What does your kitchen kettle and whales have in common? Listen as host, Jo Fisher, chats to Bubble Acoustic Engineer and Researcher, Nikhil Mistry. Nikhil reveals just how important Acoustic Engineering is every day life, from cancer treatments to climate change.
Jo Fisher: 0:09
Hello and welcome to Universi-Tea. I'm Jo Fisher and I'll be talking to some of my amazing colleagues from the University of Southampton over a nice cup of virtual tea. We'll find out how they are adapting to this new way of working, what pearls of wisdom they can offer and asking important questions like, how do you take your tea?This week, I'm joined by Doctor Nikhil Mistry, a researcher in acoustics. Thanks for joining me. Do you have a cup of tea with you?
Nikhil Mistry: 0:56
Yes. Yes, I do.
Jo Fisher: 0:57
Excellent. What's your tea of choice?
Nikhil Mistry: 1:00
Nothing fancy, just a PG tips and I take it quite strong. I'm trying to cut down on sugar so I figure if you make it stronger, that overrides the lack of sugar taste. So just make it rich. Kind of like spoon stands up at attention when you stir it.
Jo Fisher: 1:17
I like the logic. Could you introduce yourself properly for our listeners today and tell us what you do?
Nikhil Mistry: 1:24
Sure. My name is Nikhil Mistry. I am a researcher the Oceanography Centre in underwater acoustics. My work sort of consists of looking at those little ugly creatures that live in the sediment at the bottom of the sea. The way we're looking at them is using sonar so kind of like how dolphins do to co locate. We can use sound to image or find things in the water where it's too dark to use optical methods. On my background is acoustics, so I graduated from the University of Southampton with a degree in acoustics. So I'm interested in all things that make a sound or vibrate. And we looked at the matter physics of that, and I specialised in medical ultrasound and underwater acoustics. And my PhD was all on underwater sound and the interaction between sound of bubbles underwater.
Jo Fisher: 2:14
I bet a lot of listeners, including myself right now, you underestimate how much sound impacts the world around you and I saw on Twitter that you were talking about the acoustics of making a cup of tea, which fits our podcast quite nicely. Would you be able to summarise that quite quickly for us? And then people can find the video online?
Nikhil Mistry: 2:33
Yeah, sure. So, yeah, acoustics is in our lives from the moment we wake up to the point at which we go to sleep. Then it's even present when we are asleep. You know there's some really important studies looking at sleep disturbance, the effect of living near a train station and airport. How that affects the people that live nearby, doesn't disturb them when they're sleeping, all this links to other health effects. You know, things called a thorough sclerosis of the lining of blood vessels and things like that due to stress and wrist startle responses. But, yeah, then you can go to something that seems so mundane, boiling water in a kettle and making a cup of tea. But actually, acoustics and specifically bubble acoustics are involved there. So when you're boiling that kettle, you'll notice that the sound gets really loud and people think it must be done when it's really loud, but it's not. It's actually when it goes much quieter. And then after that, the kettle's boiled. The water and the process that creates those sounds were generated. Sound is to do with the generation of these bubbles and to turn the kettle on, the water that you have in the kettle has gas dissolved in it. It's mixed up air and stuff like that from whatever journey the waters take. When you pour water out the tap, it mixes air into the kettle with water. You boil the water so you have this heating element at the bottom of the kettle, and that's getting really hot. And the water that's immediately in contact with that surface heats up. And so now all this gas starts. You get these bubbles forming and you could see this if you boil a pan of water, you start to see bubbles at the bottom. The bubbles rise up through the column of water, so they're travelling towards the surface of the water inside the kettle. But all the water further up is cooler because it hasn't heated up yet. So now the water is too cool to sustain those bubbles, so the bubble that formed at the bottom rise up and cool down. So now they collapse, and it's the collapse that generates the sound. This collapse is called capitation, it's a really powerful process. It's a bit like if you're clapping your hands in a large hall, if loads of people did this at the same time, you'd get, like a roaring sound off everyone clapping at the same time in a hall where it's really reflective. That's what's happening in the kettle. The bubbles are all popping as they rise up through the cooler water. They're creating these loud bangs inside the kettle, and you're hearing the collection of all those bangs in the kettle reverberating. As time passes more and more, that water heats up. So now, further up the kettle, the water's getting hotter and hotter, and you get to a point where the whole body of liquid in that kettle is hot enough that the bubbles could rise up without collapsing. And they don't collapse until they get to the top of the water. And then it generates a different sound because it's no longer popping in water, it's popping in air, so because fewer bubbles are popping as they travel up, that's the quietest sound that we get towards the end of the boiling process. And then, you know, the bubbles popped release hot vaper, and that's why you have all that hot stuff coming up this part of the kettle. So that's the sound generator. And that's why it gets loud first because loads of bubbles are popping and gets quiet because fewer bubbles are popping. That's the indicator that all the water is getting hot enough.
