CN101521008B - Active sound-absorption taper and manufacture method thereof - Google Patents

Abstract

The invention discloses an active sound-absorption taper and a manufacture method thereof. The active sound-absorption taper comprises a conventional sound-absorption taper, a control source, a power amplifier, a controller and an error sensor; the error sensor placed in a sound field is arranged at the front end of the conventional sound-absorption taper, and is connected with the controller; thecontroller is connected with the control source through the power amplifier; and the control source is arranged at the rear end of the conventional sound-absorption taper. The manufacture method take s the cut-off frequency of the conventional sound-absorption taper as a boundary, improves low-frequency sound absorption of the conventional sound-absorption taper through the active control using reflected sound, and forms broadband sound absorption. Compared with the conventional sound-absorption taper with similar sound-absorption performance, the active sound-absorption taper has shorter length and obvious volume advantage.

Description

Active sound-absorption taper and preparation method thereof

Technical field

The present invention relates to a kind of wedge absorber, specifically a kind of active sound-absorption taper that active control improves traditional wedge absorber low frequency absorption performance and preparation method thereof that utilizes.

Background technology

Wedge structure extensively is used in the construction between anechoic room and noise elimination, and need in the pipeline of full sound absorption terminal, wedge length is determined according to the wavelength of desired low-frequency minimum frequency, wedge is long more, cutoff frequency is low more, the length of wedge increases to be compared with the reduction of cutoff frequency, frequency is low more, cost is big more, become the hyperbolic curve rule to change, this rule makes wedge have certain space constraint in application, and the length that reduces wedge under the prerequisite that does not reduce the Wedge structure sound absorbing capabilities has great value to above-mentioned application.Active control low-frequency effect is good, thereby active control and tradition sound absorption can be combined and realize more wide band sound absorption.The mixing sound absorption that is similar to the passive combination of this master mainly contains: relief method (Cobo P, Fernandez A, and Doutres O.Low frequencyabsorption using a two-layer system with active control of input impedance.J.Acoust.Soc.Am.114 (6), 3211-3216,2003.) and impedance match method (Beyene S, Burdisso R A.A New Hybrid Passive-Active Noise Absorption System, J.Acoust.Soc.Am.101 (3), 1512-1515,1997.).Said method is primarily aimed at the systematicness acoustic absorbant, and relief method is to acoustic absorbant thickness sensitivity, is difficult for using during for wedge at acoustic absorbant; Impedance matching rule requirement acoustic absorbant flow resistance can not be very big; When therefore acoustic absorbant is wedge, all can not meet above two kinds of theories fully.Prior art does not have the wide band mixing sound absorption at wedge absorber as yet.

Summary of the invention

The purpose of this invention is to provide a kind of active sound-absorption taper and preparation method thereof, this active sound-absorption taper utilizes active control to improve traditional wedge absorber low frequency absorption performance, the present invention utilizes active control to the compensating action of wedge absorber to low frequency absorption, with active guidance system and the integrated active sound-absorption taper of traditional wedge absorber, more in the broadband higher sound absorbing capabilities is being arranged than former wedge; And length is shorter, and volume is with the obvious advantage.

The objective of the invention is to be achieved through the following technical solutions:

A kind of active sound-absorption taper, it is characterized in that: this active sound-absorption taper comprises traditional wedge absorber, Controlling Source, power amplifier, controller and error microphone, is placed on error microphone in the sound field and is arranged on the front end of traditional wedge absorber and is connected with controller; Controller is connected with Controlling Source by power amplifier, and Controlling Source is arranged on the rear end of traditional wedge absorber.

Among the present invention, described error microphone is two microphones.Described controller is the digital signal processing integrated circuit plate, and this surface-mounted integrated circuit is placed on the Controlling Source rear end with power amplifier.

A kind of method for making of active sound-absorption taper is characterized in that: this method is boundary with traditional wedge absorber cutoff frequency, improves traditional wedge absorber low frequency absorption by the active control of having used reflected sound, forms the sound absorption in broadband; May further comprise the steps:

A) with two microphones as error microphone, error microphone is arranged on traditional wedge absorber front end, the sound pressure signal of the two microphone collections controller of feeding respectively calculates incident sound pressure p _i(t) conduct is with reference to signal;

B) open Controlling Source separately, with the reflected sound p of LMS (Least Mean Squares) algorithm to calculating _r(t) modeling obtains the secondary channel transport function;

C) primary source and Controlling Source are opened simultaneously, with the secondary channel transport function that obtains, to the reflected sound p that calculates _r(t) approach with FXLMX (Filtered-X Least Mean Squares) algorithm algorithm, making it is zero, controlled device parameter.

