CN1585566A - Non-anechoic chamber measuring method based on impedance loudspeaker low-frequency response - Google Patents

Abstract

The method includes following steps: the lumped parameter electricity impedance model of system is established according to speaker structure that includes lumped parameter electricity impedance model of voice coil eddying effect and electricity input impedance curve detected in normal condition; the optimized algorithm is used to make the electricity input impedance curve obtained from model calculation to match the electricity input impedance curve obtained from actual measurement; using optimized parameter value can get form of frequency response in low frequency and amplitude frequency through calculation; then through measuring electromechanical coupling factor the actual frequency response in low frequency is obtained.

Description

Non-dead room method of measurement based on the loud speaker low frequency frequency response of electrical impedance

Technical field

The present invention relates to the method for measurement of the low frequency frequency response of loud speaker, especially based on the non-dead room method of measurement of the loud speaker low frequency frequency response of electrical impedance.

Background technology

Loud speaker is the electroacoustic transducer that can convert the electrical signal to acoustical signal and medium radiation towards periphery.Loud speaker can refer to loudspeaker unit or speaker system.Speaker system claims audio amplifier or loudspeaker enclosure again, and its type has closed enclosure, pipeline bass-reflex cabinet, empty cone bass-reflex cabinet, fourth-order band-pass case, the logical case of six rank bands etc.Here the loudspeaker enclosure that refers to comprises loudspeaker unit, casing and pipeline or empty cone, does not comprise dividing network.The schematic diagram of several loud speakers that the present invention relates to as shown in Figure 1.

The frequency response of loud speaker is to represent the output sound pressure level of loud speaker and the relation between the frequency with curve, and this curve normally records under free-field condition or half space free-field condition.Frequency response when loud speaker can be represented with lumped parameter system model when LF-response was meant low frequency.

According to national standard, the low frequency frequency response of loud speaker should be measured with microphone in anechoic chamber, as shown in Figure 2.In anechoic chamber, more than a certain frequency in predetermined distance place, can be considered free field.The anechoic chamber low-frequency minimum is low more, just requires the size of anechoic chamber big more, and cost is just high more.If in normal room, measure, comprised the information that influences of environment in the signal that microphone obtains, must cause measuring the acoustic characteristic that can not accurately reflect loud speaker.Common its low frequency measurement of time domain back-and-forth method also can be subjected to the influence in room.

In order to measure the frequency response of loud speaker in normal room, the someone proposes to adopt the near field method to measure.But when the part of radiative acoustic wave during, be difficult to determine measuring position accurately, perhaps use a plurality of microphones, operate also very complicated with a microphone more than one.As shown in Figure 3.

The electrical impedance of loud speaker is meant that the impedance of input of loudspeaker unit is with the curve of frequency change.The electrical impedance of loud speaker can measure in conventional environment.

The relevant method of having published at present:

1, the voice coil loudspeaker voice coil eddy current model in the anti-model of speaker resistor, the impedance model of various known loudspeaker, loudspeaker unit, closed enclosure, pipeline bass-reflex cabinet have proposed to add the impedance model of voice coil loudspeaker voice coil eddy current.

2, independent loudspeaker unit adds certain quality, measures the Bl value.

Obtaining mainly containing following several respects work aspect the frequency response by electrical impedance at present:

1, (1993) have proposed the impedance model value of not considering the voice coil loudspeaker voice coil eddy current of loudspeaker unit and pipeline bass-reflex cabinet, component value in the Optimization Model, obtain the T-S parameter, propose the non-dead room method of measurement of loudspeaker unit and pipeline bass-reflex cabinet, obtain LF-response according to T-S parameter and measurement volumes (non-Bl).But in the system of structural model than complexity, this method has been subjected to the restriction of formula.Referring to Withold Waldman, Non-linear leastsquares estimation of Thiele-small parameters from impedance measurements, preprint3511.(the 94th AES proceedings, Berlin in 1993)

2, (calendar year 2001) Klippel has proposed the impedance model of the consideration voice coil loudspeaker voice coil eddy current of loudspeaker unit, then according to impedance curve Optimization Model parameter, has used the laser accelerometer Displacement Measurement in secondary is measured, and obtains LF-response.Shortcoming is that the laser cost is higher, system complex.Referring to Klippel, Fast and accurate measurement of lineartransducer parameters, preprint 5308 (the 110th AES proceedings, calendar year 2001 Amsterdam).

Situation to sum up, prior art is not enough as the obvious precision of impedance model value of not considering the voice coil loudspeaker voice coil eddy current, and method the having relatively high expectations to measuring equipment that secondary has used the laser accelerometer Displacement Measurement in measuring.This shows that obtaining the LF-response aspect by electric input impedance does not also have method convenient and that using value is big to occur, and proposition is not also arranged for the method for measurement that covers the polytype loud speaker.

