The laboratory of Fisica Tecnica has a long lasting tradition of research activities developed in the fields of applied acoustics, indoor environment characterization, and thermo-hygrometric properties of materials. More recently the activities in these different fields converged on specific topics that, although often studied independently, all contribute to the research in the field of sustainable, energy-efficient, and comfortable building design. The paper outlines the researches of the group in this field: thermo-hygrometric and acoustic characterization of sustainable materials; study of PCM solutions for energy storage; use of numerical models to simulate fire dynamic, heat transfer, and acoustic problems; analysis of the interactions between technical services and buildings and their effect on energy efficiency and comfort; renewable energy; analysis of thermal, acoustic and visual comfort conditions in indoor environments, and their relation with energy optimization needs.

The paper discusses the suitability of an on-site measurement procedure to assess indoor environment quality for hypermarket workers. The method is based on the collection of both objective measurements of environmental parameters and subjective perceptions of Indoor Air Quality (IAQ) as well as thermal, acoustic, and visual comfort. Given the particular (and variable) indoor conditions observed in hypermarkets, a preliminary field study was carried out to verify the understanding of the questions and their effectiveness in describing subjects’ perceptions and the suitably of the survey method to assess indoor environmental quality and comfort. A hypermarket located in Southern Italy was selected as a pilot study during which the exposure data and subjective responses of employees were acquired simultaneously through physical measurements and questionnaires. A major aspect that required to be verified was the use of fixed positions to avoid, as far as possible, any interference with workers’ activities. In fact, workers were asked to move to the measuring point and fill in a questionnaire to rate their subjective perceptions. Measuring points were chosen to represent the typical conditions inside the hypermarket. However, in a few cases more extreme conditions (less representative of the average conditions) were selected in order to widen the range of the measured parameters and subjective reactions. Data collected at fixed point locations showed only minor (and predictable) biases due to expectation and to transition through different thermal environments, confirming that the proposed method is effective in this kind of environment and minimizes interference with working activities.

The paper presents the results of an on-site measurement procedure to assess acoustic comfort for hypermarket workers. The assessment is based on the collection of both objective measurements of environmental parameters as well as subjective ratings of acoustic comfort. The study was carried out in a hypermarket located in Southern Italy, in which four sub-spaces having similar acoustic characteristics were identified. Workers were asked to move to selected measuring points and fill in a questionnaire to rate their subjective perceptions. Measuring points were chosen to represent the typical conditions inside the hypermarket. Factor analysis and linear regression analysis were used to pick up, among the many noise indexes available in the literature, those that could better describe the staff subjective attitude towards the acoustic environment. Finally, by comparisons with subjective “comfort” thresholds, optimal intervals for selected parameters were defined. Analysis showed that the A-weighted equivalent sound pressure level LeqA and the percentile level LA90 could be used to describe subjective auditory sensations in most situations.

BACKGROUND: Thermal, acoustic and visual comfort conditions for hypermarket workers have never been investigated with scientific methods. OBJECTIVES: taking advantage of a case study, with characteristics capable of generalizing the results, analytically measure the actual comfort conditions to which workers are exposed and point out possible ameliorative proposals. METHODS: Carry out a detailed survey based on instrumental measurements combined with subjective questionnaires to assess the indoor environment. RESULTS: Even though the analysis pointed out no significant risk conditions, several smaller problems appeared in terms of local discomfort (such as cold limbs, higher sound level exposure, limited glare phenomena) for cashier workers. The origin of these problems appeared to be the pivotal position of the cash registers. CONCLUSIONS: Taking into account observed phenomena and their causes a list of "best practices" has been defined hoping that their adoption could further limit any impact on workers comfort conditions.

The limits of the procedure for the measurement of the sound insulation of building facades represent the main subject of this paper. To calculate the facade insulation, standard ISO 140-5 requires that the difference between outdoor and indoor sound pressure levels is determined. However, the measurement of outdoor pressure levels presents several critical challenges, not fully considered in the standard. In fact, the placement of an external source and receiver according to ISO 140-5 is flexible to permit adapting the measurement configuration to specific building characteristics. Unfortunately, according to the relative external source and receiver positions, destructive interferences among waves may occur in different frequency bands. Comparisons between different source-receiver combinations are hence investigated theoretically, before being compared with field measurements. The paper investigates circumstances which might lead to destructive interferences in the external final sound field. The increasing attention of reproducibility in building acoustics suggests an investigation of possible measurement errors that may occur. The influence of interference effects on the single number rating of the sound insulation is finally given.

Places of worship, as well as other performing spaces or large arenas are characterized by lightweight pews or seats, with moderate or negligible upholstery, leading to very low absorption coefficients. Consequently, the audience becomes the most important sound absorbing element, capable of playing a fundamental role in determining the acoustic characteristics of the space. Consequently accurate knowledge of its acoustic properties is required for any design purpose. Several studies have been carried out with reference to audiences seated on upholstered theatre seats but there is a considerable lack of information about occupied pews. The well known difficulty of taking into account edge effects during such measurements poses further questions as well as the effect of the density of occupation, and the seasonal variations due to clothing. This paper presents the results of a series of laboratory measurements aimed at clarifying such aspects. The measurements showed that the edge effects are negligible and that total absorption is better related to the number of persons present than to the area they cover. Nonetheless, as the density grows, or when the audience is seated, there is a reduction in absorption which may be explained by the reduction in exposed body surface. Lightweight clothes show a considerable reduction in sound absorption over all the frequency bands, suggesting that significant seasonal fluctuations in reverberation time should be expected in places where the audience is the only sound absorbing surface.

