About WOMB and hydrophones and listening in swimming pools

»WOMB« started as a project between Kajsa Lindgren and Hyperdelia and David Granström in early 2017. On 24th February 2018 we rented Storkyrkobadet swimming pool in Stockholm, Gamla Stan to record the record »WOMB«. Kajsa and David re-amped and re-recorded Kajsa’s composition through underwater speakers and hydrophones and made impulse responses of the acoustics of the pool. The next day Kajsa and David, Malte and Andreas met up and talked about the recording of WOMB underwater, about how to work with hydrophones and about voices of memory. This conversation took place at Café Uddvillan in Stockholm. The sun was still out and was shining on the frozen and snow-covered lake.

Kajsa Lindgren – »WOMB« is available as 12” vinyl LP and download via hyperdelia.com and Bandcamp.

Recording process

Andreas: How was the experience for you to record underwater, in the pool?

Kajsa: It was very different to a ‘normal’ recording situation. I knew that there would be some side effects, there always are. And you just have to adapt to these interruptions – but I like that.

It was different of course to hear the composition underwater – it felt a bit like being a child again. Being able to move and listen to it and choose your own position. A feeling of being absorbed by this being in a way. That was beautiful.

David: There were a lot of things we couldn’t foresee, how the sound would react underwater in the pool. This rattling sound, for instance, that wouldn’t go away – that was kind of interesting to deal with, there were sounds that would constantly surprise us. I am quite impressed by how it turned out.

Andreas: You were talking about WOMB being more like a state, and not so much a narrative, like a room that you are entering and leaving. The same thing was happening in the pool yesterday while swimming: I had the feeling I couldn’t swim away from it. Usually, like in a club, I would leave the room or the speakers and then everything changes, but here I had the feeling that the piece creates its own room and I am not able to leave it. I could swim around but even when I was far away from the speakers the sounds of ice cubes crackling or those of the voices were in my head. And when there was silence it was not because I moved somewhere else but because there was silence in the music.

I think I then understood what you meant with the state, you became the space, you became part of the space, not being able to swim out of it. You were just inside of it and then also taken by the composition.

Kajsa: Yes, you really hear through your whole body. That’s probably why you have that experience: you’re not listening with your ears anymore but with your whole body.

Malte: And you completely feel isolated in a way. I mean you could open your eyes and look at the ceiling, but sonically you are completely shut off. Because there is nothing else that you can hear, no distance and no orientation.

Andreas: You hear your breathing of course. I very much focused on my breathing, so much so that I wanted to stop breathing to hear the music. Holding my breath to not disturb the listening.

Malte: What do you think the pool and the underwater do to the music or the composition?

Kajsa: I think when I thought about the composition being played underwater I was thinking about what sounds to enhance, what kind of material to focus on. So far, I have been focusing very much on the voices, they have lead the composition and through them I have arranged the piece. That is one layer.

In this layer there’s a lot of low frequencies and ambiences which was a bit more difficult to handle in the beginning. Funnily, what we heard much more clearly were the detailed sounds from the other layer, layer two, which occurred not so often. That’s why I was amazed to hear voice so clearly underwater, that was really beautiful.

That’s an interesting situation also for the concert when the voices are heard so clearly: you can basically hear them very distinctly and sharp from anywhere in the pool. But to listen to the lower frequencies you have to swim towards the speakers and then it gets physical because you feel the vibrations.

Malte: It’s funny to hear sound behave so differently underwater. I like what you said about the more ambient part, which is not so much audible in the water. It is actually kind of beautiful that this frequency spectrum dissolves into the ambience of the water – when it becomes indistinguishable: is it water or the composition?

Kajsa: But those were the sounds that you would hear more distinctly above the water – as if they would only reflect above the surface.

Andreas: The whole physicality of sound was so apparent. When we were in the pool yesterday I put my feet in front of the speakers and it felt like a foot massage. You could hear and feel the frequencies shaping the waves underwater. And then also from outside the pool you could hear how the pool became a whole membrane itself. Making the air vibrate in the room.

