Compensation/variation

Strategic use of contrasting soundscapes can be employed as a way to enhance their respective differences as qualities, such as making a tranquil area seem relatively quiet in relation to a busy street¹. Variation is generally discussed in terms of enforcing tranquil qualities, as in quiet areas², quiet façade³, auditory refuges⁴ and tranquil space⁵ (Pheasant et al., 2008). However, little has been done in terms of investigating the potential for working the other way around⁶ .

References:
¹Augoyard, J.F. & Torgue, H.. Sonic experience : a guide to everyday sounds. Montreal: McGillQueen’s University Press, 2005.
²EU. Directive 2002/49/EC of the European Parliament and of the Council. (L 189). Official Journal of the European Communities: European Union, 2002.
³de Kluizenaar, Y., Salomons, E.M., Janssen, S.A., van Lenthe, F.J., Vos, H., Zhou, H., Miedema, H.M. & Mackenbach, J.P..Urban road traffic noise and annoyance: the effect of a quiet façade. Journal of the Acoustical Society of America, 130(4), 2011, pp. 1936-1942.
⁴Hedfors, P.. Site soundscapes : landscape architecture in the light of sound. Diss. Uppsala: SLU, 2003
⁵Pheasant, R., Horoshenkov, K., Watts, G. & Barrett, B. The acoustic and visual factors influencing the construction of tranquil space in urban and rural environments tranquil spaces-quiet places? The Journal of the Acoustical Society of America, 123(3), 2008, pp. 1446-1457.
⁶c.f. Whyte, W.H.. The social life of small urban spaces. Washington, D.C.: The Conservation Foundation, 1980.

Embrace wanted sounds

Embracing wanted sounds is to identify existing qualities in the soundscape and further use them to locate new functions. For instance, a new café could be located near an existing fountain to make use of the water sound as an atmospheric quality¹.

References:
¹Alexander, C., Ishikawa, S. & Silverstein, M.. A pattern language : towns, buildings, construction. New York: Oxford University Press, 1977.

Avoid unwanted sounds

This involves strategic localisation of sensitive functions in positions sheltered from noise. Sheltered positions can be secured if there is sufficient distance to the noise source or by making use of the ‘sound shadow’ from existing structures like buildings and/or topography. Noise has been shown to have negative effects on health¹ , including our ability to communicate², to sleep³, and to feel acoustic comfort⁴. It also affects our willingness to help other people⁵. Absence of noise, on the other hand, correlates with tranquillity⁶, an important quality in parks, pocket parks and housing areas.

References:
¹Basner, M., Babisch, W., Davis, A., Brink, M., Clark, C., Janssen, S. & Stansfeld, S.. Auditory and non-auditory effects of noise on health. Lancet, 383(9925), 2014, pp. 1325-1332
²Gehl, J.. Life between buildings : using public space. Copenhagen: The Danish Architectural Press, 2006.
³WHO. Night noise guidelines for Europe. Regional office for Europe: World Health Organisation, 2009.
⁴Yang, W. & Kang, J… Acoustic comfort evaluation in urban open public spaces. Applied Acoustics, 66(2), 2005, pp. 211-229
⁵Cohen, S. & Spacapan, S.. The Social Psychology of Noise. In: Jones, D.M. & Chapman, A.J. (eds.) Noise and society. Chichester: Wiley, 1984.
⁶Pheasant, R., Horoshenkov, K., Watts, G. & Barrett, B.. The acoustic and visual factors influencing the construction of tranquil space in urban and rural environments tranquil spaces-quiet places? The Journal of the Acoustical Society of America, 123(3), 2008, pp. 1446-1457.

Embrace unwanted sounds

Embracing unwanted sounds is to acknowledge (existing) noise, e.g. the row from a market, as an urban quality that may be suitable for certain functions. It has been observed that an active soundscape can have positive effects on urban situations and offering social seclusion¹. Some sounds that are arbitrarily described as noise should instead be regarded as an urban quality^2,3. Yet, it is still important to ensure that some areas are tranquil (cf. Compensation/variation).

