PROCEEDINGS of the
23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

A pilot study on the analysis of soundwalk data
Koji NAGAHATA1; Tomoki MANABE2; Shuto OKADA3
1

Fukushima University, Japan

2

Fukushima University, Japan

3

Fukushima University, Japan

ABSTRACT
Revealing the relationship between human perceived data and acoustic data is important in soundscapestudies. The annex of ISO/TS 12913-2 proposes a method in which soundwalk participants are asked to list
sound sources. Binaural recording is necessary to obtain acoustic data. In the current study, we proposed two
simple methods for expressing the relationship between perceived sound sources and acoustic data: Track
Sheet Style Chart and TM Chart. The results revealed that the Track Sheet Style chart was the most useful
method for clarifying the time structure of noticeable sounds, whereas the TM Chart was the most useful
method for clarifying the time dominance of the sound level of the respective noticeable sounds.
Keywords: soundwalk, perceived sound, sound sources, Track Sheet Style Chart, TM Chart

1. INTRODUCTION
The soundwalk method is an effective approach for understanding human sensations, responses
and outcomes, by examining participants’ evaluation of soundscapes in a particular area. Many
researchers have conducted soundwalks in soundscape studies. However, there has been little research
into methods for analyzing the relationship between human perception data and acoustic data, which
remains poorly understood. Further exploration of these methods is needed to standardize data
analysis methods in soundscape studies.
The annex of ISO/TS 12913-2 (1) recommends that lists of sound sources noticed by soundwalk
participants at respective evaluation points should be obtained. These lists constitute some of thesimplest data regarding participants’ perception. In addition, simultaneous binaural recording at theevaluation points is recommended. The relationship between the lists of sound sources and acoustic
data is the simplest relationship regarding human perception and the acoustic data obtained in thesoundwalk. Therefore, this pilot study explored two simple methods for expressing the relationshipbetween perceived sound sources and acoustic data obtained in soundwalks.

2. BASIC CONCEPTS OF DATA EXPRESSION
As a starting point, the basic concepts for expressing the relationship between perceived soundsources and acoustic data are discussed.
In the method proposed in the annex of ISO/TS 12913-2, soundwalk participants are required tolist the sound sources they notice, in descending order, starting with the most noticeable sound sources,
up to eight. In this procedure, only noticeable sound sources were listed. Therefore, we can consider
the listed sound sources as significant features (2) of the relevant soundscape. The temporal structuresof the significant features of a certain soundscape are thought to constitute one of the importantfeatures of the soundscape (3). In addition, domination of soundscapes by significant features is oneof the most important aspects of analysis, as pointed out by the World Soundscape Project (WSP)
1973 (2). Therefore, in the current study, two expression methods were examined: first, a method toexpress the temporal structures of the noticeable sounds, and , second, a method for expressing thedomination of a certain soundscape by a specific sound(s).
Regarding acoustic parameters, only the A-weighted sound pressure level was used, to simplify
the results in this study. However, notation of A-weighted sound pressure level used in this study
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nagahata@sss.fukushima-u.ac.jp

could be adapted to other acoustic parameters. Thus, sound pressure level can be easily replaced withother acoustic parameters, including loudness, if necessary.
2.1 Track Sheet Style Chart: A Method for Expressing Temporal Structures
The Track Sheet Style Chart method is based on the track sheet in Digital Audio Workstations(DAW) software. In general, DAWs typically display a time structure of a certain work, in a plane inwhich sound tracks are arranged in a longitudinal direction, while the lateral direction indicates thetime. In each sound track in the display, periods of time in which respective sounds are not present
are displayed as blanks.
Similarly, in the Track Sheet Style Chart, the temporal structure of noticeable sounds in a certain
soundscape is indicated in a plane in which respective noticeable sounds are arranged in a longitudinal
direction, and the lateral direction indicates time. At the bottom of the figure, A-weighted soundpressure level(s) are displayed. Figure 1 illustrates the basic concept of the Track Sheet Style Chart.
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Figure 1 - Conceptual illustration of the Track Sheet Style Chart
Regarding time resolution in this chart, the higher the time resolution, the more effort it takes todraw the chart. However, if the time resolution is insufficiently low, the chart cannot express the time
structure of respective sounds precisely. Considering evaluation times at soundwalks are typically 3
to 5 min, 1 unit per 1 sec appears to be an appropriate time resolution for the chart. For example, if 1
unit in Figure 1 is assumed to be 1 sec, the chart can express a 4-minute time structure of respective
sound sources.
The arrangement order of the sound sources in the chart may be arbitrary, and may depend on the
purpose of drawing the chart. The simplest method for arrangement of the data is to show the soundsources that are listed by more participants as higher on the chart. Another common method of
arrangement is to show the sound sources that are preferred by more participants as higher in the chart.
In cases where the type of sound (e.g. sounds of technology, nature, or humans) is an important point,
sound sources should be divided into appropriate types, and arranged in respective groups.
In Figure 1, the sound pressure levels of respective time units are shown using a five-step grayscale. In cases where the dynamic ranges of the sound pressure levels are broad, using a more finelystepped gray scale (e.g. a 10-step gray scale) may be appropriate.
2.2 Time Component Matrix Chart: A Method for Expressing Dominant Sounds
The basic concept of the Time Component Matrix Chart (TM Chart) was proposed by Furukawa et
al. as a method for visual expression of a soundscape (4,5). In this method, the percentage of time ofsound levels and the percentage of time of sound sources are expressed in two dimensions.
In the original method, the percentage of time of respective sound sources is defined as thepercentage of time for which the measurer(s) thinks that the sound pressure level of a particular soundsource is highest among the sounds they hear (4). According to Hiramatsu et al. (5), the percentage oftime of sound sources indicates the rates of respective sounds which are heard predominantly during
the observation period. However, in some cases, the influence of a certain sound source can be very
high, due to specific source attention processes, even if the acoustic contribution to the overall noisecaused by this source is relatively low in a physical sense (6).
From the viewpoint of the soundscape, it is clear that the noticeable sound sources identified by
the soundwalk participant(s) are more important than the sound sources the measurer(s) thinks havethe highest sound pressure levels. Thus, the authors modified the method of the TM Ch art to measure
the percentage of time in which a particular noticeable sound source listed by the soundwalk
participant(s) can be heard, instead of the percentage of time defined by the original method. Figure
2 illustrates the concept of the TM Chart. In this figure, Sound C in Figure 1 is selected as thenoticeable sound, as an example. The left cells in this figure describe the results regarding the soundthat was heard and the right cells show the sounds that were not heard. The size of each cell in the6089