Summary of the invention

The objective of the invention is: provide a kind of non-dead room method of measurement of the loud speaker low frequency frequency response based on electrical impedance, as long as the consideration of known loudspeaker The voice coil loudspeaker voice coil eddy currentImpedance model, any loud speaker can be obtained its low frequency frequency response, and measuring system is simple, and cost is less, and method of measurement of the present invention also can guarantee certain relative accuracy.The present invention also aims to propose the loudspeaker unit of all known electric impedance models and the non-dead room of loudspeaker enclosure and measure the LF-response method.This method also is based on electrical impedance, adopts lumped parameter impedance component value, does not adopt the T-S parameter, is not subjected to what restriction of component value.The measurement of Bl can be adopted additional mass method.

Non-dead room method of measurement based on the loud speaker low frequency frequency response of electrical impedance: for any loud speaker (comprising loudspeaker enclosure), at first set up the lumped parameter impedance model of speaker system according to the structure of loud speaker, and the lumped parameter impedance model that comprises the voice coil loudspeaker voice coil vortes interference, and in conventional environment, record electric input impedance curve, use optimized Algorithm (typically adopting genetic algorithm) according to electric input impedance optimization of profile model element parameter value then, make the electric input impedance curve that obtains by Model Calculation match, can calculate the shape of low frequency amplitude-frequency frequency response with the parameter value after the optimization with the electric input impedance curve of actual measurement.If on the unit, add certain mass, record electromechanical coupling factor Bl with additional mass method, record other parameter again and just can obtain real low frequency frequency response.

The present invention has proposed the non-dead room method of measurement based on the low frequency frequency response of electrical impedance of the loud speaker of all known models first.As long as the impedance model of known system and the electric input impedance curve of actual measurement just can be obtained the low frequency frequency response.The flow process of the inventive method as shown in figure 18.

Its medium and low frequency frequency response is meant and has both comprised its curve shape, comprised the frequency response curve of sound pressure amplitude size again.

Optimized Algorithm (as genetic algorithm etc.) can be according to electric input impedance optimization of profile model element parameter value, makes the electric input impedance curve that obtained by Model Calculation and the electric input impedance curve of actual measurement match.

Characteristics of the present invention are: Consideration voice coil loudspeaker voice coil eddy currentImpedance model value precision height, secondary are measured as long as measuring resistance is anti-to be worth, and need not use the high equipment of cost of Displacement Measurement such as laser accelerometer.And according to the method for measurement of this method proposition for covering polytype loud speaker.As long as the impedance model of known system and the electric input impedance curve of actual measurement just can be obtained the low frequency frequency response.Its medium and low frequency frequency response is meant and has both comprised its curve shape, comprised the frequency response curve of sound pressure amplitude size again.Device is simple, and the precision height of measurement is convenient to use on a large scale in the industrial production.

Description of drawings

Several loud speaker schematic diagrames of Fig. 1 comprise single loudspeaker unit, closed loud speaker, pipeline bass-reflex cabinet, empty cone bass-reflex cabinet, fourth-order band-pass case, the logical case of six rank bands, and this is the most frequently used several loud speaker models.

Fig. 2 anechoic chamber instrumentation plan, Fig. 3 near field method instrumentation plan

Fig. 4 loud speaker low frequency electroacoustic association class is than conspectus, Fig. 5 loud speaker low frequency electrical equivalent conspectus

Fig. 6 fourth-order band-pass box structure sketch, Fig. 7 fourth-order band-pass case frequency acoustic analogy line map

Fig. 8 fourth-order band-pass case low frequency electrical equivalent line map

The structure diagram of Fig. 9 loudspeaker unit and closed enclosure

Figure 10 loudspeaker unit and closed enclosure frequency acoustic analogy circuit

The low frequency electrical equivalent circuit of Figure 11 loudspeaker unit and closed enclosure

The structure diagram of Figure 12 pipeline bass-reflex cabinet and frequency acoustic analogy circuit

The low frequency electrical equivalent circuit of Figure 13 pipeline bass-reflex cabinet

The structure diagram and the frequency acoustic analogy circuit of the empty cone bass-reflex cabinet of Figure 14

The low frequency electrical equivalent circuit of the empty cone bass-reflex cabinet of Figure 15

The computation optimization value and the actual measured value comparison diagram of Figure 16 fourth-order band-pass case electrical impedance

The comparison diagram of the LF-response that Figure 17 fourth-order band-pass case is measured based on microphone in the LF-response of impedance bioelectrical measurement and the anechoic chamber

Figure 18 is the flow process of the inventive method

Embodiment

Figure 18 is the flow process of the inventive method, is basic skills of the present invention.

