PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Auditory evaluation of very-high-frequency sounds radiated fromthe Japanese trains part2.
Mari UEDA1; Shunsuke HANAZAKI1; Hironobu TAKAHASHI2;Masaaki HIROE3
1
2

Kanagawa Institute of Technology, Japan

National Institute Industrial Science and Technology, Japan
3Kobayasi Institute of Physical Research, JapanABSTRACT
The purpose of this research is to clarify the state of hearing high frequency sound and to ensure safety andconsideration for young people including children. In this study, we measured the hearing threshold of highfrequency pure tone for 4 college students aged 21 to 24 and high frequency sound in the train together with
conducting demonstration experiment and auditory sensation. From the measurement results of the highfrequency pure tone audible range, we could confirm everyone in the 4 people was able to list up to 16 kHz
and 3 out of 4 people were able to listen up to 22 kHz although there were individual differences in thethreshold value. Moreover, during the demonstration experiment and the auditory experiment in the train wecould confirm that some people feel uncomfortable after hearing the high frequency sound. This time there
were four participants in the experiment, but this number was sufficient to clarify the exposure condition ofhigh frequency sound and its influence became clear in everyday life.
Keywords: High frequency noise, Environment, Annoyance, Hearing threshold, Train noise

1. INTRODUCTION
In recent years the high frequency sound has been widely applied at various industries in oureveryday life such as sensors, medical equipment, welding etc. and the number of occasions whenpeople are exposed to high frequency without knowing is increasing. The products including the highfrequency components do not use high frequency as it is, but several products intentionally generate
it. As an example, there are mouse and stray cat repellers, or moreover repellers of young people
hanging around in the downtown. These are high-frequency sounds with a sound pressure levelexceeding 100 dB [1]. They use high frequency sounds around 18 kHz to 22 kHz, or higher, and in
most cases such devices are designed with consideration for the human audible range (20 Hz to 20kHz). Also, it has been reported that high-level high-frequency sound is included in railway noise [2],[3]. In some cases, it is possible to identify the source, but recent studies have revealed that highfrequency sounds with sound pressure levels exceeding 80 dB are often observed even in urban
environments with a wide variety of sounds mixed [1, 4].
On the other hand, among systematic studies on the effects of high frequency sound exposure on
living organisms there are few researches on exposure studies and measurement methods for highfrequency sounds, however the researches on hearing of high frequency sound has been conducted byseveral research groups. The target auditory of such studies is the university students and adults, andalmost no reliable data on hearing targeted on young auditory has been reported.
However, in the
study by Ueda et al. [4], we conducted experiments for children and young people, and found theaudible sound for all of eight children participating was up to 22 kHz, while all young people could
listen up to 16 kHz. Furthermore, we draw the conclusion, the higher the frequency is, the more it
feels "noisy" or "uncomfortable". Basing on these results, we concluded that it is necessary to consider
16370

m-ueda@ic.kanagawa-it.ac.jp

whether enough safety and consideration for high frequency sound exposure to young people
including children as well as adults in daily life is taken.
Therefore, in this research, we aimed at obtaining data with higher reproducibility by conducting
experiments with people with higher listening ability of high-frequency sounds basing on the listening
experience of train running sound which was taken at the Hiroe’s research. For this reason, the author
conducted the experiments concerning hearing of high-frequency sound in the moving train at first,
and after that, similar listening was conducted for 4 university students from 21 to 24 who measured
the high frequency audible range in the soundproof room. By conducting such experiments, weinvestigated the actual condition of high frequency sound exposure in the train.

2. MESURMENT OF SOUND FIELD
2.1 Outline of preliminary measurements
At first, in order to clarify the generation status of high frequency sound in the train, we actually
took the train and carried out actual measurement. Before the survey, we confirmed whether author
can hear the high frequency sound by using the measuring application on smartphone. It turned out,that high frequency sound of 18 kHz can be heard.
Surveyed was the section between Hon-Atsugi and Ebina stations on the Odakyu Odawara line on
both up and down lines. The survey period was three days from September 25 to 27, 2018, and a totalof 20 surveys were conducted. We targeted on 3 kinds of trains – local, express and rapid express.
The survey method was confirmation by the author own ears and the record of the running soundobserved in the train. For the measurements inside the train, we used a compact, inconspicuous PCM
recorder (KENWOOD, MGR-E8) and recorded the in-vehicle sound with a sampling frequency of 96
kHz and Z (flat) characteristics. The survey was conducted twice - the primary and the secondary
survey. Fig. 1 shows the target sections of the first and second surveys. In the primary survey section
surrounded by the red continuous line in the figure, there are two curved tracks (A, B in Fig. 1) andone railway bridge between Hon-Atsugi and Atsugi.

