User perspectives on outdoor noise in open-plan offices with operable windows

It seems now accepted that speech noise in open plan offices is the main source of annoyance for employees. The aim of the present study is to test in a laboratory the effect of different sound conditions representative of ambient noise in open plan offices, while the participants perform a task closer to the everyday open-plan office work. Forty-five subjects between 18 and 58 years old participated to the experiment. They were exposed to four controlled sound conditions, made of intelligible speech superimposed to babble noise: equivalent modulation index MAeq and overall level LAeq were the two control factors (two levels each). The duration of the experiment for each condition was equivalent to the duration of half a workday (four hours for each condition). The task consisted in writing a review of four newspapers. During each half-day, the self-reported mental fatigue and the perception of sound environment were evaluated several times. The statistical analyses were performed with respect to three factors, the two sound characteristics (MAeq and LAeq) and the time of the day. The results show that a high intelligibility, which corresponds to a high MAeq value, significantly increased the fatigue experienced by the participants. Lastly, the results of this experiment were compared to a previous experiment conducted by Kostallari et al. We concluded that, for all sound conditions, in both experiments, speech noise has a higher impact on the mental fatigue of the participants, compared to stationary noise or to the ?speech like? amplitude-modulated noise.

Although progress has been made over the last decade on the issue of well-being in open-plan offices, recent surveys show that employees are still dissatisfied with their working environment, particularly the noise environment, remains. However, standards exist to help ensure that open-plan offices are designed to provide the best possible working environment. But, because of the scope of these standards, their recommendations can be contradictory. For example, the French ergonomics standard NF X35-102 makes recommendations on the sizing of workstations, likely to lead to office occupancy densities that are incompatible with the ambient noise level objectives defined in the ISO 22955 standard. To resolve these contradictions, a field measurement protocol was implemented. It consists in (1) a real-time count of the number of people in the office, (2) a measurement of ambient noise, (3) a questionnaire assessing employees' perception of their physical working environment. The data collected in several French companies will make it possible to establish relationships between the ambient noise level, the occupancy density and the perception of noise levels. This paper presents an occupancy sensor developed for this study and measurements of ambient noise level and occupancy ratio during a working day in an open-plan office.

Even if the global health crisis is currently changing the work organisation in offices in the service industry, the problem of noise in open plan offices remains a major challenge with regard to occupational health and well-being. Since 2012, the French National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases (INRS) has been carrying out acoustic surveys in French open-plan offices by measuring both some usual indicators of empty offices (Tr, D2S, Lp4m, rc, Lp) and also the ambient noise levels in activity. In addition, GABO questionnaires have been proposed to employees to assess their perception of the noise environment. So far, 50 open spaces were evaluated, with more or less data collected depending on the situation encountered. Approximately 1,400 employees have already answered the questionnaire. All of the sites visited cover the entire set of activities described by the ISO 22955 standard. An analysis of the links between the acoustic parameters and the perception of employees was carried out. This analysis provides additional information to the studies on the choice of acoustic descriptors and on the use of sound masking systems that aim to control background noise to reduce noise disturbance due to intelligible conversations.

Noise in open-plan offices has become a major health issue. Intelligible speech is considered as the most annoying noise sources by the occupants of such offices. Speech level fluctuations prevent people from achieving some high-demanding tasks, thus inducing annoyance and tiredness. Many studies were conducted in order to identify a sound metric closely related to this Irrelevant Speech Effect. Hongisto et al. have shown that Speech Transmission Effect is appropriate for evaluating the annoyance due to a neighbor in the office. More recently, Schlittmeier et al. suggested that the Fluctuation Strength can be used to evaluate the effect of the fluctuations of the ambient noise on task performance. This paper intends to present a new metric. It is based on the measurement of short-term temporal modulation of sound level. Results indicate that it seems to be as efficient as STI or FS, while being more suitable for in-situ experiments and usable by practitioners.

