# Concert Halls as Nearly Adaptive Spaces
## 4 The Case Study
### The Adaptive Concert Hall as an Active Musical Instrument
The designation can be generalized to concert halls in which the acoustic response can vary rapidly without introducing noise during the variable acoustic elements'movement', the RT can change seamlessly, and the referred values are known in real time from the concert hall range RR to the congress range DD (Table 1). A control through a DT to identify all the RT in between to properly assign the designation (R, mR, D) has to be included (Table 1). At the beginning of the score, over the treble or bass cleft of the pentagram, the composer indicates the initial reverberation condition of the hall; then, under the pentagram, corresponding to the beat in which the reverberation time change happens, the dynamics of the room's response is indicated as happens when the dynamics of musical instruments are specified (Figure 12). The dynamic designation of the concert is visualized in the DT. For the composers involved in the designation, the dynamic range of the hall must be big enough to gradually identify the five different steps from RR to DD and vice versa, also considering a precise equal interval from each corresponding RT subdivision (RR, R, mR, D, DD) to be less relevant. To define the hall as an active space, however, the total RT dynamic range has to be estimated at no less than 0.8 s.  
For these reasons, the two configurations, characterized by homogeneously distributed curtains equal to the 25% and 75%, were accepted to create the dynamic responses, R and D, of the hall. For the same reasons, and since the measurements determined three main dynamic steps (RR, mR, DD), an interpolation was accepted to discover the corresponding RT values for R and D.  
Generally, since evaluation of the RT dynamic range has been considered to be much more important than the precise determination of the RT values of every single dynamic range subdivision, the estimate of the corresponding curtain area % (or vice versa) was considered to be acceptable by applying the Sabine equation in real time via digital twin. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Dynamic Designations’ Analogy**} \\ \hline \hline
**Musical Instruments** & **Active Concert Halls** \\ \hline pp & RR \\ P & R \\ mf & mR \\ f & D \\ ff & DD \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Dynamic designations’ analogy between musical instruments and active concert halls. A database with the same information, coming from a room acoustic software prediction, could be also uploaded in the DT architecture [5]. Computer simulations could be especially useful in spaces characterized by complex geometry, such as vineyard concert halls, to optimize the RT homogeneity based on a curtain's location and possible asymmetric distributions. Considering that the hall dynamic plays a 'role in a score', composers have considered the study of other acoustic parameters to be secondary and have confirmed the use of the Sabine equation as sufficient for their purpose. Whether using computer simulations or simplified algorithms to control the dynamics of the hall, specific encoders need to be installed to read the curtains' banner length. In fact, curtain control systems usually memorize a layout, but they are not able to read the curtain dimensions unrolled in the hall. These specific encoders are absolute encoders that generate unique position values, and they work like \"lap counters\" of the curtain bar. Information about the number of revolutions of the bar on specific the curtain unrolls, the position, the angle of rotation, or the speed can all be derived. Sensors can communicate with a programmable logic controller, which is part of the curtain control system. Their information is exported to be part of the DT process and visualization. Curtain movements are recorded by the control system from a starting point to a stopping point. A preset time (subject to maximum speed) and a preset speed, with a default acceleration or deceleration towards a registered profile (using joystick or gear wheel), are included.