Spatial Sound

Sonic Agency of Marine Mammals: Orcas in Captivity (2020)
Alifiyah Imani

This reflective essay based on readings, recordings and transcription analysis puts forth the context behind the work Re.flex.ion : Orca by Spatial Sound Institute artist-in-residence Alba Vega Mulet. 


September 2020 

artistic residency project: Re.flex.ion : Orca (2020) by Alba Vega Mulet

recorded interviews with:
Alba Vega Mulet, Jordie Hoovergoost and Robin Koek

author & transcription analysis:

Alifiyah Imani
Ana Amorós López

published by:
Spatial Sound Institute


1 Ladich, Friedrich, and Hans Winkler. Acoustic Communication in Terrestrial and Aquatic Vertebrates. The Company of Biologists Ltd | Journal of Experimental Biology (2017), 2017,

2 Ketten, Darlene. The Marine Mammal Ear: Specializations for Aquatic Audition and Echolocation. The Evolutionary Biology of Hearing, 1992,

3 “Hearing in Cetaceans and Sirenians, the Fully Aquatic Ear.” Discovery of Sound in the Sea, University of Rhode Island and Inner Space Center, 12 Feb. 2020,

4 “Marine Mammals And Sound.”, Baltic Sea Information on the Acoustic Soundscape, 3 Dec. 2013,

5 Marine Mammal Hearing and Sensitivity to Acoustic Impacts

The following narrative intends to have the artist’s personal voice and is presented as such by the authour through observations and reflections evolving out of transcription analysis. 

Original research for this essay was made possible through recorded conversations with Alba Vega Mulet, Jordie Hoovergoost and Robin Koek. Documentation was conducted with Ana Amorós López during the residency period along with the support of the Spatial Sound Institute. Extremely grateful to Vladimir Razhev, Ana Amorós López and Paul Oomen for their support and feedback in the realization of this essay and its presentation.


When we hear

As sound waves travel through air, the outer ear catches the waves that traverse a narrow passage called the ear canal. The sound waves reach the eardrum, a membrane about half the size of a centimeter. The vibrations that occur in the eardrum, in turn vibrate three small auditory ossicles — hammer (malleus), anvil (incus) and stirrup (stapes) in which the vibrations amplify before the cochlea receives it. The form of the cochlea has the appearance of a snail shell and the vibrations allow the fluids inside to ripple and produce waves. Stereocilia in the inner ear protrudes and responds to fluid movement and is bundled together as cochlear hair cells. The waves roam the hair cells within the cochlea, causing movement that transforms it into electrical signals. As bundles of hair cells are transferred, ions rush up and trigger chemical releases at the bottom of the hair cells. Such chemicals connect the auditory nerve cells together to generate an electrical signal that passes to the brain along the auditory nerve. 

We interpret this as sounds.

Various hair cells are sensitive to different sonic frequencies that we hear and recognize. The frequency measured in Hertz reflects the lower to higher pitch of a sound. The boundaries of the human hearing range are considered at 20 to 20 000 Hertz with high sensitivity raised at specific frequencies. Loudness remains a perceptive and subjective property of sound depending on the frequency, exposure period, environment and personal hearing capacity  — but it is widely agreed that even brief sound exposure louder than 120 dB SPL can cause ear injury and irreversible internal ear damage above 140 dB SPL.

Human hearing and its intricacies holds the distinction of being widely researched in evolutionary biology and scientific studies, but we are not the only reactive species to sound’s physical nature and effects.

Evidently each territory of the earth has its own sound transcription, a complex and powerful foreground and background that could make detailed investigation possible. When studied among marine mammals, the idea of the vast ocean, at once infinite, spacious and unknown —  could sound have a different kind of dependency and expression?

