Case-study evaluations of the acoustical designs of renovated university classrooms

The acoustical characteristics of 14 university classrooms at the University of British Columbia were measured before and after renovation—seven of these are discussed in detail here. From these measurements, and theoretical considerations, values of quantities used to assess each classroom configuration were predicted, and used to evaluate renovation quality. Information on each renovation was determined with the help of the university campus-planning office and/or the project acoustical consultant. These were related to the evaluation results in order to determine the relationship between design and acoustical quality. The criteria focused on the quality of verbal communication in the classrooms. Room-average Speech Intelligibility (SI) and its physical correlate, Speech Transmission Index (STI), were used to quantify verbal-communication quality. A simplified STI-calculation procedure was applied. The results indicate that some renovations were beneficial, others were not. Verbal-communication quality varied from ‘poor’ to ‘good’. The effect of a renovation depends on a complex interplay between changes in the reverberation and changes in the signal-to-noise level difference, as affected by sound absorption and the source outputs. Renovations which reduce noise are beneficial unless signal-to-noise level differences remain optimal. Renovations often put too much emphasis on adding sound absorption to control reverberation, at the expense of lower speech levels, particularly at the backs of classrooms. The absorption and noise contributed by room occupants has apparently often been neglected.     

Influence of staff number and internal constellation on surgical site infection in an operating room

Prediction of bacteria-carrying particle (BCP) dispersion and particle distribution released from staff members in an operating room (OR) is very important for creating and sustaining a safe indoor environment. Postoperative wound infections cause significant morbidity and mortality, and contribute to increased hospitalization time. Increasing the number of personnel within the OR disrupts the ventilation airflow pattern and causes enhanced contamination risk in the area of an open wound. Whether the amount of staff within the OR influences the BCP distribution in the surgical zone has rarely been investigated. This study was conducted to explore the influence of the number of personnel in the OR on the airflow field and the BCP distribution. This was performed by applying a numerical calculation to map the airflow field and Lagrangian particle tracking (LPT) for the BCP phase. The results are reported both for active sampling and passive monitoring approaches. Not surprisingly, a growing trend in the BCP concentration (cfu/m³) was observed as the amount of staff in the OR increased. Passive sampling shows unpredictable results due to the sedimentation rate, especially for small particles (5–10 μm). Risk factors for surgical site infections (SSIs) must be well understood to develop more effective prevention programs.     

Influence of staff number and internal constellation on surgical site infection in an operating room

Prediction of bacteria-carrying particle （BCP） dispersion and particle distribution released from staffmem- bers in an operating room （OR） is very important for creating and sustaining a safe indoor environment. Postoperative wound infections cause significant morbidity and mortality, and contribute to increased hospitalization time. Increasing the number of personnel within the OR disrupts the ventilation airflow pattern and causes enhanced contamination risk in the area of an open wound. Whether the amount of staffwithin the OR influences the BCP distribution in the surgical zone has rarely been investigated. This study was conducted to explore the influence of the number of personnel in the OR on the airflow field and the BCP distribution. This was performed by applying a numerical calculation to map the airflow field and Lagrangian particle tracking （LPT） for the BCP phase. The results are reported both for active sampling and passive monitoring approaches. Not surprisingly, a growing trend in the BCP concentration （cfu/ms） was observed as the amount of staff in the OR increased. Passive sampling shows unpredictable results due to the sedimentation rate, especially for small particles （5-10 i~m）. Risk factors for surgical site infections （SSls） must be well understood to develop more effective prevention programs.     

Assessment of pulmonary air trapping and obstruction in expiration: an experimental MRI study

PURPOSE: The aim of this experimental study was to evaluate the potential of a simple expiration technique by means of magnetic resonance imaging (MRI) in an animal model to detect pulmonary air-trapping areas after artificial bronchial obstruction. MATERIAL AND METHODS: Sixteen pigs were evaluated by means of a modified T1-weighted FLASH with fat saturation in respiratory arrest (TR=4.6 ms, TE=1.8 ms, alpha=10 degrees, S.D.=3-5 mm). A measurement of the signal intensity (SI) in the peripheral lung tissue was made in both inspiration and expiration before and after inhalation of 2 ml of 0.5% acetylcholine to simulate a bronchial obstruction. A final measurement of the lung SI was also made after bronchospasmolytic induction through salbutamol (beta2-mimetic bronchodilator). RESULTS: In expiration, a mean SI increase in peripheral lung tissue of about 183% was seen in comparison to inspiration (mean SI increase of 11-32). After inhalation of 0.5% acetylcholine, the expirational signal increase in peripheral lung tissue was only 114% of the original SI. The expirational signal homogeneity decreased after inhalation of acetylcholine. After inhalation of salbutamol, the lung tissue signal elevation in expiration was 193%. CONCLUSION: We interpret the low expiratory signal elevation after acetylcholine inhalation as a result of an air-trapped bronchial constriction in certain areas. The simple expiratory technique in an animal model showed that it is suitable to demonstrate obstructive air trapping using MRI.     