References:
¹Whyte, W.H.. The social life of small urban spaces. Washington, D.C.: The Conservation Foundation, 1980.
²Cerwén, G.. Urban soundscapes: A quasi experiment in landscape architecture. Landscape Research 41 (5), 2016, 481-494.
³Hellström, B.. Noise design : architectural modelling and the aesthetics of urban acoustic space. Diss. Stockholm: KTH, Stockholm. Ejeby, 2003.

Vegetation for noise reduction

This concerns the role vegetation can play in some contexts to reduce noise. The measurable effect of vegetation in reducing noise has been debated, yet if the layer is thick and dense, the effect can be substantial^1,2. The ground effect related to the soil substrate should be raised in this context³, as well as visual screening (cf. Visual masking) and the sound of rustling leaves (cf. Auditory masking and Effects of vegetation).

References:
¹Van Renterghem, T., Attenborough, K. & Jean, P.. Designing vegetation and tree belts along roads. In: Nilsson, M., Bengtsson, J. & Klæboe, R. (eds.) Environmental methods for transport noise reduction. Boca Raton: CRC Press (Imprint of Taylor & Francis), 2015
²Bucur, Voichita. Urban forest acoustics. Berlin: Springer, 2006.
³HOSANNA. Novel Solutions for Quieter and Greener Cities. Bandhagen: EU FP7, 2013.

High noise screens

High noise screens are approximately 1.8 m and above. These screens should be located as close to the source (or listener) as possible for optimal effect¹. The effect depends on a number of factors, where height is the main determinant². In addition to conventional usage, high noise screens can be used in a creative manner, as part of urban design solutions incorporating features like seating^3,4, water and/or vegetation^4,5.

References:
¹Forssén, J., Kropp, W. & Kihlman, T.. Introduction to traffic noise abatement. In: Nilsson, M.,Bengtsson, J. & Klæboe, R. (eds.) Environmental methods for transport noise reduction. Boca Raton: CRC Press (Imprint of Taylor & Francis), 2015.
²HOSANNA. Novel Solutions for Quieter and Greener Cities. Bandhagen: EU FP7, 2013.
³Fusaro, G., D’Alessandro, F., Baldinelli, G. & Kang, J.. Potential of a soundscape element design. Conference Paper: 17th CIRIAF National Congress, Perugia, Italy, April 6-7, 2017.
⁴Cerwén, G.. Urban soundscapes: A quasi experiment in landscape architecture. Landscape Research 41 (5), 2016, 481-494.
⁵Hellström, B., Torehammar, C., Malm, P. & Grundfelt, G. (2013). Stadens Ljud – Akustisk design & hållbar stadsutveckling [City Sounds – Acoustic design and sustainable development]. Stockholm: Exploateringskontoret, 2013.

Low noise screens

A low noise screen compensates for its lower height (up to around 1 m) by increased proximity to the noise it is screening. The effect can be substantial in some cases¹, but there are practical issues like maintenance and traffic safety to consider. Like high screens, low screens can be combined with creative solutions that incorporate water and vegetation to form part of an urban design solution.

References:
¹Defrance, J., Jean, P., Koussa, F., Van Renterghem, T., Kang, J. & Smyrnova, Y… Innovative barriers. In: Nilsson, M., Bengtsson, J. & Klæboe, R. (eds.) Environmental methods for transport noise reduction. Boca Raton: CRC Press (Imprint of Taylor & Francis), 2015.

Buildings as screens

Strategically located buildings can be used as less obvious, yet effective, noise screens, also in combination with conventional screens. Besides the height of the buildings, the shape, location and materials applied in the building are important¹. If the buildings are intended for housing, care needs to be taken to avoid sleep disturbance². Noise exposure on one side of the building can be compensated for to some extent by a quiet façade where bedrooms can be located³.