While a detailed analysis of hearing is an extremely complex process to precisely determine and relies on many factors including the internal body structure and the medium through which the interaction is happening — what we would know, is that along with the gaseous atmosphere that surrounds the sounding earth, water and the propagation of sound through it is much more rapid and travels over far greater distances than in air. Air plays an essential role for on-surface hearing, as it has a higher percentage of presence in our environment. However, air as an area of contact when replaced by water for aquatic creatures significantly changes various acoustical properties. Air simply is not very dense. There is not much friction for movement with the particles far apart, so it doesn’t take much to start a wave but it won’t move as fast. Water as a medium eigth-hundred-twenty-nine times more dense contains particles held much closer, and that takes a great deal of energy to start the vibration, yet when it is transmitted, it moves four to five times faster than it would in air.1 

Equivalent to this assessment, the significance sound could have underwater and for the marine life that thrives beneath, is a subject that whispers more strenuously than ever that humans are not the only acoustic beings among the terrestrial species. We can assume that marine mammals in the ocean and other marine habitats live with another level of sound sensitivity; one of great intensity and extreme range - although compared to our knowledge of the human hearing, still much of the supporting knowledge on the hearing functions of marine mammals remains uncharted.

Ongoing research into their habitat marks substantial findings and speculations to their complex sound-producing mechanisms that enable many of these species to hear sounds well outside the human scale of sound making. While sound propagation in the complex structure of the human ear is well suited for air, it would not work in the same way when submerged in water. The morphology and function surrounding the biological tissue which mainly contains water content would allow sound to move but with very little resistance from the water and into the body, that would circumvent the outer ears and ear canal, and not trigger the eardrum as in air conduction. Hence, hearing sensitivity is much lower and locating the path of a sound in space would be almost non-existent.

Marine mammal’s ears are different, although the degree of adaptation to the marine environment varies as some are amphibious and only the Cetacea and Sirenia are completely aquatic - unable to move, reproduce, or feed on land. Structural changes in the ears of marine mammals correlate with their degree of aquatic adaptation, ranging from mild in amphibious coastal species, such as otters and sea lions, to extreme in massive pelagic whales.2

Streamlining recent findings of marine mammals with a fully aquatic ear as in toothed cetacean whales, suggest that the structure of the ear canal is mostly non-functional as it is filled with sea water, debris and wax.3 Research also shows that the eardrum does not have an ear canal connection. How would sound then get to the middle ear?

The sound instead conducts through the head from the lower jaw which is filled with a unique type of “acoustic fat” with high sound conducting characteristics. This acoustic fat connects to the middle ear at its other end which is enclosed in a bony shell called the acoustic bulla, considered as one of the thickest and toughest bone structure found in animal species and is uniquely adapted for pairing the sound in the fat channel through the movement of the middle ear ossicles.4 Analogous to this knowledge, hearing in odontocete cetacean species is theorized to have incredibly advanced biosonar fields — instant high frequency clicks, pops, whistles to forage, steer and explore; communicate and interact socially. The variety of sound calls made by these aquatic beings measure some of the broadest frequency bands found in the animal kingdom. Communicative sounds typically range from a few hundred Hertz to several tens of kilo-Hertz and echolocation clicks can reach over a 100 kHz.5

The marine ecosystem of sound communication — the human may only hope to perceive.

Enter Re.flex.ion : Orca by Alba Vega Mulet

On 27th February 2020, the Spatial Sound Institute presented Re.flex.ion : Orca, by Amsterdam-based Acoustics and Telecommunications Engineer, Alba Vega Mulet.

The composition comprises sixty four audio tracks composed on the 4DSOUND system, intended to illuminate and reflect underwater acoustics and its relationship within the sonic marinescape of orcas. The engagement, unveiled as a three-part composition, constructs an acoustic space that is challenged by the question of ‘how to portray the unheard’.

Sound situates and is transposed to fit within the human audible range to provide an embodied experience as to how confinement in concrete and glass tanks for breeding, performance and entertainment reasons subjugates the oceanic orcas. The experience reflects the deprivation this kind of captivity entails for the orcas, in contrast to the freedom of how they communicate in the depths of their natural environment.

