Multiplex cinema halls: Design and construction of six halls in the city of Mar del Plata

Transcription

1 Multiplex cinema halls: Design and construction of six halls in the city of Mar del Plata Roberto Daniel Ottobre, Marcelo Ottobre, Agustín Arias, María Pérez Maraviglia, and Oscar Cañadas Citation: Proc. Mtgs. Acoust. 28, (2016); View online: View Table of Contents: Published by the Acoustical Society of America Articles you may be interested in Acoustics of the Border Cultural Centre in the neighbourhood of Palermo, city of Buenos Aires, Argentina Proceedings of Meetings on Acoustics 28, (2017); / Monte Carlo simulation of traffic noise dynamics at a bus stop based on real sound signals Proceedings of Meetings on Acoustics 28, (2017); /

2 Volume nd International Congress on Acoustics Acoustics for the 21 st Century Buenos Aires, Argentina September 2016 Architectural Acoustics: Paper ICA Multiplex cinema halls: Design and construction of six halls in the city of Mar del Plata Roberto Daniel Ottobre, Marcelo Ottobre, Agustín Arias Ottobre y Ottobre Arquitectos, Asesores en Acústica, CABA, Argentina; arq.daniel@ottobreyottobre.com.ar; arq.marcelo@ottobreyottobre.com.ar; agustinarias@ottobreyottobre.com.ar María Pérez Maraviglia, Oscar Cañadas Estudio Mariani Perez Maraviglia, Mar del Plata, Argentina, estudio@marianiperezmaraviglia.com; oacanadas@gmail.com Six cinema halls with capacities from 150 to 310 seats in a shopping promenade were built in the city of Mar del Plata, Argentina. The architects of this project were Mariani, Pérez Maraviglia and Oscar Cañadas. The employer of the project was Florencio Aldrey Iglesias, who has a long and recognized experience both locally and nationally. The place chosen by the company was the former terminal bus station in the city, maintaining the main building but reorganizing spaces and functions. In the terminal area, a new building of the shopping promenade has been built including the six cinema halls on the highest floor. The client asked the acoustical consultants to provide excellent acoustical quality, complemented by the latest technology equipment, including the new Atmos format of the Dolby Laboratories Inc. Starting from these premises, the following tasks were carried out: a sound insulation project; a HVAC systems project in strict accordance with the acoustic requirements, and an acoustic design project using simulation model. The projects with the construction details, the acoutsic simulation executed on software and the measurements in the halls are presented. Published by the Acoustical Society of America 2017 Acoustical Society of America [DOI: / ] Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 1

3 1. INTRODUCTION It is common to find cinema halls that do not meet the appropriate parameters. In Argentina such cinema halls are seen in many multiplexes, skimping materials during the construction works. The city of Mar del Plata hosts the film festival at which productions from around the world are presented. In 2015, films were screened in the hall complex "Paseo Aldrey," called as the new promenade built in the city. It was therefore necessary to design the halls with appropriate technical framework due to the importance of the festival. Moreover, in recent years there has been a paradigm shift in relation to the film format. The film production exclusively uses digital systems. This means a great simplification of production processes and thus reducing costs 1. With regard to sound, the digital system implies an increase in the dynamic range since extra audio compression processes disappear. In addition to the usual recommendations for sound insulation and acoustic conditions in this type of hall, one of the halls must have the surround sound system Dolby ATMOS 2. The performance of building systems was needed to be optimized to get the best sound condition of the halls in a framework of economical requirement and short deadlines. There were three premises: 1) Sound Reduction Index R w of 70 db between the halls; 2) noise profile of NC 25, mainly caused by HVAC systems 3 ; and 3) reverberation time as flat as possible, around 0.5 s in the larger halls and about 0.4 s in the smaller ones, 4 for the intelligibility 5. The acoustic project was initiated from agreements with members of the study of Architecture, followed by verification by simulation models, continuous monitoring on site, and confirmation by measurements at the end of each task. 2. SOUND INSULATION The sound insulation design took into account of previous experiments carried out by acoustic consultants and recommendations of Saint-Gobain. As shown in Figure 1, the halls have surface contacts with each other. Moreover the two central halls (called Sala 3 and Sala 4) have contacts with the machine room. A typical problem in a cinema hall is the mechanical transmission through the partitions, floors, and ceilings due to low frequency sound energy generated by the of movie reproduction system. The first guideline of insulation was to keep all joints with anti-vibration material and make a floating floor. This structure was raised over the existing slab as shown in Figure 2. Several kinds of vertical partitions were used 6 in the halls. The partitions between the halls were designed to realize the Sound Reduction Index R w of 70 db (Figure 3). An internal air gap was not designed due to the required width for the circulation areas. This partition was designed from a structural profile for the support of all the facing, with its highest point at 9 m. The galvanized sheet structure holds the gypsum boards and was mounted on these main profiles, using three of each side and the last being varied in stiffness and weight of the material. Inside the partition, glass wool with a total thickness of 200 mm was installed, surrounding the metal columns which support the complex. Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 2

