2. General Noise Control

2.1 Landscape design
As former section mentioned, the first step is a general organisation of soundscape. More specifically, it is the removal of low frequency noise. The reason for that is the attenuation of low frequency sounds in air is very low compared to higher frequency sounds (Leventhall, 2003, p. 8). If low frequency sounds take a dominant role, the other sounds are much easier to be overlaid or even nearly unrecognised in the soundscape. Their range is mainly from approximately 10Hz to 200Hz. It is important to point out that attenuation is specially low at around 63Hz (in average air condition), which is the typical range of traffic noise frequency (Leventhall, 2003, p. 9). So in most cases, it is the reason that traffic noise is more likely to be removed.

Speaking of sound, it is a wave phenomenon, which is also known as vibration that originates from some source and propagate through matter (Pierce, 1989). It means the noise control, is actually about manipulation of sound vibration. So aiming to depleting noise until inaudible, increasing the distance of propagation path before it reaches people’s ear is one of the mostly applied methods. Corresponding to this

theory, there is an example near Schiphol Airport in Amsterdam, this airport is one of the busiest transportation hub, but its neighbourhood is one of the most tranquil areas (Young, 2015). Designers formed this area with 150 ridges of 10 feet high and 36 feet wide, which drives the noise reflected in between those walls of ridges, so the aircraft sounds are more likely to be reduced within it (Shown in Figure 1). When locals passing by this area, they are able to enjoy the benefit of natural environment, and avoid being disrupted by noise pollution at the same time. This method is very suitable for relatively permanent noise control of large scale area, both environmentally friendly and professional.

2.2 Sound masking

Apart from using physical design to reduce noise, there are less costly method such as sound masking also helps for general noise control. It uses a ‘cover’ sound to make excess sounds less noticeable (Cambridge Sound Management, 2018). The constitution of sound masking depends on the context. For instance, sound of fountains are well able to cover city centre drone as a broadband mask. However, it may be considered as annoyed if it is located in a residential area with walls around. It causes sound disruption for the residents (Augoyard & Torgue, 2005). Therefore, it is obvious that sound masking is not quite performing as a way of noise reducing, but to adjust acoustical condition by manipulating people’s attention. Additionally, on the aspect of soundscape ecology, sound masking can be harmful to living beings such as birds. Pijanowski et al. (2011) said that most birds use their songs for sake of self protecting, finding partner and other sorts of message transmission. If the bird living area is covered with sound masking, then their songs could be inaudible and they will lose communication with others as well as with environment.

Though sound masking is quite economically friendly regarding to its outcome, it is not very efficient with avoiding close sound sources during on site experiment. In fact, most noises are quite closed rather than in distance or ambient, such as traffic along the street (Hoshowsky, 1997). Most traffic noise also reaches a high decibel level (See Figure 2), which is too noisy to use sound masking (Heinze, 2016). It becomes less of assistance when target sound is over acceptable volume, so it is important to measure decibel level of noise source before using this method.

2.3 Active noise cancelling
While sound masking provides improvement for ambient noise, another acoustical technique, active noise cancelling, is qualified to precisely eliminate intended sounds within certain area. Active noise cancelling utilises an opposite wave of sound source to offset the vibration so that the sound source disappears with it (See Figure 3). This technology has been developed to reduce up to 10 dBA in the range of 30-1000Hz, cutting out up to 90% of a sound (Silentium, 2017). As a result, it leads to a quiet zone (See Figure 4), with both noise and hidden sounds removed, which is not quite the project expected. It is else quite complicated for practising elimination of a few specific sounds rather than most sounds in an area. Even so, the noise cancelling effect of active noise cancelling is still undeniable, so it would be the first thing to consider for future refinement of this project.

Figure 4: operation principal of active noise cancelling in earphone.

Figure 5: Quiet BubbleTM technology developed in Silentium to minimise distracting noises.

