Guest writer: Making sense of sound by Nikhil Mistry

by | Sep 11, 2020 | Guest Writers | 0 comments

This post is written by Nikhil Mistry. Nikhil is an Acoustical Engineer and Research Fellow at The National Oceanography Centre in Southampton, UK. His work focusses on underwater acoustics and medical ultrasound; for example, designing sonar to ‘see’ animals in the water, looking at the interaction between sound and bubbles, and using sound and bubbles for cancer therapy. To find out more about Nikhil’s work, follow him on Twitter and Instagram. He also creates content for the Institute of Sound and Vibration Research’s Twitter page and Youtube channel.

Your alarm goes off and you begrudgingly wake up. You live near a train station, but you didn’t hear anything and slept uninterrupted through the night. You mumble to your smart home assistant, “Alarm off”. Even though it’s tucked away in the opposite corner of the room, it hears you clearly and knows exactly what you asked. Time to get ready for the day.

You’re walking to the train station and you’re transported to another world as you listen to your audiobook and your noise cancelling headphones drown out the noises from around you. You get to the train station and, “Ping!”, your friend surprises you with good news that she’s pregnant, sending you a photo of her latest ultrasound scan. You catch your train and have a smooth journey to work.

In those first few hours of your day, at least 6 acoustical engineers were involved in the things you see and use, the places you visit and the journeys you took.

I was quite unprepared at school; I didn’t really know what I wanted to do, and I was too busy joking around to give it any thought. Fortunately, I was interested in ‘how things work’ and I’ve always been someone to do something a bit different.

You could say I stumbled into Acoustical Engineering. I was at the University of Southampton for their open day and was leaving the Civil Engineering tour and talk, when I saw a group of visitors leave a small building. Some of the parents in the group were shaking hands with the lecturer guiding them and saying, “That was really interesting?!” and “I never knew there were rooms like that!”. I had to have a look myself. The lecturer happened to be the admissions tutor for the Acoustical Engineering degree and said he had time to give us a little personal tour…

The building had a couple of chambers, one filled with 1m long foam spikes to absorb sound and another with non-parallel, smooth and hard walls for reinforcing echoes (some can last for up to 14 s). These chambers were really cool and as the lecturer began to describe the kind of work a student does in the degree, I was already picturing myself studying there, at the Institute of Sound & Vibration Research (ISVR). That was in 2009 and since then I have finished my degree and completed a PhD there. Now I work in their National Oceanography Centre, developing sonar to look at little animals that live at the bottom of our seas.

Sound and vibration play a vital role in our lives and the field of acoustics concerns the study of them. How does sound travel? Where do vibrations go? How can they affect humans and how can we control them? If we can control them, how do we use them to our benefit?

The applications of acoustics are far and wide, from studying the seas and the animals that live within and understanding the health of our planet, to delivering drugs in the body and obliterating cancer cells using bubbles and ultrasound, or restoring the ability to hear in young children who were born with hearing impairment. Think back to the noise cancelling headphones, that technology has been around since the 1950s – they work by adding sound to the noise that comes in from the outside, to cancel it out!

That same technology in headphones is used in small planes too, to cancel out the sound created by the fan blades turning outside, but instead of using loudspeakers, little shakers cause the inside panels of the aeroplane to make tiny vibrations that generate the sound to cancel out the droning from the blades spinning outside.

I am mostly interested in underwater acoustics and medical ultrasound. I spent some time at the Institute of Cancer Research (ICR), working with a team designing systems to provide cancer therapy using ultrasound. Ultrasound is the name for sound that is too high in frequency for us to hear. If you direct high-intensity ultrasound, and make it focus in on somewhere inside the body, the tissue inside absorbs the energy, vibrates and starts to heat up. Essentially, you can ‘cook’ a tumour. Heston Blumenthal watch this space. We can even use the same ultrasound to vibrate bubbles in tissue and use them to tear apart tumours from the inside, or even blood clots. Usually we think of air bubbles in the human body as dangerous, but these ones are generated under controlled conditions. A similar kind of effect is already used to break kidney stones in lithotripsy.

Have you ever seen a pod of Humpback Whales hunting together as a pod? They swim around and create plumes of bubbles around the fish and then one whale makes a loud call and then they all lunge up from underneath, with their mouths wide open, and gobble up as many fish as possible? It’s not the bubbles that are stopping the fish, but rather, the bubbles trap the sound of that loud call so now the fish are surrounded by a wall of scary loud sound. The bubbles slow down the speed of sound and that’s how the loud call gets trapped in the bubbly layer.

I’m a bit mad about bubble acoustics, that’s what I did in my PhD, but there really is a powerful relationship between sound and bubbles underwater. We can monitor climate change, tear apart tumours, deliver drugs in the body and even use the same science to clean surfaces, tackle bacterial infections and fight anti-microbial resistance.

Honestly, I could go on forever about acoustics; how amazing it is, where in the world it has taken me and what cool science I have been working on. Thinking back to my time at school, being confused about my degree and what I wanted to do for a career, I’m glad I followed my curiosity and ended up where I am today. A life in acoustics has given me SO MANY opportunities and taken me ALL over the world. From working in cancer research, to modelling symphony halls or designing quieter neighbourhoods and studying the way marine mammals use sound in the ocean. I entered this world curious to know what acoustics was and interested in the industries it reached. I’m still learning new stuff every day and I’m keen to keep pursuing new projects that sound interesting and I want to continue exploring the many applications of acoustics. It didn’t matter that I wasn’t sure what I wanted to do, I think the important thing is to keep chasing whatever interests you and giving it everything you’ve got.

This year is the International Year of Sound and has been extended into 2021 because of COVID-19. There will be plenty of events to engage with the acoustics, learn how sound and vibration affect you in your life. Follow @ISVRsouthampton on Twitter for all kinds of interesting news and snippets on the science of sound and find out how you could study or work in acoustics. I’ve been making videos on the ISVR YouTube channel too, so definitely go check them out, you can even learn how to make a recorder out of a carrot!