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Leonardo Fierro: Sharing experiences for a better doctoral student life

For doctoral student Leonardo Fierro, rap music was the steppingstone that brought him to Aalto. In the ‘Walk in my shoes’ interview, he says that it was love at first sight with Finland.
Photo: Leonardo Fierro.
First photo: Paulo Pannuzzo. Other photos and videos: Leonardo Fierro

Can you tell us something about your background and how you ended up in Aalto?

I come from Italy. My town is called Brescia and it’s one hour from Milan. I spent my childhood there, and I have a bachelor’s in telecommunications engineering, and master’s in communication technology and multimedia.

Towards the end of my university years in Italy, I decided to explore my new-found passion for audio and to pursue master’s thesis in audio signal processing. Thanks to my grades I won a scholarship to do the thesis abroad, and I contacted my current supervisor Vesa Välimäki at Aalto University for a thesis work. I visited the lab for three months at the end of 2018, and a few months later Vesa Välimäki proposed that I would come and do a PhD at Aalto.

It was love at first sight with Finland. I love the cold, snow, and nature. Even darkness is not that bad, even though I can feel the impact of it.

Which came first, rap music or audio signal and processing research?

I started to listen to rap music when the movie 8 Mile came out, but my journey as a songwriter did not start until I was 16. In the beginning, I felt very embarrassed by what I was trying to do: I did my first recordings by myself, late at night, waiting until everybody else was sleeping. I had a cheap USB microphone from the Guitar Hero game, and I used that to record my songs – whispering, so nobody could hear me. I didn’t want anyone to find out! I was lacking self-confidence, and of course the first songs were really not that good.

Now I have two official records and two extended plays out. I’ve had a music project with a rap-metal band, and I still have a rap duo with a long-time friend who lives in Italy. I sing and write in Italian.

So, rap music was probably the steppingstone that eventually brought me to Aalto and into audio signal processing research. I was learning by myself how to mix, master, and record, often having to come up with makeshift solutions to compensate for the non-existent budget. That was my first contact with the world of audio signal processing. Now at the Lab nearly every one of my colleagues is a musician: we even have a drum set and a guitar set up in our coffee room!

Photo: Leonardo Fierro.

What is your research about?

The title of my PhD research is transient processing for audio applications. I deal mostly with transient sounds, that are e.g., knocks, claps, and plosives. They are basically a burst of energy that is narrow timewise, and they must be treated with particular care.

The main application of my research is time-scale modification, a process of speeding up and slowing down a sound without altering it. For instance, on YouTube you can speed up a video and still hear the sound quite clearly. There are lots of applications, such as audio books, language learning, and DJing, where you match the tempo of two songs. Transient sounds are a big problem in this task because, when you slow them, they tend to lose their clarity and sound blurred, so I have been working on ways to address that, with pretty good success I would say.

Can you share a story about learning from failure?

Between the second and third year of my doctoral studies, I was stuck working on one paper. It took almost a year to finalise the research, write the paper and send it to a big journal. After six months waiting for the review, the paper got rejected. I felt they misunderstood the article, and my first reaction was despair. Up to that moment, I had always excelled: good grades, accepted papers... That left me thinking: ‘what do I do now?’.

My supervisor Vesa Välimäki simply said: ‘yeah, we are just going to improve the article and send it to another journal’. We paused the research for a few weeks and then started working on it again. We submitted it to another journal, and it went through. When I went back to read the original paper, I noticed that it looked so much worse than what we just submitted.

Rejection happened for a reason that I didn’t realise in the beginning. But it led to a better scientific contribution and forced me to face a big failure. Of course, I lost a lot of time. But now I’m less fearful of failing. I know how to put things into perspective. It was a good lesson to learn that failing is part of the process of succeeding.

After the failure, I am also very happy to talk about my research. In the beginning I was afraid, because I believed that my research was not good enough to be discussed with my peers. Now I know that maybe it’s not world-changing, but it’s good research!

Can you share something about teaching as well?

It was probably my second year in the Acoustics Lab, when I really wanted to get involved in some teaching activities. I joined the teaching team of the bachelor’s course of Applied Digital Signal Processing which needed assistance. The only problem was that the course is taught in Finnish.

So, there I was, correcting reports in another language. I had to make sure that I’m giving the students a fair grade, so I had to make the effort of understanding. Luckily most of the course was based on coding, and that’s a universal language. Then I started to pitch ideas on how to improve the course grading system, and eventually I asked if I could take over a lecture, and the teacher in charge agreed. I had the stage to talk to the students about audio stuff, and I absolutely loved it. Teaching ended up being the best part of my job in the past two years. We also got two awards for high-quality teaching, in 2022 and 2023!

Have you done research collaboration?

I haven’t done a proper research visit, and that’s the thing I regret most about my doctoral studies. I moved to Finland just before Covid hit. During my first two years, all the conferences were virtual. I truly believe that attending one of those conferences with my papers that early would have been a small boost of confidence. It would also have allowed me to do networking. Later, it took a couple of conferences to realise how things can be done. But it’s too late, it’s my fourth year already, so I kind of missed the chance to build those connections and to make research visits or collaborate with someone outside Aalto university.

What in Aalto do you think needs developing?

There should be more sharing between different teaching groups. We were having a discussion in the coffee room a few months ago about some of the problems we have encountered in our teaching activities. Plenty of us faced the same challenges and got to the same solutions. What if we had access to this kind of shared knowledge, or moments of sharing, saving us a lot of time? And teaching is just an example: we could also talk more openly about the challenges we face during our PhD. I would encourage sharing experiences.

Photo: Leonardo Fierro

What is it like to walk in your shoes?

It’s a very busy life. I am passionate about way too much stuff. For eight hours a day I’m here at the lab. Most often I have a rugby bag with me: I either have my own training or I have some coaching duties with my club or the Finnish women rugby national team. I still try to be active with music too. I host a podcast about sport sciences, and on top of that I have a very active social and private life.

I find it fantastic to look back at certain events in my life and see that where I’m now is a combination of certain events or choices that looked insignificant when they happened. It’s also a good reminder: if you can, it’s always good to take any opportunity that comes to you. You never know where they could lead to.

Interview and text: Tiina Aulanko-Jokirinne

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