4 R. D. Ottobre et al. Multiplex cinema halls: Design and construction SALA 6 2 SALA 2 SALA SALA SALA Figure 1: Plan of the cinema halls and the engine room. 100 Polyethylene thk. 100 microns Carpet acc. to project Distribution armor Slab 7cm PF Panel thk. 20mm Levelling carpet Slab 15 Figure 2. Cross section of the floating floor Structural profile Knauf Diamant board thk. 15mm Two gypsum rock boards thk. 12.5mm thk. 100mm 5kg/m3 thk. 50mm 35kg/m3 Support + Sealant Knauf elastic band Figure 3. Cross-section of the hall partition. Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 3

5 Structural profile thk. 100mm 35kg/m3 Knauf Diamant board thk. 15mm Two gypsum rock boards thk. 12.5mm thk. 100mm 35kg/m3 Andina Isoacoustic board thk. 50mm 35kg/m3 thk. 100mm 35kg/m3 Figure 4. Cross-section of the partition walls and the ceiling. Structural profile Fiberglass thk. 100mm 35kg/m3 Two gypsum boards thk. 12.5mm Cementitious board thk. 15mm Concrete block 9x19x39 thk. 100mm 35 kg/m3 Perforated metal sheet Aluminum frame thk. 50mm 35 kg/m3 Perforated metal sheet thk. 100mm 35 kg/m3 Figure 5. Cross-section of the partition between the hall and the engine room. A similar configuration was used for the closing walls to the emergency exits as well as the projection room, reducing the thickness of the glass wool and the gypsum boards. It realized the index R w of 55 db. For ceilings, a casing composed of gypsum boards with a 100 mm thick glass wool was chosen, expecting the index R w of 55 db. The sound absorbing ceiling is supported by this set of materials, as shown in Figure 4. Finally, the most critical insulation was designed for the halls adjacent to the machine room. A concrete block wall was built to increase the insulation since the noise level from the machine rises above 85 dba, characterized as tonal noise in the 250 Hz octave-band. In addition, the noise increases with the passage of time due to unbalanced turbines and bearing wear. As shown Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 4

6 in Figure 5, the wall was completed with the addition of "half linings" composed of gypsum boards on each side, expecting the index R w greater than 70 db. 3. ACOUSTIC TREATMENT OF THE CINEMA HALLS According to preferences of the architectural and acoustical designers, various surface materials were selected to obtain both an optimum reverberation time and an appropriate sound field. Computer simulation were performed by using the software E.A.S.E. (Enhanced Acoustic Simulator for Engineers), incorporating the rooms geometry and the materials chosen. Ceiling panels of rigid glass wool with black veil were installed on rooftops. These boards have 20 mm thickness and dimensions of 610 x 610 mm or 610 x 1210 mm. To avoid an excess sound absorption at high frequencies, gypsum boards of 9.5 mm thickness with the dimensions equal to the glass wool boards were added. They were placed in a checkerboard-style, i.e. not covering the entire ceiling, from the fourth row of the audience area to the back of the halls. Thus, a strongly absorbed surface was mounted for the first reflection, according to the recommendation for this type of halls. Figure 6 shows the configuration used. A layer of glass wool (supported on a metal grid) with 100 mm thickness and a density of 35 Kg/m 3 was placed inside the air chamber behind the ceiling, at a distance of 200 mm. Thus, a low frequency trap was set up to provide absorption near the 80 Hz band. On the side walls, membrane resonators were designed for the absorption at middle and low frequencies. They are composed of a plywood board from 6 to 8 mm thickness with a surface density of 4.5 kg/m 2. This material is placed alternately in modules on both walls. In addition, modules of 50 mm thick and 50 kg/m 3 density glass wool were added on each wall. Their face was covered with cotton fabric with flame retardant and anti-acarus treatment. Then, modules compounds of the same cotton fabric were added in an interleaved with the resonators, leaving a rear air gap of 100 mm. The combination of these three coatings is shown in Figure 7. The rest of the surfaces correspond to the partition for the insulation. Figure 6. Distribution of materials on the ceiling. Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 5

