Every city has a unique set of sounds. Despite the omnipresence of sound, designers have made rare attempts to create urban spaces that consider the aural sense as the primary target. Parameters that determine the sonic character of a city include cultural influences such as language and religion. Technology and constant change add a set of sonic events to the urban soundscape: The larger and older the city, the greater and more complex the sonic character.
Literature shows a division in response to this urban sonic feature. Some researchers embrace it as a token of the greatest achievement and testament to the progress of the species (CHENEVY, 1920). Such research aligned with the opposing side argues that noise is a sign of the stagnation of civilisation. If the “Big City” pandemonium was once thought to be a sign of progress in the early twentieth century, this is no longer the case (SCHAFER, R. Murray, 1993). Sonic events are not distributed uniformly within the city; rather, acoustical character changes owing to differences in social and programmatic organisation between districts, morphology, urban texture and geographic location. This section discusses urban sound character, main principles and spatial relationships to determine the urban soundscape.
Soundscape, a concept first formulated by R. Murray Schafer in 1977, is a discipline that mixes aural architecture and sound sources. It is not simply the sum of simultaneously broadcasting tonal signals nor is it merely a by-product of architecture. The term soundscape is the dynamic sonic equivalent of the phrase landscape; it is an integral essence of the environment and exists when the landscape is used. Existing literature attempts to classify sound in various ways. Pierre Schaeffer’s sound classification charts a paradigm that links the sonic event to the object that creates it. In addition to the physical description, each sonic event is classified according to a number of properties, including distance from the receiver, strength in ambience, environment reflectivity and the relationship of the sound to the larger context (SCHAFER, R. Murray, 1993).
Schafer classifies soundscape sound into six main categories with various subcategories, including natural, human, cultural, mechanical, indicator sounds and the absence of sound (i.e., silence). This method measures the beginning (attack), middle (body) and end (decay) of the sound against its duration, frequency and dynamics (SCHAFER, R. Murray, 1993). Many sonic disciplines know and use these terms extensively. The attack is the onset of the event accompanied by an electrostatic noise: The more sudden the attack, the more powerful the sound. If the sound is gradual, the electrostatic noise is less present and even tonality occurs. The body is the middle part of a sonic event, and the ear perceives this signal as ‘stationary.’ Some sounds do not have a body (e.g., bells and gongs). The decay is the time lapse from when the end of the sound to the point at which the sound energy decays to one millionth of its original strength (REAS, Casey and Fry, Ben, 2007). In addition to the mentioned physical and perceptual properties, these three sound attributes are significant derivatives of the volume and shape of an urban arena (SCHAFER, R. Murray, 1993).
The volume of a large-scale urban arena depends on the sonic property of the target sound and acoustic geography. The geomorphology and macroclimate of the area are natural shaping factors, and urban morphology and materiality are synthesised factors. Geological formations can act as sound barriers or sound conduits. Steep terrain casts large sound shadows while valleys propagate the target sound across large distances. Vegetation is another parameter of auditory demarcation. Grass reduces the reflectivity of the ground and trees absorb airborne sound waves, which casts large sound shadows. A forest on the outskirts of a town creates a thick vegetation edge that stops the propagation of any sound wave. Effectively, the forest acts as a visual and aural barrier, and delineates and aligns the urban arena within the boundaries of a town. Calm bodies of water act as sound reflectors, which increase the size of the urban arena. Conversely, high windshield factors and turbulence along coastlines affect the directionality of sound waves and cause high interference, which can reduce the volume of the urban arena where the coastline is beyond the threshold (BLESSER, Barry and Salter, Linda-Ruth, 2006).
A suburban area after a heavy snowstorm produces similar properties to an anechoic space. Snow is a highly absorbent medium, and if it covers the ground thoroughly, a receiver can detect only direct sound waves. Opaque spaces occur in urban settings in different forms. Small alleys in densely built areas create the effect of an acoustically opaque small space. Buildings act as sound barriers and reflect low-frequency sounds. Pedestrian tunnels, spaces under bridges and narrow streets between high-rises produce the same acoustical effect. Alleyways between suburban gardens where fences and hedges could impede visual interaction and allow sonic permeation are examples of acoustically transparent urban spaces (BLESSER, Barry and Salter, Linda-Ruth, 2006).