Technical Specifications

Orca Sounds — Two main recordings (extracting 13 calls) — Authorization: Ocean Sounds
Healthy Marine Environment for Orcas — Recordings by Alba Vega Mulet, Ocean Sounds, Royalty free sounds

Underwater Ambience — Two main recordings (from Costa Rica & Mexico) by Alba Vega Mulet
Water Tank — Composition by Alba Vega Mulet & Robin Koek

Total Audio Clips: 64
Audio Recording Device: Hydrophone (Model: Reson TC 4032), handheld recorder
Water Tank Dimensions (based on Tilikum’s tank proportions transposed to human scale):  5,7m x 9,5m x 2,1m (length x width x height)

Duration: approx. 20 minutes

External Collaborators

Jordie Hoogervorst - Data Analysis, Research & Strategy
Robin Koek - Composition, Ableton Live (with Max4Live) Water Tank Resolution
Marina Mulet i Gay à - Artistic Direction Assistance
Ruben Hoogervorst - Media Coverage

Early Encounters

The initial perspective to Re.flex.ion : Orca began for me when I learnt about a particular dolphin hunting tradition in Japan, that has been going on for decades in the coastal town of Taiji, Wakayama. The hunt in its alarming force and scale recurs annually and starts with local fishermen leaving on a fleet of motorized boats in search of dolphin pods. When located, they position themselves at equal distance, and lower several steel poles in water on each side of the boats. Underwater, the vibration from the poles that are continuously struck with hammers by the fishermen hunters produces amplified noise and the dolphins who by their nature and biology are far more sensitized in their hearing range, get caught between the chaos created by this sonic atrocity. It completely breaks their point of reference and their innate ability to communicate between themselves and in this liminal state, they are diverted from their migratory and feeding routes and forced into a cove where the majority are slaughtered with knives for their meat and others are sold to aquariums and aquatic amusement parks for entertainment purposes.

It is a heavy matter that haunts the depths of a world that is unknown to us. I still follow it every year. Although, a painful and violent reminder, the question that it brings up: to what degree is this terror a catalyst for activism?

There is a lot of opposition to this in the last few years. It is still a long way to go for a topic as big as this but there has been a massive social change. Many individuals and organizations are working to end this, though they may not be fully aware of the details. This is also the reason why I joined Sea Shepherd, a global marine conservation organization that works at the front lines to protect ocean life and diversity.  

I am curious about human minds creating these methods, and what the meaning is to them. Systems are installed knowing perfectly what it does. I was quite shocked by the notion of sound — a subject so close to me, intentionally used against animals who use it as their main sense for so many aspects of their lives.

I realized I have something to say about it.

Let's Talk Orcas

Orcas in captivity is a line of inquiry that was seeded in 2015 for me. I’d say that it is a trigger of many questions and causes that don’t always directly correlate with the project but I had to go through those moments of contemplation. It's the reality of the process.

When you think broadly about such a subject, you do want to do justice to it, although I'm not the only advocate here. Anti-captivity rhetoric has been on the rise especially since 2013, primarily sparked by expose-style documentary Blackfish, that was broadcast by CNN.

Along with the moral and biological consequences of captivity, it highlighted acoustical details to me that I started to understand a lot better through studying what is really happening to them inside of the glass tanks where they are typically held captive.

In an enclosed space, sound is always reflecting, it will always give you big feedback. For us, it is usually just a matter of location, when we realize what space we are moving into, and with that comes the almost automatic acceptance of how sound behaves in it. Can we grasp how it must be for them?

Sound travels at a speed of 1546,2 m/s in saline chlorinated water. Glass is reflecting about 92-98 percent of the sound, which causes it to bounce back with almost the same intensity. With walls that mirror virtually all sound with the same power back into a space where sound keeps feeding back, a glass tank becomes a warped and horrifying resonating sonic environment.

Now picture the captive Orca who is traumatized due to their specific call and response communication system within pods. A second pod member will always repeat the received message and provide the answer. In the tank, the captive orca who sends the call believes it is surrounded by members of the family who receive the message but never send the response. It goes on until they comprehend through echolocation that they are in a prison created of their own sound.