Noise in open-plan offices, connected with an unintentional hearing of conversations and related distraction of attention, causes annoyance of employees. The article presents the calculated range of speech intelligibility in a selected open-plan office room. The speech transmission index (STI) was examined in a real room of 300 m3. The room was equipped with a sound absorbing suspended ceiling, acoustic screens and sound absorbing materials on the walls. Initial tests were conducted in order to verify the assumed computational model from ODEON software, as well as the geometrical and acoustic data describing the room. The verification process consisted of comparing the calculations and measurement results. In the main part of the study, the range of speech intelligibility was calculated for several locations of the speech source, i.e., areas in which the STI > 0.5. The results of the calculations and the results of the measurements of physical quantities, characterizing the acoustic properties of the open-plan office room (including STI), showed good agreement. For speech emission, the ranges of speech intelligibility were determined on several work stations. The use of calculation methods to simulate the sound field in open-plan office rooms is possible when the calibration of the room model is initially performed. Determination of the speech intelligibility range provides important information about the distance of negative acoustic interactions between work stations. This range can be used to determine the interaction between work stations or to assess various technical solutions to reduce the negative interaction. Med Pr. 2019;70(3):327-42.

Investigation of the sound insulation and natural ventilation performance of a metamaterial-based open window

There are many noise sources inside the classrooms such as heating, ventilating, and air-conditioning(HVAC) noises. Also, there are outdoor noises near classrooms such as road traffic noises. Under these situations, teachers are using loudspeaker system in order to enhance the speech transmission. The present study aims to investigate the students’ subjective responses to teacher’s speech under many different noise situations. in order to this, questionnaire survey was undertaken to 60 students in two different classrooms. They were asked to mark their subjective listening comprehension and speech intelligibility in 5-points scale at every cases when three conditions were changed including opening status of doors and windows, operating HVAC system, and usage of loudspeaker system. Also, sound levels were measured in each case. As a result, it was found that only 17% of subjects responded that they were prevented from noises from outdoor and HVAC system. Also, it was responded that using loudspeaker system can enhance the listening conditions 2.7 times more than normal condition. Nevertheless, there are 33% of negative responses to loudspeaker system due to the artificial tone of speech. Thus, it can be concluded that indoor and outdoor noises cause by opening windows and operating HVAC system do not affect student’s speech intelligibility much in general cases, Also, using loudspeaker system in small classroom should be used cautiously considering students’ preferences.

Are Humans Good Sensors? Using Occupants as Sensors for Indoor Environmental Quality Assessment and for Developing Thresholds that Matter

Novel plenum window with sonic crystals for indoor noise control

Outdoor environmental noise is a major source of annoyance in urban areas and exposure to it can increase the risk of severe health issues. Consequently, it has been the focus of research for decades. Even though people spend the majority of their time indoors, most studies use outdoor noise levels and do not include indoor noise measurements to estimate real exposure levels. This study conducted simultaneous indoor and outdoor noise measurements for 24 h in four multi-unit residential buildings to identify the levels and sources of outdoor noise heard indoors and quantify the effects of outdoor noise on indoor levels. The measurements were conducted in unoccupied suites that are most exposed to traffic and other outdoor noise sources. Surveys were administered following building occupancy to collect information regarding perceived acoustic comfort levels due to outdoor noise. The indoor LAeq,24h in three of the study buildings were above 40 dB(A) and exceeded WHO’s noise level limits. Regression analysis showed that outdoor noise only explains 14%–58% of the variability in indoor noise levels. This is mainly because of heating, ventilation, and air conditioning (HVAC) system noise which resulted in consistently high indoor noise levels despite variations in outdoor noise. Analysis of the survey showed a poor correlation between reported annoyance and measured noise levels. But annoyance strongly depended on other factors such as suite location and noise sensitivity. The findings show that outdoor noise measurements alone may not be good predictors of exposure levels and the effects of outdoor noise on occupants.