During low frequency, the analogy conspectus of the electroacoustic combination of loudspeaker unit and loudspeaker enclosure can be represented with Fig. 4.Bl, S _DBe respectively electromechanical coupling factor, the effective radiating area of loudspeaker unit.Z _LEThe electrical impedance of expression voice coil loudspeaker voice coil, Z _ASThe acoustic impedance of expression loudspeaker unit vibrational system, Z _APThe acoustic impedance of the element of expression radiative acoustic wave, may there be other element in the ellipsis representative.U _DBe the volume velocity of loudspeaker unit, U _OBe the volume velocity in the element of radiative acoustic wave in air, if the element of radiative acoustic wave is during more than one, U _OFor the vector of each component size speed and.If when loudspeaker unit or closed enclosure, Z _APAnd Z _ASBe combined into same element; During for the fourth-order band-pass case, be different elements, and the centre there is other element.

Fig. 4 considers The voice coil loudspeaker voice coil eddy currentImpedance model.

Fig. 5 is the low frequency electrical equivalent conspectus of loud speaker.Z _ESCorresponding to the Z among Fig. 4 _AS, Z _EPCorresponding to Z _APIf input voltage is E _g, output voltage is E _OInput impedance is Z _i, be the electric input impedance of speaker system.As seen from Figure 4, according to the electro-acoustic analogy relation, be the electrical equivalent circuit from the acoustic analog line transfer, be through the conversion of circuit types, the volume velocity U of acoustic circuit among Fig. 4 _OCorresponding to the output voltage E among Fig. 5 _OThe transformational relation of each element is:

$Z_E=\frac{{\left(\mathrm{Bl}\right)}^2}{Z_A{S_D}^2}---\left(1\right)$

$E_0=\frac{U_o\mathrm{Bl}}{S_D}---\left(2\right)$

Z wherein _AElement in the expression acoustic analog circuit, Z _ECorresponding element in the expression electrical equivalent circuit.

And during low frequency in the free field expression formula of sound pressure amplitudes be:

$\left|p\right|=\frac{\mathrm{f\ρ}}{2r}\left|U_0\right|---\left(3\right)$

F is a frequency, and ρ is an atmospheric density, and r is a radiation length.

Wushu (2) substitution formula (3) can get the acoustic pressure at 1 meter:

$\left|p\right|=\frac{E_g\mathrm{\ρ}{R}^2}{4\mathrm{Bl}}\left|\frac{{\mathrm{sE}}_0}{E_g}\right|---\left(4\right)$

R is S _DEffective radiation radius of corresponding loudspeaker unit, s=j2 π f.

When measuring the frequency response of loud speaker, microphone can receive environmental information, makes measurement result inaccurate.Therefore the frequency response of directly measuring loud speaker with microphone will be carried out in anechoic chamber.And the influence of the change of electric input impedance raying acoustic impedance in varying environment of loud speaker is minimum, can ignore, its method of measurement is the signal of telecommunication at direct measuring unit two ends simultaneously, need not microphone, so just be not subjected to the influence of environment, can think that the electric input impedance that records under the conventional environment is consistent with measurement result in the anechoic chamber, the measurement of electric input impedance does not rely on anechoic chamber.

(4) E in the formula _O/ E _gCan represent according to impedance dividing potential drop relation with the element in the electrical equivalent circuit of Fig. 5.If in conventional environment, record earlier electric input impedance curve, use the parameter value of element in the genetic algorithm optimization electrical equivalent circuit then, make the electric input impedance curve that obtains by Model Calculation match, utilize the parameter value of the element that optimization obtains just can obtain E with the electric input impedance curve of actual measurement _O/ E _g, know again the value of other parameter in (4) formula so just to obtain the low frequency frequency response, thereby realize measuring based on the non-dead room of the LF-response of electrical impedance.

The measurement of Bl value can be adopted additional mass method.

Genetic algorithm is a kind of algorithm of existing maturation, is the bionical class algorithm based on the solving-optimizing problem of Darwinian natural evolutionism and Mendelian hereditary variation theory, is a kind of intelligentized global search algorithm.Genetic algorithm comprises three main operation operators such as selection, intersection, variation.Produce the N group when this algorithm is initial at random and separate, each group is separated and is body one by one, and the set that these many groups are separated is called a population.Calculate each individual fitness then, selection operation has the big individuality of fitness and duplicates probability more greatly, can accelerate convergence of algorithm speed, interlace operation produces more excellent individuality by two parents are carried out gene swapping, mutation operation then can bring new gene to colony, avoids being absorbed in local optimum.Be exactly operation, optimize colony generation generation ground and constantly evolve, finally converge on optimum state by these three kinds of operators.