7 Screen Fiberglass Acustiver P (Isover) Cotton fabric algodón s/sobre Two plates of gypsum rock Membrane resonator membrana Figure 7. Distribution of materials on the walls. A. ACOUSTIC PARAMETERS The following acoustic parameters were calculated for each room: reverberation time (Eyring and Schroeder); spatial distribution of sound pressure level; speech intelligibility (%ALCons and STI); clarity (C 50 ) index for speech and its frequency response. To perform these analyses, the software E.A.S.E. was used. B. SIMULATIONS RESULTS The results for the Hall 3 are presented below. These results are representative and similar to those of the other halls. Figure 8 shows the values for the Eyring reverberation time with the lines of tolerance range. The values at mid-frequencies are about 0.5 s with slight deviations at low frequencies. The exceeding values at the lower frequencies are corrected by the bass traps as explained in Section 3, although the software does not provide accurate results in that frequency range. These results indicate that the reverberation time in each frequency band is close to the recommendation. To evaluate the other parameters, the chosen loudspeakers were installed in the simulation model, considering its directivity and real sound power level. The loudspeakers of the brand QSC are used in all halls, precisely the "Stage SC-323" model for the L-C-R system and the "Sub SB-5218" model used as subwoofer. Figure 9 shows the results of the %ALCons to quantify the degree of speech intelligibility. The values calculated are below 3% which classifies the intelligibility throughout the halls as "excellent". Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 6

8 Figure 8. Eyring reverberation time calculated (Hall 3). Figure 9. ALCons calculated (Hall 3). Then, an evaluation of reflections by geometrical acoustics model was performed on various listening positions throughout the audience area in each hall. In total rays were emitted from each of the sound sources. The reflections were analyzed discretely with the addition of a statistical decay tail that allows obtaining other acoustic parameters of interest. Figure 10 shows the reflectgram at the seat 3 (row 11, at 2 m from the central axis of the hall). Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 7

9 Figure 10. Reflectogram at seat 3 (Hall 3). The distribution of reflections is homogeneous in all the reflectograms and there are no unwanted echoes or extreme colorations represented by late reflections with significant energy content above the reverberant tail. The frequency responses calculated at each of the seats show that the spectral content is uniform over all the frequency range under analysis and there are no significant colorations. Figure 11 shows the result for the seat 3. Figure 11. Frequency response at seat 3. Hall 3. Then reverberation times were analyzed by the Schroeder s method to evaluate variations in different listening positions. Figure 12 shows there is a good correspondence between the two calculation methods, with some variations that suggest that the reverberation time turns out to be slightly higher than that obtained with the statistical method (Eyring), due to the addition of the statistical tail. Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 8

