The physical effects of sound on humans and animals have been fairly well studied. Whenever discussing matters relating to sound and sonic experience, it is however clear that one always must make a distinction between airborne acoustics or sound waves and ultrasonic noise that travels through matter or a given environment.
Following the human hearing curve, one can note that with sounds above a frequency range of 16 kHz the threshold level of hearing is dramatically increased and sound is neither perceptible nor harmful to the hearing organ. Several animals, such as bats, whales and dolphins, can however „hear“ the register known as ultrasound. Not much research has been conducted on the physical and psychological effects of sound on human bodies that the human ear cannot perceive. Some theories claim that intensified exposure to high-pitched frequencies can affect internal organs, breathing rate, and pulse. There are also suggestions that this is even more apparent in “sensitive” animals. As an example, sonic radar experiments in the Bay of Bengal have recently been proposed as plausibly connected to the increase of beached short-finned pilot whales off the coast of India.
What clearly is problematic in these more speculative accounts is, however, that the actual deterrence and expulsion of ultrasound is disputed. It is technically difficult to transmit this register of sound. A few years ago we made experiments with rats that failed. We also failed when we tried the experiments with pigeons. The economic benefits of a successful procedure could have been massive. We have thus considered other strategies, such as encoding warning cries and transmitting them through ultrasound, but have not yet followed up on these ideas. One can however assume that the rats would be tactically superior to humans in this regard.

One of the main problems of ultrasound is that of dissemination. The physical resistance of air concentration makes it difficult to conduct the sound waves. The second physical hurdle is material sound absorption, which increases with the heightening of frequencies, and in turn makes the transmittable range of airborne ultrasound relatively limited. One approach to overcoming this problem is to modulate ultrasound together with audible, lower-frequency sounds. Simply put, this entails the use of suitable amplifiers that transmit loud and quiet ultrasound embedded within a pulse of audible sound. This way one can create a wave of audible sound, „sitting“ on top of an ultrasonic wave delivering a clearer focus.

On-site Collective Work-Process


The research group practice and working schedule built on suggestions, determinations, and intuitions of the six participants concerning exercises, tasks, activities, and excursions. The group went through phases of dispersion and concentration, gathering information and processing or discarding it. The ambition was to allow fluidity and a combination of information in the approach and articulation of the relationship between content and form.

To Inform, To Offer: Artistic Practices Around 1990 at mumok, 2016; A Proposal to Call at KEX, 2015). The group also visited the Freud museum. Here, the strongest impression that was left on them was by a mirror in which Freud could see the reflection of his own face while sitting at his desk. In the present installment, the mirror remained at the same place, while the desk was removed. The group noticed that standing visitors see the area of their private parts when looking in the mirror.

Perhaps this was the point when the group found the distinction between the curatorial and the exhibition as a phenomenological, physical manifestation was a more relevant one to make: Should the group’s thinking be illustrated through a selection of works? Or does thinking take place through the works themselves? Does one think of the spatial components of exhibitions as being the/a medium? Or can one instead exhibit the space itself? Should the process of collective research be present in the space and, if so, how?

Schallwirkungen auf Mensch und Tier  is the line between impact and disappearance. It is the diagonal in between. The exhibition works with and against the walls. It is the suspension of a temporary non-ephemeral process. The European soccer championship takes place. The exhibition is the shadow. Visitors merge with mass celebration. Schallwirkungen auf Mensch und Tier is a facilitator focusing on presence more than on the physicality of its proposition. How to hide the shadows without switching on the light? It is also a summer show. Light energy is sucked by a black hole, which in turn disappears. 2006, 2016, 2026? Backward. Working the space is the research. Long discussions about the height of the walls, no time to watch, words remove thinking. The 3rd eye is an editor. It is more than a two-week process. The exhibition is not the artwork. The space answers the exhibition. It is violent, intimate, and generous at the same time. Moods change the light. The new moon is on the 5th of July. The exhibition is not about light. Schallwirkungen auf Mensch und Tier is on display.