The definition error function is a variance:

$e\left(\stackrel{\‾}{x}\right)=\underset{i}{\mathrm{\Σ}}{|Z_{\mathrm{ic}}(j2\mathrm{\π}{f}_i,\stackrel{\‾}{x})-Z_{\mathrm{im}}\left(j2\mathrm{\π}{f}_i\right)|}^2$

Wherein i is a discrete point, Z _Im(s) the electric input impedance value for measuring, Z _Ic(s) the electric input impedance value for calculating, x is one group of given parameter value.

On fitness function was selected, we had adopted normalized function, i.e. f (x)=1/ (1+e (x)).Whole genetic algorithm calculating process is as follows:

(1) initialization Control Parameter: population size N is set; Crossover probability P _CThe variation probability P _M

(2) in the specification of variables scope, produce initial population at random.

(3) existing colony is carried out following operation: 1. calculate each individual fitness f (x in the colony _i), i=1,2 ..., N; 2. implement selection operation according to roulette wheel mechanism, the selecteed probability of the individuality that fitness is big is big; 3. select two individual x at random _iAnd x _jAs parent, according to probability P _CCarry out interlace operation, produce two new individual x _i' and x _j', the fitness of four individualities of calculating is selected two wherein maximum individualities; 4. to the individuality after intersecting with probability P _MCarry out mutation operation, receive the new explanation after making a variation.

(4) if satisfy the condition of convergence, then withdraw from evolutionary process, otherwise go to (3).

Utilize the present invention to calculate the low frequency frequency response of fourth-order band-pass case

The structure diagram of fourth-order band-pass case and frequency acoustic analogy circuit are shown in Fig. 6,7.Wherein, the acoustic impedance Z relevant in the loudspeaker unit with voice coil loudspeaker voice coil _LSRepresent; R _AS, C _AS, M _ASBe respectively acoustic resistance, acoustic compliance and the acoustic mass of speaker vibration system; C _AB1Acoustic compliance for closed box; C _AB2, R _AB2Be respectively the acoustic compliance and the acoustic resistance of opening casing; R _ALLeakage acoustic resistance for the opening casing; M _AP, R _APAcoustic mass and acoustic resistance for acoustic conducting pipe.

The transforming relationship that utilizes Fig. 4 is according to Fig. 7, and the low frequency electrical equivalent circuit of fourth-order band-pass case as shown in Figure 8.Wherein, R _E, L _E, L _E1, R _E1The electrical impedance of having formed voice coil loudspeaker voice coil has been considered the eddy current effect of voice coil loudspeaker voice coil, corresponding to the Z in the acoustic analog line map _LSR _ES, C _MES, L _CES, L _CEB1Correspond respectively to the R among Fig. 7 _AS, M _AS, C _AS, C _AB1L _CEB2, R _EB2Correspond respectively to C _AB2, R _AB2R _EL, C _MEP, R _EPCorrespond respectively to R _AL, M _AP, R _APOrder:

$Z_{\mathrm{FB}}=\frac{{\mathrm{sR}}_{\mathrm{EB}2}{L}_{\mathrm{CEB}2}}{R_{\mathrm{EB}2}+{\mathrm{sL}}_{\mathrm{CEB}2}}---\left(5\right)$

$Z_{\mathrm{FP}}=\frac{1}{\frac{1}{R_{\mathrm{EP}}}+{\mathrm{sC}}_{\mathrm{MEP}}}---\left(6\right)$

$Z_{\mathrm{LE}}=R_E+{\mathrm{sL}}_E+\frac{{\mathrm{sR}}_{E1}{L}_{E1}}{R_{E1}+{\mathrm{sL}}_{E1}}---\left(7\right)$

So electric input impedance

$Z_i=Z_{\mathrm{LE}}+\frac{1}{\frac{1}{R_{\mathrm{ES}}}+{\mathrm{sC}}_{\mathrm{MES}}+\frac{1}{{\mathrm{sL}}_{\mathrm{CES}}}+\frac{1}{{\mathrm{sL}}_{\mathrm{CEB}1}}+\frac{1}{R_{\mathrm{EL}}+Z_{\mathrm{FB}}+Z_{\mathrm{FP}}}}---\left(8\right)$

$\frac{E_0}{E_G}=\frac{Z_i-Z_{\mathrm{LE}}}{Z_i}\frac{Z_{\mathrm{FP}}}{R_{\mathrm{EL}}+Z_{\mathrm{FP}}+Z_{\mathrm{FB}}}---\left(9\right)$

It is as follows to utilize electrical impedance to find the solution the process of fourth-order band-pass case low frequency frequency response: the electrical impedance that at first measures system under conventional environment, the electric input impedance optimization that utilizes the genetic algorithm basis to record obtains the value of each element in the low frequency electrical equivalent circuit, component value is brought into (8) (9) formula again and is obtained E _O/ E _g, then (9) formula is brought into (4) formula, as long as know other parameter value in (4) formula again, free field sound pressure level in the time of just can calculating low frequency, thus the non-dead room of realizing frequency response is measured.The low frequency model of loudspeaker unit and closed enclosure is seen Fig. 9-11

