In contrast with the the conventionally recognized notion that architecture is a visually static environment ,aural architecture by nature is a dynamic one. Even though the physical spaces may be inert, the activity held within is continuously changing, and along with it the aural design. Moreover, an aural design differs from a visual, where the architect is not the sole creator of the space, but along with the occupants.

Although, the architect’s design may directly influence the programmatic aspects of the space, as well as, the relationship among the occupants, the occupants inherently have the control to create a sonic event that temporarily changes the dynamic within the physical space. For example, if one sonic event dominates a single room the aural boundaries could align, extend beyond the physical boundaries, or there could be a matrix of aural boundaries, acting as virtual cubicles, within a physical boundary.

“An acoustic arena is a region where the listeners are a part of a community that shares an ability to hear a sonic event” Blesser, B. and Salter, L.R

Within a performance space, the physical area of the stage is much smaller than that of the seating area. However, when it is in use, the acoustical architecture is designed to amplify the sounds created by activities on stage while diminishing any events produced in the seating area. Thus, diminishing the seating auditory area volume and allowing the stage arena volume to claim most of the performance space’s physical boundaries. On the other hand, if there is a debate session one of the audience has the prerogative to create and expand his/her voice’s arena. Hence, changing the sizes of the existing arena’s proportionately.

When a specific sound source, sound event, is loud enough to be heard, by a group of listeners more clearly than the adjacent events, an acoustic arena is formed. Anyone that cannot hear this sound, even if they can visually see the source, are consider to be beyond the boundary of the arena. As a result, an acoustical arena is volume centered around a sonic event.

Acoustical arena volumes are as dynamic as the activities that create the sonic event. They are in a constant Darwinian dynamic combat, where one arena can encroach into, substitute, or completely engulf another. All aural architectural spaces are designed to the principles of acoustic arenas. A successful acoustical design has the ability to manipulate this interplay, by enhancing the auditory connection between a specify sonic event and a listener, over another. This connection is known as an auditory channel.

Aural spatial awareness is one of the possible channels of information that this thesis is concerned with, along with the information received by the human auditory organ and its many sub channels. A listener can receive information through multiple auditory channels when more than one sonic event exists within their horizon. Hence, a listener can exist in more than one arena simultaneously, receiving information through multiple connections. The sonic event does not necessarily need to be overwhelming. The connection is contingent upon the sonic properties of the auditory channel, and if a sonic event is in close proximity, or loud enough to broadcast information, and establish an auditory connection, then it is consider to be within the listeners acoustic horizon.

“An acoustic horizon is the maximum distance the listener and a source of sound, where the sonic event can still be heard” Blesser, B. and Salter, L.R

Not unlike the acoustic arena, an acoustical horizon is a dynamic auditory space that is centered around a listener. Background noise, which is either a sonic event that intrudes, is too soft, or distant to be discernible, defines the shape and volume of an aural space. In addition, curve linear spaces have a direct effect on, not only the shape and volume of aural spaces, but also their location. The shape of the space can be manipulated by concentrating the target sound’s energy in a specific direction. In consequence amplifying the sonic event in one direction rather than a uniform distribution. Aural arenas can have radical shapes; one arena can exist in two nonadjacent physical spaces, simultaneously. This can be achieved by devices such as acoustical mirrors, and whisper galleries .

Acoustical mirrors, or “listening ears” were used during World War I until they were replaced by radar technology. In fact, in the 1930′s there were attempts to establish a sonic connection between England and France across the channel. However, the reason that these attempts were not completely successful is that the distance the reflection can propagate, is highly dependent on the sensory modality. Lately, science museums exhibit this phenomena as a novelty, where two parabolic surfaces are places 100 meters apart fusing two arenas, at the foci of both surfaces, into one sonic arena. Currently, there are new experimentations conducted in the California Institute of Technology (Caltech), where a grid of small sonic lenses are used to amplify and focus sound energy to a localized point, creating sound bullets (1) .

The volume of an arena can be manipulated by reverberation and frequency. A physical space that has long reverberation time, such as a performance stage, creates a significantly larger acoustic space. Whereas, sonic events that have sharp frequencies often create a small arena. On the other hand, an aural architect can increase an arena’s volume without increasing reverberation time, when it is undesirable; like in a conference hall. This can be achieved by creating strong reflections that reach the listener shortly after the direct sound, where the human aural sensory perceives them as one strong aural channel.

The auditory demarcation is the equivalent to a visual partition, which delineates an arena or horizon and, therefore, defining an auditory community. This phenomena exists at many scales, from an intimate , personal, conversational, to a public or urban scale. In the abstract, the scale of an arena centered around one sonic event with no interference, is considered to propagate uniformly creating a spherical space. The volume of an intimate arena is approximately 1/2 a meter. The most obvious example is an arena of two people whispering. Less mentioned examples , are the intimate spheres that form within highly noisy environments, like speaking loudly within a nightclub, or on a cliff through a strong gust of wind. A personal arena’s volume is approximately 1 meter in diameter, and the conversational sphere can extend to 4 meters width. These two arenas are exemplified as a normal conversation within a space with a negligent amount of noise. Similarly, these diameters shrink in size within environments with strong interference. Finally, the public and urban scales, which are the concern of this thesis, have significantly larger diameters. The volume is contingent upon the sonic property of the target sound.

