Engineering Group, Division 1
Ryoki Fukatsu
In our daily lives, we often experience "noise" and "vibration. When these are small, they are not a problem, but when they become large, they can affect people's physical and mental health, such as causing stress or health problems. Sometimes they can develop into pollution problems, with far-reaching and serious consequences.
In this issue, we will briefly discuss noise and vibration as perceived by humans, focusing on the differences between the two.
What is "noise" and "vibration"?
Noise and vibration are both waves (waviness), but with different properties.
noise
- Waves that travel mainly through air as vibrations
- The range of sound that humans perceive (can hear) is approximately 20-20,000 Hz (Hertz)
- Main noise sources: daily life noise, traffic noise, construction noise, etc.Unpleasant and undesirable sounds
vibration
- Waves that travel mainly through solids such as ground and buildings
- The range of vibrations that are easily felt by the human body (perceived as shaking) is approximately 1 to 100 Hz (hertz).
- Main vibrations: Vibrations caused by natural phenomena (wind, earthquakes), traffic vibrations, machine vibrations, construction vibrations, walking vibrations, etc.Unpleasant and undesirable vibrations
Sensory evaluation of noise and vibration
How should we evaluate the actual noise and vibration?
This section describes how to evaluate noise and vibration as perceived by people.
Noise Level
For noise rating,Noise Levelfor the following reasons.
The sound pressure level is a logarithmic representation of the pressure (sound pressure) caused by sound in the air, with a weighting called the "A characteristic" (Figure 1) that takes into account the sensitivity of the human ear. The sound pressure level is calculated by formula (1).
Figure 1. frequency weighting characteristics of sound (flat characteristics refer to sound pressure level characteristics)
Table 1 shows the approximate noise levels. A noise level of 45 dB or less is considered a standard for a room in a typical apartment complex.
Table 1. approximate noise level
| Noise level (dB) | Assumed location |
| 80~90 | Inside pachinko parlors and game arcades |
| 70~80 | In airplanes, on trains, around major highways, cicadas |
| 60~70 | Shinkansen bullet trains, buses, coffee shops, family restaurants |
| 50~60 | Around bank counters, in museums, around government office counters, in bookstores |
| 40~50 | High-rise residential area (daytime), quiet office, cemetery (daytime), in museum, detached residential area (daytime), in library |
| 30~40 | High-rise residential area (at night), detached residential area (at night), hotel rooms |
Vibration Level
For vibration evaluation,Vibration Levelfor the following reasons.
The vibration level is the vibration acceleration level, which is the logarithmic representation of the acceleration of vibration, with a frequency correction (Figure 2) that takes into account human vibration sensation. The vibration sensory correction differs for the vertical and horizontal directions, respectively.
As with noise, the unit is expressed in decibels (dB), but sound is expressed in logarithms of pressure (Pa), whereas vibration is expressed in logarithms of acceleration (m/s).2) that are measured in logarithmic form are different from those that are measured at all.
Vibration acceleration levels are calculated by Equation (2).
Figure 2: Frequency weighting characteristics of vibration
Table 2 shows the approximate vibration levels.
Table 2. vibration level guidelines
| Vibration level (dB) | sense of people |
| 110~ | Cannot act of their own volition. |
| 105~110 | Difficulty in standing |
| 95~105 | Feeling extremely fearful, many people try to protect themselves. |
| 85~95 | Quite a sense of fear, some people try to protect themselves. |
| 75~85 | Most people indoors feel the tremors. |
| 65~75 | Many people indoors feel the tremors. |
| 55~65 | Some people indoors feel a slight tremor |
| ~55 | People are less likely to feel shaking. |
How to measure noise and vibration
This section describes how to actually measure the loudness of sound and vibration and the differences between them.
How to measure noise levels
- Measuring equipment: Sound level meter
- Measurement position: At least 1.2 to 1.5 m above ground level, at least 1 m away from walls, etc.
- Measurement unit: Noise level decibel (dB)
- Measurement standard: Based on JIS Z 8731:1999 Environmental noise indication and measurement method
- Time constant: Fast (125ms), Slow (1s)
Figure 3. measuring instrument (sound level meter)
How to measure vibration levels
- Measuring equipment: Vibration level meter
- Measurement position: Directly on the ground or floor
- Unit of measurement: Vibration level decibel (dB)
- Measurement standard: Based on JIS Z 8735:1981 Vibration Level Measurement Method
- Time constant: 630 ms
Figure 4: Measuring equipment (Vibration level meter, right: sensor)
References
New Pollution Prevention Techniques and Laws 2025 Noise and Vibration Edition Pollution Prevention Techniques and Laws Editorial Board
JMA seismic intensity class related commentary table