The structure diagram of loudspeaker unit and closed enclosure and frequency acoustic analogy circuit are shown in Fig. 9,10.Wherein, the acoustic impedance Z relevant in the loudspeaker unit with voice coil loudspeaker voice coil _LSRepresent; R _AS, C _AS, M _ASBe respectively acoustic resistance, acoustic compliance and the acoustic mass of speaker vibration system; C _ABThe acoustic compliance of expression fully sheathed case.When the expression loudspeaker unit, C _AT=C _ASDuring the expression fully sheathed case, C _ATBe C _ASWith C _ABSeries value.

The transforming relationship that utilizes Fig. 4 is according to Figure 10, and the low frequency electrical equivalent circuit of loudspeaker unit and closed enclosure as shown in figure 11.Wherein, R _E, L _E, L _E1, R _E1The electrical impedance of having formed voice coil loudspeaker voice coil has been considered the eddy current effect of voice coil loudspeaker voice coil, corresponding to the Z in the acoustic analog line map _LSR _ES, C _MES, L _CETCorrespond respectively to the R among Figure 10 _AS, M _AS, C _ATSo electric input impedance $Z_i=Z_{\mathrm{LE}}+\frac{1}{\frac{1}{R_{\mathrm{ES}}}+{\mathrm{sC}}_{\mathrm{MES}}+\frac{1}{{\mathrm{sL}}_{\mathrm{CET}}}}---\left(10\right)$

$\frac{E_0}{E_g}=\frac{Z_i-Z_{\mathrm{LE}}}{Z_i}---\left(11\right)$

The low frequency model of pipeline bass-reflex cabinet

The structure diagram of pipeline bass-reflex cabinet and frequency acoustic analogy circuit are as shown in figure 12.Wherein, the acoustic impedance Z relevant in the loudspeaker unit with voice coil loudspeaker voice coil _LSRepresent; R _AS, C _AS, M _ASBe respectively acoustic resistance, acoustic compliance and the acoustic mass of speaker vibration system; C _AB, R _ABBe respectively the acoustic compliance and the acoustic resistance of casing; R _ALLeakage acoustic resistance for casing; M _AP, R _APAcoustic mass and acoustic resistance for acoustic conducting pipe.

The transforming relationship that utilizes Fig. 4 is according to Figure 12, and the low frequency electrical equivalent circuit of pipeline bass-reflex cabinet as shown in figure 13.Wherein, R _E, L _E, L _E1, R _E1The electrical impedance of having formed voice coil loudspeaker voice coil has been considered the eddy current effect of voice coil loudspeaker voice coil, corresponding to the Z in the acoustic analog line map _LSR _ES, C _MES, L _CESCorrespond respectively to the R among Figure 12 _AS, M _AS, C _ASL _CEB, R _EBCorrespond respectively to C _AB, R _ABR _EL, C _MEP, R _EPCorrespond respectively to R _AL, M _AP, R _APAs shown in figure 13.Order:

$Z_{\mathrm{VB}}=\frac{{\mathrm{sR}}_{\mathrm{EB}}{L}_{\mathrm{CEB}}}{R_{\mathrm{EB}}+{\mathrm{sL}}_{\mathrm{CEB}}}---\left(12\right)$

$Z_{\mathrm{VP}}=\frac{1}{\frac{1}{R_{\mathrm{EP}}}+{\mathrm{sC}}_{\mathrm{MEP}}}---\left(13\right)$

$Z_{\mathrm{LE}}=R_E+{\mathrm{sL}}_E+\frac{{\mathrm{sR}}_{E1}{L}_{E1}}{R_{E1}+{\mathrm{sL}}_{E1}}---\left(14\right)$

Electrical impedance so

$Z_i=Z_{\mathrm{LE}}+\frac{1}{\frac{1}{R_{\mathrm{ES}}}+{\mathrm{sC}}_{\mathrm{MES}}+\frac{1}{{\mathrm{sL}}_{\mathrm{CES}}}+\frac{1}{R_{\mathrm{EL}}+Z_{\mathrm{VB}}+Z_{\mathrm{VP}}}}---\left(15\right)$

$\frac{E_0}{E_g}=\frac{Z_i-Z_{\mathrm{LE}}}{Z_i}\frac{Z_{\mathrm{VB}}}{R_{\mathrm{EL}}+Z_{\mathrm{VP}}+Z_{\mathrm{VB}}}---\left(16\right)$

The low frequency model of empty cone bass-reflex cabinet

The structure diagram of empty cone bass-reflex cabinet and frequency acoustic analogy circuit are as shown in figure 14.Wherein, the acoustic impedance Z relevant in the loudspeaker unit with voice coil loudspeaker voice coil _LSRepresent; R _AS, C _AS, M _ASBe respectively acoustic resistance, acoustic compliance and the acoustic mass of speaker vibration system; C _AB, R _ABBe respectively the acoustic compliance and the acoustic resistance of casing; R _ALLeakage acoustic resistance for casing; M _AP, R _AP, C _APAcoustic mass, acoustic resistance and acoustic compliance for empty cone.

