People feel and perceive various stimuli.
Sound is perceived primarily by the sense of hearing. Vibrations are perceived by the cutaneous sense, the sense of balance, as well as by sight and hearing.
Sound and vibration are periodic in units of frequency (or frequency of oscillation). Figure 1 shows the frequency range of common vibrations and sounds.
Figure 1 Frequency range of vibration and sound
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(1) Frequency (frequency)
The number of times a periodic phenomenon is repeated in one second.
The unit is Hz (hertz). There is a relationship T = 1/f between the period T (seconds) and the frequency f (Hz).
(2) Low frequency sound area (very low frequency sound area)
Refers to sounds with a frequency of 100 Hz or less.
Loud sounds are not only noisy, but can also cause fittings to shake and people to experience unpleasant symptoms such as headaches, insomnia, and dizziness. In addition, sounds below 20 Hz, a frequency normally inaudible to humans, are sometimes referred to as the very low frequency range.
(3) Human audible range area
Sounds between 20 Hz and 20,000 Hz are usually considered the range that people can hear. Some people may hear sounds at even lower or higher frequencies. All common noise problems refer to sounds in this region.
(4) Ultrasound field
Sounds with frequencies above 20,000 Hz. Sound too high to be heard by normal people. No effect on humans.
(5) Solid propagating sound region
Refers to sound that is transmitted through a solid as vibration and radiated as sound by vibrating objects such as floors, walls, and ceilings.
In general, higher frequency vibrations are less easily converted into solid sound, with frequencies ranging from 20 Hz, the lower limit of the human audible range, to about 500 Hz, unless the vibration is very loud.
(6) Wind vibration
Wind vibration, which is handled in Environmental Vibration, refers to horizontal vibrations that occur on building floors when wind strikes a high-rise building. Generally, the frequency is about 0.1 Hz to 1.0 Hz※ 1for the purpose of this project.
1 Goto and Hamamoto: Easy-to-understand knowledge of environmental vibration, p. 76
(7) Seismic motion
Ground motion caused by earthquakes. It has a unique period depending on the ground. Spectra of recent typical earthquakes have 0.1 Hz to 10 Hz components※2The following is located in the
2 Japan Meteorological Agency, Ministry of Land, Infrastructure, Transport and Tourism HP: Spectrum of seismic waves
https://www.data.jma.go.jp/eqev/data/kyoshin/kaisetsu/outou.html
(8) Plant and traffic vibration
Vibration frequencies vary depending on the type of train, car, or machine in operation, but in general, vibrations of frequencies between 1 Hz and 60 Hz*3 are the main types of vibration.
3 Goto and Hamamoto: Easy-to-understand knowledge of environmental vibration, p.65~70
(9) Pollution and vibration
The frequencies of concern as pollution are 1 Hz to 90 Hz*4It is considered to be a
4 Ministry of the Environment: Environmental White Paper Fiscal 1972, Chapter 5, Section 1
(10) Microvibration area
Although small vibrations are not a problem for humans, they are a problem for machines (precision instruments) such as electron microscopes, where even small vibrations can be problematic.
of tolerance standards for precision machinery.VC Standardis 1 to 80 Hz, but the frequency range varies in specifications for precision machinery.