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The Rooms to be set up present different situations that require technological improvements in favor of more effective communication.
In various rooms, the difficulty in using the audio which does not give the desired feedback in terms of speech intelligibility was underlined, due to the type of loudspeakers used, their positioning, the type of microphones and the switchboard which are inadequate.
Furthermore, the acoustics of the restaurant rooms negatively affect the understanding of the word due to the reverberation present and therefore a difficulty has been detected in maintaining a pleasant conversation without effort.
In particular, the will to obtain this new ideal situation emerged from the interview:
The multipurpose room must be able to be used more easily and therefore both as a conference and meeting room in order to host events or meetings or parties or dinners. The presence of a completely intelligible audio system, faithful and usable by all and suitable for holding events, would therefore be appreciated. The audio must also be amplified outside, with the possibility of dividing the various areas according to needs and different types of events. The room must also be acoustically corrected to allow the system to function even more easily and optimally.
The restaurant halls will also need to be acoustically corrected in order to allow for pleasant conversation by the diners.
You will have Environments designed and organized to work at the maximum technological possibilities.
Anyone who uses your Sale will find a wonderful coherence between the advanced technology and the contents conveyed.
You will have continuously guaranteed assistance to handle any emergency with elegance and competence.
Sound and Images will become perfect allies to bring every word and every conscious and unconscious concept to the heart of the listener.
You will have the certainty of using every single instrumentation with the maximum technological response obtainable from your working environments.
Acoustic and audio comfort will be total: both on the part of those who will provide the interventions, and on the part of those who will be able to enjoy the best possible technological response.
It will be a pleasure to talk, listen and see everything around you.
The natural transmission of both sound and images will give you the sensation of being in the right place and having (and also giving) the best.
“Every environment requires a made-to-measure suit that corresponds to the values to be transmitted. Only in this way will the message be coherent.”
In any closed environment, the sound that is heard is the result of a combination of sound waves that reach the listener directly and sound waves that arrive reflected, or that propagate from the source until they affect the various rigid surfaces that delimit the environment from where they are reflected, often several times, before reaching the listener. The quantity that describes this acoustic characteristic of closed environments, often erroneously referred to as “echo”, is the reverberation time (TR), i.e. the time during which a certain amount of sound energy continues to persist inside a closed environment after the beep has stopped. The longer this time is, the greater the contribution of the reflected sound compared to the direct one. For example, if a sound source ceases to radiate in a room, the sound level decreases the more slowly the lower the sound absorption of the walls.
Reverberation has negative aspects, such as the risk of masking speech syllables or musical phrasing, and positive aspects, such as reinforcing the intensity of the source; however, the latter aspect can become a negative aspect in potentially noisy environments such as canteens, corridors, and gyms, as the internal reverberation contributes decisively to increasing the sound intensity, leading to excessively noisy environments. The elements present inside a closed environment (walls, furnishings, people, etc.) condition the acoustic propagation, since they absorb the sound energy that affects them to varying degrees. These phenomena can alter and deteriorate the quality of the sound perceived by the receiver, causing, for example, the degradation of verbal communication or listening to music.
To define the acoustic quality of a room, the quantity called “reverberation time” has been identified, which indicates the time, in seconds, necessary for the sound level to decrease by a certain amount in a point of a closed room compared to that which occurs when a sound source is interrupted. As a rule, the reverberation time T60 is used, i.e. the time interval in which the sound energy decreases by 60 dB after the source is switched off. In an environment having spatial dimensions fairly close to each other, the value of T60 can be calculated according to Sabine’s formula.
T=0.161V/A (s)
where V is the room volume in m3 and A is the total absorption equivalent area in m2. The value of A is obtained with the following relationship:
A = Σ αi Si (m2)
where αi is the i-th absorption coefficient and Si is the i-th surface area of the elements present in the environment. Acoustic absorption represents the ability of a material to convert the energy of an incident sound wave into a form of energy other than acoustic energy (usually into heat).
The determination of the reverberation time of an environment is therefore fundamental in order to be able to judge its acoustic characteristics and decide whether to intervene on the structures that delimit it, increasing its sound absorption capacity. It is necessary to intervene if the value of the reverberation time T60 is not at least close to the optimal value, obtained on the basis of table values in the literature or from sector standards.
By way of example, the diagram below shows the optimal values of the reverberation times as a function of the volume of the room and its intended use, taken from the literature on the subject.
