CN105973459A - Estimation method for theoretical sound pressure level of free sound field in anechoic chamber calibration - Google Patents

Abstract

The invention discloses an estimation method for a theoretical sound pressure level of a free sound field in anechoic chamber calibration, wherein the method is used for calculating theoretical sound pressure level data in anechoic chamber calibration. A multi-channel acoustic analyzer is used for measuring testing sound pressure level data, generated by a testing sound source at a path under a frequency, of a measured anechoic chamber; according to a practical testing environment of the measured anechoic chamber, a sound pressure level attenuation coefficient alpha is calculated; two unknown parameters A and r0 in a new theoretical sound pressure level calculation model are calculated by using a non-linear curve fitting method; an air absorption attenuation part is added into the calculation model; and a theoretical sound pressure level is estimated by using a non-linear least square method fitting way. Therefore, precise estimation of the theoretical sound pressure level of the measured anechoic chamber can be realized; the deviation distribution becomes reasonable; and the calibration precision is improved effectively.

Description

The evaluation method of free found field theory sound pressure level in the calibration of a kind of dead room

Technical field

The present invention relates to the evaluation method of free found field theory sound pressure level in the calibration of a kind of dead room, be used for calculating dead room Theoretical sound pressure level data in calibration.Belong to field of acoustics.

Background technology

Along with the development of acoustic-electric technology, the dead room application in the field of manufacture is increasingly wider, real as a kind of acoustics Testing room, its Main Function is to provide the low noise test environment in a free found field space.Good dead room calibration system can Effectively to evaluate the performance indications of dead room, promote the innovation of dead room, improve the quality of dead room.In order to judge dead room Acoustical behavior, need dead room is carried out place calibration, the development to dead room has indispensable meaning.

At present, the domestic calibration operation Main Basis for dead room and semianechoic room GB 6882, ISO 3745 annex The calibration procedure of regulation in A and JJF 1147 dead room calibrating standard, the main collimation technique index of dead room has two, bag The qualification of the frequency range of free found field and spatial dimension and background noise, wherein, the maximum free sound of tested dead room are included Field radius need to meet measurement sound pressure level and inverse square rate sound pressure level maximum allowable offset scope.At free found field frequency and space model In the qualification enclosed, the free found field theory sound pressure level model of above-mentioned national regulations disclosure satisfy that acoustic pressure is put down with the anti-of range attenuation Square gauge is restrained, but the measured value obtained by GB theory sound pressure level computational methods and theoretical value aberration curve exist near-end deviation The un-reasonable phenomenon relatively big, far-end deviation is less, i.e. free found field deviation " near big and far smaller " problem, the most existing theoretical sound pressure level Computation model in not yet consider air attenuation by absorption amount, have impact on precision and the accuracy of calibration result.

For the problems referred to above, the present invention is after the problem that analytic set code computational methods exist, it is proposed that Yi Zhonggai The dead room theory sound pressure level computational methods entered.Air attenuation by absorption part is added computation model by new method, uses non-linear Theoretical sound pressure level is estimated by the mode of least square fitting, makes deviation profile tend to reasonable, is effectively improved calibration accuracy.

The present invention can be applied to the calibration of dead room and the qualification of free found field, it is possible to effectively estimates that tested dead room is certainly By the theoretical sound pressure level of sound field, the optimization for dead room calibration steps provides theoretical foundation and Engineering Guidance with improving.

Summary of the invention

The present invention is directed to free found field deviation " near big and far smaller " that existing GB theory sound pressure level computational methods cause and not The problem considering air attenuation by absorption factor, it is proposed that a kind of for estimating free found field theory sound pressure level in dead room calibration Method, the final theoretical sound pressure level obtaining dead room free found field.

The inventive method, it specifically comprises the following steps that

The first step: utilize microphone, multiple channel acousto analyser, PULSE test n point of systematic survey tested dead room (n >= 10) sound pressure level, measurement result is designated as L_Pi, unit be dB, i be 1 to n, i-th is designated as r with the distance at measuring sound source center_i。

Second step: allow dead room be in standard atmosphere pressure, measure the Celsius temperature T of dead room, relative humidity h_r, sound source Frequency f, calculates sound pressure level attenuation quotient α according to following formula.