The group considered and discussed references and examples of artistic and architectural practitioners that could be invited to contribute to the questioning of the format Exhibition articulated by the group with an intervention. The questions of ‘art-work’ and ‘authorship’ were still central at this point of the process. In order to refine the positioning and vision(s) of each participant – as individual but also as component of a group – a working session was dedicated to articulating his/her personal approach to what the exhibition could be. The following keywords appeared central for all the participants: humor, specificity of the site, theatricality, and fun. The exhibition in process became a facilitator and the space became a body.


An analysis of the history of KEX and its archive supported the concretization of the following thoughts. The exhibition umbau display ausstellen re-position from 2006 became a reference point. During this show, the movable wall units – that are used as multipurpose exhibition architecture to this day – were built. How have these elements affected the productions of the past 10 years? Could one create an exhibition that might – 10 years after this last intervention – once again operate as a support structure for the institution itself, responding to its present and future needs? And if so, what would be the main problems of the space that such an intervention could address in 2016?


Building on the idea of an exhibition proposal that would operate as a support structure to KEX, the group discussed the possibility of transforming or replacing the mobile wall units in order to adapt them to the new architectural structure of the space. They are 35 cm too high to stand or pass underneath the recently added metallic structure (2013) that consolidates the building. Unfortunately, such a contribution was financially impossible for Six Formats.

Nonetheless, there is a complex physical mechanism called acoustic radiation pressure that also has to be taken into consideration.
The effect of this mechanism is impressive.
We once experienced sound emission of ultrasound modulated with birdsong from an acoustic parabolic antenna. One could focus and hear the bird as if it was very near by. In this way one might be able to create a placebo effect by using the illusion of ‘audio-presence’. Furthermore, the exposure to acoustics emitted by ultrasound devices can provoke both hearing and “‘non-hearing” physical effects (such as thermal effects, subjective symptoms and functional changes).

Subtlety and Visibility: communicating without revealing.


The working group for format Exhibition wanted to interfere as little as possible with KEX’s appearance while playing with a durational presence of the exhibition Schallwirkungen auf Mensch und Tier going beyond its exhibition period – this without imposing changes, especially architectural, to upcoming exhibitions. The (more or less) subtle manifestations are based on the given structure of KEX – especially ‘tools’ of communication KEX uses for exhibitions – but also on intuitions coming out of ‘the doing’ and happenstance…


When entering KEX, the visitor encountered a “clean” exhibition space.

1/ At first sight, one could see:

- The adapted three mobile wall units were placed in front of the untreated mobile wall units – which remained at their dedicated position when not in use in exhibitions. This aimed to emphasize the existence of one of the two interventions of Schallwirkungen auf Mensch und Tier.

- At the entrance of KEX’s exhibition space, a sign ‘Bitte Schuhe ausziehen’ asked visitors to remove their shoes. This sticker was aiming to bring attention to sound and perception, and was also present to invite visitors to feel cozy and non-hierarchal in the space. The working group had for hypothesis that being barefoot and feeling the floor could increase attentiveness to other sensory inputs.

In parallel, issues of acoustics and sound appeared as the most relevant – in some of the participants’ own experiences, as well as that of the institution itself, both noise from the club below and an echo in the room can make it very difficult to follow talks held in the space. To work with the acoustic situation appeared to be an area for a concrete intervention that might benefit KEX and at the same time allow the group to play with and concretise the various interests that had been articulated so far. The focus on sound highlighted questions of visibility and sensory perceptibility. What is it to transform a space without transforming its appearance? What does it mean to present and communicate an invisible materialization of, for, and as an exhibition? Would such a gesture foreground the supporting structures and types of labour that carry any presentation or display of art?


‘Invisible’ was a central notion and ‘hiding’’ was a strategy the group explored to approach the frame and tools of communication used by KEX when displaying exhibitions. The group materialized a series of subtle hints aiming to activate the perception of the interventions realized for and during Schallwirkungen auf Mensch und Tier. As showing the invisible is closely connected to showing the inexistent, the concept of ‘placebo’ became central, especially in the booklet that accompanied the exhibition. It created parallelism between ‘space’ and ‘knowledge’, and overlapped the (in)visibilities of their respective appearances.


