Room Criteria Research Articles

Environmental controls of air-conditioned noise with the aid of the Psychoacoustics Perception Scale (PPS)

It is known that an air-conditioning system is an essential component of modern buildings for maintaining good indoor environmental quality. However, the adverse effect due to air-conditioned noise can offset its benefits. Although several noise indices such as Noise Criteria (NC), Noise Rating (NR), Room Criteria (RC), and A-weighted equivalent continuous sound pressure level (LAeq) have been developed to assess the acceptability of indoor noise environments, the noise feature of the environments and its psychological impacts on the occupants are not comprehensively evaluated. Psychoacoustics Perception Scale (PPS) is a psychometric tool to assess the psychological impacts about general judgment (Evaluation, E), sensitivity to the magnitude (Potency, P), and sensation of the temporal and spectral compositions (Activity, A) of noise on occupants. This study aimed to evaluate the air-conditioning building environments by using the traditional noise indices, psychoacoustic metrics, and the PPS. The significant correlations were found between the objective and subjective data. The results of the study provided the useful knowledge on future designs of the environmental controls of air-conditioned noise.

Elevator equipment noise mitigation for high-rise residential condominium

A new high-rise hotel and residential condominium building had elevator equipment rooms between residential spaces. During construction, elevator equipment noise was audible in adjacent unfinished residential spaces. The developer and architect requested evaluation by an acoustical engineer. Investigatory observations with acoustical and vibration measurements were conducted to determine sources and paths of vibration and noise transmission. Construction noise and the unfinished condition prevented measurements reflective of actual future conditions in occupied spaces, but 1/3 octave vibration measurements in the elevator equipment rooms and on wall surfaces of residential space indicated structure borne vibration transmission that could result in re-radiated audible sound. Sound spectrum measurements in the elevator equipment rooms compared with anticipated airborne noise transmission loss through the demising partition indicated potential levels of residual elevator equipment noise in residential spaces. Primary acoustic sources were determined by observations and validated by vibration and measurements in the equipment room. Anticipated noise levels due to airborne sound and structure borne vibration were compared to full-octave background noise Room Criteria (RC) to determine attenuation requirements. Recommendations for noise and vibration mitigation were developed. Mitigation measures implemented by the construction contractor will be enumerated with subjectively determine results.

Lab vibration complaints due to secondary or questionable indicators

Researchers complained about lab vibration in a new multi-floor academic laboratory building after observing surface ripples in water glasses on lab shelves. Structural vibration and low frequency noise can effect sensitive laboratory equipment, degrade experimental specimens and reduce staff efficiency and productivity. Investigatory observations and measurements were undertaken to determine vibration and noise conditions and develop a plan of mitigation. Permissible 1/3 octave Vibration Criteria (VC) and full-octave background noise Room Criteria (RC), including maximum limits for low frequency noise, had been used for building design. Central plant equipment, including pumps and compressors are on ground level. The facility is served by remote campus chillers. The building air handlers, exhaust fans, and boilers are in a penthouse mechanical equipment room and on roof. Structure borne vibration and airborne noise may be transmitted to laboratory spaces via building columns and beams, in pipes and ducts and through vertical duct and pipe shafts. Floor vibration and airborne sound spectra were measured during normal business hours (while the facility was occupied) at various locations for comparison with vibration and noise criteria. Results will be graphically shown on charts. Mitigation measures implemented by the facility management will be enumerated with subjectively determine results.

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.

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.]

Relating human productivity and annoyance to indoor noise criteria systems

The goal of this research is to determine a noise criteria system which best relates the effects of background noise to human productivity and annoyance. A number of indoor noise criteria systems are currently used to rate the background noise in built environments, including noise criteria (NC), balanced noise criteria (NCB), room criteria (RC), room criteria Mark II (RC-Mark II), and others. Many questions still remain about the accuracy of these predictors in assessing human response to background noise under the variety of ambient noise situations encountered. To support the use of any individual criterion, subjective testing was performed under a range of background noise situations and statistically related to the various noise criteria predictors listed above. Subjects completed an annoyance survey and performed typing and proofreading tasks in an acoustically controlled environment under 12 simulated background noise settings. These settings varied across three sound levels and four spectral qualities. Subjective testing methodology and results are presented. [Work supported by INCE and ASHRAE.]

Room noise criteria—Time for common sense

The acoustical environments of the many types of rooms designed for occupancy are supposed to be established in the design phase of a new project or during a project retro-fit so that the intended use of a room is not compromised by intrusive noise sources. A major tool in accomplishing the desired environment is the application of room noise criteria. However, given the many types of noise sources with a wide range in sound quality, frequency content, and temporal features, it seems impossible to achieve a desired, yet cost effective, acoustical room environment by using venerable noise criteria (NC) curves alone. ANSI S12.2-1995 is an attempt to include the means to account for different characteristics in noise sources by introducing the balanced noise criteria (NCB) and room criteria (RC) methods for evaluating noise. As a result of the introduction of ANSI S12.2-1995, a controversy has arisen over the practicality and even the viability of the new standard(s). The people who must live or work in the designed space will ultimately determine whether an adequate acoustical room environment has been achieved. The economics of the acoustical design often dictates whether a working solution is ever implemented at all. A practical basic criteria with just a handful of adjustment factors and guidelines to account for quality, frequency, and temporal anomalies, would be better suited to standardizing the design methodology in room acoustics. This paper provides examples of applications of standards in the everyday world of environmental acoustics. [See NOISE-CON Proceedings for full paper.]

Lighting the operating room—criteria and choice

Lighting the operating room—criteria and choice