TM chart is proportional to the audible/inaudible percentage of time of the noticeable sound and thepercentage of time of the sound pressure levels.
No Sound C

Percentage time of sound levels (%)

Sound C

Percentage time when the sound can be heard (%)

Figure 2 - Conceptual illustration of the Time Component Matrix Chart (TM Chart)
The noticeable sound in this chart could be changed to a group of sounds. For example, tounderstand preferred sounds, the percentage of time in which the preferred sounds were heard may be
more appropriate. If the percentage of time of a group of sounds is used, the cells showing the groupof sounds heard can be divided in the lateral direction into sub -cells, indicating that sounds belonging
to the group are heard.

3. EXAMPLEThis section shows examples of usage of the two data visualization methods for results obtained
from soundwalks. The soundwalks in this study were conducted to elucidate the appropriateness oflocations in which benches are installed for resting spots for pedestrians around Fukushima Station,
the main station of the Fukushima city (7). There were 2–6 participants in each soundwalk. All
participants were students at Fukushima University. None of the participants were residents of thesoundwalk area, but had visited the soundwalk area at least several times before participating.
Regarding the noticeable sound sources, participants were required at each evaluation site to list
up to eight noticeable sounds in descending order, starting with the most noticeable sound sources, as
recommended by Annex C of the ISO/TS 12913-2. In addition, participants were required to evaluateeach noticeable sound they listed in terms of whether the sound was preferable or not.
Regarding acoustic data, binaural recordings were performed simultaneously using dummy-headmicrophones (B&K; 4100 or Southern Acoustics; Type 2500R II) and a digital audio recorder(TASCAM; DR-60D) around the benches.
The data obtained at two evaluation sites were analyzed, as described below.
3.1 Benches Installed at a Square Facing a Main Road
The first site for analysis was a square facing a main road. This square had only one tree, planted
at the far side from the main road, with benches installed around it. On the days of the soundwalks,building construction was being carried out diagonally across the intersection facing the main road.
At the intersection, acoustic traffic signals for visually impaired persons were installed.
Concerning the list of the noticeable sounds at this site, footsteps, sounds of bicycles, road traffic
noise, acoustic traffic signals and construction noise were pointed out by at least one participant inevery soundwalk. Regarding preferences for those sounds, only footsteps were evaluated as preferable
sounds, although these sounds were not pointed out by all participants. In contrast, all participants
listed road traffic noise and construction noise as unpreferable sounds. Some participants evaluatedthe sound of bicycles and acoustic traffic signals as positive, while some evaluated these sounds as
negative, and others did not list them as noticeable sounds. Regarding participants’ impression of thesite, the square was evaluated as monotonous (7).
Figure 3 shows the Track Sheet Style Charts for the square on the day on which the number of thenoticeable sounds was lowest. In this figure, a cell in each track shows 1 (sec). As the figure shows,the two noticeable sounds listed by all the participants were continuous sounds. This may be one of6090

the reasons participants evaluated the soundscape of the square as monotonous.
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Figure 3 - Track Sheet Style Chart of a square facing a main road
Figure 4 shows the TM chart regarding construction noise at the square, on the same day as thedata shown in Figure 3. Because road traffic noise continued throughout all measurement periods, thisfigure also shows the TM chart regarding unpreferable sounds at the square. From this chart, it is clearthat the rate of time of higher sound levels is higher when the construction noise was heard than when
it was not heard. In contrast, it is difficult to understand this from Figure 3.
As this example shows, this chart is suitable for discussing time domination of higher sound levelsof respective sound sources.

