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

Frequency characteristics of oppressive and vibratory feeling tolow-frequency soundMakoto MORINAGA 1; Ippei YAMAMOTO1; Tomohiro KOBAYASHI2;
Koichi MAKINO2; Hiroaki OCHIAI2; Hideki TACHIBANA3
1

Defense Facilities Environment Improvement Association, Japan
2Kobayasi Institute of Physical Research, Japan
3

The University of Tokyo, Japan

ABSTRACT
Although experimental results on oppressive and vibratory feelings due to low-frequency sound are widely
known, those studies were conducted about 40 years ago in Japan and some questions remain to be examined.
For example, “oppressive feeling” and “vibratory feeling” are generally unfamiliar terms, but it is not clear
how these terms were explained to or understood by participants. In the present study, an experiment wasconducted using a method similar to the previously reported method, and the frequency characteristics ofsound that induced oppressive and vibratory feelings were reviewed. Using one-third octave band noise withcenter frequencies ranging from 10 Hz to 630 Hz, a laboratory experiment was conducted to investigate thesound pressure level at which oppressive or vibratory feeling tended to appear for each frequency.
Participants were divided into two groups. One was provided an explanation of the meaning of oppressive
and vibratory feelings, and the other was provided no such explanation, and results were compared between
the groups. The results suggest that sound pressure levels where these feelings tended to occur were slightly
different between the two groups. Furthermore, the feelings appeared even in the higher frequency bands
compared with previous studies.
Keywords: Low-frequency noise, oppressive feeling, vibratory feeling

1. INTRODUCTION
Much research has been conducted on the evaluation of impressions of low-frequency sound.
Tokita et al. (1) reported the existence of oppressive feeling and vibratory feeling as sensations uniqueto low-frequency sound. Also, they showed the frequency characteristics of sound pressure levels thatinduced these feelings, finding that these feelings tended to occur prior to others. The results of thatstudy have been cited in various works (2-4). However, the experiments were conducted over 40 years
ago, and there appears to be room for improvement.
Given that “oppressive feeling” and “vibratory feeling” are generally unfamiliar terms, it isnecessary to adequately explain the meaning of the feelings to participants in the experiment. To ourknowledge, however, none of the previous studies has reported details of the instruction provided tothe participants. According to a report written in Japanese (5), some participants misunderstood themeaning of the “vibratory feeling”. In addition, the experiment was conducted simultaneously with 3
to 10 participants in the experimental room, so the presented sound pressure level might have slightly
differed among the participants depending on their position in the room.
In the present study, we conducted an experiment with individual participants and used a method
similar to the one in the previous report (1). Participants were divided into two groups. One wasprovided an explanation of the meaning of oppressive and vibratory feelings (explanation group), andthe other was provided no such explanation (no explanation group), and results were compared
between the groups. The purpose of this study was to provide up-to-date findings on the frequency
characteristics of sound pressure levels where oppressive or vibratory feeling tends to occur due tolow-frequency sound.
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morinaga@dfeia.or.jp

2. EXPERIMENTAL METHODS
2.1 Procedure
The experiment was conducted in an experimental room at the Kobayasi Institute of PhysicalResearch that was specially designed for investigations of low-frequency sound exposure. As shownin Fig. 1, sixteen 38-cm loudspeakers for reproducing low-frequency sound were installed in theceiling of the chamber, which had dimensions of 2.8 m (L) u2.1 m (W) u 2.2 m (H). The experimentalroom was the same as used in the previous study by Tokita et al (1). Participants were 43 adults whowere divided into the explanation and no explanation groups. The experiment was carried out for eachparticipant individually. A total of 36 kinds of stimuli were presented to the participants, and they
selected one from eight impressions shown in Table 1 that most matched with their impression to thestimulus. The explanation group used the item shown in Table 1A, and the no explanation group used
the item shown in Table 1B. The participants in the explanation group were told that oppressive feelingand vibratory feeling referred to the sensations that a part of the body (head, chest, or abdomen) isbeing compressed and vibrated, respectively. In the no explanation group, participants used the samerating item as in the previous study, and they were not given a detailed explanation of the meaning ofoppressive and vibratory feelings.