2.4 Simulation of general noise control

After introducing three main approaches of general noise control, it is perceptible that they are mainly fit for large-scale project. It is also undeniable that they have limits on a couple of sides. Landscape design and sound masking are intended to reduce ambient noise rather than particular sounds, and the former technique also takes lots of efforts to build. Active noise cancelling is hardly able to assure its performance on varied sound source. Therefore for research project as ASP, it is more reasonable to find a way to simulate similar effect of general noise control. In acoustical processing, sound filtration has same effect as the techniques mentioned above. There are a few softwares, such as Audacity2, MaxMSP3 and Ardour4, are proper to work with. This project is mainly put into practice via MaxMSP for its massive function and the benefits of associating with interaction design. The digital filtration process typically starts with Sonic Visualiser5 (See Figure 5), which displays the frequency spectrum of a market sound recordings. This is where basic data such as sound volume or pitch are measured and analysed. For special signal shown in the soundscape spectrum, Sonic Visualiser can be combined with Audacity to enable listening to this certain range of frequency sound, so researcher can generally define where does the main sounds locate in frequency spectrum. For instance in Figure, below 140 Hz is mainly the broadband traffic sounds and there is sound of pouring rice into the bag between 1171Hz to 1593Hz. The orange spectrum between 656Hz to 984Hz concludes mainly market seller cry. These sounds can be the hidden sounds this research explore for in the soundscape. And then, the recordings are transferred to MaxMSP for initial filtration as well as further particular exposure. More details will be discussed below.

3. Hidden sounds excavation

After fundamental modification of soundscape, it is required to target specific sound, and make them more obvious than others in soundscape. So it is necessary to introduce following step of archeological process to discover those sounds and process them via MaxMSP to achieve the purpose.

First of all, the fundament of acoustical simulation is based on sound recordings, subsequent reveal process and soundscape composition mentioned below are both processing on them. The essential factors of recording is not how to implement, but where and what to be recorded. As Truax (2012) suggested that sound walking is a way to begin, to purely listen to the environment without interruption of operating equipment. This would help perceive the acoustical environment and define where and what would be proper to recorded. However, discarding operating recorder is unrealistic in the research, so the alternative way of documenting sound walking is setting the recorder aside or keeping it always on during listening, so that researcher can focus without distraction for a certain while. Through this approach, ASP researcher experienced and documented soundscapes of central London. These recordings are later extracted into five pairs of field recordings, and will be further explored and revealed below.

Similar to the discovery of older soil layer in archeological exploration, finding specific hidden sounds also takes lots of work and patience. Besides, It is more crucial of ‘how’ to find than the finding itself. Westerkamp (1972) stated that noise created a gap between people and the environment, between human body and thoughts. It is hard to imagine organising imbalanced soundscapes when our body is not

associating with our mind, so bring them together before further exploration is truly essential. It leads to another early stage research about soundscape and listening, “Hearing and touch meet where the lower frequencies of audible sound pass over to tactile vibrations. Hearing is a way of touching at a distance and…” (Schafer, 1994, p. 102). It is believed that the early stage explanation of sound is quite credible in view of the less chaotic acoustic environment back then. Recently, Furlonge (2011) added that listening is distributed all over human body. It enacts the process of sonic literacy, which is the way of articulating understanding and processing interaction of people and soundscapes. Through sonic literacy, human beings will be able to manifest relationship with soundscapes.

In the other word, in order to pursue a better hearing, it is beneficial to allow our body to touch and explore the sound installation. Therefore, ASP project is prototyped with touch sensors to explore each soundscape, and it keeps this touching system in further prototype interaction. Truax (2012) said sound installations may help people understand the real world by linking inputs such as acoustical signals and touch from that real world. This effect can be even more obvious in the simulated soundscape, since the input, which is human touch in ASP, is taking the dominant role. Along with sensors, ASP also programmed a Max patch translating touch into a soundscape filtration based on a patch named Forbidden Planet. As shown in the process model (See Video below), five sensors are connected with MaxMSP, enabling touching and releasing to draw a spectrum of frequency filter, so that the output is a selected range of frequency. Through repetitious touch and listening, it leads to the reveal of hidden sounds by degrees.

4. Soundscape Composition

Apart from generating undesired soundscape, noise pollution also causes the negative effect on people’s listening behaviour. It ensues when people do not bring listening into focus (Schafer, 1994, p. 95). In other word, it results when people are not attempt to listen because noise are learned to be ignored. But as Furlonge (2011) stated, listening is the sensory way of developing sonic literacy. If people stop thinking about listening, then it obstructs researching about any observation and definition of soundscape. In general, soundscape research is a realm positioned between science, society and the arts (Schafer, 1994, p. 96). This educes the society and arts aspect of soundscape research, which discusses about how to organise soundscape in a similar way of musical composition, also known as soundscape composition. Martin (2018) stated that soundscape composition intended to encourage people using ears to perceive the place. Kang et al. (2016) have emphasised that soundscape research became more relevant to managing acoustic environments for putting human perception and experience with acoustic environments in priority. To be more specific, the project needs to ‘concern about the meaning of sounds within a community, the relationship that people have with these sounds and the role of people as sound makers within their own environment’ (Martin, 2018). In short, they are mostly relevant to individual experience which can influence people’s estimation of each soundscape, in where the starting point is established. These contents are going to be further illustrated through two respects of soundscape meaning and human reaction. These two respects are never two separate subjects, as a matter of fact, they are intersected for the most parts.

