Experimental Measurements of Effects of Occupancy Class on Reverberation Time

2016 ◽  
Vol 820 ◽  
pp. 466-471
Author(s):  
Dušan Dlhý ◽  
Julia Zrneková
Keyword(s):  
White Noise ◽  
Sound Source ◽  
Experimental Measurements ◽  
Main Task ◽  
Pink Noise ◽  
Reverberation Time ◽  
Inflated Balloon ◽  
Excitation Signal ◽  
Measurement Results ◽  
Noise Impulse

Experimental measurements have been focused on the issue of change in reverberation time T20 and T30 (s) in a selected room (classroom) due to its occupancy by persons (students) and changes in reverberation time T20 and T30 (s) as a result of the excitation signal during measurement. Reverberation time was measured in a standard room at the Faculty of Civil Engineering of the Slovak Technical University in Bratislava (classroom B318) by the use of NORSONIC (NORSONIC NOR 280 amplifier, an omnidirectional sound source - NORSONIC NOR 270, NORSONIC TYPE 118, and microphone and preamplifier). The room (classroom B318) was selected as a model classroom in terms of its dimensions, i.e. volume (225 m3), arrangement of furniture, and maximum number of students during standard lectures (up to 24 people). The main task of this study was the inter-comparison of measurement results of reverberation times T20 and T30 (s), with regard to room occupancy of students (100%, 50%, 0%), the position of students (sitting and standing), and the excitation signal (pink noise, white noise, impulse - bursting of an inflated balloon).

Finite element sound field analysis on measurement of absorption coefficient in a reverberation room -Relationships between inclination of walls and measurement results-

2021 ◽  
Vol 263 (1) ◽  
pp. 5571-5577
Author(s):  
Reiji Tomiku ◽  
Noriko Okamoto ◽  
Toru Otsuru ◽  
Shun Iwamoto ◽  
Shoma Suzuki
Keyword(s):  
Finite Element ◽  
Absorption Coefficient ◽  
Sound Field ◽  
Field Analysis ◽  
Reverberation Time ◽  
Absorption Coefficients ◽  
Sound Fields ◽  
Measurement Results ◽  
Coefficient Measurement ◽  
Absorption Performance

The absorption coefficients in a reverberation room are most representative measure for evaluating absorption performance of architectural materials. However, it is well known that measurement results of the coefficient vary according to a room shape of the measurement and area of the specimen. Numerical analyses based on wave acoustics are effective tools to investigate these factors on absorption coefficient measurement in reverberation room. In this study, sound fields for the measurement of absorption coefficient in reverberation room are analyzed by time domain finite element method (TDFEM). This study shows effectiveness of the analysis for investigation on causes of variation in the measurement results and improvement methods of the measurement. First, some measurement sound fields for absorption coefficient in reverberation rooms the walls of which are incline or decline are analyzed by the TDFEM. Next, reverberation times in each sound fields are calculated from the results obtained by TDFEM and the absorption coefficients are evaluated from the reverberation time of the room with and without specimen. Finally, the relationships among room shape, degree of inclination of the wall, the sound absorption coefficient of the specimen, frequencies and the measurement absorption coefficient are investigated.

scholarly journals The Study of the Proscenium Area in an Opera House

2017 ◽  
Vol 42 (3) ◽  
pp. 515-526
Author(s):  
Anna Sygulska ◽  
Krzysztof Brawata
Keyword(s):  
Sound Source ◽  
Decay Time ◽  
Chamber Opera ◽  
Reverberation Time ◽  
Existing Building ◽  
The Subject ◽  
Opera House ◽  
Acoustic Conditions ◽  
Opera Houses ◽  
Center Time

AbstractThe paper describes issues of the proscenium area shown on the example of two opera houses. The subject of the analysis was the design of the Chamber Opera House in Kalisz and the already existing building of the Opera House in Krakow. It covers the influence of the proscenium walls and forestage ceiling on the acoustic conditions in the auditorium. Another subject of the investigation was the influence of the primary proscenium, designed in the very first opera houses in Baroque. The analyses were carried out by means of two computer softwares: Ray Model and Catt Acoustic, and such parameters as sound strength (G), reverberation time (RT), early decay time (EDT), C80(clarity) index and center time (TS) were calculated. The parameters were further analyzed in the auditorium for three positions of the sound source on the stage.