Their frequency spectrum of emitting sound from 500 Hz to 120 kHz makes this alarming situation a call for attention to human ignorance.

I was curious — what if I could show what is going on under that glass surface? What would that experience be? The sonic reality that we never think about.

While digging more into this in Amsterdam, where I had relocated for work some years ago, I met with Jordie who shared the same intrigue for Orcas but came from a completely different background and this helped me a lot to validate my research and balance my technical approach to the discussion of what these animals are in a general sense. As our conversations oscillated, the project matured, encouraging me to continue, and led us to take a trip in 2017 to Norway in pursuit of more experiential research.

In Andenes, we had joined a small arctic expedition where you are able to go on a boat and get a view to dive and swim with free orcas in their natural habitat. The expedition can be a bit of a venture. The orcas are only there at a certain time and it can be difficult to expect that you will see them and that getting into the water would be safe as the weather can be very unpredictable.

I had accepted that we might not even see them when I learnt on the boat that a calf was stranded and the whole pod was sad, but when the boat stopped moving I suddenly saw this gigantic fin coming towards the side. We attempted to slide smoothly in the water so as to not startle him. Underwater I could barely see anything at first, but then I suddenly saw it coming towards us from a distance.

It was the male orca who approached us first, as the females shield the younger ones because of their matriarchy structure. I was gripped by its presence near me and with my camera I was able to record him. He was huge and could read me and I was instantly aware of how intelligent they are. By the time we got back to our boats Jordie and myself were freezing but we had big smiles on our faces. I ended up crying too. It is a very strong feeling to make the connection in that moment by perceiving the sound waves. Even if you can't hear them, they still send it and can recognize who you are.

After all, they are acoustic beings. They are creatures of sonicity. Sound is what they are mapping the entire space with, the situation, the orbit, everything.

At the strategic end, we had also embarked on the trip to approach organizations and inquire whether they had any interesting material of their sonic landscape and hoped to make connections with scientists and conservation experts working with orcas. There were some who were interested to meet but had very tough schedules out in the ocean. On our second last day, we drove to continue our research all the way down to Lofoten Islands. It was an intense seven hour ride and we were exhausted. We stopped for coffee at this isolated place at the tip of the island. I was a little disappointed and gave up thinking we would get the orca sounds and the strangest thing happened afterwards.

Jordie spotted a sticker in the café’s toilet which read "Ocean Sounds". We had never heard of this independently run organization before and it seemed to capture the spirit entirely. The sticker had their contact information and mentioned that they were researching the acoustics of the ocean.

Back in Amsterdam, I contacted them and explained the project. Their immediate enthusiasm to collaborate by allowing me to use their licence, provided me access to their library of clean and clear high-quality recordings of different orca sound interactions which made this project real and advanced it many steps forward.

Listening to their sounds for the first time, I felt myself there with them — can only imagine what the Ocean Sounds crew were feeling when they put their hydrophones to record and listen to this: I could hear what I thought they were saying, I could hear different situations, different interactions, different members, different voices, different messages.

The word sentir is to simultaneously feel and hear as it finds meaning in Catalan, my native language. This expression was truer than ever to me as it captured the many textures of sentient life under the ocean.

The same year I also had the opportunity to test the effects of the water tank acoustic model I had been working on for some time. Understanding all the calculations from my side, I tried to recreate what sound was doing inside the tank and experimented with the results at a place in Hague, where I could work with spatialized sound in a Wave Field Synthesis setup. It was the first time I experienced it physically. I knew sound would create those patterns because of theoretical studies on it but I never heard it.

It was interesting to hear but also horrible — what these animals had to endure. It is rather difficult to imagine, these kinds of sounds are just unheard of, it’s not like you would hear it on the radio.

Jordie stood in the midst of all those speakers and declared to me: “I couldn’t have imagined that you could do something like this with sound”. I could see the fire light up in his eyes, he had a glimpse of what was possible and he understood much more vividly in that moment, what I wanted to do. I remember him leaving the experience really empowered.