Kajsa: That’s cool. Like asphalt, when it gets hot on the surface. It was kinda like that.


Malte: I feel you can listen to the piece without knowing anything about the voices and what they are talking about and still you are transported somewhere or some place, maybe to this idea of a state of mind. That’s why I like this notion that everything comes together in the water – it carries this idea of calmness and contemplation.

Where did the idea with the interviews and voices come from? Because this was the starting point really, right?

Kajsa: That was the longest process of the whole project really, to get that material.

I sent a question to both specific people and also more widely on facebook and only described the project in one sentence. I wanted to have a recording of voices talking about sound from a perspective that was nostalgic or happy or loving. It felt kinda cheesy to ask for that but it was actually very nice. And some of the interviewees really went for it.

I was surprised that they felt so comfortable and open to talk to themselves into a microphone – because they recorded their voices mostly themselves, I wasn’t involved in the recording. None of them talked about a specific sound but much more about the whole situation in which sounds occurred.

I could almost in every interview hear some sort of, not sadness, but some kind of loss. Very beautiful in a way.

All of these interviewees sent a few minutes of material which I worked through and used some sentences. I wrote down the sound sources and categorised them. And from there, I went through all that material and made field recordings based on their recordings and stories.

Malte: The field recordings had to do with what the voices were saying in the interviews?

Kajsa: Every field recording is based on what the interviewees had said. I really like that it’s in a way impersonal or at least it’s not about my feelings, but it invites other people and listeners into it. This is also one of the reasons why I was thinking of the pool situation, to let the audience experience the piece in their own way by swimming around.

When I had all the recordings and memories of the interviewees at hand I had to think of this scene from Harry Potter. I think it’s the third movie, when Dumbledore is watching a small pond and he has his wand and he can pick up memories with it. That was not what I had in mind from the beginning but I realised the pool had kind of become this memory pond.

Andreas: One of the voices is your grandmother. How did you record her?

Kajsa: That’s from when I was at a residency at NOTAM in Oslo, working with WOMB. And since she is living in the North of Sweden we talked on the phone and I recorded that conversation. My grandmother is really good at talking so I would just sit there quiet and she would talk.

There was also this one interviewee, he had this really funny memory of being a kid and using a pitch fork and putting it to his eye lashes and feeling it vibrate. And he talked about that and at the end of it he played the pitchfork. It was really interesting to hear how different everybody approached the situation.

Another one talked about a mechanical piano that she heard when she grew up in New York, in a house, when she was a kid and it was really difficult to get that recording. I have a small Spieldose and a toy piano so I recorded that instead and added them together.

Pool setting

Andreas: How did you decide on the set up of the recording then, with four underwater speakers and two hydrophones? Was it related to the composition or more an experimental set up?

David: I remember that we talked about this, in practical terms and about the technical challenges: how do we mount the hydrophones in the water? How do we place them in water? We did some research and found some multichannel microphone model for underwater recording, a microphone holder. We also came up with our own device, but it was also very ambitious compared to what we did in the end.

In the end it was much simpler, but functional. We just hung one bar of plastic pipes over the pool on which we mounted the hydrophones. We used these pipes because we were wondering which materials we could use: wood is difficult because we might not be able to reuse it. Would it be safe to use it in the water? You know, all these very practical considerations. In the end this was really cheap to make.

We also had discussion about different configurations, different positions to place the microphones and speakers in the pool – but in the end we only had two positions. One where we hung the hydrophones across the pool in the middle with the speakers in the four corners and then another one where we had them at the end of the pool, further away from the speakers, so that we would get a really wide stereo. In the end there were a lot of practical considerations that made it what it is now.

Kajsa: It is also interesting to realise that the hydrophones that we used are not meant to record this kind of music in this setting. They are industrial products and not very user friendly.

David: Yes, they are aimed for industry purposes.

Andreas: I read hydrophones are also used to clean pipes. Through putting them into pipes you can see if there is leakage.

Kajsa: Yes, these ones are specifically made for that, to look for wholes in ships or pipes or for leakage generally.

