worker Performance

Finding Connections Among Indoor Noise Criteria, Human Perception, and Worker Performance

Relationship between noise criteria and room criteria ratings

The September 2000 issue of Noise/News International featured a paper entitled ‘‘Room Noise Criteria—The State of the Art in the Year 2000’’ by Gregory C. Tocci. The paper in part investigated the relationship between NC (tangency), NCB, and RC ratings for a series of 268 spectra measured in building spaces during the course of Cavanaugh Tocci Associates, Inc. consulting work. These spectra ranged from uniform to widely varying in shape. This presentation extends this work to document the relationship between RC and NC tangency ratings for these 268 spectra, which was not included in the original 2000 NNI paper.

Development of method for assessing traffic noise in certain typical conditions

Assessing traffic noise is difficult in certain typical conditions in New York City due to changed street geometries, challenges of collection of non‐traffic noise components, and levels of existing noise affected by heavy traffic at adjacent streets, among other variables. In general, a proportional model, i.e., a logarithmic equation to compute total passenger car equivalents (PCEs), is employed to assess traffic noise impacts based upon the noise methodology and the noise criteria under the City Environmental Quality Review (CEQR) guidelines. However, in some typical conditions, such as significant changes in roadway or street geometry, roadways that currently carry no or very low traffic volumes, and existing noise levels that are the result of multiple sources, the FHWA Traffic Noise Model (TNM) can be used to better compute project‐generated traffic components. This paper presents a development of noise analysis method dealing with these conditions. Once a proportional model identifies any potential noise impacts for screening purposes, TNM computations can be conducted for more thorough and detailed noise analyses. The results demonstrate that while a proportional model provides a practical and convenient noise analysis for most situations, TNM can provide more accurate noise assessments for the conditions listed above.

Evaluations of indoor noise criteria systems based on human response

The goal of this research is to examine human response to background noise, and relate results to indoor noise criteria. In previous work by the authors, subjects completed perception surveys, typing tasks, and proofreading tasks under typical heating, ventilating, and air‐conditioning (HVAC) noise conditions. Results were correlated with commonly used indoor noise criteria systems including noise criteria (NC), room criteria (RC) and others. The findings suggested that the types of tasks used and the length of exposure can impact the results. To examine these two issues, the authors conducted a new study in which each test subject completed 38 total hours of testing over multiple days. Subjects were exposed to several background noise exposures over 20, 40, 80, and 240 minute trials. During the trials, subjects completed a variety of performance tasks and answered questions about their perception of the noise, the thermal environment, and various other factors. Findings from this study were used to determine optimum testing conditions for on‐going research examining the effects of tonal or fluctuating background noise on performance, annoyance, and spectral perception. Results are being used to evaluate the effectiveness of commonly used indoor noise criteria systems. [Work supported by INCE and ASHRAE.]

Suggested noise criteria for plumbing systems

The issue of noise that is generated by plumbing systems has been addressed in several articles and texts in the acoustic literature, but most of this information deals with a description of the various noise generation mechanisms and recommended methods of controlling noise from plumbing fixtures and piping. As with any noise source that has the potential for generating annoyance, the question of how much noise is too much noise eventually arises. Chapter 47 of the 2003 ASHRAE Applications Handbook contains newly published guidelines for plumbing noise criteria as it impacts building occupants. This paper discusses the ASHRAE guidelines, and it also suggests additional noise criteria for other plumbing‐related sources of noise in multitenant buildings.

Recommended noise criteria for siting industrial facilities near residential communities with extremely low ambient sound levels

Noise limits or criteria in many residential communities are based on an allowable increase in level above the prevailing ambient sound level, usually on the order of 3 to 5 dBA. The theory is that such a small increase results in masking of the new or existing intruding facility noise by the environmental ambient sound. However, many facilities are planned for installation or already exist in remote and very quiet ambient environments with residual levels as low as 25 dBA during the day or nighttime. This paper summarizes a study conducted to determine appropriate criteria in such remote and quiet areas where little or no noise masking will occur from ambient sources. The paper discusses both audible noise measured by the A-weighted level, low frequency noise characterized by the C-weighted level and tonal noise.

