António P. O. Carvalho

Relations between rapid speech transmission index (RASTI) and other acoustical and architectural measures in churches

The use of rapid speech transmission index (RASTI) in churches is studied and the relationships with acoustical and architectural parameters identified using a major survey of Catholic churches in Portugal. It was found that the vast majority of churches tested have RASTI values below 0.45 giving a poor rating in the quality of speech intelligibility. RASTI values within churches can be reasonably predicted by the use of center time (TS) at 1000Hz. Loudness (L) does not appear as an important characteristic regarding RASTI values supporting the idea that the intelligibility of speech, under reverberant conditions does not depend on loudness. A prediction equation using three architectural parameters was calculated to estimate the average RASTI in churches. The eAect of the architectural styles and the use of pulpits on RASTI values was also studied. # 1998 Elsevier Science Ltd. All rights reserved.

Church Acoustics and the Influence of Occupancy

Speech intelligibility is usually evaluated, by the use of objective parameters, in unoccupied rooms, due to practical considerations. However, under normal conditions, the room occupancy can increase or decrease the values of speech intelligibility by the effect of the additional sound absorption present in the room or by the change in S/N ratio. Measurements were carried out in six churches, with and without occupancy. The results show that occupancy induces a mean increase for the speech intelligibility of ΔSTI (STIoccup–STIunoccup) of 0.050 with the use of a public address system (PA) and 0.035 without a PA. This increase is caused mainly by the reduction of the room reverberation time, due to the increased sound absorption and by the reduction of the additional RT induced by the PA (using loudspeakers with strong directivity oriented towards the congregation area). The variations in the speech intelligibility values with occupancy can be predicted in churches by employing new empirical formulations. The decrease in S/N ratio (due to the background sound level augmentation by the presence of people and by sound level decrease with distance in the congregation area), or the poor directivity and orientation of the sound sources, could reduce the speech intelligibility gain in particular cases. Other effects induced by the congregation, such as the variations of humidity and temperature, generally have negligible effect on speech intelligibility.

Chronic exposure of rats to cotton-mill-room noise changes the cell composition of the tracheal epithelium.

The work environment of cotton mill rooms of modern textile plants is characterized by noise pollution. We have taped and reproduced this noisy environment to study its effects on experimentally exposed rats. Because we have previously documented that chronic noise causes alterations in the respiratory epithelium, we have focused our investigation on the morphology of the tracheal lining. Wistar rats were exposed to the textile-type noise from 1 up to 7 months, with an average 40 hours weekly exposure of the animals. The rats were sacrificed monthly and the tracheas were studied by scanning electron microscopy (SEM) to quantify the areas of the airway lining that were covered by ciliated, serous or other cells of the epithelium. We found that noise exposure of the rats caused a significant loss of tracheal ciliated cells; an increased density of serous cells on the epithelium balanced this change. This modification of the rat trachea was already established after 1 month of noise treatment of the animals; it did not change significantly throughout the 7-month course of the herein investigation. Loss of ciliated cells was more intense in areas of the tracheal epithelium located between the regions of cartilage rings. We conclude that the ciliated cell is an elective target for damage caused on the respiratory epithelium by the workplace noise occurring in cotton mill rooms. This modification of the respiratory epithelium is likely to impair clearance of the airways since this function depends on the activity of ciliated cells.

ANALYSIS OF SUBJECTIVE ACOUSTIC MEASURES AND SPEECH INTELLIGIBILITY IN PORTUGUESE CHURCHES

This study reports on subjective acoustical field measurements made in a survey of 36 Catholic churches in Portugal built in the last 14 centuries. The same group of college students were asked to judge the quality of speech and music at all the churches. Two sets of listeners in each church evaluated live music performance (cello and oboe) at two similar locations in each of the rooms using a seven-point semantic differential rating scale. An acoustical evaluation sheet was used to measure listeners overall impression of room acoustics qualities, and each of the factors that can contribute to that perception as loudness, reverberance, intimacy, envelopment, directionality, balance, clarity, echoes and background noise. Speech intelligibility tests were also given to the same group in each church. One-hundred-word lists were used in live speech tests using a theater college student as speaker. The results are graphed and analyzed by comparisons. Variations of subjective and speech intelligibility qualities were identified among the different churches and within each of the churches as well. The subjective qualities that contributed to overall acoustical impression were also identified.

REDUCTION OF RAT PLEURAL MICROVILLI CAUSED BY NOISE POLLUTION

Scanning electron microscopy (SEM) was used to investigate whether chronic exposure to noise modifies pleural morphology. Rats were submitted to 8-h/day schedule of noise that is similar to the working hours at cotton-mill rooms. Morphometry of the area occupied by microvilli on the pleural surface showed a decrease in microvilli after 3 months of rat exposure to noise. The reduction of microvilli was 10% after 3 months of noise exposure (reaching 20% after 7 months of noise treatment) and is consistent with pleural effusions found in some of the patients working in noise-polluted environments.