David: And the speakers are yet another story, those are mostly used for hearing music underneath the water, like in swimming contests.

Kajsa: And synchronised swimming.

Andreas: When we were planning the recording I had to think of recording situations in a studio environment, where you have a room, let’s say with marble walls, and you want to record a bass drum, with a specific bass drum microphone, a specific acoustic characteristic of the bass drum itself, different acoustic positions of the bass drum in the room, different microphones and different microphone positions – so you have all these things that you can have control over.

In such a situation I can listen back to it via headphones and monitors and I can then decide, what kind of sound I am going for – soft, hard, airy, whatever. I am saying this because in such a normal studio setting you are completely in control of the whole sound environment.

Did you have the same feeling in the pool setting, that you kind of have a controlled environment or was it very chaotic compared to what you are used to? Did you have the feeling that you could control the environment?

David: I was surprised. I thought if no one was going to be in the pool, it’d be a very controlled environment, because we had prepared everything. But I was surprised to see that it would be otherwise. The frequency response for instance showed very unusual levels, something that I wouldn’t have predicted. And then there was also a lot of background noise, which I hadn’t expected either, and which actually accounted for almost -40dB on its own. And then we had sudden spikes and peaks in there as well, so we had to have a lot more headroom than I’d expected.

Malte: What where those spikes?

David: I think they appeared when tiny bubbles popped, it spiked almost like 8 or 10 dB. For less than a second.

I guess the equivalent to above water is in a windy environment and you have a sudden gust of wind that blows into the microphone.

Andreas: That’s interesting, it feels like we chose a very difficult and unpredictable environment. I was almost scared at the beginning that the pool would just be a very nice sounding equalizer, so it’s actually kind of beautiful that it became that unpredictable environment.

Malte: And it also made so much sense with the whole project, with regards to what you were saying earlier, Kajsa, this notion of not knowing, of the unknown and unpredictable. There is this sort of unknown thing that you are trying to capture or at least follow by recording it.


Malte: We did not only record the piece underwater but you also took impulse responses from the swimming pool. What happens now with the material and what are these impulse responses used for?

David: These impulses responses are basically the filter response characteristic of the pool.

Andreas: And what did we measure exactly? The room, the pool or the water?

David: The room basically. How sound behaves underwater. And we measured the whole frequency span with a sweep from 20 Hz to 20 kHz – if the room above water also resonated and it went back down, this will also be part of it.

We did this so that we can take any sound that we want and filter it through the reverberation of the room basically, including the water of course.

Malte: You also used it to simulate the acoustics for the web installation, right?

David: Probably, yes. We could even use it in real time. There is this convolution engine and web audio API, but we could also use it pre-processed.

Kajsa: And also the tracks that I made – they can be adapted for that impulse material. We could maybe go now from track to track and hear how the whole soundscape is changing when we filter impulses with the material. It might be interesting to play with those changes of soundscapes, so that you maybe don’t know and hear what it is that changes. Like going through the tracks of the album as if you are walking through different rooms in the space of just one second.

Malte: That’s what I like so much about the whole project – this completely absurd layering: like renting a whole pool to do recordings and impulse responses to then within seconds change the whole atmosphere of the composition on the record.

This then converges with all these different outlets that we created: pool concert, LP release, web installation, remixes, probably future installations above water, and more. All of this happens through the same initial material.

Kajsa: Yes, and it keeps on transforming.

Andreas: In the end we put this whole piece on a vinyl record – you place the needle on your vinyl and listen to all these weird steps of processes: sound played out into a pool, and taken out again, in order to put it back on an analogue medium.

It’s kind of weird, but I think it makes total sense when you consider what we talked about earlier as well: all these things we kind of subconsciously encode when we write or produce. It doesn’t matter much, if you know about it and hear it or not, it will affect everything else nonetheless. And when I listen to this music I feel like – even though there’s these hidden messages inside everywhere and no one knows about them – it will very much have an impact on the listener.