Design and analysis of a hemi-anechoic chamber at Michigan Technological University

A four-wheel chassis roll dynamometer test facility was installed on the campus of Michigan Technological University (MTU). The chassis dynamometer was enclosed in a soundproof hem-anechoic room in order to conduct noise radiation measurements on test vehicles. All surfaces of the room, except the floor and control room window, were acoustically treated with donated tetrahedral acoustic cones and panels. The acoustic absorption properties of these materials were characterized through reverberation chamber and impedance tube testing, and the effects of air gaps, cone orientation, and cone mounting materials were qualitatively evaluated. The design of the wall, ceiling, and door treatments of the chamber was based on the sound absorption properties of these materials, in addition to spatial constraints and cost considerations. The treated chamber acoustics were predicted based on the amount of acoustic material that could be applied to given chamber dimensions and would still preserve the functionality of the room. These predictions were validated through evaluation of the actual room treatment based on average reverberation time at 100-Hz third-octave band, free sound field characteristic 6-dB reduction in sound pressure level (SPL) per doubling in distance from source, noise reduction at the chamber boundaries, and background SPL Noise Criteria (NC) Rating.

Personal computer, printer, and portable equipment noise in classrooms

The American National Standard on classroom acoustics (ANSI S12.60-2002) presents criteria for background noise in classrooms. The criteria in ANSI S12.60 do not apply to the noise from portable or permanent built-in equipment used during the course of instruction, such as computers, audiovisual equipment, and printers. ANSI S12.60 provides general guidance on the selection and installation of such equipment; however, the standard does not present specific recommendations for schools to purchase these products to ensure they meet acoustics needs. This paper updates the recommendations made in a NOISE-CON 2003 paper by the authors on an approach for ensuring that computers and instructional material are acceptable acoustically in classroom environments. Schools should use unambiguous purchase specifications based on product A-weighted sound power level criteria. Schools should then install and operate the equipment in a manner to minimize noise emissions—considering both location of products and students and special noise reduction techniques. This paper recommends a purchase specification format; product sound power criteria based on experience and existing environmental criteria; and procedures for installing and locating such equipment in the classroom to minimize noise.

Plumbing noise in multifamily dwellings: 50 years and counting

Historically, plumbing sound was only of concern in luxury buildings and plumbing noise was rarely addressed explicitly in building codes or design guidelines. The last couple of decades have seen marked increases in population density, occupant expectations and sensitivity to noise, and the number of noise‐related lawsuits. These demographic factors have considerably increased the importance of adequately addressing plumbing noise in multifamily projects, as shown by the increasing number of published guidelines (such as in the latest ASHRAE Handbook). Over the course of our firm’s history, we have attempted to determine the relationship between the sound level from plumbing systems and the acceptability to the occupants. Our current criteria for plumbing noise and the reasoning behind them is discussed, including test cases and lawsuits, as well as the materials and methods available to meet those criteria, and their impact on the design of multifamily projects.

Noise, vibration and harshness (NVH) criteria as functions of vehicle design and consumer expectations

The criteria for NVH design are to a large degree determined by the types of vehicles and the perceived desires of the purchasers of vehicles, as well as the cost of incorporating NVH measures. Vehicles may be classified into specific types, e.g., economy car, midsize passenger, near-luxury and luxury passenger cars, sports cars, vans, minivans, and sports utility vehicles of varying sizes. The owner of a luxury sedan would expect a quiet ride with minimal vibration and harshness—however, if that sedan is to display sporting characteristics, some aspects of NVH may actually have to be increased in order to enhance a feeling of driver exhilaration. A discussion of the requirements for specific types of vehicles is provided, with due regard for effects on the usability of installed sound/video systems, driver and passenger fatigue, feel of steering mechanisms and other mechanical components, consumer market research, etc. A number of examples of vehicles on the market are cited.

Comments on draft ANSI S12.2, American National standard on criteria for evaluating room noise

In 1995, American National Standard S12.2‐1995 on room noise criteria was issued. Two methods for specifying and evaluating room noise were presented, the NCB noise‐criterion curves [J. Acoust. Soc. Am. 86, 650–664 (1989)] and the RC curves [Noise Control Eng. J. 45, 243–250 (1997)]. The NCB curves were derived from the characteristics of hearing with emphasis on speech interference level and loudness level, while the RC curves were derived from experimental studies in offices where the HVAC noise was low enough that there were no complaints from room occupants. The NCB curves were applicable to rooms ranging from concert halls to factory spaces, while the RC curves were largely restricted to office, hospital, and residential spaces. The two sets were incompatible at low frequencies and low sound levels. The NCB curves assumed that the HVAC noise was free of surging and strong turbulence. The RC curves demanded lower levels at low frequencies, thus permitting some degree of surging and turbulence. The new draft standard specifies two methods for evaluating room noise, the NC [Noise Control 3, 19–27 (1957)] and the RNC methods [Noise Control Eng. J. 48, 85–96 (2000)]. The former (NC) have found widespread use and the latter (RNC) bridges the differences between the NC (and NCB) and the RC criteria curves. This paper comments on the promise of the new RNC method and compares measured data were available.

