Music and noise

How to distinguish between music and noise? It is all based on personal subjective judgment. A good sound is music, and noise is a bad sound. Therefore, even a beautiful piano performance may become noise in the ears of others in the middle of the night.

The intensity of the noise (decibel, dB)

Decibel is a unit used to express the intensity of sound, recorded as dB. Noise pollution has become a prominent problem in society. According to the survey, every decibel increase in noise level increases the incidence of high blood pressure by 3%, which affects the nervous system and makes people impatient and irritability. It is difficult for a person to fall asleep, and occasional and excessive noise can wake people up during sleep, which can disrupt sleep, cause sleep deprivation or feel tired. Sounds of 40-50 decibels can interfere with sleep, 60-70 decibels can interfere with learning, and noises above 120 decibels can cause earaches and even permanent hearing loss.

Frequency weighting, A weighting, C weighting, D weighting, G weighting

The human ear is a very special organ. In order to convert the noise signal measured by the noise instrument into the amount of noise heard by the human ear, it is necessary to perform frequency domain weighting or weighting on the signals measured by the noise instrument in different frequency domains. The audible range of the human ear is 20-20K hertz (Hz), and the human ear has different weighting curves (Weighting Curve) for different sound intensities

The most common weighting curve is A-Weighting, C-Weighting is generally used to measure noisy mechanical noise, D-Weighting is generally used to measure aviation noise, and G-weighting is used to measure ultra-low-frequency noise, most of which are structural noise caused by low-frequency vibrations.

Time weighting: Fast, Slow, Impulse

When using a noise meter to measure noise, it is necessary to select an appropriate time weighting (or dynamic characteristic) for the noise characteristics. Generally, the slow characteristic (SLOW) is used for stable noise, and the fast characteristic (FAST) is used for rapidly changing noise. For impulsive noise, the IMPULSE feature is used.

Residential acoustic design purpose

Sound is invisible, it cannot be seen by the eyes or touched by the hands. It can only be heard by the ears or felt by the body. The feeling of sound is subjective. A beautiful sound is called music, while a bad sound is called noise, so architectural acoustic design generally has the following items:

1. In the initial design stage, it is necessary to consider the appropriate volume of the room in the future, so as to avoid interference from external and internal equipment noise.

2. Make the residence have a good acoustic environment (work, rest, sleep, entertainment) and the privacy of the residents.

3. To avoid future impact, it will take several times the time and cost to deal with the aftermath, or even be unable to deal with it.

4. Improve the sound environment quality of the residence and enhance the value of the residence.

5. Comply with domestic regulations (noise control standards).

Residential acoustic performance evaluation projects

There are many sources of residential noise, including outdoor traffic, machinery, construction, indoor equipment, vibrations on upper and lower floors, etc. The most effective way to improve noise is to remove the "noise source" or "block it" on the "sound transmission path".  Therefore, the overall acoustic performance evaluation items of the residence include:

1. The sound insulation performance of the partition wall.

2. Sound insulation performance of exterior wall openings.

3. Floor impact sound insulation performance.

4. Electromechanical and pipeline equipment sound insulation performance.

Indoor noise criterion (NC) curve

Generally, the evaluation of indoor noise is usually represented by the measurement of the A-weighted total noise, which can be used in the preliminary evaluation, but in actual engineering applications, the A-weighted total noise is used as the design specification or acceptance. However, the standard is a little too loose, and a more appropriate evaluation should use the "noise criterion curve" evaluation method.