The transforming relationship that utilizes Fig. 4 is according to Figure 14, and the low frequency electrical equivalent circuit of empty cone bass-reflex cabinet as shown in figure 15.Wherein, R _E, L _E, L _E1, R _E1The electrical impedance of having formed voice coil loudspeaker voice coil has been considered the eddy current effect of voice coil loudspeaker voice coil, corresponding to the Z in the acoustic analog line map _LSR _ES, C _MES, L _CESCorrespond respectively to the R among Figure 14 _AS, M _AS, C _ASL _CEB, R _EB, R _ELCorrespond respectively to C _AB, R _AB, R _ALC _MEP, R _EP, L _CEPCorrespond respectively to M _AP, R _AP, C _APOrder:

$Z_{\mathrm{PB}}=\frac{{\mathrm{sR}}_{\mathrm{EB}}{L}_{\mathrm{CEB}}}{R_{\mathrm{EB}}+{\mathrm{sL}}_{\mathrm{CEB}}}---\left(17\right)$

$Z_{\mathrm{PP}}=\frac{1}{\frac{1}{R_{\mathrm{EP}}}+{\mathrm{sC}}_{\mathrm{MEP}}+\frac{1}{{\mathrm{sL}}_{\mathrm{CEP}}}}---\left(18\right)$

$Z_{\mathrm{LE}}=R_E+{\mathrm{sL}}_E+\frac{{\mathrm{sR}}_{E1}{L}_{E1}}{R_{E1}+{\mathrm{sL}}_{E1}}---\left(19\right)$

Electrical impedance so

$Z_i=Z_{\mathrm{LE}}+\frac{1}{\frac{1}{R_{\mathrm{ES}}}+{\mathrm{sC}}_{\mathrm{MES}}+\frac{1}{{\mathrm{sL}}_{\mathrm{CES}}}+\frac{1}{R_{\mathrm{EL}}+Z_{\mathrm{PB}}+Z_{\mathrm{PP}}}}---\left(20\right)$

$\frac{E_0}{E_g}=\frac{Z_i-Z_{\mathrm{LE}}}{Z_i}\frac{Z_{\mathrm{PB}}}{R_{\mathrm{EL}}+Z_{\mathrm{PP}}+Z_{\mathrm{PB}}}---\left(21\right)$

Referring to Figure 15.

The present invention has compared with prior art proposed the non-dead room low frequency measurement method based on electric input impedance of all speaker types first.As long as the low frequency lumped parameter impedance model of known loudspeaker and the electric input impedance that records under conventional environment just can be in the hope of the low frequency frequency responses.This method has overcome the restriction of anechoic chamber, need not microphone, only needs to measure the signal of telecommunication, optimizes on common computer, measures simply, has operability, can produce good economic benefits.

Concrete measuring process embodiment

Be example with the fourth-order band-pass case below, illustrate by electrical impedance and realize the process that the non-dead room of loud speaker LF-response is measured.

According to measuring flow process, at first set up the anti-substitutional connection model of lumped parameter low-frequency resistance as shown in Figure 8, measured the electric input impedance of fourth-order band-pass case simultaneously, optimize parameter value in the electrical equivalent line map 8 with genetic algorithm then, make the electrical impedance curve that calculates according to (8) formula by model parameter value and the electrical impedance curve of actual measurement match, make L _CET=L _CESL _CEB1/ (L _CES+ L _CEB1).

It is as follows to obtain parameter:

R _E＝7.4Ω， L _E＝2.38×10 ^-4H， L _E1＝1.25×10 ^-3H， R _E1＝14.17Ω，

R _ES＝40.8Ω， L _CET＝1.77×10 ^-2H， C _MES＝3.5×10 ^-4F， L _CEB2＝2.3×10 ^-2H，

R _EB2＝450Ω， R _EL＝2.1Ω， C _MEP＝2.07×10 ^-4F，?R _EP＝330Ω。

(8) formula that parameter value is brought into calculates the theoretical value of electrical impedance.Figure 16 is the comparison of electric input impedance computation optimization value and actual value.As seen the computation optimization value and the actual value of the electric input impedance that is calculated by genetic algorithm optimization are coincide.