Jo Fisher: 5:43
I had no idea there was so much science involved in making a hot drink.
Nikhil Mistry: 5:53
If you weren't making tea, you're making coffee or hot chocolate, and you might be using hot boiled water. You can then do another experiment at home, where you pour this boiling water into a mug. You pour your coffee Granules into it, or your powder -it's really good with fine powders. Chocolate powder. You stir it up and you notice all these bubbles. And then what I suggest you do is tap the base of the mug. Put the spoon in the mug and tap the middle of the bottom of the mug and keep tapping it, and you'll notice that the pitch of the sound that it makes will go higher and higher and higher and higher and higher and that's to do with the bubbles. So the speed of sound in air is much slower than the speed of sound in water, it's almost like a five times difference. And now you've got this much faster speed of sound in water. But you've put bubbles of air in it by throwing this powder in. So now you've got lots of pockets of air in the water, so the water represents the characteristics of air more than water itself. So now you reduce the speed of sound because you got all these pockets of air in it as you tap it over time, so those bubbles start to rise because they're buoyant, so they rise to the top. They pop, some of them might stay at the top. So now you have fewer pockets of air in the mug, so that liquid becomes more like water, not air. Because that water has become more like water and less like air over time, the speed of sand reverts back to that faster speed that it is in water. And so the speed of sound goes up over time. And there's a relationship between the speed of sound, the wavelength of sound and the frequency of sound. And so the equation is speed of sound equals wavelength times frequency. So now we look at both sides of the equation. Speed of sound goes up. Wavelength doesn't change, but the frequency has to go up to balance the other side of the equation. And that's what we're hearing. So we hear the frequency go up because the speed of sound is going up. The effect of bubbles slowing down the speed of sound well, humpback whales have used this for years and years and years, and they use this kind of effect to hunt if they hunt together. There's cool videos of David Attenborough commenting over the top where they spew out these columns of bubbles around fish, essentially creating a big net of bubbles, and then one whale makes a really loud call, and they only ever make this call when they're hunting in this way, because the bubble slow down the speed of sound, the sound gets trapped in regions where it's slower so it gets trapped in the bubbles. So it's not the bubbles that are a problem for the fish, but it's the trapped sound in the bubbles that startles them. They try and swim out of the net of bubbles and they hear this loud sound so they swim away and then they're surrounded by this sound so they school together, which kind of makes it easy for the other whales to come up from underneath and gobble them up.
Jo Fisher: 8:36
That's amazing. I didn't know anything about how the sound of boiling kettle gets louder. I've always wondered that. And now I'm gonna have to make hot chocolate just to observe the same science in my kitchen as in this depths of the sea. Amazing how it applies to so many different things.
Nikhil Mistry: 8:59
I've used hot chocolate powder, but trust me, hot chocolate with just water is really gross. So just do it to listen to something but don't drink it because I've done that to save you.
Jo Fisher: 9:12
That's amazing. I've learned so much already in such a short space of time talking to you. Obviously you're currently working from home, and I can imagine that you're quite used to doing all of this in a lab or on site or on trips. I don't know how you are finding adjusting to working from home?