Kajsa: Yes, also because the process of compiling and recording and collecting is the most important thing, maybe more so than the immediate outcome – that’s important as well of course –, but for me the most fun part is being creative with the material.

Hydrophonic sensing

by Kiki Schmalz

There’s always a soft clicking. Sounds keep on happening and moving – the dripping, the strings in the distance, a swooshing, whale like singing – and still, we find ourselves and our listening embedded in a pulse-less, calm sea. I close my window to keep the noisy wind in the trees outside.

And go back in – into the spinning grooves, submerged and slowed down by the heavy waters. Where again I am simultaneously moved and arrested. Where a howling beast greets me – from somewhere, I don’t know where from. But then I have watched Blue Planet a few days ago and my mind is full of sea creatures and whale songs. And luckily David Attenborough remains silent.

The imagery of water is prevalent though. We won’t, we can’t, we don’t want to escape the wetness. It pours over us – closes in our ears so we only hear ourselves, no outside but our own breathing. Sounds and waves and with them our resonating bones become liquid, float in and as water ~ away. Gaston Bachelard writes: “Everything in the Universe is an echo.”💧 Ear = bones = water = sound/waves.

Into the water: and the tympanic membrane shuts down, or almost. Is touched by another matter, dense and deep – not aerial but aquatic vibrations massage me. Or when played back in air: then we experience the mixing of both worlds and re-hear the environment of our ears. Both homely and eerie, both uncanny and comforting. A fine-tuning of your aerial-aural senses. We keep the ear to the waves and the earthy ground crumbles.

As we imagine becoming a creature of the sea our hearing attunes to the layers of oceanic stories and tales. From the depths we look up and we sense the glistening surface and the glimmering outside anticipates those vague memories, lived experiences trickle through, bubbles arise and pop gently at the surface. From up there we hear the strings and a voice. This voice is not mine nor does it speak to me. It addresses no one. But its calmness sings the feeling and knowing of remembrance. A vagueness and hint of recollection which we can relate to and embrace. We have not been then and there but our listening participates, travels along those echoes into the pastness of the sea.

Secretive is this listening: we dip again our heads into the deep waters. We are listening to our own skulls vibrate, these bony vibrations make our listening. And they shut us in and let us hear from within – and any trace left of self gasps/grasps for air.

„nameless waters know all of my secrets.
The same memory flows from all fountains.“💧

Water knows, and we might hear it think. Hydrophonic sensing might get us a little closer to the unknown than our too human ears – we are equipped only for ethereal sound waves, all too badly. We want to become creatures of the sea but our singing will never become the magical whale song. We try. Or rather we imagine, trace the echoes of the deep sea, attempting to follow its memories and wet sonic trails, into our own and others’ lucid timeless swirls. But there are ever only echoes of sounds and waters and ears – and no source that we might trace.

“… water … is a poetic reality.”💧

We go to the waters, go listen at the waters and to the waters to drift. And drift away. Feeling not melancholic or euphoric but at ease, liquidised, our ears dissolved into ruffled creamy and foamy waves – plunging into and out of the water, dancing its surface.

💧Bachelard, G. (1983). Water and Dreams: An Essay on the Imagination of Matter. Dallas: The Pegasus Foundation. p. 194
💧Ibid. p. 8
💧Ibid. p. 15


Recorded at: Storkyrkobadet, Stockholm

Composition & Production: Kajsa Lindgren
Field Recordings: Kajsa Lindgren
Recording: Kajsa Lindgren, David Granström
Mixing: Kajsa Lindgren, David Granström
Mastering: Rupert Clervaux
Artwork: Cathrine Bowitz
Interview & Texts for documentation: Malte Kobel
Video & Photography: Hampus Andersson
Development: Andreas Dzialocha, David Granström
Advise & Support: David Granström, Malte Kobel, Andreas Dzialocha, Ewa Jacobsson, Jana Winderen, Notam
Pool attendant: Storkyrkobadet staff
Voices/interviews: thanks to everyone who contributed with recordings of themselves sharing sound memories, and whom I promised anonymity

Supported by Kulturbryggan, Stockholm