Which type of window should be chosen for good sound insulation?

I. Don't mistake high-frequency/low-frequency noise

Low-frequency noise is a relatively special type of sound. Defining it as the sound with a vibration frequency below 500Hz is a more accurate description, and the range of 20Hz - 500Hz specified in China more specifically defines the frequency range of low-frequency noise. This means that within this range, the irregular sounds generated by 20 to 500 vibrations per second all fall within the category of low-frequency noise.

For example, in a building, high-frequency noise may be blocked by walls, doors, and windows, and the sound is significantly weakened. However, low-frequency noise can easily penetrate the walls, like an invisible force, continuously affecting the indoor environment. Sounds such as the operation of the external units of large air conditioners and the low-frequency rumbling of vehicles on the traffic road can still be clearly heard even after a certain distance and the obstruction of buildings. This is a typical manifestation of the difficulty of low-frequency noise attenuation. This characteristic makes low-frequency noise a relatively difficult noise problem to deal with, continuously interfering with people's living and working environments.

The attenuation characteristic of high-frequency noise during the propagation process is very obvious. When it travels further or encounters obstacles, its energy will be quickly dispersed and consumed. Just as mentioned before, for every doubling of the propagation distance, the noise will attenuate by 6dB, which is a very important measurement standard.

Take an example from daily life. The sound of walking is a typical representative of high-frequency noise. When we walk, the sound generated by the contact between our shoes and the ground is mainly composed of high-frequency components. When this sound propagates in a relatively open area, as the distance increases, the sound heard by the people around will become smaller and smaller. If there are obstacles such as walls in between, the weakening of the sound will be even more significant.

Unlike high-frequency noise, low-frequency noise will not change significantly due to the increase in distance, which enables it to still maintain a strong influence at a relatively far distance. For example, in a building, even if the elevator machine room is located on the top floor, the low-frequency "buzzing" sound generated when the elevator is running can spread to the lower floors along the building structure, allowing the residents on other floors to hear it. It can easily penetrate obstacles such as walls and floors. This strong penetrating power makes low-frequency noise a very thorny problem in sound insulation treatment.