Working with Cyril M. Harris at Benaroya Hall

To contribute to a project such as Benaroya Hall, now the home of the Seattle Symphony Orchestra, as team members of acoustical giant Cyril M. Harris was a golden opportunity for Robert M. Hoover and Ashton Taylor. Their involvement in the project and association with Cyril began at the early stages of the project as consultants in noise control. During the schematic design phase, Cyril dictated to the LMN Architects design team that authority for all noise control decisions rested with Bob Hoover. This led to good working relationships, especially with the mechanical engineering firm and the air-conditioning contractor. Throughout the project, Cyril insisted upon the highest standards of materials and workmanship, and relied on the expertise of his acoustical design team, even if it went against his initial idea on some issue. At the beginning with the setting of noise criteria and in the finished building when measuring background sound, Cyril participated in the noise control process. Benaroya Hall has been critically acclaimed by the media and musicians, it was an honor for both Bob Hoover and Ashton Taylor to be part of that success.

When octave bands are not enough: Case histories of indoor room noise

All of the published indoor noise criteria evaluation methods are defined on the basis of either the octave band or the overall A‐ or C‐weighted sound pressure levels. While this may be sufficient for some acoustic environments, there are many situations where these sound level descriptors are totally inadequate. This paper uses case histories to show that 1/3‐octave and narrow‐band analysis is sometimes required to properly assess the acoustic environment. To take it one step further, a recommendation is made to avoid the use of octave bands altogether and to routinely use 1/3‐octave band analysis for acoustical measurements and analysis relating to indoor noise criteria.

Structural Floor Vibration and Sound Isolation Design for a Magnetic Resonance Imaging System

This is a case study about noise and vibration control problems, and the design constraints and solutions for a proposed installation of a magnetic resonance imaging system (MRI) in an existing medical research facility. Manufacturer's data indicated that airborne sound level emissions over a broad frequency span could exceed permissible noise criteria for nearby occupied rooms. The building structure also required reinforcement to accommodate the MRI magnet's concentrated load, but invasive disturbance to a transgenic research mouse vivarium on the floor below was prohibited. The structure borne vibration paths needed attenuation or isolation. Design parameters included structural strength, stiffness and the specific platform resonant frequency (non-coincident with known vibration sources or building structure). In addition, acoustical containment was required for anticipated noises from the magnet room, to prevent excessive or annoying and distracting noise in the MRI control room or other adjacent (but unrelated) research, animal holding and office spaces. Structural “de-tuning” and architectural “decoupling” concepts were employed. A resonant frequency criterion was recommended for the new structural floor design. A combination of vibration spectrum analysis, dynamic analyses of alternate structural concepts and existing physical conflict constraints led to the design of an independent platform floor above the existing building floor. Post construction floor vibration measurements were compared to earlier measurement data to show quantitative change in performance. The modifications satisfied acoustical criteria and occupants' subjective evaluations.

Metabolic Activation-related CD147-CD98 Complex

Cell surface CD147 protein promotes production of matrix metalloproteinases and hyaluronan, associates with monocarboxylate transporters and integrins, and is involved in reproductive, neural, inflammatory, and tumor functions. Here we combined covalent cross-linking, mass spectrometric protein identification, and co-immunoprecipitation to show selective CD147 association with three major types of transporters (CD98 heavy chain (CD98hc)-L-type amino acid transporter, ASCT2, and monocarboxylate transporters) as well as a regulator of cell proliferation (epithelial cell adhesion molecule). In the assembly of these multicomponent complexes, CD147 and CD98hc play a central organizing role. RNA interference knock-down experiments established a strong connection between CD147 and CD98hc expression and a strong positive association of CD147 (and CD98hc) with cell proliferation. As the CD147-CD98hc complex and proliferation diminished, AMP-activated protein kinase (a cellular "fuel gauge") became activated, indicating a disturbance of cellular energy metabolism. Our data point to a CD147-CD98 cell surface supercomplex that plays a critical role in energy metabolism, likely by coordinating transport of lactate and amino acids. Furthermore we showed how covalent cross-linking, together with mass spectrometry, can be used to identify closely associated transmembrane proteins. This approach should also be applicable to many other types of transmembrane proteins besides those associated with CD98hc and CD147.