Figure 1 – Photos in the experimental room.
Table 1 – Impression rating items used for evaluating the stimuli
A: Explanation group1

Undetectable

5

Oppressive feeling in the head, chest, or abdomen2

Detectable

6

Vibratory feeling in the head, chest, or abdomen

3Annoying

7

Pain

4

Highly annoying

8

Feeling of impure

B: No explanation group1

Undetectable

5

Oppressive feeling2

Detectable

6

Vibratory feeling

3Annoying

7

Pain

4

Highly annoying

8

Feeling of impure

2.2 Stimuli
As is the previous study, stimuli were one-third octave band noise of 20 s duration. The ranges ofsound pressure level and frequency are shown in Table 2. Although these ranges were almost identical1479

to those used in the previous study, stimuli of 90 dB and 100 dB at 315 Hz and 630 Hz were excluded
because those sounds were too loud to safely present to the participants. Stimuli of 50 dB at 40 Hz
and 40 dB at 80 Hz were added.
Table 2 – Ranges of sound pressure level and frequency of the stimuli
10 Hz

20 Hz

40 Hz

80 Hz

160 Hz315 Hz630 Hz

110 dB*

100 dB

*

*

*

*

*

90 dB

*

*

*

*

*

80 dB

*

*

*

*

*

*

*

*

*

*

*

*

*

60 dB

*

*

*

*

*

50 dB

*

*

*

*

*

70 dB

40 dB

*

*

2.3 ParticipantsParticipants were 21 and 22 adults aged 20 to 69 years in the explanation group and no explanationgroup, respectively; the distributions of sex and age are given in Table 3. The participants wererecruited by telephone or e-mail through our laboratory colleagues and were students, homemakers,and working people. Having recruited widely from acquaintances of acquaintances, we assume thatthe participants are representative of the general population. Before the experiment, we conducted ahearing test using a pure-tone audiometer and calculated average hearing levels for 125 Hz, 500 Hz,
1 kHz, 2 kHz, and 4 kHz (6). All participants had an average hearing level of 25 dB or less. The World
Health Organization (7) states that a hearing level over 25 dB marks the onset of mild hearing loss.
Accordingly, we considered that all participants had normal hearing ability.
Table 3 – Distributions of age and sex of the participants
A: Explanation groupAge (years)

20-29

30-39

40-49

50-59

60-69

Male (n=10)

12

2

2

3Female (n=11)

223

3

1

Age (years)

20-29

30-39

40-49

50-59

60-69

Male (n=11)13124Female (n=11)

21

34

1

B: No explanation group

3. RESULTS & DISCUSSION
3.1 Comparison of the results between the groups
The selection rates of each feeling shown in Table 1 were calculated for each stimulus; Table 4shows the feeling with the highest selection rate for each stimulus. As in the previous study, the rateof selecting either oppressive or vibratory feeling was calculated. In the frequency range from 10 Hz
to 80 Hz, the tendency was very similar between the explanation and no explanation groups, and thefeeling with the highest selection rate was mostly the same. However, participants in the explanationgroup more frequently selected oppressive or vibratory feeling in the range of 80 dB to 100 dB at 1601480