Among the present invention, incident sound pressure p _i(t) and reflected sound p _rBeing calculated as follows (t):

If the microphone standoff distance is d, the signal that two microphones pick up is respectively p ₁(t) and p ₂(t), that close primary source is p ₁(t); If between two microphones apart from d much smaller than institute's controlled frequency scope sound wave minimum wavelength, but then between two microphones acoustic pressure approximate representation of intermediate point be:

$p\left(t\right)=\frac{p_1\left(t\right)+p_2\left(t\right)}{2}---\left(1\right)$

But some particle velocity approximate representations are in the standing wave tube:

$u\left(t\right)=u_0+\frac{1}{{\mathrm{\ρ}}_{0}d}\underset{0}{\overset{t}{\∫}}(p_1\left(t\right)-p_2\left(t\right))\mathrm{dx}---\left(2\right)$

In the formula, u ₀Be the particle velocity initial value, ρ ₀Be atmospheric density; And below cutoff frequency, the particle velocity of pipeline midplane ripple can be expressed as again

$u\left(t\right)=\frac{1}{{\mathrm{\ρ}}_0{c}_0}(p_i\left(t\right)-p_r\left(t\right))---\left(3\right)$

In the formula, c ₀Be the velocity of sound, the acoustic pressure of intermediate point also can be expressed as again between the microphone:

p(t)＝p _i(t)+p _r(t) (4)

In conjunction with (3), (4) two formulas, can calculate incident sound pressure and reflecting acoustic pressure

$p_i\left(t\right)=\frac{1}{2}(p\left(t\right)+{\mathrm{\ρ}}_0{c}_{0}u\left(t\right)),p_r\left(t\right)=\frac{1}{2}(p\left(t\right)-{\mathrm{\ρ}}_0{c}_{0}u\left(t\right))---\left(5\right)$

P in the formula (t) and u (t) are obtained with 2-microphone sound by formula (1) and (2).

The invention has the beneficial effects as follows: utilize active control to wedge absorber to the low frequency absorption compensating action, combine with traditional wedge absorber by active guidance system, integrated active sound-absorption taper is more having higher sound absorbing capabilities in the broadband than former wedge; And compare with the traditional wedge absorber with close sound absorbing capabilities, length of the present invention is shorter, and volume is littler.

Adopt the present invention, with the performance of the long active sound-absorption taper of the integrated 40cm of the long sponge wedge of 20cm and active system, suitable with the wedge absorber performance of the length of the about 80cm of tradition.

Description of drawings

Fig. 1 is the structural representation of active sound-absorption taper of the present invention;

Fig. 2 is an experimental situation synoptic diagram of the present invention;

Fig. 3 is the acoustical absorption coefficient spectrum of the wedge of the apneusis cotton wedge of sound of 40cm when active control is opened and closed;

Fig. 4 is the acoustical absorption coefficient spectrum of the wedge of the continuous wedge in 20cm Changhai when active control is opened and closed.

Embodiment

The present invention will be described with reference to accompanying drawing below by example:

A kind of active sound-absorption taper of the present invention, see Fig. 1, this active sound-absorption taper comprises traditional wedge absorber 1, Controlling Source 2, power amplifier 3, controller 4 and error microphone 5, is placed on error microphone 5 in the sound field and is arranged on the front end of traditional wedge absorber 1 and is connected with controller 4; Controller 4 is connected with Controlling Source 2 by power amplifier 3, and Controlling Source 2 is arranged on the rear end of traditional wedge absorber 1.Error microphone 5 is two microphones.Controller 4 is DSP evaluation board, and this DSP evaluation board is provided with Controlling Source 2 rear ends with power amplifier 3.

A kind of method for making of active sound-absorption taper of the present invention adopts a rectangular duct as implementing environment, and the position of elementary sound source, Controlling Source, wedge absorber, error microphone and measuring microphone position are as shown in Figure 2.

