The effects of noise on man

In recent years, noise-related disputes caused by construction equipment have increased, resulting in delays and cost overruns in the construction process. To deal with this challenging issue, passive noise control methods such as soundproof barriers and enclosures have been widely used. However, these methods have a limited effect when used to attenuate low-frequency noise. This research aims to suggest a noise management model and to demonstrate the applicability of active noise control (ANC) as a new approach to supplement the limitations of passive noise control. Simulations were conducted to demonstrate and identify the noise reduction effect by active noise control for construction equipment. The simulation results show that noise cancellation can be highly efficient in the low- and mid-frequency bands below 1,000 Hz and that the reduction effect degraded as the frequency increased. On the basis of the findings presented in this research, an environmental manager will be able to mitigate noi...

Construction Noise Management Using Active Noise Control Techniques

Acoustic evaluation and adjustment of an open-plan office through architectural design and noise control.

This research investigated differences in task performance and perception under six non-time-varying ventilation-type background noise spectra with differing tonality. The results were related to five indoor noise criteria systems: noise criteria, balanced noise criteria, room criteria, room criteria mark II, and the A-weighted equivalent sound pressure level (LAeq). These criteria systems are commonly used in the U.S. building industry, but concerns exist over whether they are appropriate for all noise situations. Thirty test subjects completed three types of performance tasks (typing, reasoning, and math) and answered questions about their perception of the indoor environment under each noise condition. Results showed that performance scores did not change significantly across the six noise conditions, but there were differences in subjective perception. For example, perception trends for tonality, annoyance, and distraction changed based on the frequency and prominence of discrete tones in noise. Howev...

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Implications of Human Performance and Perception under Tonal Noise Conditions on Indoor Noise Criteria

Construction activities are associated with various noise-related issues, including health problems, cost overruns, and schedule delays. These issues could be averted by conducting comprehe...

Construction Noise Prediction Model Based on Case-Based Reasoning in the Preconstruction Phase

A number of indoor noise criteria systems are used to quantifj; the background noise in a built environment, including Noise Criteria (NC), Balanced Noise Criteria (NCB), Room Criteria (RC), Room Criteria Mark II (RC Mark II), Aweighted Equivalent Sound Pressure Level (L Acq)' and others. An ongoing debate exists in the acoustical community over which criterion is the most appropriate to use in the variety of ambient noise situations encountered. In an effort to quantitatively support the use of an individual criterion, this project subjectively correlates these various criteria with human task performance and perception. Eleven subjects participated in a pilot study by completing ~)ping and proofreading tasks, as well as subjective ratings of loud ness, annoyance, and spectral quality. Results show that there were no significant differences in productivity scores among the 12 noise exposures tested; howevel; significant relationships were found between indoor noise criteria predictions of level and subjective perception of loudness and annoyance. In this study, RC and RC-Mark II were found to be the most correlated with level perception, although NC, NCB, and LAeq were also strongly correlated. Additionally, interesting relationships were found between subjective perceptions o.frumble or roar and criteria predictions of such. The authors are in the process of extending the pilot study to more subjects, as well as examining the effects of tonal and fluctuating background noise spectra on criteria predictions.

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OR-05-6-4: Relating human productivity and annoyance to indoor noise criteria systems: a low frequency analysis

Most people at one time or another have found themselves irritated or distracted by the background noise in a building. The irritation might have resulted in minor aggravation or may have been dramatic enough to hinder their work. This leads us to ask whether occupants are increasingly aggravated by noise the longer they are exposed to it, or if they naturally habituate to their acoustic environment. In an effort to answer this question, a study was completed in the Indoor Environment Lab at the University of Nebraska. This lab resembles a typical office and was specially constructed to be acoustically and thermally controlled. Subjects completed 38 total hours of testing in the lab over multiple days, during which time they were exposed to several background noise conditions 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. End results aid in understanding the prolonged effects of typical heating, ventilating, and air-conditioning (HVAC) noise on worker productivity and annoyance.

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Effects of Noise on Productivity: Does Performance Decrease over Time?

Currently there are a number of indoor noise criteria used to quantify the level of background noise in rooms, including Noise Criteria (NC), Balanced Noise Criteria (NCB), Room Criteria (RC), Room Criteria Mark II (RC Mark II) and others. This paper reviews the pros and cons of each of these and then compares the values measured in existing classrooms in the Omaha area. The authors are in the process of subjectively comparing these various criteria to determine which method best correlates with human perception. The subjective testing methods and preliminary results are discussed.

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Performance Review of Indoor Noise Criteria

This project collected data detailing the current status of classroom acoustics while simultaneously increasing awareness of educational acoustics and exposure to acoustical engineering research in local schools. In 8 Omaha‐area schools, 2 acoustical aspects which directly influence speech intelligibility were measured and studied: (1) background noise levels resulting from a building’s mechanical systems; and (2) reverberation times within the classroom. Prior to each measurement session, a presentation on good classroom acoustic principles was presented to the teacher and students in that classroom. Subsequently, the teacher and students assisted the principal investigator and research assistants in the measurement of the acoustic data from their classroom. In total, 13 classrooms were studied, with the assistance of 425 middle and high school students in 14 different classes. The background noise results have been associated with commonly used noise criterion curves. Results are compared to recommended background noise levels and reverberation times suggested by ANSI standard S12.60‐2002. The resulting database provides knowledge on the current status of classrooms in Omaha, and may be indicative of classroom situations across the midwestern United States.

Classroom acoustics in Omaha, Nebraska: Measurements and outreach

Overall loudness is not the only quality of indoor background noise that affects occupants. The distribution of noise across frequency (pitch), whether or not the noise contains tones, and whether or not the noise changes over time must also be considered. There are several indoor noise criteria systems available to quantify the background noise in rooms, but many of them do not account for these factors. These systems are commonly used by architects and engineers, and often incorporated into manufacturer’s data, design guides, and standards. There is much debate over which of the criteria systems best reflect how occupants will respond to noise. To examine these issues, an extensive study is being completed at the University of Nebraska investigating the effects of various types of air-conditioning noise on occupant productivity and perception. Results from performance tests and questionnaires are used to evaluate a number of these noise criteria systems. Specific implications of this project on characterizing noise in the workplace will be discussed.

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Erica E. Bowden

Papers

OR-05-6-4: Relating human productivity and annoyance to indoor noise criteria systems: a low frequency analysis

Effects of Noise on Productivity: Does Performance Decrease over Time?

Performance Review of Indoor Noise Criteria

Classroom acoustics in Omaha, Nebraska: Measurements and outreach

Appropriate Characterization of Background Noise Levels in the Workplace