This was also a significant point for me as I could finally apprehend closely how others might react to the influence of sound.

Future Directions and Open Questions

The experience of composing the acoustic space with the 4DSOUND system has opened many doors into the subtle and the extreme sounds that would put such a subject at the threshold  —  I realized the possibilities of composing, integrating scientific data, testing how different materials acoustically behave and can be applied as frequency-based reflections and absorptions, psychoacoustic differences to the degree that sounds are interpreted by humans — there are so many aspects that could impact the situation I want to describe.

I tried to do it as accurately as possible although I realized there would be stages to develop the piece over time, that is part science, part exploration and part activist reform.

After all, it had been five years of researching the subject and experiments of sonic capabilities in the project, that I found myself within reach of a technology system, where I could sketch a sonic landscape to enact the complex acoustic journey of orcas.

The sound material itself is kept as raw as possible with the least effects to match the integrity of the reference and is limited to the frequency spectrum perceived by our human ears. I would like to continue to work on this at a later stage in order to reach a recording result that can import their own range.

In the first part of the piece, I composed with two main recordings of orca calls, keeping in mind the communication structure and the distribution that they normally have inside a pod when they are in the ocean. These recordings are mainly from carousel feeding orcas. Researchers can say whether the whales are foraging, resting, or socializing, based on variations in the use of calls, whistles, and clicks. I could hear dialects.

The composition effects I used are primarily concerned with spatial acoustics and parameters. In its generic sense, this refers to the localization of sound sources into a situation where you can orient its path and intensity.

Later on as we arrive into the creation of the tank, the second part of the piece, this becomes a heavy load of technicalities. An endless oceanic calmness reduced to a tank’s dimensions. It has been a lot of work to achieve this accurately to a certain extent, by understanding the environment — the incongruous distortion of specific frequencies from the orca’s voice as the main object, all the feedback and resonance from the tank itself and another low frequency layer which is the sound of the tank’s cleaning motor. The proportions are modelled in relation to an adult orca tank but transposed to human scale and reflect the conditions of saline chlorinated water in which they are kept.

There were many previously unknown points of view regarding the project in this process. For instance the brain response time of orcas: their processing speeds are much quicker compared to humans and as I was working, this was unfolding for me.

I want to take a closer look at this to understand — what is the actual message, how fast is it arriving to orcas and how is it perceived by them; relative to how we would translate this information when it arrives to our brains? This would involve a number of variable factors that are interesting for me to explore further.

It is always a struggle to maintain sight of what to let go of — fortunately, the decisions I made were not arbitrary but had the knowledge and voices of a group of people who confer a special status.

Robin Koek was here at a crucial stage of the creation of the tank so we could compose the data in a way that the 4DSOUND engine could simulate the sound in the space for these conditions. With Robin, I also worked on many compositional and musical aspects of the piece  — contributions I regard to have been essential to the process. To have another pair of ears in the room while I am working, insights into the various aspects of composing that isn’t my strength —  having experts in the field helped a lot to translate the research to the level of practice and experience. 

The goal for listening, as a first presentation, is to highlight the ability of sound to imitate the free habitat of orcas' voices — a tale of their sonic existence and their ecology as if coming from the ocean itself. From this perspective, we hear the other end of the line where the piece expresses the pain of captivity and the magnitude of terror unleashed by humans crossing the line to dominate and displace the lives of orcas. While this has been important to demonstrate, I chose not to conclude menacingly through this listening ordeal — the third and last part of the piece therefore releases us from the tank’s stress back into the ocean. The specific recordings used here also come from Norway, and we can hear them again in an environment that is healthy for them.

Perhaps, I deliberately present a rather literal reading, so the listener cannot escape the message.

The discussion that I hope to create across the wide range of the listener profiles, is about what kind of emotional responses does this evoke?

Does it affect our capacity to empathize?

This is where I question its potential for sonic agency.