Nikhil Mistry: 9:38
I found it quite tough, finding it quite hard to keep motivated, stay focused on the work, and I end up getting quite distracted. I had loads of ideas for public engagement and stuff like that, and I keep breaking through them and trying to realise those ideas. I'm having ideas now because actually, it's kind of a blessing in disguise that we're all stuck at home, engaged online. This is the perfect time to be cracking out lots of online content. But even like trying to sit down and put the content together, I'm still just really struggling to just sit down and focus for a long period of time. The other problem for me is that actually, just before we were told we had to come and work from home, we were supposed to go out on a field trip to collect animals to then conduct experiments, which means actually, my work specifically has kind of come to a halt. It is tough just to stay motivated, especially when you're in your own house. Like I guess if you had to go to a cellular office every day and work, at least you're getting out and doing something. If you're in your own house, you see this stuff when you come home from work anyway, you see that cupboard, you see that wall, you know what it is. The other drawback is that you've seen that crack in that wall that you need to fix. You've seen that garden that needs digging up, and that's a lot of stuff I've been doing when I'm not focused. My partner and I, we bought a house in October, so there's loads of stuff to be getting on with anyway. Another blessing from this lock down is that I can get out in my lunch breaks and just dig up part of the garden.
Jo Fisher: 11:10
I've had a lot of people talking about their problems with focusing and motivation, and and I think the thing that's coming through is so many people have distractions like you said about what's in your house, the people you're with, you know, maybe you've got kids you need to home school and there's projects with the house that you've also got this huge distraction of the global pandemic that's happening outside of our windows. I think you know, it's very, very difficult to work as you usually would, because this isn't usual. This isn't normal circumstances. Do you have an office space or are you working in space that you can find around the house? Or have you dared work from the comfort of a sofa or bed yet? Or has it got to that point?
Nikhil Mistry: 11:53
No, we're quite lucky. We've got this third room, which is kind of like a small box room, But we already knew we were going to turn it into an office. So we're really lucky, because I've seen a lot of friends who were like, "I've had to fashion this, I don't know, this little table in the side of the living room into a desk or I have to work on my laptop on the sofa", and for me, at least, it would ruin the living room or the dining room, because then I can't associate that with a place of eating or resting. I'd always be like I'm working here anyway. Where we have our dining table, I've made a little library near it, so there's like a whole wall covered in books. So actually, if I wasn't doing some other work in here, I would have taken this call down there just cause the library makes for a really nice backdrop. You know, kind of like the BBC interviews. They've really prepped their room to look good. And you've got all these old books on the wall that make it make a great backdrop.
Jo Fisher: 12:45
I've seen people joking on Twitter that they won't trust people doing TV now if they don't have a wall of books behind them, maybe we we will need to re think our working situations to make sure we look reliable and trustworthy. If only I had a library in my small flat. But there we go. At least I'm not working using an ironing board as a desk or something like that, which I have also seen. So you just have to make the most of your situation, don't you? You mentioned that you would normally be going out into the field and collecting samples or animals for your research. What I was going to ask is what would you be doing now if you weren't working from home and it was business as usual?
Nikhil Mistry: 13:24
I would be be conducting experiments in the lab. So this is where I've spent a few months building the system, checking it worked, to knowing how to process the data. And so now was the point where we thought, Okay, we're ready to go and get these animals, get some mud and start conducting experiments. You start to try and use sonar to study these sediments where animals are living in it. The idea is to look at does the fact that animals live in the mud have an effect on how the mud responds to sound? I know that sounds really weird just as a sentence in itself, but actually being able to do that, being able to image an area using sound a bit like how a dolphin paints an image in its head of what's under this sand when it's clicking away means we can study these locations where, actually we can't get a camera because it's too dark or, you know it's too remote for anything else, and we can drop something down kilometres deep and deploy this acoustic equipment to scan the bed of some area of water. Then we can bring it back up or we can have a tether that brings the data back up. We can create an image of what's down there and maybe we discover something that we didn't know before or weaken the behaviour of these animals in response to something like climate change. So we could have a lab where we re create that environment and see, are these animals behaving differently? And if they are, how does that then have an effect on the rest of the environment? You know, if they're not living and breathing and excreting, reproducing in the same way, how does that affect the greater ocean? And how does that then affect the land?
Jo Fisher: 15:09
So you've mentioned a bit about your career so far, moving from some of your studies into the world of work and then returning to academia. Could you tell us a bit about yourself? Your journey and some career highlights and some standout moments that maybe have helped you to become who you are today?
