NoiseCapture - Interview with the developer of a fantastic app

Did you have any prior development or coding experience?

Yes. We are a team of French public researchers and engineers, working on this domain (noise assessment) since 2008. In this context, we are developing open-source tools and software (such as NoiseModelling, OrbisGIS (http://orbisgis.org/), H2GIS (http://www.h2gis.org/) and NoiseCapture) and thus having a strong culture in development. For instance, all our codes are publicly open on our Github repository (https://github.com/ifsttar/ and https://github.com/orbisgis/ .)

What was the most challenging aspect of developing mobile app?

A crucial point concerned with the development of the library, that allows the acquisition and analysis of sound levels. NoiseCapture does not record surrounding sounds. It simply extracts the knowledge (indicators) from the soundtrack. This reduces the weight of the data to be processed and above all guarantees total confidentiality (since it is not possible to reconstruct a discussion for example), which was very important for us.

_{Noice Planet}

Gwendall Petit, the interviewee, is a study engineer at the french National Centre for Scientific Research (CNRS - Centre National de la Recherche Scientifique), specialized in geographic information sciences. He is a founding member of the Noise-Planet platform (http://noise-planet.org), which synthesizes the work carried out by two teams of researchers in acoustics and geographic information sciences, since 2008. The NoiseCapture application is one of the flagship tools of this initiative.

Name a few of your favorite apps and reason you love them.

Generally speaking, we like all applications that, like us, work for open and citizen science or for the common good.
In this respect, and by way of example, we particularly appreciate the Street Complete application (https://play.google.com/store/apps/details?id=de.westnordost.streetcomplete) which allows us to enrich the OpenStreetMap (https://www.openstreetmap.org) open map base in a very simple and intuitive way. For example, we rely on this application to improve the data that is then fed into our NoiseModelling sound propagation model (http://noise-planet.org/noisemodelling.html).

How long have you been working on this app?

From the beginning to the first official release (september 2017), it took us more or less 2 years to develop this app and the infrastructure behind it, that allows to collect, clean and share the resulting data.

What need of the user did you have in mind when developing this app?

Our application is based on the principle of citizen science. This means that we hope that the maximum number of people will be able to use it, whether they are experts or not, and whether they are acoustically aware or not.
Therefore, we wanted the application to be as simple as possible, especially in terms of the graphical interface.
We also wanted the measurements made by users to be visible on the online community map (http://noise-planet.org/map_noisecapture/index.html) as soon as possible. This is an interesting point, especially in the context of the campaigns of citizen measures, called the NoiseCapture Party (http://noise-planet.org/noisecapture_party.html), which we organize and where participants want and need to see the result of their contributions concretely and quickly. Currently, we estimate that it takes less than 5s to publish online data transmitted by NoiseCapture.

In what way do you think your app is better than similar apps on the market? Please describe in detail what innovation you think you bring and what you are proud of in your app.

One of the key points in this type of application is the confidence that can be placed in the measure. Many applications rely on the smartphone microphone, trusting it fully and without providing the possibility to calibrate the measurement.
Being a team, half of which is made up of acoustics researchers (the other half being researchers in geographic information science), we were keen to propose a serious application from this point of view.
In addition, some applications propose to apply an automatic correction depending on the model of the smartphone. In our opinion, this solution has the following two problems:
- if we want to be exhaustive, we would have to be able to acquire and test thousands of different smartphones
- This does not take into account the differences in quality that have been observed between identical smartphones (same model).
This is why we have developed different calibration methods, from the simplest for novices to the most advanced for experts.
In this context, and for information, a Swiss center of expertise called EMPA has been commissioned by the Swiss Federal Office for the Environment (FOEN - https://www.bafu.admin.ch/bafu/en/home/topics/noise.html) to test various applications in the field and assess their quality.
Our NoiseCapture application was the winner for Android applications (the other SPL Pro application is for iPhone). See more: http://www.laerm.ch/fr/bruit-et-calme/applis-et-tools/applications-sonomtre/apps.html
Finally, our application is one of the only ones to have an unlimited spatial dimension. Some noise measurement applications propose, as we do, to place the measurement in the space, but they are often constrained to a territory (e.g. a large city like Paris, San Francisco, ...). From the beginning, we wanted to remove this barrier so that we can make measurements anywhere in the world. Today, we have measurements taken in all countries of the world (more than 150 per day).
One last point that sets us apart from other applications is the openness dimension. The code of the application is open. The tools we use are open and more importantly, the data produced is open (see https://data.noise-planet.org/). So people are free to reuse the results of the community.

What are your future plans and expected features of the coming new versions of this app?

We want to make the calibration method even simpler for users. This is a crucial point if we want to have reliable measurements. However, it raises a lot of complex methodological issues. In order to move forward, we rely on our team of acoustics researchers who are developing new processes (such as the calibration via road traffic, which will be integrated into the new version).
At the same time, we still have the wish to develop the iPhone version. This project is currently at a standstill due to a lack of dedicated financial resources.

Assuming new users of your app are reading this page. What do you want to ask them to do (contact you about X, Share the app, etc.)?

Noise measurements performed by NoiseCapture allow to enrich a world map, which is useful for everyone (citizens, decision-makers, ...) but also and above all for acoustics researchers like us.
These data allow us to feed our environmental noise simulation models and thus provide concrete tools for the fight against noise pollution.
So we invite users to take measurements and thus contribute to science by helping us to make increasingly reliable and realistic simulations.
Whenever possible, we ask them to calibrate their smartphone before taking the measurements.
And finally, because it is a collaborative application, we ask them to talk about it in their entourage if they are sensitive to our approach.