Traditional city networks evolve around a central public space with defined landmarks. Scholars find that these foci usually have socially significant landmarks associated with unique sounds, namely soundmarks. Soundmarks customarily create large urban arenas. Traditionally, anyone who lives beyond the aural space (i.e., cannot hear it) is not considered a citizen of that town (Blesser & Salter, 2006). Corbin (1998) states that an elevated sense of territorial identity is a direct result of soundmarks and regular aural urban architecture.
Individuals of different ethnic, socioeconomic, and social backgrounds who live in the same region and who are subjected to the same set of sounds recognise these sounds as ‘home.’ Research finds that aural heritage induces a sense of belonging to a community and national pride when residents hear these soundmarks (Corbin, 1998). Soundmarks can also vary in scale and dynamics. For example, a regular peddler chanting the same tune every day is a dynamic soundmark that may link a number of districts. Trains are another type of dynamic soundmark. A less obvious example of aural heritage is the national morning news tune that emanates from the radio. This type of sonic events creates acoustic arenas that can potentially cover countries (Blesser & Salter, 2006).
Soundmarks are also associated with social hierarchy. Societies have established power, time and cultural identity by giving significance to soundmarks. Cultures preceding the industrial revolution adopted human vocals as soundmarks (Blesser & Salter, 2006). During the industrial revolution, a common soundmark in the western world was the bell, in which only the most prestigious and powerful institutions invested (e.g., churches, monasteries, civil governments and entrepreneur factories).
Bells held power in Europe for an exceedingly long time. In 1784, the French went so far as to cast thirty-eight bells for the Abby of Saint Armand Les Eaux to create the largest aural arena possible. The number and synchronisation of bell towers connected close parishes within the amplified arena. Considering the importance of bells, their loss, capture, or destruction were common practices by invading armies as signs defeat. In 1813, Napoleon followed a well-established sixteenth-century tradition of melting down bells as a sign of power inauguration (Corbin, 1998).
Another common soundmark is the clock. The term ‘clock’ derives from the Middle English word ‘clok,’ which is a Middle Dutch and German word for bell. This word appeared with the earliest mechanical timepieces in Europe during the fourteenth century found in monasteries to inform pious monks of prayer times. These timepieces were designed to sound time, not show it, and they became communal foci. At the time, some argued that the clock was the most notable invention, not the steam engine, and the associated sonic event created a culture of efficiency and punctuality. During the industrial revolution, clocks became a means to ‘synchronise men’ who lived in worker towns near factories. Clocks became linked to factory whistles, which sounded to inform workers of shift change intervals (Levine, 2006).
In the East, early Islamic townships also employed soundmarks to establish time (i.e., prayer time), power and territory. The acoustic geography of the region and primitive available technologies prompted human vocal soundmarks. The designated person (Moazen) was chosen for the quality of his voice, and was given social status and bodily protection during war. At designated prayer times, the Moazen took to the highest vantage point to establish the largest aural arena possible. Moazens climbed tall towers or ‘minarets’ built to project the prayer calls across large areas. At the height of the Islamic empire, the status moved from person to architecture. Gradually, the height and number of towers, along with the volume of the arenas centred on them became significant signs of power (Bianca, 2000).
Acoustical Arenas and Urban Spaces
Parallels and Divergences
Aural and urban design theories share commonalities in spatial concepts. Humans live in the built and natural environments and create an aggregation of human-shaped atomically indivisible units. Programmatic designations and social unit structures determine both types of territories. These associations are the result of the corresponding relationship between the city and soundscape. Urban factors, activities and morphologies determine the aggregate pattern of aural spaces. In turn, sonic character affects social order within urban patches. Aural designs do differ from urban designs in a number of order aspects owing to the ascents of physical restrictions such as gravity and the physical nature of sound. This section draws parallels and contrasts between these two concepts.
Aural design units follow the same principles of atomic indivisibility. Acoustic arenas are the equivocal components of rooms. These aural spaces can be aggregated to create larger and more complex soundscape patterns within urban spaces. For example, the acoustic signature of the public square at the Covent Garden in London corresponds to the activities held in its subdomains, including cafés, markets and performances. These separate domains have associated arenas that are in a continual interplay that define the volume, shape and intermediate threshold zones of the arenas that create the sonic patterns of the space [Refer to: Figure 3. 15]. Amplified sonic events (using microphones and speakers) form large aural spaces that interfere with and affect the volume of other activities. Conversely, domains may contain an aggregation of aural subdomains (e.g., normal conversations at individual tables in a café). These types of subspaces are centred on human voices that occur within a certain frequency band. The collective events amplify the effect of the aural space in the café and encroach upon adjacent aural arenas.
