Picture 5.png

1. Noise pollution

In recent years, in the complaints received by the environmental protection department every year, the elevator noise detection is up to standard but is considered to affect normal life, accounting for about 35% of the noise complaints.

In the face of more and more serious low-frequency noise pollution, relevant experts told reporters that in the past, China's cities focused more on the treatment of water, gas and garbage pollution, often ignoring the sound pollution. Now, more and more people realize that noise is also harmful to human health, which is a cause of disease.

2. What is low frequency noise?

Low frequency noise, the frequency is read in Hz, low frequency noise refers to the frequency below 500 Hz (octave band). In the range of human ear, it is low frequency from 20Hz to 500Hz, that is to say, the irregular sound produced by shaking 20 to 500 times in a second is called low frequency noise.

As early as the early 1990s, low-frequency noise has quietly begun to affect people's lives.

Elevators in high-rise buildings, heavy and low-metal sound in entertainment places in residential areas, and transformers and pumps moved into residential buildings have become the "culprits" of low-frequency noise.

"It's also 70 decibels of sound, 100 Hz and 1000 Hz, and the human ear senses different sounds," said an environmental acoustics expert at Fujian environmental monitoring center. The natural frequency of organs in the human body is basically in the range of low frequency and ultra-low frequency, which is easy to resonate with low-frequency sound, so people will worry and feel uncomfortable. "

However, the current domestic acoustic environment quality standards and monitoring methods are only for the detection of high-frequency noise, and there are no complaints about low-frequency noise caused by transformers, elevators, central air conditioning and "subwoofers" installed in the building. However, the environmental protection department is unable to control the low-frequency noise pollution due to the lack of law enforcement basis and the support of punishment standards.

3. Transmission way of low frequency noise

The low-frequency noise can be divided into structural, air and standing waves.

Structural sound transmission refers to that the elevator host, transformer, water pump and central air conditioning host installed in the building transmit the low-frequency vibration sound wave to each household through the basic structure beam and bearing beam of the residential building.

Air borne noise refers to the low-frequency noise directly transmitted to the residential area through the air.

Standing wave refers to the standing wave formed by multiple reflections during the propagation of low-frequency noise. The amplitude of low-frequency noise in the wave belly is the strongest, and it is the most harmful to human health.