RU2030525C1 - Method for noise insulation - Google Patents

Abstract

FIELD: noise insulation. SUBSTANCE: method for noise insulation provides for use of multilayer reflector with channels 3 formed by plates 1 and 2 of reflector. Gas or liquid is pumped through channels 3 to increase effect of sound insulation. As coefficient of passage of sound wave in moving medium is less than that in medium at rest, pumping of gas or liquid through channels 3 results in increased effect of sound insulation. EFFECT: higher efficiency. 3 dwg

Description

 The invention relates to construction and can be applied to reduce acoustic noise in industrial premises, in land, air and water vehicles.

 A known method of isolating noise by reflecting sound waves with a single-layer fence [1].

 The disadvantage of the noise isolation method is its insufficiently high efficiency.

 Closest to the technical nature of the proposed is a method of noise isolation by reflecting sound waves with a multilayer fence [2].

 The disadvantage of this method of noise isolation is that the improvement of sound insulation is achieved mainly by increasing the mass of the fence.

 The purpose of the invention is to increase the effect of sound insulation.

 This is achieved by the fact that in the method of isolating noise by reflecting sound waves with a multilayer fence, it is new that through the channels formed by the fencing plates, gas or liquid is pumped.

 In FIG. 1 shows a device that implements the proposed method; in FIG. 2 - calculation model; in FIG. 3 - dependence of sound insulation ΔL of a polystyrene layer with a thickness of d = 50 mm on the frequency of sound waves at various speeds of pumping gas (air) through the channels.

 The device consists of insulating plates 1 and 2, channels 3 and a pumping device. The pumping device may consist of a compressor, a circulation pump, or a similar device providing high speeds for pumping gas or liquid.

 The noise isolation method is as follows.

The channels 3 formed by the plates 1 and 2 of the fence carry out the pumping of gas, in particular air or liquid. Sound waves falling on plate 1 from a medium with parameters ρ ₃ (density) and C ₃ (speed of sound in a medium) at an angle θ ₃ partially reflect and partially penetrate into channel 3 with medium parameters ρ ₂ , C ₂ and fall under angle θ ₂ on the plate 2 of the fence, which is also partially reflected, and partially penetrate into the insulated medium with parameters ρ ₁ , C ₁ . The process of passage of sound waves through a moving medium with parameters ρ ₂ , C ₂ is associated with a significant decrease in sound intensity. This is due to the following fact.

,
где V - коэффициент отражения;
Z₁=

- импеданс в среде с параметрами ρ₁С₁;
Z₂=

- импеданс в среде с параметрами ρ₂, С₂;
Z₃=

- импеданс в среде с параметрами ρ₃, С₃;
α₂=

;
k₂= ω /C₂ - волновое число;
ω - круговая частота;
М_i=U/C_i - число Маха в среде;
U - скорость движущейся среды.For a moving medium, the transmission coefficient has the form W = 1 + V:
V =

,
where V is the reflection coefficient;
Z ₁ =

- impedance in a medium with parameters ρ ₁ С ₁ ;
Z ₂ =

- impedance in a medium with parameters ρ ₂ , C ₂ ;
Z ₃ =

- impedance in a medium with parameters ρ ₃ , C ₃ ;
α ₂ =

;
k ₂ = ω / C ₂ is the wave number;
ω is the circular frequency;
M _i = U / C _i is the Mach number in the medium;
U is the speed of the moving medium.

= 20lg·

Исходя из этого, был проведен расчет модели, представленной на фиг. 2. Между плитами из полистирола толщиной d=50 мм движется поток воздуха со скоростью U. Звук падает на плиту 1 под углом θ=70^о. Результаты расчета приведены на фиг. 3. Сплошной чертой на фиг. 3 показана звукоизоляция Δ L многослойной конструкции при U=0. Пунктирной чертой показана звукоизоляция при U=33 м/с. Пунктирной чертой с точками - звукоизоляция при U=165 м/с.Sound insulation of any design is expressed through the ratio of the intensity I _{1 of the} sound falling on the obstacle and the intensity I _{2 of the} sound passing through it,
ΔL = 10lg

= 20lg

Based on this, the calculation of the model shown in FIG. 2. Between the plates of polystyrene thickness d = 50 mm moves air flow of U. sound falls on the plate 1 by an angle θ = ⁷⁰ °. The calculation results are shown in FIG. 3. The solid line in FIG. 3 shows the sound insulation Δ L of a multilayer structure at U = 0. The dashed line shows sound insulation at U = 33 m / s. The dotted line with dots is sound insulation at U = 165 m / s.

 As follows from the above graphs, with an increase in the air pumping rate, an increase in sound insulation is observed in the entire frequency range under consideration.

Claims (1)

 METHOD FOR NOISE ISOLATION by reflection of sound waves by a multilayer fence with channels formed by fencing plates, characterized in that gas or liquid is pumped through the said channels.

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