Acoustic panels facilitate learners with different languages

The typical Italian school is situated in an old building with big volumes, stone walls, high ceilings and ceramic tiles as floors. In other words – poor acoustic standards. There is also another important structural issue connected with these old buildings. The loading capacities of the ceilings in these buildings are limited or insecure, as the material often is old and poor. Several accidents have occurred in Italy, one in Turin some 10 years ago where a student died of a falling ceiling. Therefore, legislation is toughening, and ceilings must be thoroughly investigated before mounting suspended ceilings.

As part of the research project “Io Ascolto” (I listen), professor Arianna Astolfi and post-doc fellow Giuseppina Puglisi at the Politecnico di Torino applied suspended acoustic ceilings and acoustic wall panels in two classrooms in the Muratori school. The purpose of the intervention was not only to improve the acoustic conditions. It was also to guarantee a higher degree of safety from a structural point of view.

“It is compulsory in Italy to verify the safety with respect to these structural factors,” Arianna Astolfi says.

Different languages are challenging

The Muratori school is situated on the outskirts of Turin, where a lot of immigrants live, and so many learners have different native languages.

“The classrooms were noisy because the children were talking different languages. It was a clear problem and a challenging situation for both the children and the teachers. The acoustic situation was sad, and the teachers were stressed because of the noise,” Arianna Astolfi says.

“The classes also had two or three children with hearing impairment,” Giuseppina points out and says that the Muratori school is quite representative for the acoustic conditions in Italian schools.

“The school is typically located in a historical building. It does not allow isolation between rooms. The doors are not adequate, so they have acoustic bridges from inside the classrooms to the outside.”

The classrooms also have problems with outdoor noise. Italian schools are typically situated in urban environments close to heavily-trafficked roads and streets.

“In old buildings, the windows are not high performing regarding the acoustic and thermal isolation” Giuseppina remarks.

Simulations suggest big improvements

For the project, the researchers used two classrooms that were similar in all respects: in materials, dimensions and ceiling height. Both the ceiling and the walls of the two classrooms were treated with acoustic panels, in accordance with the new Italian standard for acoustic environment in schools, UNI 115332-2, published in early 2020.

Due to the pandemic, the researchers have not been able to interview the teachers or learners after the intervention.

But they have done measurements to predict speech intelligibility, together with researchers at the University of Oldenburg in Germany. According to these measurements, where the classrooms were simulated being occupied with children and teachers, they have managed to improve the conditions substantially.

The reverberation time on 1 000 hertz decreased from 1.50 seconds to 0.42 seconds. Also, speech clarity has improved a lot. In one of the classrooms, the early sound reflections that have a positive effect on speech clarity increased by about 10 decibels on average in a central position of the classroom. That is to be considered a great improvement.

“From these measurements, I think we can say that we have gone from a poor to a very good situation,” Giuseppina says.

“And it is very cheap. This could be implemented in every classroom in every school in Italy,” Arianna notes.

Higher reading speed with better acoustics

Arianna Astolfi and Giuseppina Puglisi have also researched the effect of sound on children’s ability to read.

“We have seen that in classrooms with better acoustics, the reading speed is higher. Most of all, we have seen a statistically significant correlation with speech clarity. That is why we think that one should not only focus on reverberation time, but also on having a uniform and very high speech clarity all over the classroom,” Giuseppina underlines.

She adds that classroom acoustics may also support other learning tasks, like mathematical tasks.

“Children tend to be faster in counting and matching numbers when the classroom’s acoustics are better.”

A tool for creating the best acoustic design

To have good acoustic standards is even more important in schools in which the learners have different native languages. Different languages have different prerequisites when it comes to speech intelligibility. For this reason, the researchers at Politecnico di Torino have developed a tool to evaluate speech intelligibility for several languages, optimized for about 20 languages.

“This tool is able to assess speech intelligibility and gives us accurate results that are perfectly comparable across different languages. This makes it possible to create the best acoustic design,” Giuseppina says.

“We are also now studying the speech intelligibility for children with hearing impairment, using different face masks. With this research we can evaluate which face mask is best for these children in future coming pandemics,” Arianna says.

A big step forward

Arianna Astolfi is also one of the authors of the new Italian standard for acoustic environment in schools. This standard has become mandatory not only when building new schools, but also when refurbishing existing schools. Giuseppina Puglisi welcomes the new standard.

“This is a big step forward. It does not provide thresholds with values that are only prohibited to exceed. The new standard provides specific, optimal values for different kinds of spaces and for different kinds of prerequisites among the learners, such as hearing impairments. These values must be obtained within a small tolerance range,” she explains, adding:

“For example, the old standard had a threshold on reverberation time of 1.2 seconds. But it is a huge different between, let’s say, 0.3, 0.6 and 0.9 seconds. In my opinion, this makes the new standard human-centered, with the students in focus.”

The effect of the new standard is clear, according to Giuseppina Puglisi.

“In the most recent two or three years, the acoustics are being considered more and more. The new schools are perfect from an acoustic point of view – and now we can also start looking at existing older school buildings.”

Text: Lars Wirtén

Footnote: Ecophon has supported the project in the Muratori school with materials, mounting and experience.