4.1 Meaning of Soundscape
With regard to the reason behind people’s estimation of soundscape, the constituent sounds of that soundscape is obvious of great concern. The estimation of soundscape is mostly based on whether people think the soundscape is positive or negative. Researchers found that natural sounds and human sounds are the point of reference of that positiveness, conversely mechanical sounds are regarded as low pleasantness. It is reasonable to propose a view that the reason is on grounds of sound meaning. Natural sounds have be linked to quietness and peacefulness, while human sounds deliver message of civilisation related (Davies et al., 2012). So most of the time, a positive soundscape depends largely on its constituent. So for ASP project, this theory is very helpful to define which sound should be removed or focused in a soundscape. Natural sounds and human sounds are ranked high, while mechanical sounds are ranked low in the sound filtration system. High ranking sounds are more likely to be remained in the soundscape, and low ranking sounds are more likely to be removed. This positiveness also depends on foreground and background sounds. There is a relatively balanced rhythm of foreground and background sounds in each soundscape, it will cause human anxiety when the rhythm has a noticeable variation (Ihde, 1976, p. 87). For example, it is more likely to be ignored if the background hum remains low intensity, but solo and distinct sound can constantly attract people’s attention (Ihde, 1976, p. 88). Another similar example is cocktail party effect, which proves that people can focus on sound signal that they are attractive to in a complex acoustic environment (Maddox, 1994). Besides, Davies et al. (2012) mentioned that participants were very likely to label what they heard as foreground or background sounds. So the evaluation of soundscape also depends on the constitutes of foreground and background sounds. For instance, in a complex urban soundscape, traffic noise is usually regarded as background sound. If it largely covers other sounds, it is more likely to be removed. In a crowded urban space such as market, human sounds can be distracting to a certain extent, so in this case, human sounds are likely to be decreased in order to expose more subtle and natural sounds. So by positive soundscape, it means the foreground and background sounds are harmoniously mixed together. Conversely, if foreground sounds stand out loudly, being constant and changeable, its belonging soundscape can be regarded as negative (Davies et al., 2012). In general, this part of filtration process is for the sake of uncovering the positive part of the soundscape.

Apart from the basic meaning of sounds, there are some subtle features in a soundscape that also affect individual perception. Sound colour is an important part of them, which is an awareness accumulated after long-term soundscape experience. The colouring could also be perceived when an alteration of filtration is occurred (Augoyard & Torgue, 2005). The researcher has also given an example that being in daily locations such as churches and seasides can return various hidden images to human mind. This sensation acts as a way of evoking memories and causing anamnesis, so that it makes anything relating to timbre and filtration as a trigger (Augoyard & Torgue, 2005). Thus, positive soundscape can be regarded as a valuable resource capable of transferring images of memories from various space and time. It is an essential consideration in ASP project, since most valuable message this project supposed to deliver occurs after this trigger.

Meanwhile, this triggering response can be easily affected by individual preference to some extent. Most of this preference is unable to be described and explored, it is even not part of beauty. It is more of an intuition than conscious reasoning. It brings to consideration of sharawadji, which is ‘an aesthetic effect that characterises the feeling of plenitude that is sometimes created by the contemplation of a sound motif or a complex soundscape of inexplicable beauty’. For instance, some people consider sounds of starting motorbike as beautiful strangeness (Augoyard & Torgue, 2005). Sharawadji effect is reasonably considered in ASP project, so the recording samples presented with installation are randomly selected in order to avoid composer’s judgement. Additionally, ASP installation is not intended to build sharawadji phenomena in any way, but to create as many possibilities as it could of sharawadji emergence for participants to experience during interaction.

4.2 Human Reaction

Westerkamp (1999) said early before that soundscape composition must conclude exploration of both sound material and its sonic environment. In other word, it brought attention on how to transmit meanings about location, context, time and acoustical perception through soundscape composition. The key of this is building the relationship among composer, audience and soundscape. The following sections will discuss further with this on the aspect of human reaction.