Nikhil Mistry: 15:25
I kind of got into the degree by accident. When I was at school, I didn't really know what I wanted to do, So when it came to choosing a levels. I wasn't really sure what I should pick. And I thought, OK, to be safe I'll do a language, do maths. I'll do a science and I did English as well. I just thought if I do a wide range of things, I'm sure I could get into something. Then it became clear doing physics and maths that I was really into engineering. When I came to see Southampton and go on an open day and look at their civil engineering department, I then saw the acoustical engineering department. My dad and I just thought that was quite interesting. Quite cool. I thought I might add this to my application and I got the place and actually, I haven't looked back since. Like, I don't regret picking it over all the other ones. I got really passionate about it really quickly. I was given loads of opportunities because I was really keen, and the year abroad that I took that was in Australia. So I worked as a consultant engineer for a year in Australia, and I got to meet some amazing people, see some amazing things and I got a good taste for the working environment in acoustics. When I came back, I chose one of the optional modules for my third year as underwater acoustics and ultrasound. Some of the stuff I learned was wicked. I ended up going to the Institute of Cancer Research in Surrey to work as a researcher over a few months in the summer. Then I was just kind of sold on the idea of doing a PhD. Unfortunately, we couldn't get funding for some of the cancer research projects that I wanted to get involved with. But then one of my supervisors came forward with this other project in bubble acoustics in the Ocean. And so I went for that, and I've still been able to stay in touch with all that stuff through bubble acoustics. So the first life changing thing, or like cool moment milestone, was going to Australia. That really was a really cool experience, not just because it was a trip to Australia, but it was great to see another culture but also practise acoustics and see how it's used around the world. And I still talk to almost everyone I met there, like I'd still keep in contact with people I worked with and the friends I made, so that was fantastic. The second great moment was being at the institute for Cancer Research. That was really cool. Everything I do now, almost all the public engagement I do now is just stems from underwater acoustics. Because I loved it so much. And then, yeah, I guess the PhD is probably the biggest thing. You probably hear this from loads of people when they talk about their PhD, but it was a really bumpy ride. It's really not easy at all, and you come out of it a bit scarred or bruised. You know, you start to wonder whether you have the confidence that you thought you once had. But if you actually sat down and looked back and wrote down what you achieved in it, most PhD students will find, if not all, will find that they did way more than what they might have done had they just got into a job and taken a job that they might not be necessarily passionate about. I ran a comedy club where we were getting researchers to talk about their work in life as an academic through comedy, and that's probably one of my proudest achievements to do that. We ran that for three years. We had a YouTube channel podcast and it was great because not only will we show the public what work was going on in Southampton on giving them a night of comedy, but we were also giving these researchers like an opportunity to just stand up and talk about whatever they want in their life in academia, almost like getting something off their chest and giving them the confidence to present about their work.
Jo Fisher: 18:48
There's a lot going on there, and I actually think I was at the university when that comedy club was going on. I heard so much about it. I think it's an amazing opportunity for, like you say, researchers to get to do something a little bit different. So you mentioned that you worked for a bit at the Institute of Cancer Research, looking at acoustics and tumours. Could you tell us a bit more about that?
Nikhil Mistry: 19:11
So at the Institute of Cancer Research, I was working in the focused ultrasound surgery team. What they were doing was they're using ultrasound instead of the radiotherapy. So radiotherapy uses electromagnetic waves, these airwaves, associated with light, and in the ultrasound surgery you're using sound, which you fire into tissue to cook it. What I mean by cooking is sound is a vibration. When I talk in the air to someone, the vibration is in the air particles. We sense ultrasound through the tissue. It is vibrating the tissue we want to vibrate so you can focus the sound to a particular point instead of just having one source of sound. Let's call it a loud speakers is easier to imagine. If you have one loudspeaker, there's only like one beam of sound coming out of it. If you have loads a loud speakers together and you programme them correctly so different speakers play the sound at a different time. The beams of sound interfere with each other, and at some points they destructively interfere. So you don't have any sound in a location, and some places they constructively interfere, so they add up and reinforce and get stronger. So with ultrasound, you can have all these different points. These little sources of ultrasound , they fire into one point, you programme it so that they constructively interfere at a point inside the body. Let's say where there's a tumour. The idea is that those vibrations from that sound, they vibrate the tumour and that turns into heat energy. So it's heating up the tissue so much that, like I said, you kind of cook it. The idea is that you have this accuracy around it. The shadow region around the treated area isn't as large. So actually you can get like, you know, a grain of rice accuracy.
