Towards a Typology of Sonic Thresholds 


In order to sketch a preliminary typology of sonic thresholds of the Source Bleue, I shall confront the corpuses developed in the research – the descriptive text, the soundwalk, and the sound recordings – with two documents. The first is Barazon’s text from 2010, in which she introduces a range of meanings for thresholds across different disciplines; the second is a 1995 text by Jean-François Augoyard and Henry Torgue on sonic effects as a tool for describing and nominating changes in sonic environments.


Silence as Buffer 

The urban oasis is composed of spaces that, despite being clearly delimited and well defined, nevertheless enjoy a high degree of porosity thanks to the intentional presence of thresholds. They are intermediate spaces that take different forms: bent entrances, doors, or a change in level. I can only approach the spring through these bent entrances – short passages marked by a succession of right angle turns. These thresholds have their own micro-ambiances, highlighting an important influence on atmosphere: as the space becomes narrower and darker, the body is enveloped and protected from the sun’s rays. The change can take place either through an abrupt cut-off effect[5] or a gradual crossfade effect.[6] Sonically, the threshold consists of a buffer space dominated by silence in which the usual animation of the city is attenuated, and a simple event like the passage of a person completely fills the auditory space. 


Approaching thresholds as physical spaces, Barazon analyses them from an anthropological point of view; she states that a threshold must be understood in relation to physical rituals of entry, waiting, and departure. Following this approach, she underlines two important threshold states, the first being the introductory state. In rituals of passage, thresholds form marginal spaces, preparing the participant’s arrival to the main scene. In fact, in the urban context of the Source Bleue, the thresholds around the spring accentuate the process of access to and prepare the approach to the water. The second is the transient state experienced by the passerby or visitor. Crossing thresholds – especially those of a house – correlates to changes in state of the one who crosses them: passing from the state of a stranger to the state of a familiar, for example. Penetration into the private space concurrently imposes a sense of respect for the rules that govern the house (Barazon 2010: 5).


These senso-spatial features create an atmosphere of pause that allows the body and the ear to relax and open up to better capture the rustling of the nearby falling water. The contrast between shadow and light, animation and calm, space and narrowness, the alternation of contraction and relaxation awakens the senses and solicit perception. The sudden silence becomes a buffer that reinforces the feeling of entering. Through its preparatory and protective nature, the sensory space sends a message and the passerby experiences the sacred dimension of water. At the end of the journey, the sound of water is born.


Multiple Sonic Perceptions of Water

Familiar connotations associated with a spring are: a natural environment, low slope flow, moderate sound level, kharïr alma’a. Here, the experience is unexpected: the spring, recently rehabilitated to flow into two basins at different levels, now generates a waterfall of a few meters, with accompanying high sound levels. Active only a few hours per day, this manmade waterfall provides a daily rhythm to the space: absence of the water sound when it is not working, gurgling during the start-up and when shutting down, and a steady rush when it is active. The changes in sound constitute a series of sono-temporal thresholds that coincide with the variation of the intensity of the water flow throughout the day. 


Furthermore, the architectural form reconfigures the listening experience: the various articulations in level and the presence of many subspaces create masking effects within the sonic environment. A physical experience of these architectural levels reveals the relationship between the body and sounds: the listener on the steps of the amphitheater perceives the waterfall frontally, while in the closed space of the khettarates, where the sound is transformed by the reverberation effect, the sound envelops them. 


Sound Center vs Hollow 

The soundscape of the two spaces, the Source Bleue and the Kasbah Aghenaj, constitutes a dual atmosphere, separated by a busy street that actualizes a sonic wall effect.[7] Whereas the waterfall constitutes a sound center that masks small sounds – footsteps, conversations, cries of children, etc. – the Kasbah manifests a sound hollow where sounds exist primarily on the edges of the space. Here, the ocher walls, delimiting stage and theater, produce the same nesting effect, both visually and sonically. This is why the enclosed space is very quiet, and the slightest sound attracts attention: children jumping from step to step or moving in and out of the space. The rectangular form of the Kasbah produces a strong reverberation effect; the listener perceives the sound echoing in front of and behind them. Immutably, at sunshine and sunset, the birds perch on the merlons, and their songs their songs fill time with rhythm. 