References:
¹Hellström, B., Torehammar, C., Malm, P. & Grundfelt, G. Stadens Ljud – Akustisk design & hållbar stadsutveckling [City Sounds – Acoustic design and sustainable development]. Stockholm: Exploateringskontoret, 2013.
²FHWA. The Audible Landscape: A Manual for Highway noise and land use. Cambridge, Massachusetts: Federal Highway Administration, 1976.
³de Kluizenaar, Y., Salomons, E.M., Janssen, S.A., van Lenthe, F.J., Vos, H., Zhou, H., Miedema, H.M. & Mackenbach, J.P. Urban road traffic noise and annoyance: the effect of a quiet façade. Journal of the Acoustical Society of America, 130(4), 2011, pp. 1936-1942.

Changed topography

The shaping of the landscape topography can be used to form hills, berms or strategically shielded valleys. Earth berms along major infrastructure constitute a well-known application¹. The detailing of berms in terms of shape and use of vegetation material can have a substantial effect on performance².

References:
¹MTH. Noise control earth berms: Guidelines for the use of earth berms to control highway noise. British Columbia: Ministry of Transportation and Highways, 1997.
²HOSANNA. Novel Solutions for Quieter and Greener Cities. Bandhagen: EU FP7, 2013.

Reduce source activity

This cathegory constitutes a broad number of measures that are aimed to influence the way an activity is carried out, so that noise is reduced. This might for example concern traffic speed, which can be approached from different angles. One is to enforce the rules (e.g. speed limits), an other is to find design solutions that affect certain behaviours (e.g. reduced lane size and shared space solutions). In the latter approach, a parallel can be drawn to the notion of environmental affordances¹, a term which has also been applied to sound environments².

References:
¹Gibson, J.J.. The ecological approach to visual perception. Hillsdale, New Jersey: Lawrence Erlbaum Associates, 1986.
²Thibaud, J.-P.. The Acoustic Embodiment of Social Practice. In: Karlsson, H. (ed.) Proceeding of Stockholm, Hey Listen!, June 9-13. Stockholm: The Royal Swedish Academy of Music, 1998.

Abolish certain functions

Abolition or complete transformation of functions that produce unwanted sounds, like the transformation of a car road to a walking path, can be considered. Such a development would seem likely in relation to densification and sustainable development.

References:
No references

Maintenance

Everyday maintenance of outdoor space can have negative influences on the soundscape, particularly through use of machines with combustion engines. Maintenance can be considered by landscape architects in maintenance plans, but also in design solutions¹. For instance, a meadow is less likely to result in noisy maintenance activities than a mown lawn. Maintenance may contribute qualities in the soundscape, as when hand-driven tools are used or when animals are involved.

References:
¹Cerwén, G..Fridfulla ljudlandskap? [Tranquil soundscapes?]. Tidskriften Stad. Alnarp: Movium, 2017.

Absorbing qualities of materials

The absorbing qualities of certain materials can be used to reduce the impact from sound, particularly in conjunction with unwanted source activities like roads¹. An interesting and useful example is vegetated soil, but there are also other strategies under development in collaboration with acousticians².

References:
¹Forssén, J., Kropp, W. & Kihlman, T.. Introduction to traffic noise abatement. In: Nilsson, M., Bengtsson, J. & Klæboe, R. (eds.) Environmental methods for transport noise reduction. Boca Raton: CRC Press (Imprint of Taylor & Francis), 2015.
²HOSANNA. Novel Solutions for Quieter and Greener Cities. Bandhagen: EU FP7, 2013.

