In the previous articles of “Noise pollution and health” (link) and in the article “How can measure the noise” some definitions were introduced and how noise is measured. If we make a brief reminder, it was commented that the measuring devices that currently exist detect noise accumulated in a certain time interval. This makes it quite complicated, with current technology, to know how many decibels (dB) a certain noise source emits if many are produced at the same time.
On March 18th, 2017, while are preparing the stage and holding one of the concerts of the Terrassa Jazz Festival located in the Plaza Vieja, a studied of the decibels of noise produced by the different sounds emitted. The data collected was compared with that issued at the same time one week earlier (Fig. 1).
Figure 1. Graph of the decibels of noise that were detected during the concert and compared with the previous week.
Source: Terrassa City Council.
Most of us, we have seen in the movies how a concert is prepared, starting with the arrival of the trucks with the material and the unloading of these, the installation of the stage, tests of the equipment and the sound to finally carry out the concert.
But first of all, we will explain the graph in figure 1, to facilitate understanding and we will place special emphasis on the two shades of blue that can be seen. The light blue hue refers to the noise readings that were generated a week before the concert, specifically on 03/11/2017, while the dark blue hue refers to the noise readings captured during the concert preparation stages and during this.
On a normal day, the recorded noise level is quite regular, approximately above 60 decibels (dB), but that Saturday, March 18th, 2017, the neighbors lived a different day.
At first, it seemed like a Saturday like any other, with a lot of trankility and calm, where the residents of the center heard the chime of the bells at 9 in the morning of the Parish of Sant Esperit while they ate breakfast. But after 9 o’clock, they began to notice movement. They began to hear the movement of trucks, unload heavy objects, hammer blows… A louder than normal noise. The most curious, approached to find out what was happening. What a surprise they were when they saw that they were setting up a stage for a concert and not just any one; the stage for the Bcn Jazz Orquestra & Susana Sheiman that would start at 12 noon.
The installation of the stage and its infrastructure finished and, after 10 o’clock, the equipment tests began where the technicians were in charge of studying the acoustic space of the plaza, installing and testing microphones, amplifiers, … Once all the material was prepared, the artists began to make sound tests to leave everything ready for the concert. Although the technicians were used to preparing concerts, they were always nervous when arrived this moment; since the success of a concert depended on this phase and they didn’t have much time frame. People began to arrive and gathered in front of the stage talking animatedly among themselves and smiling, some were standing, others sitting in the chairs enabled near the stage. Everything was on silk and, finally, at 12 the concert began. It was a success and people did not stop applauding when it ended at 2pm.
If we look at the graph in figure 1, it can be detected when they started mounting the stage, generating noise above 70 decibels (dB) with peaks slightly above 80dB. It is easily identified how long the equipment and sound tests last and what noise level they generated in each case. During the concert, apart from knowing the beginning, the end, the rest between songs and the level of noise they emitted, it is interesting to note that, once the concert is over, the noise recorded by the sound level meter, as time progresses, it approaches the levels recorded the previous week, being close to the normal 62-65dB during the day.
This study of noise was possible since it was a controlled area, without many changes or factors that distorted the noise detected by the sensors. We hope that in the near future spectral noise sensors can be installed in our city to be able to know the level of noise emitted by each of the emission sources (works, movement of vehicles, be they motorcycles, buses, cars, trucks, screams, …) and can carry out policies and changes to improve the acoustic quality of our environment).
JAZZTERRASSA. 36 FESTIVAL JAZZ A TERRASSA (2017). Bcn Jazz Orquestra & Susana Sheiman [online]. Retrieved from: https://www.jazzterrassa.org/ca/node/38841