Once the group had decided to pursue the option of acoustic improvements at KEX, Peter Böhm was invited. It is important to state that the research-oriented process conducted by the group was not about sound-related knowledge in itself but on ‘how’ sounds – from different sources – could (co)exist with KEX’s activities.


The public access system is combined with an alarm system. It has to be proven that all the loudspeakers are working. Each of them is connected to a lamp that you light up with an invisible light that has too high a frequency to be perceived. Let‘s say you use X-rays and you get an impulse response from the lamp telling you: “I am working”. Then you are sure that in case of an emergency all the system is operational. This is a major thing. The other thing is that it should of course never fail. If it fails, it should reboot quickly, and so on. In the exhibition space, all the loudspeakers are functioning – proofed with ultrasonic sounds, because you do not want to hear such things. But be careful. Once, a dog visited the exhibition space. It was a little too much for the dog. The barking was running wild. This led to two possibilities: “Dogs are not allowed, they would ruin the show” or „Bring your pets at your own risk“.

- A cardboard box presenting the A5 booklet – such as is customarily distributed at all shows produced at KEX. As one of the few visible components, the booklet became the space where the working group carefully addressed the questions of visibility, perception, and imagination, or ‘placebo’ that had been central to the group’s thinking about - what was after all still called - an ‘exhibition’ or a ‘show’. Describing in the booklet exactly what had been done would destroy the efforts: one task of the working group was hiding the hidden… to show something that should not be seen… an experience of something that was not there...


Dealing with acoustics from an artistic, conceptual, and non-technical point of view, the working group decided to use the concept of ‘ultrasound’. Such non-audible sound waves were conceptually used to link to the intention of ‘non-visible presentation’ carried by Schallwirkungen auf Mensch und Tier. A combination of five short texts – slightly fictionalised scientific inputs in images and one text, a sound related anecdote, a non-descriptive presentation text, acoustic information, and the history of the walls – aimed to open a space for imagination or to trigger expectations.


Flirting with the borders of the perceivable, the booklet invited visitors to the search for an expected effect. In between fiction and reality, Schallwirkungen auf Mensch und Tier could lead to a placebo effect (as ultrasounds were not used in the exhibition presented at KEX).


Shockwaves – a form of sound pulse that encompasses a higher pitched frequency - are also related to ultrasound. Americans were planning to build weapons based on this technology during the Vietnam War. Fortunately the attempts failed. This research has, however, led to technology like lithotripsy: a noninvasive device that pulverizes stones by focusing shock waves on a patient immersed in a water bath. Sound spreads much better in liquids than solids and therefore the effects are, so to speak, more efficient.
The direct ultrasonic effects of air-borne ultrasound in humans and animals (including vermin such as rodents and insects) are widely disputed. As ultrasound falls within the range of non-ionizing radiation, the German Federal Office for Radiation Protection is currently investigating it.

Format Exhibition     Schallwirkungen auf Mensch und Tier is the manifestation of ‘the format Exhibition’, which is part of the art-based research project Six Formats. The formats are publication, exhibition, symposium, lecture-performance, screening, and workshop. For each format, Six Formats facilitates a triangle constellation with a partner institution and a research group (constituted of the main researchers of Six formats and invited co-researchers).

To interrogate the format of an exhibition, Kunsthalle Exnergasse (KEX) was approached by Six Formats as both context and partner, out of an interest in its specific history as a non-commercial, project and theme oriented Kunsthalle in Vienna.

The proposal for the format Exhibition – articulated by Ingrid Cogne and Elske Rosenfeld spring 2014 – included the use of the notion ‘time’ as a filter (‘time’ is, in other words, not the theme of the exhibition, but a notion that permeated everything discussed). What are the temporalities created by and in an exhibition space? How to work with or alongside and set into play different time-based or time-specific strategies towards future/s, present/s, and past/s? How to work not about, but with time?

When Cogne and Rosenfeld (Six Formats) began the dialogue with Schafler (KEX) spring 2015, more questions regarding the format Exhibition arose: What happens when this format of communication and presentation – of an articulation, content, process, or objects – enters into relations with art-based research practices? What are the requirements and what is the framing of the format Exhibition in relation to these practices? What constitutes its specific analytical approach? What are the needs of the exhibition space?