Auditory masking

The term auditory masking implies that a sound (masker sound) influences the perception of another sound (target sound), so that the focus shifts from the target to the masker sound¹. There are two general types of auditory masking; energetic and informational. In energetic masking, the target sound is rendered inaudible or less loud. In informational masking, both sounds are audible but the main focus lays on the masker sound. Masking is a complex phenomenon that depends on several cues for successful implementation, including physical characteristics of sound sources and their relative location in space². Some scientists suggest that it is not fruitful to use this strategy if the sound pressure level exceeds 65-70 dBA³. If the intention is to achieve tranquil qualities, significantly lower levels than this is required in most cases^4,5. A possible exception is when tranquillity is associated with social seclusion, in which case it may be desirable to have higher sound pressure levels in order to obstruct (spoken) communication⁶.

References:
¹Moore, B.C.J.. An introduction to the psychology of hearing. Bingley: Emerald, 2012.
²Cerwén, G.. Urban soundscapes: A quasi experiment in landscape architecture. Landscape Research 41 (5), 2016, 481-494.
³Zhang, M. & Kang, J.. Towards the evaluation, description, and creation of soundscapes in urban open spaces. Environment and Planning B-Planning & Design, 34(1), 2007, pp. 68-86.
⁴Pheasant, R.J., Fisher, M.N., Watts, G.R., Whitaker, D.J. & Horoshenkov, K.V.. The importance of auditory-visual interaction in the construction of ‘tranquil space’. Journal of Environmental Psychology, 30(4), 2010, pp. 501-509.
⁵Nilsson, M.E. & Berglund, B.. Soundscape Quality in Suburban Green Areas and City Parks. Acta Acustica United with Acustica, 92(6), 2006, pp. 903-911.
⁶Whyte, W.H.. The social life of small urban spaces. Washington, D.C.: The Conservation Foundation, 1980.

Visual masking

The general idea with visual masking is to hide the visibility of an unwanted sound source, and thus shift the focus away from the noise and reduce its negative impact. A typical application of visual masking is to use vegetation to hide a road, with the vegetation having multiple other effects as well (cf. Vegetation for noise reduction and Effects of vegetation). The appropriate application of visual masking has been debated and the usefulness is concidered to depend on the situation. Some researchers suggest that visual masking is a fruitful strategy as long as the noise is not too evident¹, but that the illusion is difficult to achieve with more obvious noises.

References:
¹Botteldooren, D., Andringa, T.C., Aspuru, I., Brown, A.L., Dubois, D., Guastavino, C., Kang, J., Lavandier, C., Nilsson, M.E., Preis, A. & Schulte-Fortkamp, B.. From Sonic environment to Soundscape. In: Kang, J. & Schulte-Fortkamp, B. (eds.) Soundscape and the Built Environment. Boca Raton: Taylor & Francis Group, 2016, pp. 1-16.

Sounds of water

“It gurgles, it splashes. It goes plop, plop, plop. And fshzzzsh. And spaatzzz!”¹

Water is a classical component in landscape design that can be used for multi-sensory effects. There are multiple possibilities to control the sonic character of water features, including timbre, rhythm and strength^1,2. The sound of water is commonly used as part of masking strategies^3,4,5(cf. Auditory masking).

References:
¹Halprin, L.. Cities. Cambridge, Massachusetts: MIT Press, 1973 [1963]. p. 143
²Nikolajew, M.. At læse vandet : et redskab til analyse af vandkunst og fontæner [Reading the water: an approach to the analysis of water art and fountains]. Diss. København: The Royal Danish Academy of Fine Arts, 2003.
³Brown, A.L. & Rutherford, S.. Using the sound of water in the city. Landscape australia, 2(2), pp. 103-107.Galbrun, L. & Ali, T.T. (2013). Acoustical and perceptual assessment of water sounds and their use over road traffic noise. Journal of the Acoustical Society of America, 133(1), 1994, pp. 227-37.
⁴Galbrun, L. & Ali, T.T.. Acoustical and perceptual assessment of water sounds and their use over road traffic noise. Journal of the Acoustical Society of America, 133(1), 2013, pp. 227-37.
⁵Rådsten Ekman, M.. Unwanted wanted sounds : perception of sounds from water structures in urban soundscapes. Diss. Stockholm: Stockholm University, 2015.