Fig.1－Target section in survey 1 and 2 (Hon-Atsugi – Sagami-ono Stations up and down lines) * A to F
in the figure indicate curved trajectories. © CCBYSA / OpenStreetMap contributors

6371

2.2 Results of measurements
First, as a result of the first survey, a lot of high frequency sounds were confirmed in the curves
around Atsugi station (A, B in FIG. 1). Furthermore, as a result of analyzing the recorded data, it wasfound that high frequency sounds in the vicinity of 35 kHz actually occurred from 20 kHz. Figures 2and 3 show examples of analysis results. Next, the distribution of points where high-frequency soundwas heard Re survey 2 is shown in Fig.4. Similarly to survey 1, although it was not possible to hearon the straight line, there were total of 6 curved tracks between Atsugi station and Sagami Ono station"Hon-Atsugi station" near (A), "Atsugi station" near (B), "Zama – Soubudai-mae" There are a total of6 curved tracks of 1 place (F) and 3 places (C, D, E) between "Ebina station and Zama station". At
five of the above station the high frequency sound was recorded with frequency of more than 10 times.

Fig. 2－FFT analysis result of survey 1 (A: Hon-Atsugi - Atsugi).

Fig. 3— FFT analysis result of survey 1 (B: Atsugi ~ Ebina).

6372

Fig.4—The place of occurrence between Atsugi station and Sagamiono station.
© CCBYSA / OpenStreetMap contributors

3. AUDITORY EVALUATION FOR COLLOGE STUDENTS Intellectual Property
3.1 Outline of auditory experiments
In this auditory experiment, in order to verify whether the high frequency sound can be heard in
the train or not, after checking the hearing threshold for the high-frequency sound in the soundproof
room, we actually took a train and conducted a listening experiment as in the surveys 1 and 2.
3.2 Measurement pf pure tone hearing thresholds of high frequency soundFirst, in order to confirm the degree of hearing of the high frequency sound of the experimentparticipants, the pure tone auditory threshold was measured in the soundproof room. There were 4experiment participants (3 male, 1 female) from 21 to 24 years old.
The test sound used for measuring the threshold was repeatedly presented at a cycle of once persecond with a windowing (Hanning) with onset and offset for sinusoidal wave 200 ms and steadystate part 600 ms respectively. The frequency was tested on 11 sounds at 1 kHz, 2 kHz, 4 kHz, 8 kHz,12 kHz, 14 kHz, 16 kHz, 18 kHz, 19 kHz, 20 kHz, 22 kHz in total. As shown in Fig. 5, it wasreproduced from a speaker (YAMAHA, MSP 3) located 500 mm away from the front of theparticipant's face. To measure this pure tone hearing threshold, the limit method of ascending sequence
was used. In the limit method, there are disadvantages that measured values are susceptible tocognitive bias such as prediction and beliefs, and constant method and adaptation method are often
adopted to avoid this. However, on the other hand, the constant method and the adaptive method
require dozens of operations to obtain one measurement value. Moreover, there is a disadvantage thatthe restraint time of the experiment participants is extended. For this time, we adopted the extreme
method which can measure the threshold value in a short time. However, we tried to avoid theinfluence of cognitive bias etc. by inserting catch trial as appropriate.
In the threshold measurement, at first, the limit method of the ascending sequence which starts froma sufficiently low level which cannot be heard by experiment participants was used. The level increase
per time is 3 dB, and the listener raises a signal once the inspection sound could be heard. The averageof several times of the presentation level at this time was taken as the minimum audible range value.

6373

Mandatory Registration of Authors
An invited or contributed paper may be part of the Conference program and proceedings only if aregistration fee (Regular Participant or Student) has been paid by the deadline for the paper submission
for the Proceedings. One registration fee is valid only for one paper. If the same author submits morethan one paper, the “Additional paper” fee shall be paid for each additional paper submitted(exception: multiple invited contributions).