scholarly journals Study of the Cu-Ni Productive Suite of the Pechenga Structure on the Russian-Norway Border Zone with the Use of MHD Installation “Khibiny”

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 96 ◽  
Author(s):  
Abdulkhai Zhamaletdinov
Keyword(s):  
Barents Sea ◽  
Northern Region ◽  
Border Zone ◽  
Experimental Measurements ◽  
Main Task ◽  
Northern Norway ◽  
Mhd Generator ◽  
Current Pulses ◽  
The Barents Sea ◽  
Technical Character

The tracing of current-conducting channels of the Pechenga structure from Russian to Norwegian territory was the main task of this research. The study was carried out in the framework of the Soviet-Norwegian cooperation “Northern Region” to estimate the prospects for discovery of Cu-Ni deposits in northern Norway. In addition to previous publications of technical character, the emphasis here is on geological description. Experimental measurements have been performed in the field of the “Khibiny” dipole and with the use of DC electrical profiling. The “Khibiny” dipole consists of 160-ton aluminum cable flooded in the Barents Sea bays on opposite sides of the Sredny and Rybachy peninsulas. Measurements were implemented as in the mode of single pulses generated by 80 MW magneto-hydrodynamic (MHD) generator “Khibiny” (“hot” launches) and in the accumulation mode of rectangular current pulses of 0.125 Hz frequency generated by a 29 kW car generator (“cold” launches). From results of measurements, it was concluded that the most promising potential for Cu-Ni deposits Pil’gujarvi formation of the Northern wing of the Pechenga structure is rather quickly wedged out in Norway, while the conductive horizons of the Southern part of Pechenga, which have a weak prospect for Cu-Ni ores, follow into Norway nearly without a loss of power and integral electrical conductivity.

Acuity of Sound Localisation: A Topography of Auditory Space. II. Pinna Cues Absent

Perception ◽  
1984 ◽  
Vol 13 (5) ◽  
pp. 601-617 ◽  
Author(s):  
Simon R Oldfield ◽  
Simon P A Parker
Keyword(s):  
White Noise ◽  
Sound Source ◽  
Normal Hearing ◽  
Auditory Space ◽  
Sound Localisation ◽  
Access Hole ◽  
The Absolute

The acuity of azimuth and elevation discrimination was measured under conditions in which the cues to localisation provided by the pinnae were removed. Four subjects localised a sound source (white noise through a speaker) which varied in position over a range of elevations (-40° to +40°) and azimuths (0° to 180°), at 10° intervals, on the left side of the head. Pinna cues were removed by the insertion of individually cast moulds in both pinnae. Each mould had an access hole to the auditory canal. The absolute and algebraic, azimuth and elevation errors were measured for all subjects at each position of the source. The variability of azimuth and elevation error was also computed. The performance of the subjects was compared to their performance under normal hearing conditions. Insertion of the pinnae moulds was found to increase substantially elevation error and the number of front/back reversals. The importance of the cues provided by the pinnae in these discriminations was thus confirmed. However, the increase in elevation error did not result in a corresponding increase in azimuth error. These findings provide support for the proposition that azimuth and elevation discrimination are coded independently.

scholarly journals EFFECT OF A RESONANT SUSPENDED CEILING ON THE ACOUSTIC PROPERTIES OF A HALL/REZONANSINIŲ KABAMŲJŲ LUBŲ ĮTAKA SALĖS AKUSTINIAMS RODIKLIAMS

1996 ◽  
Vol 2 (7) ◽  
pp. 64-69
Author(s):  
Vytautas Stauskis
Keyword(s):  
Sound Source ◽  
Sound Absorption ◽  
Acoustic Properties ◽  
Subjective Perception ◽  
Technical Equipment ◽  
Analog To Digital Converter ◽  
Digital Converter ◽  
Reverberation Time ◽  
Analog To Digital ◽  
Hard Surface