Sounds of vegetation

The sound of vegetation is often associated with leaves that rustle in the wind. This particular effect can be enhanced through strategic choice of plants, like poplar, bamboo and winter beech^1,2. Windy positions, such as open fields, mounds and wind tunnels, can be utilized for the same purpose³. An additional benefit of vegetation in such locations is the reduction of unwanted impacts from the wind. Vegetation can also improve or enhance other sounds. For example, the sound of rain can be enhanced by certain species such as bamboo, lotus and plantain².

References:
¹DeGroot, J.. It’s even been speculated that plants send audible messages to each other. Observer, November 20, 2015.
²Yang, S., Xie, H., Mao, H., Xia, T., Cheng, Y. & Li, H.. A summary of the spatial construction of soundscape in Chinese gardens. Conference Paper: 22nd International Congress on Acoustics, ICA 2016, Buenos Aires, September 5-9, 2016.
³Cerwén, G., Pedersen, E. & Pálsdóttir, A-M.. The role of soundscape in nature-based rehabilitation: A patient perspective. International Journal of Environmental Research and Public Health 13 (12), 2016, 1229.

Walking materials

Walking constitutes an interaction with the landscape that can be enhanced through sonic feedback. Gravel and wood (in particular) are examples of materials that could give positive results¹. Research has shown that walking sounds have an impact on soundscape quality², yet more studies are needed to assess different kinds of materials. Interestingly, it has been shown that the surrounding soundscape can influence the walking pace³.

References:
¹Cerwén, G., Pedersen, E. & Pálsdóttir, A-M.. The role of soundscape in nature-based rehabilitation: A patient perspective. International Journal of Environmental Research and Public Health 13 (12), 2016, 1229.
²letta, F., Kang, J., Astolfi, A. & Fuda, S.. Differences in soundscape appreciation of walking sounds from different footpath materials in urban parks. Sustainable Cities and Society, 27, 2016, pp. 367-376.
³Maculewicz, J., Erkut, C. & Serafin, S.. How can soundscapes affect the preferred walking pace? Applied Acoustics, 114, 2016, pp. 230-239.

Atmospheric design (loudspeaker-based)

Speakers are increasingly being used for various purposes in urban situations. Sounds emitted through speakers can be used to design qualities in the environment. These installations are not necessarily audible, but they can improve architectonic qualities, particularly regarding the atmosphere. Studies that assessed the users’ perceptions of such installations conclude that there is potential to explore this approach further^1,2. There are also reports from designers and artists sharing their experiences^3-6.

References:
¹Billström, N. & Atienza, R.. CAN we improve acoustic environments by adding sound? Conference Paper: Inter Noise, New York, August 19-22, 2012.
²Hellström, B., Nilsson, M.E., Axelsson, O. & Lunden, P.. Acoustic design artifacts and methods for urban soundscapes: a case study on the qualitative dimensions of sounds. Journal of Architectural and Planning Research, 31(1), 2014, pp. 57-71.
³Lacey, J.. Sonic rupture : a practice-led approach to urban soundscape design. New York: Bloomsbury, 2016.
⁴Dyrssen, C., Hultqvist, A., Mossenmark, S. & Sjösten, P.. Ljud och andra rum [Sound and other spaces]. Göteborg: Ejeby, 2014.
⁵Hellström, B., Sjösten, P., Hultqvist, A., Dyrssen, C. & Mossenmark, S.. Modelling the Shopping Soundscape. Journal of Sonic Studies, 1(1): A04, 2011.
⁶Licitra, G., Brusci, L. & Cobianchi, M.. Italian Sonic Gardens: An Artificial Soundscape Approach for New Action Plans. In: Axelsson, Ö. (ed.) Designing Soundscape for Sustainable Urban Development. Stockholm: Environment and Health Administration, 2010.