Hz. Table 5 shows differences in the selection rate of oppressive or vibratory feeling between thegroups. Oppressive or vibratory feeling tended to be more frequently selected in the frequency range
from 10 Hz to 80 Hz by the no explanation group but in the range of 160 Hz or higher by theexplanation group,. These results suggest that whether or not an explanation of oppressive andvibratory feelings was given affected the evaluation by the participants, and it is expected that theexplanation enabled adequate evaluation of the feelings.
Table 4 – Frequency characteristics of sound pressure level for the selected feelings
A: Explanation group
10 Hz
20 Hz
40 Hz
80 Hz
160 Hz315 Hz630 Hz110 dB
O.V.
100 dB
Ann.
O.V.
O.V.
O.V.
O.V.
90 dB
Und.
O.V.
O.V.
O.V.
O.V.
80 dB
Und.
Und.
H.A.
H.A.
O.V.
O.V.
O.V.
70 dB
Und.
Ann.
Ann.
H.A.
H.A.
H.A.
60 dB
Und.
Ann.
Ann.
Ann.
Ann.
50 dB
Und.
Det.
Ann.
Ann.
Ann.
40 dB
Det.
Ann.
B: No explanation group
10 Hz
20 Hz
40 Hz
80 Hz
160 Hz315 Hz630 Hz110 dB
O.V.
100 dB
Det.
H.A.
O.V.
O.V.
O.V.
90 dB
Und.
H.A.
O.V.
O.V.
O.V.
80 dB
Und.
Und.
H.A.
H.A.
H.A.
O.V.
O.V.
70 dB
Und.
Ann.
Ann.
H.A.
H.A.
O.V.
60 dB
Det.
Ann.
Ann.
Ann.
Ann.
50 dB
Und.
Det.
Ann.
Ann.
Ann.
40 dB
Det.
Ann.
Und.: undetectable; Det.: detectable; Ann.: annoying; H.A.: highly annoying; O.V.: oppressive or vibratory
feeling.
Table 5 –Differences in the selection rate of oppressive or vibratory feeling between the groups

110 dB
100 dB
90 dB
80 dB
70 dB
60 dB
50 dB
40 dB

10 Hz
-1%
-8%
0%
0%

(explanation group minus no explanation group)
20 Hz
40 Hz
80 Hz
160 Hz315 Hz
-24%
-7%
-4%
0%

-10%
-5%
-20%
-12%
-9%
-5%

4%
-24%
-16%
1%
-14%
-5%
0%

20%
26%
25%
6%
-4%
0%

19%
10%
-4%
-5%
-9%

630 Hz

0%
0%
10%
5%

3.2 Level at which 50% of participants experienced oppressive or vibratory feeling
The sound pressure level at which 50% of participants experienced oppressive or vibratory feelingwas estimated by linear regression analysis with the sound pressure level of the stimuli as anindependent variable and the z-value of the selection rate of oppressive or vibratory feeling as thedependent variable in each octave band, and those levels were compared between the explanationgroup, the no explanation group, and the previous study (1). The results are shown in Table 6 andFigure 2. The values from the previous study shown in the table were read from the figure in thepublished report. The estimated 50% levels were different between the explanation and no explanationgroups, especially at 160 Hz. Although the 50% levels from 10 Hz to 80 Hz were almost identical in1481

the explanation group and the previous study, the results suggest that oppressive or vibratory feelingat 160 Hz may tend to occur at a lower sound pressure level when an explanation is given. Additionally,
the sound pressure level for oppressive or vibratory feeling was above the hearing threshold specified
in ISO 226, and a similar tendency is also shown in Table 4.
Table 6 – One-third octave band level at which 50% of participants experienced oppressive or vibratory
feeling: Comparison between the explanation group, the no explanation group, and the previous study
Previous study
[dB]
105
93
78
84
96