After parameters optimization result obtains, below parameter value substitution (8) formula is obtained electric input impedance, substitution again (9) formula obtains the ratio E of input and output voltage _O/ E _g, last basis (4) formula obtains the theoretical value of pressure response, and it is as follows to have surveyed parameter in addition:

E _g＝2.83V，R＝55mm，Bl＝6.61N/A。

Figure 17 is based on the LF-response of impedance bioelectrical measurement and uses the comparison diagram of the LF-response of microphone measurement in Nanjing University's anechoic chamber.Anechoic chamber is measured with instrument as follows: B﹠amp; K 2012 audio analyzers, B﹠amp; K 2706A power amplifier, B﹠amp; K 4191 microphones and B﹠amp; K 2669 preamplifiers.

As seen from the figure, from 35Hz～200Hz based on the difference of the LF-response of using microphone to measure the LF-response of impedance bioelectrical measurement and the anechoic chamber in the 1dB scope.This shows that this method is coincide fine with the LF-response of measuring in large-scale anechoic chamber.

Claims (6)

1, non-dead room method of measurement based on the loud speaker low frequency frequency response of electrical impedance: it is characterized in that for any loud speaker, at first set up the lumped parameter impedance model of system according to the structure of loud speaker, and the lumped parameter impedance model that comprises the voice coil loudspeaker voice coil vortes interference, and in conventional environment, record electric input impedance curve, use optimized Algorithm according to electric input impedance optimization of profile model element parameter value then, make the electric input impedance curve that obtains by Model Calculation match, can calculate the shape of low frequency amplitude-frequency frequency response with the parameter value after the optimization with the electric input impedance curve of actual measurement.If record electromechanical coupling factor BI and other parameter again, just can obtain real low frequency frequency response.

2, the non-dead room method of measurement of the loud speaker low frequency frequency response based on electrical impedance as claimed in claim 1: the method that it is characterized in that setting up the lumped parameter impedance model of speaker system is, concern according to electro-acoustic analogy, from the acoustic analog line transfer is the electrical equivalent circuit, through the conversion of circuit types, the volume velocity U of the element of outside radiative acoustic wave in the acoustic circuit ₀The output voltage E of corresponding electrical equivalent circuit ₀The transformational relation of each element is:

$Z_E=\frac{{\left(\mathrm{Bl}\right)}^2}{Z_A{S_D}^2}----\left(1\right)$

$E_0=\frac{U_0\mathrm{Bl}}{S_D}----\left(2\right)$

Z wherein _AElement in the expression acoustic analog circuit, Z _ECorresponding element in the expression electrical equivalent circuit, BI, S _DBe respectively electromechanical coupling factor, the effective radiating area of loudspeaker unit.

And during low frequency in the free field expression formula of sound pressure amplitudes be:

$\left|p\right|=\frac{\mathrm{f\ρ}}{2r}\left|U_0\right|----\left(3\right)$

F is a frequency, and ρ is an atmospheric density, and r is a radiation length.

Can get the acoustic pressure at 1 meter:

$\left|p\right|=\frac{E_g\mathrm{\ρ}{R}^2}{4\mathrm{Bl}}\left|\frac{{\mathrm{sE}}_0}{E_g}\right|----\left(4\right)$

R is S _DEffective radiation radius of corresponding loudspeaker unit, s=j2 π f, E _gInput voltage for the electrical equivalent circuit.

(4) E in the formula ₀/ E _gCan represent according to impedance dividing potential drop relation with the element in the low frequency electrical equivalent circuit of loud speaker.If in conventional environment, record earlier electric input impedance curve, use the parameter value of element in the genetic algorithm optimization electrical equivalent circuit then, make the electric input impedance curve that obtains by Model Calculation match, utilize the parameter value of the element that optimization obtains just can obtain E with the electric input impedance curve of actual measurement ₀/ E _g, know again the value of other parameter in (4) formula so just to obtain the low frequency frequency response, thereby realize measuring based on the non-dead room of the LF-response of electrical impedance.

3, the non-dead room method of measurement of the loud speaker low frequency frequency response based on electrical impedance as claimed in claim 1: the low frequency frequency response that it is characterized in that the fourth-order band-pass case is measured in order to following method:

The loudspeaker unit acoustic impedance Z relevant in the frequency acoustic analogy circuit of fourth-order band-pass case with voice coil loudspeaker voice coil _LSRepresent; R _AS, C _AS, M _ASBe respectively acoustic resistance, acoustic compliance and the acoustic mass of speaker vibration system; C _AB1Acoustic compliance for closed box; C _AB2, R _AB2Be respectively the acoustic compliance and the acoustic resistance of opening casing; R _ALLeakage acoustic resistance for the opening casing; M _AP, R _APAcoustic mass and acoustic resistance for acoustic conducting pipe.