A perpetual occurrence of sound energy exists as the difference between these two types of spaces, and design concepts reflect this divergence. No equivalent concept exists of the street-building pattern relationship in aural design. Rather, the threshold zones between arenas are those regions where a receiver cannot recognise and consciously interpret a sonic event. In these threshold zones, the receiver detects sound energy as ambient sound. Another contrasting factor is the effect of physical elements, as gravity does not prevent a three-dimensional aggregation of acoustic arenas. In this case, the aural design informs the physical configuration. Supporting spaces (e.g., mezzanine levels) are designed to enable the receiver to experience the three-dimensional pattern.
Order & Growth
Aural design is successful when the volume allows for its designated spatial use, and the size and number of users that inscribed the volume and form an aural arena. For example, at an outdoor concert, the broadcasted sonic event located at the stage should be heard clearly throughout the entire space. Curbing external interference and spatial design techniques ensure that the aural arena encompasses the entire audience. Soundscapes and sonic patterns flow and inform the urban morphology.
If Stephen Marshall’s concept that the social structure of a city follows a characteristic order is taken as true, then aural urban design would follow that same order. Social groups create acoustic territories with specific aural codes that identify cohesive social structures. For example, the Heathrow Express train has designated silent cars where it is considered discourteous to speak on the phone. The same code holds true for American suburbia (LABELLE, Brandon, 2010). Thresholds between communities and aural arenas have blurred demarcations, and the volumes and patterns of urban acoustic subdomains follow urban patch morphology, which is a direct result of inhabiting social group order.
Historically, the foci of concentric growing traditional cities were central squares or markets that had specific acoustical signatures or soundmarks. Evidence shows that the location of a soundmark and the volume of the resulting arena within a town are significant factors that determine the morphology of growth. A series of acoustic arenas associated with activities conducted in the extending areas translates and informs the growth of a town. These aural spaces characteristically decrease in SPL and volume as the distance from the central square and the resolution of the street increases. The acoustical signatures of central squares also have a reciprocal relationship with the climate, culture, technology and economics of a city. The density of the aural space network follows that of the urban pattern.
Urban public spaces are programmatically movement domains. The spatial organisation of these networks is a direct result of information flow. Sonic events are a large subset of this information, and they have a reciprocal relationship with the morphology of these spaces. The characteristic hierarchy of these elements is also reflected in the density of aural arenas that occur within these spaces. As such, SPL and the number of sonic events dissipate outward from the centre and follow the hierarchical fractal structure of the network.
The topology of traditional urban networks is a highly connected configuration. The permeability of this network decreases to create narrow spaces as the distance increases from the central square. The resulting spaces are acoustically opaque owing to the circumscribing mass of the buildings. Except for soundmarks, sonic events that occur in central squares seldom permeate through these spaces. The attenuation of sonic events within an impermeable urban fabric creates navigational cues that steer citizens through the public-private gradient. These cues include change in SPL, tonal coloration of low frequencies reflected within tight spaces, and acoustic shadows of distant sounds. Sound pressure levels and ambient sounds become a reciprocal interpretation of the private-public spatial configuration.
Public Spaces & Interstitial Spaces
The aural arenas associated with public spaces follow the same private-public topological order of subdomains. Domains can be mutually exclusive, nested, or in archipelago order. The ephemeral attribute of sound allows for the amalgamation of these topologies. In the absence of physical dividers between domains, the manipulation of physical attributes is key in creating social filters. Ground level changes create social filters, and the qualities of sound define elevation and amount of grade change. For example, an elevated stage creates an exclusive physical domain, and the sonic event that occurs in that space forms an inclusive aural arena, while a fully submerged area (e.g., Vietnam Memorial) creates both an exclusive space and aural arena.
Urban design theory informs this research in that a city is an aggregation of indivisible atomic units. The relationship between these units follows a specific order that results in what is identified as city shapeness. Social logic also defines the growth morphology and network configuration of urban components. Similarly, aural design units are atomically indivisible and aural arenas are sound subcomponent equivalents of physical rooms. Aggregating these subcomponents creates a large and complex urban component or soundscape of the urban space. The aural unit is a sonic event or a sound that occurs within a space and creates a dynamic domain centred on it, namely an acoustic arena. Humans perceive this domain aurally and recognise it as a territory with social coherence. The form and volume of acoustic arenas are determined by the physical properties of the sonic event and the materiality and geometry of the space.