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 cases4,5. 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.
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.
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.
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
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 strength1,2. The sound of water is commonly used as part of masking strategies3,4,5(cf. Auditory masking).
1Halprin, L.. Cities. Cambridge, Massachusetts: MIT Press, 1973 .
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 beech1,2. 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.
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 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.
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 further1,2. There are also reports from designers and artists sharing their experiences3-6.
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 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.
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.
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 vegetation3,4. 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.
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.
Areas intended for specific human activities, like cafés or playgrounds, generates 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)
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 landscape1,2,3.
1Pallasmaa, J.. The eyes of the skin : architecture and senses. Chichester, West Sussex, UK: Wiley, 2012 .
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 .