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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 ¦Á 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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