10 Figure 12. Reverberation times (Eyring Schroeder) at seat 3 (Hall 3). Several visits were made during the construction process to verify the project's compliance and to perform some measurements. It was necessary to evaluate the acoustic insulation according to the relevant regulations. It was also necessary to verify the characteristics of the sound fields once the surface materials were installed. The background noise was also measured. For these purposes the measurements were made using a sound level meter 01 db Metravib model "Solo", connected to a computer with the dbbatti32 V5.2 software of the same company. C. INSULATION BETWEEN HALLS An evaluation of the sound insulation for the division masonry (wall) between the Hall 2 and Hall 3 was performed. The evaluation procedure followed the Argentine standard IRAM (corresponding to ISO 140-4) 7. The apparent sound insulation index is plotted in Figure 13, verifying the target value R w 70 db for the insulation between halls. D. BACKGROUND NOISE AND REVERBERATION TIME In October 2015 the background noise with the HVAC systems and the reverberation time of the Hall 4 were measured to test the final stage of the acoustic design. Figure 14 shows the photo of the hall during these measurements. With the air conditioning system in operation, the background noise levels in octave bands correspond to NC-25 profile recommended in IRAM The hall meets the requirements of the signal-to-noise ratio recommended for movie reproduction. Note that these values were obtained under unoccupied condition. In the case of air conditioning system off, the room satisfied the NC-20 profile. The background noise levels under unoccupied condition, fulfilled an extensive list of recommendations made by the acoustics consultants and proved a great work done by the members in charge of the installation of the HVAC system. The main recommendations were: making ducts covered with glass wool; independent and separated equipment and branches for each hall; injection speed below 1 m/s; inserting an acoustic filter in feed and return ducts to minimize the difference between the noise generated and that radiated in the first outlet; and finally the anti-vibration mount for all system components. Above all the things, the wills of the employer, the project architects, installers and builders should be highlighted for complying with all the requirements. Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 9

11 In situ Measurement of sound insulation between rooms Apparent sound reduction index R db Octave-band frequency [Hz] Figure 13. Sound insulation index according to IRAM Figure 14. Interior of the Hall 4 during the measurements. The reverberation time were measured at eight positions in the hall. An average at each position and a global spatial average of the room were performed to avoid problems caused by local colorations or by local modes at the measurement points in each case. The measurements Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 10

12 procedure followed ISO Figure 15 shows the comparison between the spatially-averaged reverberation time and the simulations for Hall 4. Finally, the evaluation of the reverberation time shows that the objective has been achieved. It is worth considering the fact that elevation of 0.1 s in the reverberation time at 315 Hz is associated with the resonances produced by the access to the room below the level of the seats. Also the bass trap behind the ceiling worked for the frequencies below 60 Hz. 0.7 Tiempos Reverberation de Reverberación Time Comparison 0.6 Tiempo Reverberation de reverberación time [s] Simulated Simulado Average Promedio Frecuencia por Octave-band bandas de 1/3 frequency de octava [Hz] Figure 15. Comparison of the reverberation times between the spatial-average and the simulation for Hall CONCLUSIONS The acoustic insulation performance highlighted that the design of the partitions between rooms, even without indoor air gap and reduced in thickness, comfortably achieved the required index R w. The background noise level due to HVAC systems also comfortably reached the target, overcoming extreme difficulties in our situation. Finally, it should be noted this acoustic project was accomplished by all the members in the work: entrepreneurs, designers, directors, builders and installers. REFERENCES 1 Remaking the Movies. Digital content and the evolution of the film and video industries, Organization for Economic Co-Operation and Development, Dolby Atmos Next-Generation Audio for Cinema, Dolby Laboratories Movie theatre construction experience in the USA, Cavanaugh, W, Acoustic Seminar, Marseilles, France, Technical Guidelines for Dolby Stereo Theatres, Allen, Ioan, Dolby Laboratories Incorporated, USA, Acústica Arquitectónica, Recuero López, M Universidad Politécnica de Madrid, Madrid, Spain, Sound insulation in movie theatres. Jacobi, G, Acoustic Seminar, Marseilles, France, Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 11

13 7 IRAM Standard: Acústica, Medición del aislamiento acústico en los edificios y de los elementos de construcción - Parte 4: Medición "in situ" del aislamiento al ruido aéreo entre locales ; corresponding to ISO Standard: Acoustics -- Measurement of sound insulation in buildings and of building elements - Part 4: Field measurements of airborne sound insulation between rooms, Buenos Aires, Argentina, IRAM 4070 Standard, Ruidos. Procedimiento para su evaluación utilizando los perfiles NC y RC, Buenos Aires, Argentina, ISO Standard; UNE-EN ISO 3382 Standard, Acústica. Medición del tiempo de reverberación con referencia a otros parámetros acústicos, Madrid, Spain, Proceedings of Meetings on Acoustics, Vol. 28, (2017) Page 12