The acoustical absorption coefficient of active wedge end is measured with transfer function method.Use B﹠amp; The microphone of K PLUSE7700 system and model 4190 is used for the measurement of acoustical absorption coefficient spectrum; The ADSP-21161N series DSP evaluation board of AD company, as the controller of signal generator and realization FXLMS algorithm, measuring-signal is a white noise.Selected the microphone of the model 40AE of G.R.A.S. company in addition for use, the microphone preamplifier of model 26CA, the signal conditioner of the model 482A16 of PCB company are used for Acquisition Error signal and the power amplifier of Classic board model 8.0B.The error microphone spacing is 6cm, and error microphone is 60cm to the distance of wedge absorber substrate, Controlling Source and the about 3cm of wedge absorber substrate distance.Adopt white noise to test in the experiment.The experiment frequency range is defined as 100～1000Hz, and what propagate in this frequency range pipeline is plane wave, and can measure more accurately.

Two microphones are as error microphone, and error microphone is at the wedge front end, and the sound pressure signal of the two microphone collections controller of feeding calculates incident sound pressure p _i(t) conduct is with reference to signal; Reflected sound and incident sound are calculated as follows, and establish microphone standoff distance d, and the signal that two microphones pick up is respectively p ₁(t) and p ₂(t), that close primary source is p ₁(t).If between two microphones apart from d much smaller than institute's controlled frequency scope sound wave minimum wavelength, but then between two microphones acoustic pressure approximate representation of intermediate point be:

$p\left(t\right)=\frac{p_1\left(t\right)+p_2\left(t\right)}{2}---\left(1\right)$

But some particle velocity approximate representations are in the standing wave tube:

$u\left(t\right)=u_0+\frac{1}{{\mathrm{\ρ}}_{0}d}\underset{0}{\overset{t}{\∫}}(p_1\left(t\right)-p_2\left(t\right))\mathrm{dx}---\left(2\right)$

In the formula, u ₀Be the particle velocity initial value, ρ ₀Be atmospheric density.And below cutoff frequency, the particle velocity of pipeline midplane ripple can be expressed as again

$u\left(t\right)=\frac{1}{{\mathrm{\ρ}}_0{c}_0}(p_i\left(t\right)-p_r\left(t\right))---\left(3\right)$

In the formula, c ₀Be the velocity of sound, the acoustic pressure of intermediate point also can be expressed as again between the microphone:

p(t)＝p _i(t)+p _r(t) (4)

In conjunction with (3), (4) two formulas, can calculate incident sound pressure and reflecting acoustic pressure

$p_i\left(t\right)=\frac{1}{2}(p\left(t\right)+{\mathrm{\ρ}}_0{c}_{0}u\left(t\right)),p_r\left(t\right)=\frac{1}{2}(p\left(t\right)-{\mathrm{\ρ}}_0{c}_{0}u\left(t\right))---\left(5\right)$

P in the formula (t) and u (t) are obtained with 2-microphone sound by formula (1) and (2).

Open primary source separately, (GB/T 18696.2-2002, the measurement part 2 of acoustical absorption coefficient and acoustic impedance in the impedance tube: transfer function method) the measurement active system is closed the acoustical absorption coefficient spectrum under the situation with transfer function method.

Open Controlling Source separately, the reflected sound p that the controller of being fed by two microphone sound pressure signals is calculated with LMS (Least Mean Squares) _r(t) modeling obtains the secondary channel transport function;

Primary source and Controlling Source are opened simultaneously, with the secondary channel transport function that obtains, and the reflected sound p that the controller of being fed by two microphone sound pressure signals is calculated _r(t) carry out reflected sound control with FXLMX (Filtered-X Least Mean Squares) algorithm, making it is zero, controlled device parameter.

Measure the acoustical absorption coefficient spectrum of the active wedge under the active control unlatching situation with transfer function method.

Fig. 3 is the acoustical absorption coefficient spectrum of the cotton wedge of ultra-fine sound absorption when active control is opened and closed, and wedge length is 40cm.The cotton wedge absorber of ultra-fine sound absorption has higher acoustical absorption coefficient more than 300Hz, after active control is opened, 100-300Hz low frequency absorption performance has obtained bigger improvement before the control, is 0.98～1.00 suitable with the sound absorbing capabilities of the long traditional wedge absorber of 80cm at 100～1000Hz acoustical absorption coefficient.