Application of fuzzy control to a road tunnel ventilation system

This paper deals with the serious problems of ventilation system in a large road tunnel. Higher visibility and lower concentration of carbon monoxide are the key issues concerning the ventilation system. Prior to designing the fuzzy control model, a configuration layout of the ventilation system including sensing, control and traffic prediction as well is conceptually constructed. Based on the layout that offers assignments of sensors and control elements, a fuzzy logic control model is developed. Membership functions of sensor errors and control increments are physically submitted in order to set up the fuzzy logic rules. Timing and spacing filtering in terms of weighting approaches is employed in the fuzzy logic rules. A dynamic equation describing the concentration of air pollution is also given so as to cooperate with the fuzzy logic rules and to play roles in the computer simulation. The result of computer simulation involving five cases indicates that a multi-level scheme is able to solve the engineering problems.     

Effect of source location on particle dispersion in displacement ventilation rooms

A proposed computer model for predicting aerosol particle dispersion in indoor spaces was validated with experimental data found in the literature,and is then used to study the effect of the area and point source locations on particle dispersion in displacement ventilation (DV) rooms.The results show that aerosol source location has a strong impact on the spatial distribution and removal rate of indoor particles.Particle removal performance depends strongly on ventilation efficiency and particle deposition rate on indoor surfaces.Important consideration for both relative ventilation efficiency and deposition rate consists of the position of the aerosol source relative to the main airflow pattern and the occupied zone.     

Effect of source location on particle dispersion in displacement ventilation rooms

A proposed computer model for predicting aerosol particle dispersion in indoor spaces was validated with experimental data found in the literature, and is then used to study the effect of the area and point source locations on particle dispersion in displacement ventilation （DV） rooms. The results show that aerosol source location has a strong impact on the spatial distribution and removal rate of indoor particles. Particle removal performance depends strongly on ventilation efficiency and particle deposition rate on indoor surfaces. Important consideration for both relative ventilation efficiency and deposition rate consists of the position of the aerosol source relative to the main airflow pattern and the occupied zone.     

The acoustic performance of ventilated window with quarter-wave resonators and membrane absorber

Noise and air pollution problems become significantly in a busy city such as Hong Kong since buildings usually located close to the heavy traffic lines. Traditional openable window cannot fulfill all the functions of noise reduction, lighting and natural ventilation. A new ventilated window combines the multiple quarter-wave resonators (silencer) and the new wing wall designs aim to make a balance between acoustic and ventilation performances at the same time. Furthermore, the use of multiple-wave resonators and membrane absorber which made plexi-glass plastic sheet replace absorption material can improve the durability; avoid small particle emission and light transparency.The acoustic and ventilation performance of new ventilated window were examined in this study. Noise attenuation of the new ventilated window design has improved significantly by combine flexible absorber and quarter-wave resonator effects. Transmission loss of 10–22 dB can be achieved in the frequency range of 500 Hz–4 kHz band. Outlet air flow velocity of ventilated window design is higher than that of “an open window”. Thus, both the acoustics and ventilation performance of the new ventilated window is essential. Wind-driven natural ventilation is an effective strategy in maintaining the comfort and health of the indoor environment.     

Design of an acoustic enclosure with duct silencers for the heavy duty diesel engine generator set

Diesel engine generator sets in heavy industry plants and residential/official buildings can cause serious noise problems. In this paper, a low noise diesel engine generator set is developed through constructing an acoustic enclosure with ventilation duct silencers that effectively block the acoustic flow but guarantee good thermal flow. Acoustic design of the enclosure, which is initially layout by rule of thumb, is evolved systematically through numerical reanalysis procedure, based on indirect boundary element method (IBFM) with a commercial acoustic analysis code. The cooling performance of the acoustically determined enclosing structure is checked and confirmed through numerical heat flow analysis. The acoustic and cooling performances of the developed low noise diesel engine generator set are confirmed by the experiment.     

CFD simulation of methane dispersion and innovative methane management in underground mining faces

This study addresses methane dispersion in a mine tunnel with discrete methane sources and various methods to handle it. Air flow behavior and methane dispersion in the tunnel are simulated utilizing the computational fluid dynamics (CFD) approach. Various possible conditions which may occur in a mine tunnel are investigated. Simulation results indicate that methane dispersion inside the mine tunnel is influenced significantly by the number as well as location of the sources and quantity of methane released from each source. Furthermore, application of an innovative flow divider which comprises volumetric flow control and flow director, is investigated. It is found that by properly directing the ventilation flow to the location where methane is accumulating can reduce methane concentration below the safe level. In addition, it is noted that focusing the ventilation flow at a point is more effective as compared to dispersing it at several points. This study provides some new ideas for designing an “intelligent” underground mine ventilation system which can cost-effectively maintain methane concentration below the critical value.