Outdoor noise can enter an office workspace through an open window. An active noise Control system Is described that can provide global reduction in the workspace of noise from outside the window. The system uses (1) a microphone array outside the window to detect the magnitude and direction of incoming sounds; (2) a sparse array of loudspeakers in and around the window to radiate sound into the office space to cancel the entering outside sound, and (3) a processing system to derive appropriate signals from the microphone array to drive the speaker array to achieve cancellation. The sparse array leaves the window mostly open and unobstructed. Array shading coefficients that match the radiation pattern of the array to that of the window aperture can be derived in advance. ANC processing on each outdoor noise source provides the signals to drive the cancellation array. A feedforward system built to this design concept should provide reasonable cancellation with minimal window obstruction and fewer optimization channels than a more conventional window cancellation system.

Field study of mixed-mode office buildings in Southern Brazil using an adaptive thermal comfort framework

Coventry England, 15–18 June 1964 planning and design for protection from noise

A new trapezoid-shaped Frisch-grid ionization chamber (TFG-IC) has been built as a part of a varDelta {E}-E telescope system for the detection and identification of charged particles at energies down to a few MeV. To study the effect of the drift electric field uniformity, two types of sealed windows, namely a pair of SSA (split-strip aluminized mylar film) and a pair of DSA (double-sided aluminized mylar film) sealed windows have been investigated. The detector’s performances were studied using a standard ^{241}Am source at different gas pressures, and the total energy-deposit resolution achieved is about 1.1%(FWHM). The varDelta {E}-E telescope, which was composed of TFG-IC and a DSSSD (double-sided silicon strip detector), has been tested using a three-component alpha source and the ^{241}Am source under laboratory conditions. The results show that the energy resolution with the SSA sealed windows which provide uniform drift electric field has a smaller fluctuation than that with the DSA ones; the fluctuations are about 1% and 4% for the former and the latter, respectively. Simulations using the COMSOL software also confirmed the electric-field distortion at the edge of the detector with the DSA windows. A correlation curve between energy resolution and energy deposit of charged particles at various gas pressures and for two gas species is derived for TFG-IC with the SSA sealed windows using the measurement with the ^{241}Am source. Incorporating the above results, we performed Monte Carlo simulations to evaluate the particle-identification capability of the telescope. The results show that the telescope can be extended to the identification of low-energy particles.

A growing attention has been paid in the last years to the indoor pollutants’ concentrations. In particular, several European Administrations focused on the Particulate Matter with less than 2.5 µm in diameter, i.e., the PM2.5, since it can cause severe respiratory and other health hazards. In the early 2024, the European Union tightened IAQ standards by lowering the annual average PM2.5 threshold value from 25 to 10 µg/m3. Even if PM2.5 generation in the indoor environments is typically linked to printers and office appliances, a significant share is due to natural ventilation through openings adjacent to congested streets or factories.Recently, attention has been paid also to air purifiers, which can contribute to removal of PM2.5, reducing the need for window opening and, consequently, ventilation heat losses. Impact of air purifiers on the energy performance of naturally ventilated buildings, however, has not been investigated in detail, with primary focus put solely on IAQ.In order to discuss the potential of air-purifiers to improve IAQ while optimizing natural and hybrid ventilation strategies, in this research we analyzed a public office building located in Bolzano, Italy, representative of offices designed and constructed in the 1990s in the Italian northern regions. Although the building is equipped with mechanical ventilation system, this is operated only for the removal of pollutants one hour during lunch break, before and after occupancy. In the remaining worktime, employees rely on natural ventilation solutions to improve the IAQ conditions, increasing in such a way thermal losses during the heating season. Furthermore, part of the offices are adjacent to a congested street, meaning that windows opening may allow ingress of outdoor PM2.5 in those spaces. Given these premises, in this research we explored the potential of hybrid ventilation strategies based on optimal window opening schedule and installation of portable air purifiers to improve both IAQ and building energy performance.Whole annual building simulations with a calibrated TRNSYS and TRNFLOW model were performed to estimate energy consumption and CO2 and PM2.5 concentrations in all considered scenarios. Results confirmed that outdoor sources contribute significantly to the increase of indoor PM2.5 concentrations and internal air flows to their distribution to adjacent environments. Air purifiers proved to be effective in controlling PM2.5 in the room where placed, as well as to reduce energy consumption while keeping adequate air changes and CO2 concentrations, with an overall improvement compared to the current practice in the building.