Fig. 4 is the acoustical absorption coefficient spectrum of sponge wedge absorber when active control is opened and closed, the long 20cm of sponge wedge absorber, and material is a high density sound absorption sponge.The sponge wedge absorber has higher acoustical absorption coefficient more than 600Hz, the control back is at 100～1000Hz, the acoustical absorption coefficient of sponge wedge absorber is 0.98～1.00, the combine sound absorbing capabilities of the long traditional wedge absorber of the active sound-absorption taper that always is about 40cm that constituted and 80cm of the long sponge wedge absorber of active guidance system and 20cm is suitable.

The present invention utilize active control to wedge absorber to the low frequency absorption compensating action, combine with traditional wedge absorber by active guidance system, integrated active sound-absorption taper is more having higher sound absorbing capabilities in the broadband than former wedge; And compare with the traditional wedge absorber with close sound absorbing capabilities, length is shorter, and volume is littler.

Claims (5)

1. active sound-absorption taper, it is characterized in that: this active sound-absorption taper comprises traditional wedge absorber (1), Controlling Source (2), power amplifier (3), controller (4) and error microphone (5), is placed on error microphone (5) in the sound field and is arranged on the front end of traditional wedge absorber (1) and is connected with controller (4); Controller (4) is connected with Controlling Source (2) by power amplifier (3), and Controlling Source (2) is arranged on the rear end of traditional wedge absorber (1).

2. active sound-absorption taper according to claim 1 is characterized in that: described error microphone (5) is two microphones.

3. active sound-absorption taper according to claim 1 is characterized in that: described controller (4) is the digital signal processing integrated circuit plate, and this surface-mounted integrated circuit is placed on Controlling Source (2) rear end with power amplifier (3).

4. the method for making of an active sound-absorption taper, it is characterized in that: this method is boundary with traditional wedge absorber cutoff frequency, improves traditional wedge absorber low frequency absorption by the active control of having used reflected sound, forms the sound absorption in broadband; May further comprise the steps:

A) with two microphones as error microphone, error microphone is arranged on traditional wedge absorber front end, the sound pressure signal of the two microphone collections controller of feeding respectively calculates incident sound pressure p _i(t) conduct is with reference to signal;

B) open Controlling Source separately, with the reflected sound p of LMS algorithm to calculating _r(t) modeling obtains the secondary channel transport function;

C) primary source and Controlling Source are opened simultaneously, with the secondary channel transport function that obtains, to the reflected sound p that calculates _r(t) approach with the FXLMX algorithm, making it is zero, controlled device parameter.

5. the method for making of active sound-absorption taper according to claim 4 is characterized in that: incident sound pressure p _i(t) and reflected sound p _rBeing calculated as follows (t),

If the microphone standoff distance is d, the signal that two microphones pick up is respectively p ₁(t) and p ₂(t), that close primary source is p ₁(t); If between two microphones apart from d much smaller than institute's controlled frequency scope sound wave minimum wavelength, but then between two microphones acoustic pressure approximate representation of intermediate point be:

$p\left(t\right)=\frac{p_1\left(t\right)+p_2\left(t\right)}{2}---\left(1\right)$

But some particle velocity approximate representations are in the standing wave tube:

$u\left(t\right)=u_0+\frac{1}{{\mathrm{\ρ}}_{0}d}\underset{0}{\overset{t}{\∫}}(p_1\left(t\right)-p_2\left(t\right))\mathrm{dx}---\left(2\right)$

In the formula, u ₀Be the particle velocity initial value, ρ ₀Be atmospheric density; And below cutoff frequency, the particle velocity of pipeline midplane ripple can be expressed as again

$u\left(t\right)=\frac{1}{{\mathrm{\ρ}}_0{c}_0}(p_i\left(t\right)-p_r\left(t\right))---\left(3\right)$

In the formula, c ₀Be the velocity of sound, the acoustic pressure of intermediate point also can be expressed as again between the microphone:

p(t)＝p _i(t)+p _r(t) (4)

In conjunction with (3), (4) two formulas, can calculate incident sound pressure and reflecting acoustic pressure

$p_i\left(t\right)=\frac{1}{2}(p\left(t\right)+{\mathrm{\ρ}}_0{c}_{0}u\left(t\right)),p_r\left(t\right)=\frac{1}{2}(p\left(t\right)-{\mathrm{\ρ}}_0{c}_{0}u\left(t\right))---\left(5\right)$

P in the formula (t) and u (t) are obtained with 2-microphone sound by formula (1) and (2).

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