Fig.5 －Measurement of pure tone threshold of high frequency sound.

Table 1 shows the average of the measurement results of the high frequency pure tone thresholds
for each experiment participant. Up to the frequency of 8 kHz, there was no big difference for 4people, but a difference began to appear between 1 and 3 other people from 12 kHz, andsignificantly big difference was seen in 4 people over 16 kHz. Even if the experiment participants
were almost the same age, there was a big difference in the audible range of the high frequency
sound. It turned out that some people cannot hear if the high frequency sound is not at a high soundpressure level or someone cannot hear it even at a high sound pressure level.
Table 1－Average of the measurement results of the high frequency pure tone thresholds for eachexperiment participant.
Frequency and1234

1 kHz

22.1 dB

20.2 dB

20.2 dB

21.6 dB

2 kHz

23.6 dB

20.2 dB

20.2 dB

22.9 dB

4 kHz

20.2 dB

20.2 dB

20.2 dB

20.2 dB

8 kHz

24.7 dB

20.2 dB

20.2 dB

22.0 dB

12 kHz33.2 dB

20.2 dB

20.2 dB

20.2 dB

14 kHz29.3 dB

20.2 dB

20.2 dB

20.2 dB

16 kHz41.3 dB

20.2 dB

35.0 dB

22.7 dB

18 kHz65.8 dB

44.4 dB―

30.8 dB

19 kHz57.7 dB

43.7 dB―

39.6 dB

20 kHz63.9 dB

38.7 dB―

35.1 dB

22 kHz77.6 dB

42.6 dB―

57.4 dB

Participants No.

* "-" indicates that measurement is impossible

6374

3.3 A field experiment
Next, the same experiment participants conducted a simple listening experiment in the runningtrain to ascertain whether or not high frequency sound can be heard within the train.
Experiment participants, as in Section 2.1, got on the train in the interval between Atsugi stationand Sagami-ono stations on the Odakyu Odawara line and checked the position of the train where
the high frequency sound was heard with Google Maps with ● on the map handed in advance. In
addition to answering whether it feels unpleasant high-frequency sound heard by ○ or x with aside.
The object of this auditory experiment was two types of express and local trains. This isbecause the highest auditory frequency of high frequency sounds is at express trains as it comesfrom the frequency on the local trains is the second most. Moreover, the number of times ofstoppage and vehicle type are different from those of the other two models.

4. CONCLUSIONSThe purpose of this research is to clarify the state of hearing high frequency sound and to ensure
safety and consideration for young people including children. In this study, we measured the hearing
threshold of high frequency pure tone for 4 college students aged 21 to 24 and high frequency soundin the train traveling on the Odakyu Odawara Line together with conducting demonstration experimentand auditory sensation.
From the measurement results of the high frequency pure tone audible range, we could confirm
everyone in the 4 people was able to list up to 16 kHz and 3 out of 4 people were able to listen up to22 kHz although there were individual differences in the threshold value. Moreover, during the field
experiment and the auditory experiment in the train we could confirm that some people feel
uncomfortable after hearing the high frequency sound. This time there were four participants in theexperiment, but this number was sufficient to clarify the exposure condition of high frequency soundand its influence became clear in everyday life.
We will continue to increase the number of participants in the experiment and clarify the influenceon human exposure to high frequency sound exposure.

REFERENCES
1. M. Ueda et al., “Investigation on high-frequency noise in public space Part1,” Forum Acusticum Krakow,
pp.1-15, 2014.
2. Masaaki Hiroe et al., “The survey of the high-frequency sounds above 10 kHz radiated from the Japanesehigh speed and conventional railways”, Proceeding of inter-noise 2011, 43154321, (2011).
3. M. Hiroe et al., “Auditory evaluation of high-frequency sounds radiated from the Japanese high speedrailways,” Inter noise 2018, Chicago, pp. 1-7, 2018.
4. M. Ueda, “Measurement of ultrasound radiated from rodent repellents used in an occupational space, andauditory evaluation of the sound.,” ASA Minneapolis (2018).
5. M.Ueda et al., Proc. 11th International Congress on Noise as a Public Health Problem, 2014.

6375