Jo Fisher: 21:09
I don't know if you happen to have anything or an object in your room or your home that reminds you of your career or your research that you'd like to share with us.
Nikhil Mistry: 21:20
I have tattoos that I have on me. The first tattoo I got was kind of in the middle of my PhD where I was having a tough time, and I just thought, You know what? I want to do something different, and I went on a holiday. I went on holiday to Germany and I just saw some really cool designs on the walls and stuff. And I got inspired to, like, start drawing up bits myself. So the 1st 2 tattoos that I have, I drew myself. I thought you know what? Let's just do it. I had no tattoos before that. Let's do something. Actually that kind of reinvigorated me to just wake up and do stuff in life and get on with my PhD. So I have pi as in, like, Greek symbol pi on my arm. I have sigma on another side, and they've all got that like cool different patterns like paisley and geometrical patterns around them. And then the thing I was telling you about the humpback whales. Well, I have a humpback whale spewing out a bubble net on my upper right arm. So that was like a big one I did towards the end of my PhD. And that kind of like is there to remind me of my work I did in bubble acoustics. I'm really into the ocean. I really am interested by these animals and what they do so when I passed my PhD, I got Dr Pikachu tattooed on my left wrist. So pikachu in a lab coat. And then I have a baby emperor penguin on my other arm. That's when I got engaged to my partner. I have a narwhal, which I got when I submitted my thesis. So slowly collecting them.
Jo Fisher: 22:49
I love that. I know it's a cliche when you get asked if you've got a tattoo, everyone immediately says, What does it mean? What does it mean? But I love that all yours have meanings, especially the humpback whale. I'm so happy that you've got a tattoo about acoustics and bubble acoustics. That's brilliant. Thank you for sharing that. Obviously, you know, it's not something that's easily shown, Yeah, but it's like a personal reminder for you that you can carry all the time. So I wasn't expecting that to be your item, and I'm surprised by the tattooed researcher. Apart from obviously trying to work and trying to sort of stay motivated in terms of your research at home, you've really mentioned a little bit about your garden and the work you want to do in your house. Have you developed any hobbies to keep you occupied and busy when you're not working or are you finding it quite hard. You know, obviously, time to relax is important to you as well.
Nikhil Mistry: 23:59
I will do anything, anything to get me away from the computer. I've always been into cooking food, really interested in exploring different flavour. Now everyone's baking sour dough and banana bread. So I thought, Why don't I do that? And I'm really interested in it and acted as an academic, even like with tattoos or the garden or anything else I do. I really like to get into the nitty gritty of it. So there are plenty of people on YouTube on forums, that really go into this precise details of, you know, why does a sour dough taste this way? How do you make it better? What are the different flours you can use? How did they change it? So I've been doing that. I've got a few starters with different flours all at the same time. They've got different names. I feed them. I feed them every day. I've been making some loaves and looking at the different effects. And now I've got to a point where I think I need different tools. So three other day I spoke to my partner. We looked at each other. I was like "We've always wanted a stand mixer. Shall we get one?" So they're quite expensive and because we love bake off, I thought, Let's get KitchenAid. But then I sat online, as I do in academia, did a little research and actually the the KitchenAid are Okay, but there are better ones, but everyone gets them because they're really pretty, and they're on the great British bake off. But I think we might order one today actually-really excited. But one thing I have learned while making the dough is that actually, you should get to know your bread by your hands, because that tells you a lot about how the bread might turn out. So I'm not afraid to get my hands dirty, I've been doing a lot baking. I made some really cool cookies on the weekend. Actually, they were like tennis ball sized. Oh, bigger than a tennis ball, and then you put them in the oven. They make really gooey cookies, and I just put like half a kilo of dark chocolate and pecans in there -was really good. That was really fun to make, actually, and they look good on Instagram.
Jo Fisher: 27:14
That's what you want from baking. You're making my my baking attempt sound utterly pitiful as well. So I'm gonna have to up my game after talking to you. I love that you're busy applying your academic need for being precise and researching into things. Just baking, which is brilliant. So enjoy using your mixer when you do eventually get it, and we can all hopefully follow your progress and see what you end up coming up with and how the bread develops as well.