In autumn 2015, the proposal was to think about Exhibition as a format of communication. In other words: for the research group to produce an exhibition for itself was not the main goal. The intention was to question the format Exhibition through doing.

2/ When exploring the space, one could find:


- An A4 copy of the legally binding contract with KEX was placed in between two of the mobile wall units at the back of the room. It was potentially visible, though its presence was not, in any way, advertised. The writing of the contract, developed in dialogue with the institution, introduced an additional layer of conceptual thinking around issues of duration and time. The contract allowed the group to extend the exhibition duration from 6 weeks to 6 months (till December 2016) and from thereon potentially for another 10-year-period ending in 2026 (extending the wider temporal frame from 2006 via 2016 to 2026). Ultimately, the final proposition of the intervention gave the institution something that KEX did not ask for. Every gift is an expression of intent that comes with a price and the group agreed that this dynamic could also be defined and articulated through the use of the contract. For the exhibitions between July 5th and December 31st the intervention is an (almost invisible) imposition that is, at the same time, a possibly generous, gesture of support.


- A small visible component manifests more permanently the entire process within the exhibition space: a metal plaque with the text Schallwirkungen auf Mensch und Tier 2016 – 2026 was attached on the floor next to the storage wall, behind which the main sound intervention is situated. As stipulated in the contract, the plaque will remain visible as long as the intervention is in use. The metal plaque also symbolizes the presence of a title in the space.


Background and setup


Six Formats, which runs from 2015-2018, is an art-based research project funded by the Austrian Science Fund (FWF, PEEK, AR291-G21) and hosted by the Academy of Fine Arts Vienna. Six Formats creates situations of dialogue in, on, and between each of its formats, around a particular theme, and in a particular constellation of a partner institution and a group of participants invited as co-researchers. Each format is a collaborative process of ongoing self-reflection and re-articulation aiming for reciprocal attentiveness to the respective needs of the project and its partners and co-researchers.


One of the conceptual approaches of the art-based research project Six Formats includes inviting a person working at the partner institution as co-researcher: the person is thought of as a ‘filter’, connecting the format to its context.


For the format Exhibition Klaus Schafler, who has been involved in running KEX for many years, facilitated the access of the researchers to the philosophy of KEX, its status in the structure of WUK (Werkstätten- und Kulturhaus), the history of the building, the history of the exhibition space, the archive of exhibitions that took place in the past, and those coming up…


Kunsthalle Exnergasse (KEX) is collectively run. Its curating approach combines an exhibition programme selected by an advisory panel, and projects programmed by the KEX’s team, such as Format Exhibition - Schallwirkungen auf Mensch und Tier.

By Six Formats (FWF, PEEK, AR291-G21)


The design of the exposition Format Exhibition - Schallwirkungen auf Mensch und Tier is conceptualised by Ingrid Cogne and Tobias Pilz. The texts written in black are collective material from the research group that have been edited and reworked by Ingrid Cogne.


The text starting with “Physical effects of sounds on human and animals” is based on a contribution from Prof. Dr. Eike Rosenfeld to the research group for format Exhibition. It was rewritten by Jonatan Habib Engqvist and Corina Oprea for the booklet.


The quotes and statements presented in the explanations are issued from two conversations: one between Peter Böhm and the research group (Cogne, Habib Engqvist, Oprea, Pilz, Rosenfeld, and Schafler) in July 2016, and a second between Böhm, Cogne, Pilz and Dmytro Fedorenko (sound artist invited by Six Formats to contribute with acoustic-related knowledge) in October 2016.

This thinking was activated by the presence of a sticker - with “Schallwirkungen auf Mensch und Tier” written on it - in the office space dedicated to the façade of WUK where KEX’s exhibitions are announced. The working group dedicated time to the concept of ‘title’ and decided that having a large sticker in the exhibition space would settle the perception of Schallwirkungen auf Mensch und Tier as an ‘exhibition’ or a ‘show’.