Firstly, linking to the reason behind human perception of various sounds, manipulation of people’s subconscious can help draw their attention on certain sounds so that it is more likely to make people feel positive about this soundscape (André, 2012). It can be keynote sounds, which derived from geography and climate, or sound mark which is type of sound stands out in its community (Schafer, 1994, p. 101). Those sounds are very likely to make soundscape sounds different when they are or even are not in a soundscape. However, those sounds stand out in the soundscape are not necessarily related to positive perception. Similarly, those hidden sounds in the soundscape are also not necessarily connected with negative perception. It can be inferred that many positive sounds are hidden in a negative soundscape. ASP utilised this attention effect by creating touch action to switch between original soundscape and revealed sounds. This contrast brings people’s attention on the revealed sounds, and when they listen back to its original soundscape, those sounds nearly become foreground sounds, the quality and feeling of soundscape will be changed with it.

Another important factor Davies et al. (2012) mentioned is whether people think they are in control of the soundscape. It makes a major difference when people sense they can dominant their exposure in a soundscape. Thus, handing over the exposure control to participants can help deliver a positive soundscape. It is the reason that ASP project attempts to produce a relatively positive soundscape by allowing people to touch and control the installation by themselves.

In addition, memory, or even precisely, personal experience, is more directly linked to soundscape evaluation. The special part of personal experience is that it has an effect on our daily behaviour. Besides, personal preference of soundscape is particularly affected by experience and its relevant memory. Kang et al. (2016) said soundscape can build imaginary acoustic scenes of significant locations or occurrences in human impression. This can be powerful to relate sounds to human memory. The research of Davies et al. (2012) has proved that emotion-driven thoughts and past memories are particularly influential in evaluation of soundscape. As a result, ASP has selected field recording relating to old-time market, it is believed to be able to evoke people’s memory which was built when there are not much mechanic sounds. In addition, memory effect would not stop on the end of the soundscape performance. Martin (2018) said that soundscape composition actually evokes memories while people are interacting with the acoustical environment, and even continues to strengthen the effect after the performance have been completed. Therefore, through soundscape composition, specific sounds can perform as a bond between people and the living environment, and help people understand the surroundings and communities. However, relationship between participants and soundscape seems to be singular, which only evolves within one individual (Pinto, 2017). The feeling of it can be shared with other people, but it can hardly ever be analysed and documented. Pinto (2017) also pointed out that human beings are able to actively adjust the listening behaviour after they have a perception about the soundscape. This active tuning process can integrate people with environment. Therefore, ASP created a variety of sounds to be listened and played with. It is mostly intended to remind people the notion of listening and perceiving through body to brain. This intention even continues when they finish listening with the sound installation. When participants are back to the real world, their daily listening behaviour can be influenced by ASP interaction. When people start to pay attention to the constituent sounds in daily soundscapes, they will have a clearer understanding of the real environment.

4.3 Filtration Outcome

All the soundscape recordings are selected from daily soundscapes for the reason that human response of daily sound is considered to be more intensive than other sounds (Westerkamp, 2017). The daily sounds recorded are quite common in human life, and the purpose of that is to stimulate the connection between the sounds and human mind more readily and rapidly, and evoke the memory in people’s deep consciousness. With the application of theory of soundscape meaning and human reaction, ASP has specifically selected 5 soundscapes (Refer to Appendix). The soundscape shown below is a market soundscape (See Figure 6). The spectrum on the right is the filtration that screen the sounds from original soundscape on the left. It is worth mentioning that the final interaction is simplified from multiple touch sensors controlling single filtration spectrum to one touch sensor triggering one soundscape. So audience can pay attention on perceptions and thoughts without excessive distraction of operating the installation.

Figure 7: Filtration spectrum of market soundscape in Max patch.

5. Audience Interaction

Soundscape composition is about how to evoke memories of relationship established between people and soundscapes (Martin, 2018). But so far, it seems as a way of revealing composer’s awareness and inspiration of the soundscape. There are some potential risks not to mention about another important aspect, which is allowing the meanings of sound material to guide the compositional process (Westerkamp, 2017). Otherwise, the whole project can be subject to a certain extent. In this case, the project requires more participants to cooperate and experience. All these experimentation is supposed to lead to the answer of shifting composer’s intent by virtue of inherent meaning of sound materials (Westerkamp, 2017). As Martin (2018) indicated that, soundscape artworks were actually ‘giving resident control over their artistic output and an opportunity to respond, understand and document the changes to their community environment’. Participation of audience should be involved in the process of making ASP, especially the soundscape composition part. Westerkamp (2017) also suggested that the way people want to tune the soundscape exclusively rises in the middle of pursuing that. Because of that, this project is taken advantage of Work in Progress show in UCL, Here East, presented for two days, and experienced by a large group of audience (See Figure 7). It is installed with a simulated soundscape in a dark room that processing via MaxMSP. Visitors can using touch to interact with the soundscape, and rotate the prototype to see the relating visual effect on the wall (See Figure 8).