$\mathrm{\α}=8.686f^2\[1.84\×{10}^{-11}{\left(\frac{T_K}{T_0}\right)}^{-\frac{1}{2}}+{\left(\frac{T_K}{T_0}\right)}^{-\frac{5}{2}}\×(0.01275\frac{f_{rO}}{f_{rO}^2+f^2}{e}^{\frac{-2239.1}{T_K}}+0.1068\frac{f_{rN}}{f_{rN}^2+f^2}{e}^{\frac{-3352.0}{T_K}})\]---\left(4\right)$

In formula, T_kFor the absolute temperature of dead room, unit is K, T_k=T+273.15；T₀For reference temperature, size is 293.15K；F is the frequency of sound source, and unit is Hz；f_rOFor oxygen relaxation frequency, unit is Hz；f_rNFor nitrogen relaxation frequency, unit is Hz, wherein

$f_{rO}=24+4.04\×{10}^{4}h\frac{0.02+h}{0.319+h}---\left(5\right)$

$f_{rN}=9\sqrt{\frac{T_0}{T_K}}+280e^{-4.170(\sqrt[3]{\frac{T_0}{T_K}}-1)}\·\sqrt{\frac{T_0}{T_K}}h---\left(6\right)$

In formula, h and T_kFor,

$h=h_r{10}^{-6.8346{\left(\frac{T_{01}}{T_K}\right)}^{1.261}+4.6151}---\left(7\right)$

T_K=T+273.15 (8)

In formula, h is the molar concentration of water vapour, and unit is %；T is the Celsius temperature of dead room, and unit is DEG C；h_rFor phase To humidity, unit is %；T₀₁For triple point, size is-273.16K.

3rd step: 1. by A and r₀Initial value be respectively set to 0 and-0.5；

2. by L_Pi, r_i, A brings following formula into

$Q=\underset{i=1}{\overset{n}{\Σ}}{\[L_{Pi}-20\lg \frac{A}{(r_i-r_0)}-\mathrm{\α}(r_0-r_i)\]}^2---\left(3\right)$

If 3. Q > 0.5 and r₀≤ 0.5, then r₀=r₀+ 0.0001, return 2.；

If 4. Q > 0.5 and r₀> 0.5, then A=A+1, r₀2.=-0.5, return；

If 5. Q≤0.5, then record A and r now₀, terminate Q and calculate.

4th step: according to following formula and r_i, α, A and r₀Determine free found field theory sound pressure level curve.

$L_{PTi}=20\lg \frac{A}{(r_i-r_0)}+\mathrm{\α}(r_0-r_i)---\left(1\right)$

In formula, L_PTiFor distance Sound Source Center r_iThe theoretical sound pressure level at place, unit is dB.

The inventive method, utilizes multiple channel acousto analyser to measure tested dead room and is produced by measuring sound source under path and frequency Raw test sound pressure level data, the actual test environment further according to tested dead room calculates sound pressure level attenuation quotient α, then utilizes Linear curve fitting method determines two unknown parameter A and r in theoretical sound pressure level novel model of calculating₀, air is absorbed and declines Subtract part and add computation model, use the mode of Non-linear least-square curve fitting that theoretical sound pressure level is estimated, thus real The accurate estimation of existing tested dead room theory sound pressure level, makes deviation profile tend to reasonable, is effectively improved calibration accuracy.

Accompanying drawing explanation

Fig. 1 be frequency of source be 10kHz, temperature be 20 DEG C, relative humidity is when being 50%, calculated sound pressure level decays Curve.

Detailed description of the invention

Below in conjunction with the accompanying drawings and specific embodiment, the present invention is described in further details.

The first step: utilize microphone, multiple channel acousto analyser, PULSE to test systematic survey dead room n point (n= 16) sound pressure level, measurement result is designated as L_Pi, unit be dB, i be 1 to n, i-th is designated as r with the distance at measuring sound source center_i。

Second step: allow dead room be in standard atmosphere pressure, measure Celsius temperature T=20 DEG C of dead room, relative humidity h_r=50%, frequency of source f=10kHz, calculates sound pressure level attenuation quotient α according to following formula.

$\mathrm{\α}=8.686f^2\[1.84\×{10}^{-11}{\left(\frac{T_K}{T_0}\right)}^{-\frac{1}{2}}+{\left(\frac{T_K}{T_0}\right)}^{-\frac{5}{2}}\×(0.01275\frac{f_{rO}}{f_{rO}^2+f^2}{e}^{\frac{-2239.1}{T_K}}+0.1068\frac{f_{rN}}{f_{rN}^2+f^2}{e}^{\frac{-3352.0}{T_{\mathrm{\κ}}}})\]---\left(4\right)$

In formula, T_kFor the absolute temperature of dead room, unit is K, T_k=T+273.15；T₀For reference temperature, size is 293.15K；F is the frequency of sound source, and unit is Hz；f_rOFor oxygen relaxation frequency, unit is Hz；f_rNFor nitrogen relaxation frequency, unit is Hz, wherein

$f_{rO}=24+4.04\×{10}^{4}h\frac{0.02+h}{0.319+h}---\left(5\right)$

$f_{rN}=9\sqrt{\frac{T_0}{T_K}}+280e^{-4.170(\sqrt[3]{\frac{T_0}{T_K}}-1)}\sqrt{\frac{T_0}{T_K}}h---\left(6\right)$

In formula, h and T_kFor,

$h=h_r{10}^{-6.8346{\left(\frac{T_{01}}{T_K}\right)}^{1.261}+4.6151}---\left(7\right)$

T_K=T+273.15 (8)

In formula, h is the molar concentration of water vapour, and unit is %；T is the Celsius temperature of dead room, and unit is DEG C；h_rFor phase To humidity, unit is %；T₀₁For triple point, size is-273.16K.