However, the phenomenon of reverberation has both positive and negative aspects. In fact, if a certain value of the reverberation time helps to reinforce the direct sound and therefore to improve listening, on the other hand, an excessive value of the sound tail compromises its quality, making the sound muddy. Obtaining optimal reverberation time values represents the right compromise between achieving a sufficient sound level for effortless hearing, in all points of the room, and reducing the disturbance caused by an excess of reverberation. In general, for rooms intended for listening to speech, the ideal values of T60 are shorter than those for rooms intended for listening to music, as the diffusion of music requires a greater emphasis on the spatial effect. Furthermore, it is necessary to consider that an increase in the volume of the environment corresponds to an increase in the optimal reverberation time. In this case, it is necessary to slightly compromise listening in favor of a higher sound level value.
With regard to the passive acoustic requirements and the acoustic quality of the environments, it is useful at this point to underline that in July 2010 the UNI 1136700_2010 standard was published which establishes the new evaluation criteria of the acoustic requirements and the acoustic classification of the buildings, going to correct the gaps in the law in force (DPCM 5/12/97); this legislation has not yet been implemented by the legislator, therefore it is currently a voluntary acoustic quality standard.
It should be emphasized that this technical standard in Appendix C also takes into consideration the internal acoustic quality of the rooms on a general level, indicating some acoustic quality parameters including the reverberation time:
See below an extract from the aforementioned appendix C, which indicates a method for determining the optimal reverberation time for different types of environments, i.e. environments used for speech or used for sporting activities.
VALUTAZIONI ACUSTICHE
Arch. Enzo Bonardo
Il locale in oggetto di analisi è costituito da:
Salone polivalente per degustazioni di forma triangolare per una superficie interna di circa 228 mq completamente libero da strutture e partizioni, fatto salvo per alcuni locali di servizio in un vertice del triangolo.
Il locale in analisi è caratterizzato da una copertura a vela paraboloide poggiata sui 3 vertici del triangolo a differenti altezze, con altezza sui vertici del triangolo di circa 7 mt la massima, 6,5 mt quella intermedia e 1,60 circa sul vertice di appoggio a terra della stessa copertura.
La copertura è realizzata con 3 travi di bordo portanti in legno lamellare, dagli arcarecci principali sempre in legno lamellare, e dalle travi ad andamento approssimativamente parallelo che sorreggono la copertura i listelli di legno di impalcato della copertura stessa.
Il locale risulta avere un pavimento in cemento lisciato o resina, e le pareti perimetrali sono costituite da vetrate che seguono l’andamento delle travi di bordo.
Essendo un locale polivalente, ovvero con lo spazio utilizzabile ed arredabile in funzione degli eventi, ci sembra corretta l’impostazione del tecnico che ha già analizzato la sala, di inserire all’interno un ipotetico affollamento medio di circa 180 persone e quindi valutarle il comportamento acustico in tali condizioni tipiche di utilizzo.
In primo luogo mediante la formula proposta dalla UNI 1136700_2010 andiamo nel seguito a calcolare il tempo di riverbero ottimale per i locale in relazione al loro volume interno, che si è calcolato essere di:
Sala polivalente Volume interno = 1100 mc
Si sottolinea che dal volume dell’ambiente è stato escluso il volume dei locali accessori posti nel vertice basso della struttura, e che il volume è approssimativo in quanto calcolato sulla base delle altezza media dell’ambiente.
Non essendo questo un ambienti per lo sport, ma essenzialmente un ambiente dedicato all’ascolto della parola si ritiene di indicare come tempo di riverbero ottimale, il Tott calcolato tramite la formule C.1 proposte dalla UNI 1136700
Quindi il tempo di riverbero ottimale medio tra 500 e 1000 Hz per la sala in analisi risulta essere:
Tott C.1 = 1,00 s (ambienti dedicati al ascolto della parola)
Di seguito si riporta dettagli in pianta e sezione dell’ambiente in analisi
Based on the planimetry of the room in the project and the various internal surfaces that make up the room itself, on the basis of the dimensions and materials as well as the furnishings and the conformation of the walls and roofs, a mathematical environment was analytically obtained which should have the acoustic characteristics of the royal hall. To get closer to the reality of using the space, an average crowding of 180 people was assumed.
It should be noted that this model is significantly different from what was seen in the report of my colleague Ing. Saviotti. which in any case is different in the internal surfaces of the environment compared to those measured on the basis of the plan received.
Room volume 1100.00 m3
From the calculations performed on the basis of the information available, it is evident that the room needs an acoustic correction aimed at lowering the internal reverberation times and consequently also reducing the sound pressure level inside the room due to human activities.
In principle, the best surfaces for acoustic treatment should be the largest opposing reflective surfaces, which are normally the floor and ceiling.
In this solution, it is proposed to exploit the space between the secondary joists of the roof, with polyester fiber panels covered in fabric arranged in a radial pattern or following the course of the joists so as to give good coverage of the room.
Below is the plan with schematic indication of the positioning of the 60×180 cm sound-absorbing ceiling panels