- Finally, the last intervention was formed when the working group focused on the untreated elements as organised by KEX when stored. The group’s request of having them unified in one long wall aligned to the entrance door created a narrow corridor, one could think that this was on purpose, but it was not. The access to the backside of the stored elements revealed a monitor. What would finding a black screen mean for the visitors when searching for traces of the intervention? The working group decided to display a graphic visualization of the song The Sign by Ace of Base, which is also present in the contract with KEX… as a threat – in case of breach of the contract, the song should be played over and over during office hours. The graphic visualization put the concept of placebo back into play. Some visitors thinking the monitor was presenting some live measurement tried to interact with it.  


All these manifestations were ‘on display’ during the exhibition period between July 5th and 21st 2016. One of them remains present in the exhibition space of KEX to this date.


Format Exhibition - Schallwirkungen auf Mensch und Tier invites the visitors/readers to approach this exposition as a physical room they could explore as they wish - like one would walk through an exhibition space. As much as the exhibition Schallwirkungen auf Mensch und Tier played with the one-room exhibition space of KEX, Six Formats occupies a one-page exposition of JAR.


The exposition Format Exhibition - Schallwirkungen auf Mensch und Tier juggles between the relation fiction-reality that was at play at KEX - between the content of the booklet and the (non)interventions in the exhibition space and the relation product-process of the research on the format Exhibition.


The texts in grey depict a selection of the texts presented in the booklet of the exhibition. The booklet was thought as an intervention in itself; a tool of communication where the information presented could reach another layer of immaterial and unarticulated knowledge, more than a comment, an explanatory text, or a presentation of the exhibition Schallwirkungen auf Mensch und Tier.


Schallwirkungen auf Mensch und Tier is an exhibition by Ingrid Cogne, Jonatan Habib Engqvist, Corina Oprea, Tobias Pilz, Elske Rosenfeld, and Klaus Schafler, in collaboration with Peter Böhm. It took place july 6 - july 21 at KEX.


The texts in black with white background reveal the ways in which the co-researchers worked with the format Exhibition in the specific context of KEX: their process.

Acoustic Interventions


As Schallwirkungen auf Mensch und Tier deals with the perception of KEX’s acoustics, the research group decided, in order to complete its proposal of/for an exhibition, to share in this exposition the knowledge encountered when working with Böhm.


What does it mean to make the acoustics of KEX ‘better’?

For Böhm, it is essential to clarify the task to fulfil and the process of how it came to the point that something was missing or wrong regarding the acoustics of the room. A delicate question… depending on the uses of the room, ‘better’ is different: for flute concerts, better would be longer reverberation, and for talks or meetings involving many people the opposite is needed. The variability of reverberation of such spaces – exhibition spaces, galleries, and museum – always requires considering the objects present or placed in the room and the amount of persons as well (which often differs a lot between the opening and the visiting hours afterwards – when a single person could stand alone in the room). The additional requirement regarding visibility – that ‘one should not see anything’ – was not only a limitation but also an interesting challenge, Böhm said.

For Dmytro Fedorenko, it is nearly impossible and sort of against the idea of sound treatment to not add anything to the walls. In such case, his questions would be: "What actually do you want: a real sound treatment or a nice-looking gallery?"

Acoustic interventions are always visible: one can easily notice that something is different or recognize a change of cubature (volume) when the room has been made wider or narrower.

Acoustic perceptions

This paragraph does not include the perception of the audience who joined the opening or visited KEX in summer 2016, as no quantitative or qualitative collect of data was conceptually planned by the working group. However, persons involved in the process that led to Schallwirkungen auf Mensch und Tier have their own positioning regarding how he/she – depending on their respective background, training, field of knowledge but also depending on how they relate to space, perception, sound, and resonance as a person – was affected by the intervention and/or by its placebo effect.

1/ Perception or placebo effect?