Result of calculation obtains sound pressure level attenuation quotient α=0.159.

3rd step: 1. by A and r₀Initial value be respectively set to 0 and-0.5；

2. by L_Pi, r_i, A brings following formula into

$Q=\underset{i=1}{\overset{n}{\Σ}}{\[L_{Pi}-20\lg \frac{A}{(r_i-r_0)}-\mathrm{\α}(r_0-r_i)\]}^2---\left(3\right)$

If 3. Q > 0.5 and r₀≤ 0.5, then r₀=r₀+ 0.00001, return 2.；

If 4. Q > 0.5 and r₀> 0.5, then A=A+1, r₀2.=-0.5, return；

If 5. Q≤0.5, then record A and r now₀, terminate to calculate.

Result of calculation obtains A and r₀It is respectively 1890 and 0.04904.

4th step: according to following formula and r_i, α, A and r₀Determine free found field theory sound pressure level curve, as shown in drawings.

$L_{PTi}=20\lg \frac{A}{(r_i-r_0)}-\mathrm{\α}(r_0-r_i)---\left(1\right)$

In formula, L_PTiFor distance Sound Source Center r_iThe theoretical sound pressure level at place, unit is dB.

Claims (1)

1. an evaluation method for free found field theory sound pressure level in dead room calibration, it specifically comprises the following steps that

The first step: utilize the acoustic pressure of microphone, multiple channel acousto analyser, PULSE test systematic survey tested dead room n point Level, n >=10, measurement result is designated as L_Pi, unit is dB, i=1,2 ..., n, i-th is designated as with the distance at measuring sound source center r_i；

Second step: dead room is in standard atmosphere pressure, measures the Celsius temperature T of dead room, relative humidity h_r, frequency of source f, According to following formula calculating sound pressure level attenuation quotient α:

$\mathrm{\α}=8.686f^2\[1.84\×{10}^{-11}{\left(\frac{T_K}{T_0}\right)}^{-\frac{1}{2}}+{\left(\frac{T_K}{T_0}\right)}^{-\frac{5}{2}}\×(0.01275\frac{f_{rO}}{f_{rO}^2+f^2}{e}^{\frac{-2239.1}{T_K}}+0.1068\frac{f_{rN}}{f_{rN}^2+f^2}{e}^{\frac{-3352.0}{T_K}})\]$

In formula, T_kFor the absolute temperature of dead room, unit is K, T_k=T+273.15；T₀For reference temperature, size is 293.15K； F is the frequency of sound source, and unit is Hz；f_rOFor oxygen relaxation frequency, unit is Hz；f_rNFor nitrogen relaxation frequency, unit is Hz, wherein

$f_{rO}=24+4.04\×{10}^{4}h\frac{0.02+h}{0.319+h}$

$f_{rN}=9\sqrt{\frac{T_0}{T_K}}+280e^{-4.170(\sqrt[3]{\frac{T_0}{T_K}}-1)}\sqrt{\frac{T_0}{T_K}}h$

$h=h_r{10}^{-6.8346{\left(\frac{T_{01}}{T_K}\right)}^{1.261}+4.6151}$

T_K=T+273.15

In formula, h is the molar concentration of water vapour, and unit is %；T is the Celsius temperature of dead room, and unit is DEG C；h_rFor the wettest Degree, unit is %；T₀₁For triple point, size is-273.16K；

3rd step: 1. by A and r₀Initial value be respectively set to 0 and-0.5；

2. by L_Pi, r_i, A brings following formula into

$Q=\underset{i=1}{\overset{n}{\Σ}}{\[L_{Pi}-20\lg \frac{A}{(r_i-r_0)}-\mathrm{\α}(r_0-r_i)\]}^2$

If 3. Q > 0.5 and r₀≤ 0.5, then r₀=r₀+ 0.0001, return 2.；

If 4. Q > 0.5 and r₀> 0.5, then A=A+1, r₀2.=-0.5, return；

If 5. Q≤0.5, then record A and r now₀, terminate Q and calculate；

4th step: according to following formula and r_i, α, A and r₀Determine free found field theory sound pressure level curve

$L_{PTi}=20\lg \frac{A}{(r_i-r_0)}+\mathrm{\α}(r_0-r_i)$

In formula, L_PTiFor distance Sound Source Center r_iThe theoretical sound pressure level at place, unit is dB.