Introduction of latest technology for sound-absorbing materials

Sound-absorbing materials, sound-absorbing material mostly porous materials, such as slag wool, blankets and so on, its
sound absorption mechanism is the acoustic depth the porosity of the material, and the porosity mostly through openings
inside each other, by the friction of air molecules and the viscous resistance and make fines for mechanical vibrations,
so that the sound energy into heat energy. The absorption coefficient of such porous sound-absorbing material, generally
from low to high frequency increases, so the high-frequency and intermediate frequency sound absorption effect is good.
The following Xiaobian to introduce the relevant knowledge of sound-absorbing material.

Principle of sound-absorbing material

Sound from the vibrating object, which causes vibration of the adjacent air to form sound waves in the air and spread to
the surrounding medium.

When the sound incoming surface member, a part of the sound energy is reflected, part of the barrier material, since there
is a vibration member or material in which the sound propagation friction with the surrounding medium, the sound energy
into heat energy, sound energy loss , known as the sound is absorbed by the material.

Sound absorption coefficient

Sound absorption performance is good or bad, with the absorption coefficient expressed. for the absorption loss
coefficient E / E0 penetration coefficient and E through / E0 sum.

In addition to sound-absorbing properties of the material and structure, thickness and surface characteristics of the
material related to the material itself, but also the direction of incidence and frequency of the sound and relevant.

Application of sound-absorbing material

First, indoor quality control of the construction sector

In general, the larger the volume of the room, the longer the reverberation time, speech intelligibility worse, in order
to ensure clarity of language, we need to do in the room sound absorption, reverberation time control. Such as auditorium,
classrooms, sports arenas, movie theaters.

Music by buildings, in order to ensure a certain degree of fullness, longer than the reverberation time, but not too long,
can be used to control sound absorption.

In the halls of the building, in order to prevent echoes, acoustic feedback, and other acoustic sound focusing defects,
often in the walls, floor balcony railing table surface, side walls and topical absorption.

Second, sound absorption

In the workshops, factories, large open-plan space (the airport lobby, offices, exhibition halls, etc.), due to the
reverberant sound reasons, will make the same noise ratio of the sound source in the outdoor high 10-15dB. By arrangement
of sound-absorbing material in the room, you can make reverberant been siphoning off to reduce interior noise.

Acoustic noise reduction can be obtained up to 10-15dB of noise reduction. Noise reduction = 10lg (A0 / A1), when no
sound-absorbing material is added, the less indoor sound absorption, the more interior sound absorption after adding
sound-absorbing material, the better the noise reduction.

Third, the air conditioning system

Cause building noise is varied, the noise generated by the operation of the air conditioning system in which in turn
accounts for a sizeable proportion. How to reduce the noise generated in the HVAC system operation is particularly
important for the study of sound-absorbing materials to improve the acoustic environment in terms of the building.

1, ways and means of HVAC systems Noise

1.1 System design

With the air conditioning of new technologies, new processes, new materials continue to emerge, so that we can achieve the
purpose of noise reduction system run by a variety of methods. Noise control technology often used in cotton insulation,
sound-absorbing cotton, sound insulation blankets, insulation blankets, sound-absorbing panels sound-absorbing materials,
mainly in the noise source, noise propagation and acceptance point on the way to the control and processing.

Air conditioning systems, especially central air conditioning system is a large and complex system. System design will
directly affect the performance of the system. To choose high efficiency and low noise fan, so that the operating point at
or near the fan efficiency point. When the system a certain amount of wind, the safety factor selected the fan head should
not be too large, use the blower fan and share the burden back to the system's total resistance if necessary. When
conditions permit, increase the supply air temperature to reduce fan flow, thereby reducing the fan impeller outer
periphery of the linear velocity, noise generated by the fan also will be reduced.

1.2 Design and selection of sound-absorbing material

During noise reduction, we need a sound-absorbing material. Design and installation of insulation materials is an
important measure to control airflow to spread through the media noise barriers pipes and the like. A good performance
cotton insulation, can reduce airflow noise 20 ~ 40dB. According muffler noise source needed, aerodynamic performance, and
different environments, choose a different type of muffler. According to sources of noise aerodynamic performance
requirements, consider the aerodynamic performance of sound-absorbing cotton, cotton insulation the resistance loss of the
equipment can be controlled within the range of normal work. Design of sound-absorbing materials should be considered when
airflow muffler may have regenerating influence of noise, so that the muffler flow noise level is lower than the ambient
noise level allowed for the operation of HVAC systems is the main source of noise in the low-frequency-based fan using
resistive or impedance composite insulation panels can play a better silencing effect.

1.3 vibration isolation measures

1.4 Noise control room equipment

1.5 avoid improper construction noise

2, Problems and Solutions

2.1 HVAC system design and management issues

2.2 New technologies, new processes, development and promotion of the application of new materials

Encourage the development of research and development of new technologies, new processes, new materials, and actively
applied to the actual project. As conditions permit the cold air distribution technology to develop, promote composites
ventilation ducts, the new sound-absorbing insulation material (such as plant cellulose, etc.) in Engineering Application.



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