There are quite a few physical factors that define an arena’s volume, some are natural while others are a direct result of technological advances. The geomorphology and the macro climate of the area are examples of natural factors; whereas sound absorbing or reflective materials, and urban morphology are instances of acoustical design technology. Geological formations can act as sound barriers or sound conduits. For example, steep terrain would cast large sound shadows, where as valleys propagate a target sound across large distances. Vegetation is another parameter of auditory demarcation. Grass reduces the sonic reflectivity of the ground and trees absorb air-borne sound waves, casting large sound shadows. The edge of thick vegetation like a forest on the outskirts of a town, could stop the propagation of any sonic event, essentially delineating the urban auditory arena and aligning it with the visual boundary. Finally, bodies of water act as perfect sound reflector increasing the size of the urban arena. However, high windshield factors and turbulence along coast lines, can affect the directionality of the sound waves; consequently, counter acting the reflectivity of the body of water to the point that the coast line could be beyond the urban auditory arena.

Historically, humans adapted to their acoustic environments. Early humans adapted to nature and the great differences between aural and olfactory horizons. For example, where there is thick vegetation, the olfactory horizons are significantly smaller than aural horizons. Hence, the Mayan civilization shows evidence of professing aural manipulation in their temples’ architecture. On the other hand, modern humans have adapted to urban environments, public gathering spaces, and enclosed dwellings.

If a group of individuals begin to interact within an auditory arena, the space quickly is defined as territory. The territory inhabitants acquire rules and rights that distinguishes the citizens from the foreigners. Historically, communities and towns were centered around a soundmark. This is the equivalence of a landmark, where a single sonic event broadcasts a unique signal and establishes a connection with every individual, demarking the center of the aural community. Soundmarks provide local social cohesion, and anyone that could not hear this event was not considered a citizen of the township. Some of the more prominent examples of soundmarks, are church bells within Christian communities, and prayer calls within Islamic communities (2).

Broadcasting is not just a human phenomena, on the contrary. Aural communication within a shared acoustic environment is essential to the survival, and part of the complex social habits of various species (Marc D. Hauser 1997 a). Different species use broadcasting in shared environments, where acoustic horizons are much further than that of olfactory horizons like jungles and forests, to attract mates, as warning calls, or establish power. Establishing power by means of broadcasting can be achieved by injecting a sonic event into an acoustic arena. Sonic power is exemplified in historical church bells that became replaced by factory whistles in the beginning of the industrial revolution. In a less obvious way of claiming sonic power, peddlers and shopkeepers in marketplaces use their voices or various musical instruments to attract as many customers as possible. In a modern western society, broadcasting is more to alert rather than to establish political power; which is embodied as amber alerts, airport announcements, or ambulance and police car sirens.

أجراس الميلاد اذان القاهرة عبد الباسط عبد الصمد by merate barakat

Dwelling within the absence of acoustic arenas is a rare phenomena, therefore it has always been considered as a sign of wealth and power. Brandon LaBelle Speaks of an incident when he accidentally answered his cell phone while riding the silent compartment on the Heathrow express. LaBelle points out that the simple auditory arena rule of silence, created a community with its own social cohesion. It is also the easiest arena to be dominated by another event. However, by unknowingly breaking the arena’s rule, LaBelle that the reaction of the community proved he is a ‘stranger’. A strong urban example is the modern day suburbia, where it is completely disconnected from the urban sonic arenas.

There is an argument comparable to that of public spaces and how they have been renders obsolete lately. Some argue that technology has provided means of creating high quality private acoustic arenas, and provided other means that create social cohesion, making public acoustic arenas less relevant regardless of their noise level. However, this does not explain why festivals and demonstrations are still strong social events. This is evident in Greece where demonstrations are continuously held, or how the ‘Arab spring’ riots have managed to bring about change within their social structure. It would seem that this proves that aural architecture, the principles of auditory arenas, and Alain Corbin’s (1998) studies hold true. Corbin found that an elevated sense of territorial identity is a direct result of soundmarks and regular aural urban architecture .

Footnotes:
(1) The ‘Sonic Bullet’ technology is foreseen to be used for noninvasive surgeries. http://www.nature.com/scientificamerican/journal/v302/n6/full/scientificamerican0610-26b.html

(2) Functional Deafness, which is unrelated to biological deafness, is the absence of all acoustic arenas. For example, an individual that is using earphones disconnects him/herself from the all the acoustic channels around, thus they are not within any acoustic arena.

Bibliography

Blesser, B. (2007). Spaces speak, are you listening?: experiencing aural architecture. MIT press.

Castelvecchi, D. (2010). Look, Ma—No Junctions! Scientific American , 26-26.

LaBelle, B. (2010). Acoustic Territories: Sound Culture and Everyday Life. Continuum.