Absorbent acoustic treatment in rehearsal room

Presentation

This work was conducted in a Music Society. The room that we are going to study by means of a previous acoustic study is located on the 1st floor of the building. This will enable us to determine the initial characteristics of the enclosure, and will allow us to determine the deviation of the acoustic characteristics from those recommended for this type of room.

The roof of the building (hall roof) was recently changed. Although before this action, the acoustic conditions were not the most suitable, after this modification the discomfort from the reverberant noise generated inside the room increased even more.

The main rehearsal room, detailed in the following plan as room 1, has a useful area of 135.42 m2. Almost rectangular in shape, it has a gabled roof with a height of 5.2 metres at the ends and 7.5 metres in the centre, for a volume of approximately 924 m3. The materials used on the finishing surfaces of the enclosure are, in general, highly sound reflective.These are stated below:

• Floor: ceramic tiles.
• Walls: Ceramic brick, plastered. On one of the short walls, melamine type screen.
• Roof: Continuous wooden slats.
• Carpentry: varnished wood, melamine, and glass
• Furniture: Scarce with low percentage of upholstery.

The desired RT value depends on the intended use of the room (speech or music) and its volume. In this case, with an approximate volume of 924 m3, the desired RTmid in the case of music will be around 1.35 seconds. It should be noted that this value is recommended for rooms intended for listening to music. In this case, as it is a rehearsal room, the value could be lower.

We made the reverberation time measurements of the room according to the standard methods, and the outcome was as follows:

Initially, the average reverberation time in the room had a value of RTmid=3.5 seconds, far from the recommended value for music (RTmid=1.3 seconds). The times obtained at the different frequencies were too high («very lively room») which is detrimental to the development of the activity. Conditioning solutions must therefore be studied to correct this problem.

In order to estimate the acoustic materials needed to correct the reverberation curve, we prepared a 3D model of the room that allowed us to evaluate the acoustic corrections properly and accurately.

From the geometric model, we prepared the acoustic model by assigning the absorbing characteristics of each of the materials that make up the enclosure, which allows us to adjust the theoretical model to the real model in terms of the reverberation time measured (model calibration). Based on these values, we drew up a solution plan with the acoustic materials in our catalogue, arriving at the optimum solution as seen in the following image:

From the proposed acoustic treatments, we obtain the following results from the theoretical model:

With this proposal, the reverberation time is reduced by more than 2 seconds, reaching a value of RTmid= 1.3 seconds. It should also be noted that, with the room occupied, the reverberation time will be even shorter.

Once the acoustic treatments were installed in the enclosure, the result are as seen in the following image:

To verify the results obtained, acoustic measurements were made with the Acustiart absorber panels already installed. The acoustic results obtained are shown in the following figure:

The adjustment made with the treatments, is adapted precisely to the theoretical estimates that we made from the 3D model. This shows that the capacity we currently have with the calculation tools allows us to obtain very precise approximations to reality. It also allows us to help our customers make the right decisions without previous expenses through the 3D models. The degree of absorption of the Acustiart 50 and 100 acoustic panels, allows us to adjust in a suitable way all types of enclosures, including those that require a high degree of acoustic quality as is the case of the enclosures intended for musical tests.