Bubbles of Intimacy

I have borrowed this expression from the German philosopher Peter Sloterdijk who introduced the term “bubbles” in his trilogy Spheres. He interprets them as “physical forms that receive forms of human engagement in intimate spaces such as the egg and the uterus, as spaces that are both protectors and donors of life.” For him they constitute "shared, consubjective and inter-intelligent spaces; bubbles participate in the constitution of any subject" (Sloterdijk 2002: 8).


In this study, the "bubbles" are subspaces created by an immaterial membrane induced by the sound of water. The latter is a sonic threshold that forms a protective layer preserving an intimate coexisting presence by creating micro-territories within the public space through a masking effect.[8] This wrapping effect perfectly matches with the presence of the women covered with their mellafahs, the colored sub-Saharan outfit. 


I and You, a Return to Oneself

The soundwalk text offers a fluctuation between the “passive voice” (the impersonal state) and "I" (the first person) modes of expression. When experiencing public spaces, we expose ourselves fully to the world, to our “You.” However, the passage to “I” signifies a momentary return or transition to one's self. This alternation between “You” and “I” is an alternation between different states of mind that occur during an experience in which we can distinguish between former and prospective states. In this case the threshold is neither spatial nor temporal; it forms a “perceptive threshold.” 


Barazon refers to a Hegelian and Joycian dialectic. For Hegel, where the experience takes place, the self disappears temporarily; and the experience itself takes place, the self is exteriorized (entäußert) in the experience (Barazon 2010: 14). For Joyce, the “I” is externalized and becomes the experience itself; it merges into action and thus reduces the gap between the world and one’s perception of it (Barazon 2010: 8). The perceptive threshold possesses specific traits: it is dynamic, meaning that the dialectic relation between the inside and the outside defines the self as a threshold in motion, where the self ceaselessly oscillates between experience and reflection or emotions. The different states of mind are not abruptly separated but are present in a continuous mode (Barazon 2010: 6).


Regarding the soundwalk text, the return to oneself refers to two different states of mind. The state of a stranger: once the threshold is crossed, the listener enters the shared space of the Source Bleue while being completely immersed in the experience. When confronting the bubbles of intimacy, where the sound of water defines the subspaces, the listener’s state changes: they become strangers, intruders. Conversely, in the second state, the “I” returns to itself. In the Kasbah, the spatial isolation and the dominating calm create a nesting situation. The prevailing calm allows for an encounter with oneself, providing a moment of contemplation that can be experienced in this public space. 


The Incorporation of the Myth in the Water

“The Source Bleue is we!” This statement of a young girl represents the spring as a place of memory and a constructor of collective identity. The sonic environment created by the waterfall combines the power of place and the power of time. The presence of water reinforces the myth of the spring discovery: in any narration, written or oral, the holy woman remains alive. The sound of water unfolds anterior temporal strata. Through its anamnesis effect,[9] the sound of water becomes a base of collective and trans-generational memory.


This robust identity belongs to a specific type of thresholds: the thresholds of identity that unfold over a long time span. In her approach to the thresholds of time, Barazon draws upon perception, change, and memory, stating that thresholds of identity conserve a preliminary state which endures despite subsequent changes. They allow us to recognize ourselves and find ourselves, through the act of narration or self-narration, in a world that is constantly changing (Barazon 2010: 17, translated by the author).


Moreover, the myth – as related to the fertility of the female body – is still embodied in water. Up to the present, there are rites that take place around the spring – weddings, religious festivals, etc. – during which an egg, its shell or a chicken throat are thrown into the basin. Despite being immaterial, the myth becomes tangible through these rituals. The continuity of these social practices in this deliberately vernacular contemporary architecture reveals earlier temporalities and gives a thickness to the present time. The importance given to the water in the redevelopment of this space has provided a place for the myth and reestablished it within the city.