Nikhil Mistry: 27:14
It's funny, actually, because with cooking, you can just chuck stuff together if you know how things taste, generally, they'll be okay. But baking is really tricky. You do have to be precise. And that's the really annoying thing is you might not know what you've messed up or what you've missed out on. But when you finished it, something doesn't go right. It's not what you wanted and you sit there thinking, What did I do wrong? You really have to follow precise rules.
Jo Fisher: 27:15
Obviously, the kitchen is sort of a lab, isn't it? Cooking and baking is a science of sorts, so I suppose we can all pretend to be scientists when we're making a cake or baking some bread. Potentially, that's quite tenuous. But we'll go with that. You've mentioned how you enjoy public engagement and teaching other people and getting everyone involved and how being at home is the perfect time to be doing that, planning that. I've seen that you've been doing a bit online on Twitter and things and asking people to ask you questions and answering questions like the one we had about the kettle. How are you finding that, what are your plans and how can people get involved with exploring acoustics at home while they're inside?
Nikhil Mistry: 28:01
This year is the International year of Sound and that's something that's really important, and I think before the pandemic we had so many events planned for the year, and we had these plans to really go out with a bang, get people recognising that sound and vibration is all around them. They can study and play around with this stuff at home. That could appreciate all the inventions that were coming out because of lock down. I think the year of sound has sort of been pushed to continue into next year as well, and some events will start happening next year once we can get out and do stuff. But one of the things I'm trying to do is get people to tweet us with questions about things. So like we had, why does the kettle make this sound in this way? Just think about whatever you want and ask whatever you want, and we'll try and get someone to answer the question so I will then speak to people in our department or other friends of the community to answer the question the best they can. And if I can, I'll make videos to go with that and then put them on the YouTube so people can watch them again and again and try experiments. I'm trying to film, how to make things so people can start to visualise vibrations. You'll see videos of, like, gloopy material on a loudspeaker, and it makes patterns and stuff- like those things to engage with. And it's just a case of me thinking about what can I design? What can I provide for people that also allows them to do it at home, give it and not assume that you know, Jamie Oliver says, You can make this with five simple ingredients, and all you need is this egg from a dodo in it. It is if everyone has it in their kitchen, but they don't. So now I'm trying to think what do people have at home and what can they do with it, too? Then engage with The Acoustical Society. They have like a whole Web page full of activities with kids that you can do to engage with acoustic sciences and things like that. I guess it's just a case of following us at Southampton or the University of Southampton engineering Twitter feed as well.
Jo Fisher: 30:03
It sounds like there's plenty for people to be getting on with if they're feeling a little bit curious. And it also sounds like you're achieving plenty as well, even though you're not quite 100% confident that your focus and motivation is where it usually is. So I really wouldn't worry about that. It sounds like you're doing a fantastic job in current circumstances. Is there anywhere else that people who are interested in finding out about what you do or what your team does? Where can they find you?
Nikhil Mistry: 30:29
I'm on Twitter @Nikhil_Mistry. Then on Instagram @Nikhil.Mistry. You follow Twitter at Southampton and YouTube.
Jo Fisher: 30:44
Thank you Nikhil for your time and for talking to us about your experiences of the lock down and working from home and also your research. I have learned so much I have one final question for you. Do you have a favourite mug to take your tea in?
Nikhil Mistry: 31:00
Well, I really like my Le Creuset mugs because they look cool. We also have mugs with our initials like Scrabble letters on them. So I have one with 'N' on it, and then it has, like, the score next to it. I guess that could be my favourite one, because it's specific to me. The Moomin ones are pretty cool as well. They've all got cute designs on them. Let's go with the Scrabble mug one with a letter.
Jo Fisher: 31:22
It's always good to have a favourite mug, I think, to take a cuppa tea in the afternoon, thank you so much for your time. And it was great talking to you.
Nikhil Mistry: 31:30
No worries! Thank you very much for taking the time to chat to me- really good fun.
Jo Fisher: 31:35
Thank you to Nikhil for joining me for a virtual cuppa today. Make sure to subscribe to the podcast for future episodes. I'm Jo Fisjer. Thank you for listening. This has been a podcast from the University of Southampton.