Does one perceive more when informed or not? For Dmytro Fedorenko the use of the placebo effect was a crucial moment in Format Exhibition - Schallwirkungen auf Mensch und Tier: Does one really hear a difference? Does one know that something happened and try to imagine it? “I knew where to search for the interventions, and even if I have knowledge about sound and acoustics, I am not sure I heard a difference between before and after treatment. I am wondering if I would have noticed something without being informed about the project. This is an open question to me. Another question: is the difference more noticeable for the people knowing about the project because they know how it would sound like without the intervention? Could that just be on some subconscious level, as source or effect, like a feeling of being more comfortable? How much is it about self-influence or real feeling of comfort like ‘psychoacoustics’?” DF

For Böhm, from the early stage of the collaboration, the reverberation time in the exhibition space seemed pretty long, but he suggested that measurements could be the starting point for him to articulate a concept and to determine where and in what way the acoustics of the room could be improved with a limited budget* – not to forget the additional requirement of minimal visibility.

One measurement was done with sine tones to determine the frequency response in the room. A second measurement done with so-called ‘pink noise’ revealed that two frequency areas are more present or more significant. Shooting a blank pistol in the room was a third means of measurement in order to create – as much as possible – a situation where every frequency is created in one point.

At KEX, the average reverberation time is around 3.8 sec. The reverberation time is significantly longer for frequencies between 560-690 hz and 160-190 hz, which impairs the sound of speech, as the range of the human voice is between around 150 hz to 2500 hz including overtones. There is no good or bad acoustics per se. The geometry of KEX’s exhibition space is actually not bad. It is very suitable for singing choirs.

The architectural structure of KEX – the storage room and the mobile unit walls – saved the situation. Böhm had to find a ‘practical solution’ more than a scientific proposition. Two of Böhm’s suggestions for interventions were selected and implemented in the space at the end of June 2016.

*€8000 including fees can be perceived as a consequent budget to curate an exhibition, however to improve the acoustics of a room having the characteristics of KEX’s exhibition space requires architectural transformations that such a budget could not cover. This is why the budget is qualified as limited and the non-visible constructions performed by Böhm are presented as interventions.

Cogne wonders if the shift she noticed in her perception was due to a progressive process of adaptation to the conditions and characteristics of the space and if her unconscious was stronger than the actual intervention because of all the fictional aspects and parameters used in the communication. For Böhm the feeling is always the strongest thing but others’ statements (what they tell you) are also a source of conditioning.

2/ Measurement and hearing


“I think I heard more than was visible or obvious in the measurement. It is a strange effect that is, I would say, derived from the situation. If you are closer to the storage room, it is less of reverberation than on the other side: you hear a longer earlier reflection pattern from the opposite wall, which gives the feeling that you are in a bigger space on the opposite side, and when you go to the opposite side, it is suddenly:  ‘Oh, I am really in a bigger room now’ because it is more damped on the other side.” PB


In other words, the feeling is accentuated because of a difference, maybe a contrast of perceptions. In addition, Böhm had a more damped feeling at both ends of the space than in the middle layer of the room.


The general reverberation time – combining all the frequencies to which the room is responding – has changed overall: it is now shorter of around one second.


The storage wall


In the storage space, located at the wall with KEX’s office, Böhm placed two components respectively based on the principles of absorption and resonance.

The first component is a porous absorber, which is vertically fixed on the wall of the space. It functions on the principle that sound waves are trying to move the air molecules in the absorber – a 10 cm thick plate of wood wool. This porous material makes them lose orientation and energy. To understand the principle, one could say:

- The thicker the material is, the wider the range of frequencies it can absorb.

- For a lower sound, which has a longer wave, a thicker material is needed.

- And for a high sound, even a paper can absorb it.

At KEX, the lower frequencies are more problematic in this particular room than the higher ones, so a thicker material was used.

The second component is dedicated to the principle of resonance:

- Every material placed in a room vibrates with the air.

- Every material of a specific weight or dimension vibrates within a specific frequency range.

- When dampened, a specific frequency range is absorbed.

Seven horizontal elements were created and installed. Each of them is a metal structure in which a layer of foam material is sandwiched between two gypsum plates. A sound at KEX resonates with deeper waves and sets the gypsum plates in vibration. The layer of foam material functions like a cushion and dampens the vibrating movement. “It is as if you put a pendulum in the air where it vibrates and then you dip it deeper and deeper into honey: it will still vibrate, but some energy is removed.” PB

This component has to be of a specific volume and a specific weight. If the material chosen is too thick, it will not work. The material should soften or slow down the waves, but not mute them entirely. One could say that it is about ‘deadening’ or taking the energy out of the vibrations in the air. In addition, the wooden wall reflects a lot of the higher frequencies. So additional layers of foam were placed on the outside of the gypsum plates in order to stop such reflection. It is actually the distance between the two layers that matters. Furthermore, all the small objects stored behind the wooden wall are also absorbing high frequencies.