The article covers the experimental research into basic acoustic properties of a hall using a new type resonant suspended ceiling with large area cross-shaped apertures between surfaces. The research was carried out at a physical simulator of a hall. Geometric parameters, frequency range of the simulator and availability of technical equipment were taken into consideration while selecting the scale of the simulator. A recording hall of the Lithuanian radio and TV's Grand Symphonic Orchestra was chosen for the purposes of research. The dimensions of the hall are 34×22×12.7 m. The scale of a simulator for such a large hall was established as 1:25. All the wall and floor surfaces of the simulator are made of textolite. Its coefficient of sound absorption at 10 kHz is equal to 0.15. The suspended ceiling is made of 6 mm thick plywood whereof all the contours had been lacquered 3 times. The orchestra's raised platform of 116 m2 floorspace was covered with 5–6 mm thick flannel which has coefficient of absorption of about 0.5–0.6. In this case the absorption of sound in the air and characteristics of materials are of no importance, as all the research results are relative. A block diagram was used for recording of sound signals at the simulator which diagram comprised a sound source, microphone, microphone's amplifier and analog-to-digital converter. A spark impulse was used as a sound source which impulse was formed by our made spark generator with preset necessary technical parameters. The research was carried out using a 1/4” microphone. An analog-to-digital converter had been manufactured according to preset characteristics. It was designed for changing analog signals into digital form for their further processing. The number of input channels can be set up from 1 through 8. The nominal level of the input signal is ± 1 V. The converter's discrimination is equal to 12 bits. Time of conversion is 2 μs. The quantization time is equal to 5 μs, whereas the quantization frequency is 200 kHz. The experimental simulator of a hall allows to determine the dependence of basic acoustic characteristics on the form of the apertures in the suspended ceiling, their surface, distance to the hard surface, absorbing material used in side and end walls and over the suspended ceiling, as well as on the distance from the source to the microphone. The research covered by this article determines the effect produced upon the acoustic coefficient by the distance between the suspended ceiling and the hard surface while the area of the cross-shaped aperture is not changed. During the research a measurement point was chosen near the sound source. The influence of the height of the suspended resonant ceiling upon the reverberation time is expressed only up to 160 Hz, however, a more expressive dependence has not been noticed. The decrease in the reverberation time at this range reaches 0.4–0.6 s. At frequencies of 200 and 250 Hz an expressly noticeable resonance is formed at which resonance the reverberation time is reduced even by 1.1 s., which is a large figure. Under further increase in the frequency the decrease is stable and reaches about 0.4 s. Such a decrease in the reverberation time with the expressive resonance at 200–250 Hz is dependent only on the crossshaped apertures in the suspended ceiling. This indicates that they have effect on the hall's acoustics. The decrease in the early reverberation time is most expressive at very low frequency up to 100 Hz and it reaches even 1–7 s. Resonance occurs again at 200 Hz, at which resonance the reverberation is decreased by up to 2.5 s and is not dependent on the height of the suspended ceiling. The early damping period of the sound field is basically dependent on the early sound reflections. They are of crucial importance while forming the subjective perception of a sound. The coefficient of the sound absorption depends on the height of the suspended ceiling and it is higher when the height of the ceiling is reduced. In all cases this coefficient has a resonant importance at 200–250 Hz. The coefficients of the absolute absorption are reduced because there is an increased reverberation time of the entire hall and surface area. The sound absorption is expressly increased only when the distance between the height of the suspended ceiling and the hard surface is 100 cm. At resonant frequencies of 200 and 250 Hz it is equal to 60 m2. The fidelity index of music is changeable from −14 dB at lower frequencies up to 0 dB at higher frequencies. The increase in the height of the suspended ceiling begins to have effect only from 200 Hz.

scholarly journals Near-Field-Based 5G Sub-6 GHz Array Antenna Diagnosis Using Transfer Learning

2021 ◽  
Vol 11 (21) ◽  
pp. 10164
Author(s):  
Hong Jun Lim ◽  
Dong Hwan Lee ◽  
Hark Byeong Park ◽  
Keum Cheol Hwang
Keyword(s):  
Transfer Learning ◽  
Near Field ◽  
Array Antenna ◽  
Excitation Signal ◽  
Measurement Results ◽  
Field Lines ◽  
Abnormal Operation ◽  
Trained Network

In this paper, we propose a method for near-field-based 5G sub 6-GHz array antenna diagnosis using transfer learning. A classification network was implemented for normal/abnormal operation of the array antenna and the failure of a specific port. Furthermore, a regression network that could predict the amplitude and phase of the excitation signal of the array antenna was employed. Additionally, to accelerate the array antenna diagnosis, several near-field lines were sampled and reflected in the regression network. The proposed method was verified by measuring a fabricated 5G sub-6 GHz band 4×4 array antenna in various scenarios using a divider and coaxial cables. The tests showed that the trained network accurately diagnosed 29 of 30 measurement results.

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