Sound absorption by openings has been rarely considered in room acoustics. In fact, information about small openings (such as ventilation grids) may sometimes be found, but nothing is said about larger openings, possibly as a consequence of the less likely occurrence in a design. In order to fill this gap, measurements were carried out in scale models, measuring the equivalent absorption due to different openings and comparing it with theoretical results. A “practical” model, showing a simple dependence on the opening dimension, was finally obtained and subsequently validated by measurements in a real room.

Laboratory measurements of sound absorption by audiences are known to be scarcely reliable when applied to actual rooms as a consequence of several problems, among which the different area of the "sample" and the different distribution of the reflected sound may play important roles. When dealing with worship places, characterized by a variable degree of occupation and much lower absorption due to unoccupied seats, things become more complicated as absorption seems to be proportional to the number of occupants rather than to the area they cover (as normally accepted in performing spaces). The combination of these variables has been investigated by taking advantage of laboratory measurements and analysing their application to six churches, where on site measurements of reverberation time were carried out with and without occupation. The results are discussed both in terms of simple prediction formulae (Sabine. Eyring, and Arau-Purchades) and of computer simulations, showing that laboratory measurements may be reliably used in computer simulations (at least in the frequency range from 500 Hz on). At low frequencies greater attention must be paid as the absorption coefficients need to be corrected as a function of the actual distribution of the sound field in the room.

Dodecahedron sound sources are widely used for acoustical measurement purposes as they produce a good approximation of omnidirectional radiation. Evidence shows that such an assumption is acceptable only in the low-frequency range (namely below 1 kHz), while at higher frequencies sound radiation is far from being uniform. In order to improve the accuracy of acoustical measurements obtained from dodecahedron sources, international standard ISO 3382 suggests an averaging of results after a source rotation. This paper investigates the effects of such rotations, both in terms of variations in acoustical parameters and spatial distribution of sound reflections. Taking advantage of a spherical microphone array, the different reflection patterns were mapped as a function of source rotation, showing that some reflections may be considerably attenuated for different aiming directions. This paper investigates the concept of averaging results while changing rotation angles and the minimum number of rotations required to improve the accuracy of the average value. Results show that averages of three measurements carried out at 30° angular steps are closer to actual values and show much less fluctuation. In addition, an averaging of the directional intensity components of the selected responses stabilizes the spatial distribution of the reflections.

Microphone arrays represent today a state of the art solution to many acoustic problems. In architectural acoustics, for example, one of the most interesting applications is the possibility to analyse the directional information associated to a given reflection. Ambisonics microphones could provide similar information based on zeroth and first order spherical harmonic decomposition, but larger microphone arrays allow the determination of higher order components providing even better accuracy. In this case, directional information may be obtained through beamforming techniques that, although potentially more accurate and capable of resolving simultaneous reflections, are computationally heavier and provide a "discrete" sampling of the sound field. The paper compares the localization accuracy of a 32 channel microphone array by processing its output using a simple Ambisonics decomposition and a spatial sampling carried out using 32 "virtual" third-order hyper cardioid microphones. In addition, a comparison with conventional Ambisonics microphones is provided in order to point out possible differences. Results show that, when single reflections are involved and the sound field is highly polarized, the Ambsionics decomposition given by the microphone array gives good accuracy over the whole spectrum, while conventional Ambisonic microphones shows less stable results and greater variations as a function of frequency. Spatial sampling is intrinsically less accurate but allows a clearer resolution of simultaneous reflections

The position of the sound source is an aspect rarely considered in room acoustics because the shape of the space and its internal organization generally make clear where the sound source should be. However, this may not be the case in some buildings, such as churches. In these buildings, the source is not located in one position, but it moves, from choir to the altar or the pulpit. This makes problematic the analysis of church acoustics. In particular, if the reverberation time is almost constant whenever the source may be, other acoustic parameters strongly depend on the position of the sound source. This paper mainly focuses on the effect of the position of the sound source over the early lateral fraction and the center time. After an historical evaluation of most common positions of sound sources, the results of computer simulations allow discussing the influence of some of them: above the entrance, in the middle of the room, between the altar and the worshipers, and behind the altar. Then, other acoustic parameters including the sound strength and the center time for different sound source positions are evaluated. Finally, suggestions to evaluate different positions of sound source in churches are reported.

A field study was carried out in a hypermarket located in Southern Italy in order to evaluate the environmental comfort in large-scale retail trade buildings. Global and local thermal comfort conditions were studied by collecting exposure data and subjective responses of employees using both questionnaires and simultaneous physical measurements. In a few cases discrepancies appeared between subjective ratings and the corresponding PMV-index, suggesting that the latter could be unable to reliably estimate thermal comfort when clothing insulation is unevenly distributed on human body. Analysis of collected data confirmed this, with particular reference to female workers wearing skirts. In addition, such effects may be further emphasized by local thermal discomfort, which may finally influence global thermal perception. Analysis of the results showed that cold floor and radiant temperature asymmetry caused by warm ceiling played a major role in emphasizing the negative effects due to uneven clothing distribution, confirming that this particular combination of events may bias PMV model accuracy.

When creating virtual acoustic models of existing spaces, a good practice requires a proper calibration procedure, through comparison with on-site acoustic measures. This process starts with a comparison of a reference acoustic parameter (usually reverberation time). However, matching reverberation times does not ensure a good matching of the other parameters. From this point of view comparison between measured and simulated impulse responses is necessary to identify which sound reflections are responsible of the inaccuracy. A significant help to improve the quality of the acoustic simulation, comes from the additional spatial information resulting from the use of 3D sound field measurements. The paper discusses how such innovative approach can be conveniently used with reference to the modelling of the Jubilee Church “Dives Misericordiae” in Rome, by architect Richard Meyer. The complex shape of the church, made of concave shells, represents an ideal case study to test how surface discretization and model simplification may influence final results.