Percentage time of sound levels (%)

Construction noise

No construction noise

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Figure 4 - TM Chart regarding the construction noise at the square facing a main road
3.2 Benches Installed at a Pedestrian Walkway in front of a Pastry Bakery
The next site was a pedestrian walkway in front of a counter-style pastry bakery. This pedestrian
walkway was slightly broader than standard Japanese walkways on urban streets. Several benches are
installed at this pedestrian walkway. The evaluation site was located near the edge of the street
connected to the road to the prefectural office. The street behind the bench has one-way traffic, and asmall number of cars drive on the street, at a relatively slow speed. In contrast, the traffic at the roadto the prefectural office is always busy. The pastry bakery at this street is popular, especially amonghigh school girls and young women. This site is located approximately 200 m from the square analyzed
in the last section. Therefore, the construction noise could also be heard on this site, at lower levels.
Regarding the list of noticeable sounds at this site, only road traffic noise was reported on every
soundwalk. In addition, conversations, footsteps, and the sound of bicycles were reported on morethan one soundwalk. In contrast, construction noise, twittering birds and music from a pastry bakery
were reported in only one soundwalk each. Regarding preferences for respective sounds,
conversations (conversations of pedestrians and conversations between the shop clerk at the pastry
bakery and their customers) and footsteps were evaluated as preferable sounds. In particular, some6091

participants mentioned that conversation between the shop clerk and customers contributed to a
positive atmosphere around this site. The sound of bicycles was evaluated as neutral. Road traffic
noise was evaluated as unpreferable overall, but some participants mentioned that the sound of cars
behind the bench was less noisy than at the other evaluated site, because the car speed was slower.
Regarding the impression of the site, this square was evaluated as relatively comfortable (7).
Figure 5 shows the Track Sheet Style Charts of the pedestrian walkway on a day when all of thenoticeable sounds were listed. In this figure, a cell in each track shows 1 (sec), the same as in Figure
3. As the figure shows, road traffic noise was heard continuously through the whole evaluation period.
However, the noise mainly came from the road to the prefectural office. Compared with the square(Figure 3), the time at which preferable sounds were heard was clearly longer here, and this kind ofsound was heard in any given 1-minute period. This may be one of the reasons why the site was
evaluated as relatively comfortable even though the sound level of the site was relatively similar tothat of the square mentioned in the previous subsection.
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Figure 5 - Track Sheet Style Chart of the pedestrian walkway in front of a pastry bakery
Figure 6 shows the TM Chart regarding the preferable sounds at the pedestrian walkway, on thesame day as the data shown in Figure 5. From this chart, it can be seen that the preferable sounds were
heard approximately 70% of the time. In addition, the figure shows that the highest sound levels wereobserved only at the time when conversations were heard, indicating that no unpreferable sounds were
louder than preferable sounds.
This example demonstrates the suitability of this chart for understanding the time of dominance ofsound levels of respective sound sources.
Conversations

No preferable sounds

Percentage time of sound levels (%)

Footsteps

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Percentage time when the sound can be heard (%)

Figure 6 - TM Chart of preferable sounds at the pedestrian walkway

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4. FINAL REMARKS
Both the Track Sheet Style Chart and TM Chart methods proposed in this study are effective tools
for expressing the relationship between perceived sound sources and acoustic data. These two methods
should be chosen to suit the particular context: the Track Sheet Style chart is the most useful method
for clarifying the time structure of noticeable sounds, whereas the TM Chart is the useful method forclarifying the time dominance of the sound level of the respective noticeable sounds.

ACKNOWLEDGEMENTS
The authors express their sincere appreciation to all the participants of the soundwalks for theircooperation in this study. This study was partially supported by the JSPS KAKENHI Grant Number
19K12676. We thank Benjamin Knight, MSc., from Edanz Group (www.edanzediting.com/ac) for
editing a draft of this manuscript.

REFERENCES
1. ISO/TS 12913-2:2018 Acoustics - Soundscape - Part 2: Data Collection and reporting requirements.
2. World Soundscape Project. The Vancouver Soundscape. Sonic Research Studio, Communication Studies
Department, Simon Fraser University, Burnaby, Canada; 1973.
3. Schafer RM. The Tuning of the World, McClelland & Stewart, Toronto, Canada; 1978.
4. Furukawa S, Matsui T, Uchiyama I, Hiramatsu K. Measurement of sonic environment considering thediversity of sound sources: The concept of <Sound Source ൈ Sound Level> Time-component Matrix
Chart. J Soundscape Assoc Jpn; 2008; 10: 57-65. (in Japanese)
5. Hiramatsu K, Matsui T, Furukawa S, Uchiyama I. The physical expression of soundscape: An investigation
by means of time component matrix chart. Proc inter-noise 2008; 26-29 October; Shanghai, China 2008.
pp. 4231-4236.
6. Genuit K, Fiebig A. Human Hearing-Related Measurement and Analysis of Acoustic Environments:
Requisite for Soundscape Investigations. Soundscape and the Built Environment. CRC Press, Boca Raton,
USA; 2016. pp. 133-160.
7. Manabe T, Nagahata K. Evaluation of resting spaces in urban area using soundwalk. Proc ASJ Meet. on
Noise and Vibration. N-2018-50; 2018. (in Japanese)6093