Exposure to industrial wideband noise increases connective tissue in the rat liver.

Rats were daily exposed (eight hours/day) for a period of four weeks to the same high-intensity wideband noise that was recorded before in a large textile plant. Histologic observation of liver sections of the rats was used to perform quantitative comparison of hepatic connective tissue (dyed by Masson trichromic staining) between the noise-exposed and control animals. For that, we have photographed at random centrolobular areas of stained rat liver sections. We found that noise exposure resulted in significant enhancement in the area of collagen-rich connective tissue present in the centrolobular domain of the rat liver. Our data strengthen previous evidence showing that fibrotic transformation is a systemic effect of chronic exposure of rodents and humans to industrial wideband noise.

The use of agglomerated cork as an underlay for improvement of impact sound insulation in buildings

The cork‐oak is only abundant in the Western part of the Mediterranean and is an important feature of Portuguese landscape and heritage. Portugal has about 30% of the world’s cork‐oak trees and accounts for more than half of the world’s cork production. Agglomerated cork has natural cork granules (the by‐products from the production of other cork products) as its base material. The project goal was to test and characterize the use of agglomerated cork as underlay to increase the impact sound insulation. Eight different cork agglomerate products were tested to assess their impact sound insulation quality when used as underlays with four different floor coverings (linoleum, ceramic tile, and two types of wood parquet). The measurements were made on‐site (with flanking transmissions) on a coffered concrete floor without a fastened ceiling and according to International, Portuguese, and American standards (ISO‐140/6 and 717, NP‐669 and 2073, and ASTM‐E989 and 1007). The results show that the use of this under...

The use of the Sabine and Eyring reverberation time equations to churches

Reverberation time (RT) measurements were taken at several source/receiver locations in 41 Catholic churches in Portugal built in the last 14 centuries, using the impulse–response method. The use of the Sabine and Eyring reverberation time equations was tested to estimate the measured RTs in this sample of churches. The effect of coupled spaces was analyzed, and a new algorithm for the application of the Sabine equation in churches was developed producing an average of 16% in the differences between the predicted and measured RTs compared to 71% using the standard Sabine equation. Coupled spaces were found to act as windows with a characteristic absorption coefficient depending on their dimensions. The recesses in churches were grouped in three types: main altar area, chapels, and lateral aisles, each having a particular acoustical behavior. It was found that those recesses only acted as coupled spaces if their length/opening–width≳0.6 or if the aisle–width/opening–height≳0.4 in lateral aisles. The remaining differences found between the RTs measured and predicted with this new algorithm were hypothesized to be related to what was called a reverberant ceiling effect, which is presumed to be due to a two‐dimensional reverberant sound field that builds up near a very tall ceiling. [Work supported by JNICT/Ministry of Planning and Univ. of Porto, Portugal.]

BACH, A NEW BINAURAL ROOM ACOUSTICAL MEASURE

This study reports on acoustical field measurements made in a major survey of 41 Catholic churches in Portugal built in the last fourteen centuries. Binaural measurements were taken in each church using a dual‐channel real‐time frequency analyzer to calculate the coherence values between the signals at both ears in 1/3‐octave frequency bands. From the coherence values a new binaural acoustical measure was developed and called BACH (Binaural Acoustical CoHerence). Monaural acoustical measurements were also taken at several source/receiver locations using the impulse response method. BACH was shown to be an orthogonal parameter in statistical tests with nine other monaural acoustical measures (RT, EDT, C80, D, TS, L, BR—RT, BR—L, and RASTI) and fifteen architectural parameters. Information was collected regarding the quality of music in each church. ANOVA tests were performed to examine the significance of the differences among the groups of equal subjective quality ratings. The author wanted to test the hy...

Sound and noise in urban parks

The main goal of this work is to study the soundscape of urban gardens and parks using a sample of ten sites in Porto, Portugal to characterize their noise levels through the acoustic characterization of the parks exterior and interior noise levels (LAeq, LA10, LA50 and LA90) and by a socio-acoustic survey to the visitors to check their perception of acoustic quality. The measurements showed gardens/parks with interior noise levels from 47 to 61 dBA (with maximum exterior noise levels up to 67 dBA). The difference between exterior and interior LAeq was between 3 and 19 dBA. The gardens with lower noise levels are the larger and out of downtown. An “acoustic” classification for gardens/urban parks is proposed regarding their noise “isolation” capacity and acoustic ambience. Measurements done in 1990 allow for the comparison of the evolution in the last 21 years. The socio-acoustic survey concludes that Porto’s city parks are visited mostly by an elderly male population that regards these places as sites o...