The seven elements were placed horizontally on the top ledge of the storage wall, because sound waves are propagating vertically. To place them vertically, hanging down, would be less efficient. This component has the additional effect of making KEX’s exhibition space smaller: the seven elements placed on the storage space removed some of the volume of the room,** which by consequence reduces the reverberation.

So, before the acoustic intervention the sounds in the room created much more reflecting energy. “Every surface takes away a bit of the energy of a sound. For instance, if you speak to a stone block it will say, this is very nice, but I will not vibrate very much, I will not let you move my molecules… A stone is a very reflective material. But, if you would explode the stone into very little elements, they would respond to different frequencies very well. Every little piece of this stone, which was a mass before, would now vibrate and take away the speech, the energy”. PB

It is the combination of the two components – each taking care of different frequencies – that is actively optimising the acoustics of the room.


**A very old principle is to transform the volume of a room in order to change its acoustics. In certain concert halls reverberation is desirable, for that the volume of the room tends to be increased.

How to optimise presentations or talks at KEX


How do human voices interact and circulate at KEX?

“The circulation of sound is, of course, complicated as it travels in all directions with millions of reflections. The sound behaves a bit like jelly: It is vibrating and if one puts it on the table it will take some time until it wobbles to a complete halt.” PB

The best position for delivering a speech at KEX is, accordingly, in the middle of the room, two or three meters away from the wall facing the French balcony, because the distance between the two opposite walls is shorter. This also forces people to stand closer to the speaker. Secondly, this positioning reduces the possibilities of reflection.

“If you address somebody facing the balcony, you have the largest openings and windows facing you, which will let the deep frequencies through like a knife through cheese. If I play a tambourine here, a low sound, part of the waves will just pass through the window. The glass of the windows will however reflect high frequencies. When you have people standing closer to the wall, the strength of the reflection is once again reduced.”PB


Note to a speaker:

Articulation is what counts the most. The best speech would be spoken slowly with a lot of gaps – the language should be a good mixture of vowels and consonants. This is a question of clarity of voice as much as of reverberation. If a child, an adult female, or adult male speaker are trained and articulate equally well, the child might be the best choice as speaker, but not for the reason one can imagine. When a group of people is speaking in the same frequency, the first thing to do is to produce frequencies different from the ones you do not want to hear. At a children's party an opera singer with a low voice would be the best choice. If an audience is composed of people with low voices, the speaker should preferably have a high voice… and the other way around.


One can also use the mobile elements to improve acoustics:

“If you stand speaking in front of them, they will reflect your voice. If you place the walls like a V or cone behind you, you can emphasize the direct sound and the first reflection of your voice (or any sound produced). So for a clear sound, standing inside the V would be perfect.”PB

The created resonance would be under 18 milliseconds in that case, which would enrich the sound.


The mobile units

Three of the mobile wall units, used as exhibition furniture since 2006, were adapted in order to dampen the vibration of the walls – “as if one would place a hand on a tambourine to stop its sound.” PB

For that, foam material was glued directly onto the inner-side of the mobile units to dampen the vibration of the walls. The air that moves inside a mobile wall unit is absorbed by flat foam and fragmented by pyramid shaped foam.

This intervention influences the whole room; it absorbs sound energy from it. It also impacts on the resonance room inside the mobile wall.

No matter where the treated mobile wall units are positioned in the room, the resonant wall frequencies are diminished. However, because the surface of the walls still reflects the sound very much, their positions are important:

-  Their placement can be used to reduce the sound waves that reach the corners and affect the sound particle velocity.

- They can function as barriers across the length of the room to break the long wave structures.

- Last but not least, one can create a smaller room inside the room which also breaks or reduces the length of the sound waves. Here the treated mobile wall units would best be placed at the short end of the smaller room.