Sound sculptures

Sound sculptures are installations that include sound as an important and obvious part of an embellishment, and the sound may be introduced through speakers or by other means. Those works can be merged with, for instance, urban furniture as part of an interactive experience, or function as a freestanding element in the urban environment. Musikiosk, an installation built in a pocket park in Montreal and later evaluated in research, has been found to enhance mood in visitors¹ and to have a positive effect on social dynamics². Speaker installations can also be used to detract focus from noise.

References:
¹Steele, D., Tarlao, C., Bild, E. & Guastavino, C.. Evaluation of an urban soundscape intervention with music: quantitative results from questionnaires. Conference Paper: Inter Noise, Hamburg, August 21-24, 2016.
²Bild, E., Steele, D., Tarlao, C., Guastavino, C. & Coler, M.. Sharing music in public spaces: social insights from the Musikiosk project (Montreal, CA). Conference Paper: Inter-Noise, Hamburg, August 21-24, 2016.

Biotope design

Through consideration of biotopes, you can affect the attraction on birds and other animals that contribute to sonic experiences¹. The landscape architect Per Hedfors introduced the term “sonotope”,  which can be applied to emphasise the sonic character of biotopes². Songbirds are generally attracted to basic habitat features, such as access to water, food and sheltering vegetation^3,4. Vegetation and water can also produce sound in other ways (cf. Effects of water and Effects of vegetation) To attract birds, vegetation should ideally be dense, varied and in several layers. It could also be beneficial to have older (and dead) vegetation, as there is a correlation between forest stand maturity and bird species diversity⁵. Sounds of nature are generally perceived as a positive element⁶ and bird song diversity has been shown to enhance appreciation of urban landscapes further⁷.

References:
¹Dawson, K.J.. Flight, Fancy, and the Garden’s Song. Landscape Journal, 7(2), pp. 170-175, 1998.
²Hedfors, P.. Site soundscapes : landscape architecture in the light of sound. Diss. Uppsala: SLU, 2003.
³Forman, R.T.T.. Urban ecology : science of cities. Cambridge: Cambridge University Press, 2014.
⁴DeGraaf, R.M.. Trees, shrubs, and vines for attracting birds. Hanover: University Press of New England, 2002.
⁵Gil-tena, A., Brotons, L. & Saura, S.. Mediterranean forest dynamics and forest bird distribution changes in the late 20th century. Global Change Biology, 15(2), 2009, pp. 474-485.
⁶Axelsson, Ö., Nilsson, M.E. & Berglund, B.. A principal components model of soundscape perception. The Journal of the Acoustical Society of America, 128(5), 2010, pp. 2836-2846
⁷Hedblom, M., Heyman, E., Antonsson, H. & Gunnarsson, B.. Bird song diversity influences young people’s appreciation of urban landscapes. Urban Forestry & Urban Greening, 13(3), 2014, pp. 469-474.

Attract activities

Areas intended for specific human activities, like cafés or playgrounds, generate a certain kind of soundscape. Those sonic environments can offer qualitative experiences even for people who are not actively involved, but in the vicinity¹.  (cf. Embrace wanted sounds)

References:
¹Alexander, C., Ishikawa, S. & Silverstein, M.. A pattern language : towns, buildings, construction. New York: Oxford University Press, 1977.

Resonance and reflection

The acoustic qualities of materials and spaces can be used to enhance wanted sounds through resonance and/or reflection. Such effects can be used to emphasise qualities in the soundscape, e.g. around watercourses, meeting places and walking paths. The reflections may also constitute an experience of their own, in the sense that they offer a way to interact with the landscape^1,2,3.

References:
¹Pallasmaa, J.. The eyes of the skin : architecture and senses. Chichester, West Sussex, UK: Wiley, 2012 [1996].
²Blesser, B. & Salter, L.-R.. Spaces speak, are you listening? Experiencing aural architecture. Cambridge, Massachusetts: MIT Press, 2007.
³Rasmussen, S.E.. Experiencing architecture. Cambridge, Massachusetts: MIT Press, 1964 [1959].