For the prototype design, it is significant to further illustrate the concept and purpose of it. Firstly, the prototype is designed and installed in a way that encourages human being to interact with the soundscape in order to further study how people perceive the soundscape. The installation is intended to pass control of soundscapes onto participants, because they perceive differently between active anticipation of changing

sounds and passive change by sound itself (Augoyard & Torgue, 2005). For this reason, the appearance of prototype is made as analogue as possible, utilising mainly daily material such as timber. It is also applied with copper tapes to transmit current data rather than electrical wires, so that the installation seems more interactive friendly. The reliability of simulated soundscape should remain high since its performance is proved to be as the same way as real soundscape. Participants also sensed quite occupied by actively involved into simulated soundscape (Davies et al., 2012). Additionally, the entire participation process is documented with both video and recording, including the conversation between designer and audience.

6. Discussion

In general, the purpose of ASP is basically aiming at showing people the hidden soundscapes and reminding people to pay attention to listening in daily life via soundscape composition. The soundscape composition process mainly includes noise control, filtrations and soundscape reveal, and more importantly, it is combined with the theory of human reaction. The entire project is also regarded as an exploring tool for further study of individual behaviour and preference. This project attempts to embed a notion of the hidden part of soundscape into people’s mind, and expects to influence people’s listening behaviour afterwards. Only in this way, the current urban soundscape can be reinvented with new identification, and becomes detached from negative impact of noise.

At the current stage, ASP is a prototype installation for experimenting the research assumption, so obviously it requires adjustment and improvement in the next step. There are several aspects need to be improved after thesis discussion. Firstly, it seems that the recording samples are insufficient in quantity to be able to draw a conclusion. The amount of recordings will be increased in order to get close to an conclusion. The research may even take one step ahead to include non-daily sounds such as outer space sounds so that the samples are not only increased in quantities but in contents. In addition, the brain activity regarding the interrelation between people and soundscape seems to be individually dependent, which makes the research difficult to document and analyse. In fact, most theories are not entirely proved with accurate evidence. ‘Soundscape is the acoustic environment of a place, as perceived by people, whose character is the result of the action and interaction of natural and/or human factors’ (Kang et al., 2016). Because of this character, soundscape designers may find it difficult to analyse their projects in scientific dimensions or strategies. For instance, how often the memory is able to triggered by the soundscape composition, and how strong those memories perform in individual minds. These need more repeated experiments to increase the project reliability. Meanwhile, there are devices such as biosensor can record biological feedback of participants as an digital signal (Turner et.al, 1987, p. 5). Through biosensor, soundscape research is able to document the process of participation with scientific data and it leads this research to the direction of being part of scientific realm (Kang et al., 2016).

Secondly, for the participation, even though it is documented with recordings and videos, the listening behaviour learned from the prototype experience fails to be tracked. The influence on listening behaviour could be more valuable for the research than the experience quality of the prototype. The approach could be modified by changing pop-in visitors to a fixed group of volunteers. The volunteers will be invited to participate into project including joining the sound walking, experimenting prototype and being interviewed about perception and reflection of the project. In this case, the project is going to involve the response of participants through the entire process of soundscape composition.

For further development, the prototype may be improved and then displayed in the airport arrivals terminal. This could allow tourists to experience the city through compositional soundscape before they place themselves into the real urban soundscape, so that the actual listening experience could be more focused and satisfied. Then, the locations of recording may be enlarged rather than being limited in London. Even more, the interacting mode, which is mainly touch now, might be expanded to other sensing mechanism, such as relating the body weight with soundscape control.

7. Conclusion

To sum up, this thesis report takes archeological process as a reference to explore city soundscape. It discusses about how to generally remove the noise in a complicated urban soundscape to improve the listening quality. This part is illustrated with beginning of physical intervention, such as landscape design, and then acoustical intervention, such as sound masking and active noise cancelling. Subsequently, the research translate the effect of general improvement of soundscape into MaxMSP software for economic purpose. Then the soundscape filtration process is further focused onto specific reveal for memory related sounds. After that, the exploring approach is developed in a more art and humanistic way, involving human perception and behaviour, and the interrelation between individuals and soundscapes.

Finally, this research is not a closing exploration. As Kang et al. (2016) said soundscape research will continue covering more fields of study to increase more research-based proofs. In fact, there should not be standard answers to soundscape issues, constant discovery with cross discipline is the key.

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