Explanation group
[dB]
105
93
79
82
83

㻿㼛㼡㼚㼐㻌㼜㼞㼑㼟㼟㼡㼞㼑㻌㼘㼑㼢㼑㼘㻌㼇㼐㻮㼉Center frequency of1/3 octave band [Hz]
1020
4080
160

No explanationgroup [dB]
104
89
75
77102

㻴㼑㼍㼞㼕㼚㼓㻌㼠㼔㼞㼑㼟㼔㼛㼘㼐㻧㻌㻵㻿㻻㻌㻞㻞㻢㻌㻔㻞㻜㻜㻟㻕㻰㼑㼠㼑㼏㼠㼕㼛㼚㻌㼠㼔㼞㼑㼟㼔㼛㼘㼐㻌㼕㼚㻌㻾㼑㼒㻚㻌㻝㻻㼜㼜㼞㼑㼟㼟㼕㼢㼑㻌㼛㼞㻌㼢㼕㼎㼞㼍㼠㼛㼞㼥㻌㼒㼑㼑㼘㼕㼚㼓㻌㼕㼚㻌㻾㼑㼒㻚㻌㻝㻱㼤㼜㼘㼍㼚㼍㼠㼕㼛㼚㻌㼓㼞㼛㼡㼜㻺㼛㻌㼑㼤㼜㼘㼍㼚㼍㼠㼕㼛㼚㻌㼓㼞㼛㼡㼜㻻㼚㼑㻙㼠㼔㼕㼞㼐㻌㼛㼏㼠㼍㼢㼑㻌㼎㼍㼚㼐㻌㼏㼑㼚㼠㼑㼞㻌㼒㼞㼑㼝㼡㼑㼚㼏㼥㻌㼇㻴㼦㼉Figure 2 – Comparison of the results between the present study and the previous study with the ISO 226
hearing threshold shown for reference (8)4. CONCLUDING REMARKS
Studies of oppressive and vibratory feelings were conducted more than 40 years ago, and theirfindings have been used in various surveys. For example, the findings are often used for environmental
assessment of low-frequency sound in Japan. However, as shown in the present study, the resultschange depending on how the participants understand the terms “oppressive feeling” and “vibratoryfeeling”. We interviewed the participants in the no explanation group after the experiment and asked
them how they envisioned the terms of oppressive feeling and vibration feelings. Rather thansensations that a part of the body was compressed or vibrated, almost half of the participants regarded
the feelings as an auditory impression such as “sounds that are trembling” or “sounds that can beheard underwater”.

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The results for the explanation group were obtained after providing appropriate instruction, while
improving some experimental issues. A novel finding of this study is that oppressive or vibratory
feeling at 160 Hz tends to occur at lower sound pressure levels compared with estimates from theprevious study. In the future, we plan to perform further experiments after examining othermethodological issues

REFERENCES
1. Tokita Y., Nakamura S. Frequency weighting characteristics for evaluation of low frequency sound. Proc
Inter-Noise 1981; 6-8 October 1981; Amsterdam, The Netherlands 1981.
2. Hodgdon K.K., Atchley A.A., Bernhard R.J., PARTNER Low-frequency Noise Study, 2007.
3. Sharp B.H., Beeks T., Veerbeek H. Groundnoise Polderbaan overview of results, A joint Wyle, TNO andNLR Report. Wyle Report 06-02, Wyle Laboratories 2006.
4. George F, Hessler Jr. A Note on the Debate about Health Effects from Low Frequency Noise (LFN) from
Modern Large Wind Turbines. Proc Wind Turbine Noise; 12-14 April 2011; Rome, Italy 2011.
5. Ishii S, Sone T, Okai O, Tokita Y, Nakamura S. A report of the research on physiological andpsychological effects and evaluation of infrasound. Japanese Ministry of Education & Science ResearchFund, Scientific Research, Special Research, 1980. (in Japanese)
6. ISO 389-8: 2004, Acoustics-Reference Zero for the Calibration of Audiometric Equipment- Part 8:
Reference Equivalent Threshold Sound Pressure Levels for Pure Tones and Circumaural Earphones
Geneva, Switzerland 2004.
7. World Health Organization. Community-Based Rehabilitation: Promoting Ear and Hearing Care Through
CBR, Copenhagen, Denmark 2012.
8. ISO 226: 2003, Acoustics-Normal equal-loudness-level contours, Switzerland 2003.

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