In the low frequency electrical equivalent circuit of fourth-order band-pass case, R _E, L _E, L _E1, R _E1The electrical impedance of having formed voice coil loudspeaker voice coil has been considered the eddy current effect of voice coil loudspeaker voice coil, corresponding to the Z in the acoustic analog circuit _LSR _ES, C _MES, L _CES, L _CEB1Correspond respectively to the R in the acoustic analog circuit _AS, M _AS, C _AS, C _AB1L _CEB2, R _EB2Correspond respectively to C _AB2, R _AB2R _EL, C _MEP, R _EPCorrespond respectively to R _AL, M _AP, R _AP

Order: $Z_{\mathrm{FB}}=\frac{s{R}_{\mathrm{EB}2}{L}_{\mathrm{CEB}2}}{R_{\mathrm{EB}2}+s{L}_{\mathrm{CEB}2}}----\left(5\right)$

$Z_{\mathrm{FP}}=\frac{1}{\frac{1}{R_{\mathrm{EP}}}+s{C}_{\mathrm{MEP}}}----\left(6\right)$

$Z_{\mathrm{LE}}=R_E+s{L}_E+\frac{{\mathrm{sR}}_{E1}{L}_{E1}}{R_{E1}+s{L}_{E1}}----\left(7\right)$

So electric input impedance $Z_i=Z_{\mathrm{LE}}+\frac{1}{\frac{1}{R_{\mathrm{ES}}}+s{C}_{\mathrm{MES}}+\frac{1}{s{L}_{\mathrm{CES}}}+\frac{1}{s{L}_{\mathrm{CEB}1}}+\frac{1}{R_{\mathrm{EL}}+Z_{\mathrm{FB}}+Z_{\mathrm{FP}}}}----\left(8\right)$

$\frac{E_0}{E_g}=\frac{Z_i-Z_{\mathrm{LE}}}{Z_i}\frac{Z_{\mathrm{FP}}}{R_{\mathrm{EL}}+Z_{\mathrm{FP}}+Z_{\mathrm{FB}}}----\left(9\right)$

At first measure the electrical impedance of fourth-order band-pass case system under conventional environment, the electric input impedance optimization that utilizes the genetic algorithm basis to record obtains the value of each element in the low frequency electrical equivalent circuit, component value is brought into (8) (9) formula again and is obtained E ₀/ E _g, then (9) formula is brought into (4) formula, as long as know other parameter value in (4) formula again, free field sound pressure level in the time of just can calculating low frequency, thus the non-dead room of realizing frequency response is measured.

4, the non-dead room method of measurement of the loud speaker low frequency frequency response based on electrical impedance as claimed in claim 1: the low frequency frequency response that it is characterized in that loudspeaker unit and closed enclosure is measured in order to following method:

In the frequency acoustic analogy circuit of loudspeaker unit and closed enclosure, the acoustic impedance Z relevant in the loudspeaker unit with voice coil loudspeaker voice coil _LSRepresent; R _AS, C _AS, M _ASBe respectively acoustic resistance, acoustic compliance and the acoustic mass of speaker vibration system; C _ABThe acoustic compliance of expression fully sheathed case.When the expression loudspeaker unit, C _AT=C _ASDuring the expression fully sheathed case, C _ATBe C _ASWith C _ABSeries value;

In the low frequency electrical equivalent circuit of loudspeaker unit and closed enclosure, R _E, L _E, L _E1, R _E1The electrical impedance of having formed voice coil loudspeaker voice coil has been considered the eddy current effect of voice coil loudspeaker voice coil, corresponding to the Z in the acoustic analog circuit _LSR _ES, C _MES, L _CETCorrespond respectively to R _AS, M _AS, C _AT

So electric input impedance $Z_i=Z_{\mathrm{LE}}+\frac{1}{\frac{1}{R_{\mathrm{ES}}}+s{C}_{\mathrm{MES}}+\frac{1}{s{L}_{\mathrm{CET}}}}----\left(10\right)$

$\frac{E_0}{E_g}=\frac{Z_i-Z_{\mathrm{LE}}}{Z_i}----\left(11\right)$

At first measure the electrical impedance of loudspeaker unit or closed enclosure under conventional environment, the electric input impedance optimization that utilizes the genetic algorithm basis to record obtains the value of each element in the low frequency electrical equivalent circuit, component value is brought into (10) (11) formula again and is obtained E ₀/ E _g, then (11) formula is brought into (4) formula, as long as know other parameter value in (4) formula again, free field sound pressure level in the time of just can calculating low frequency, thus the non-dead room of realizing frequency response is measured.

5, the non-dead room method of measurement of the loud speaker low frequency frequency response based on electrical impedance as claimed in claim 1: the low frequency frequency response that it is characterized in that the pipeline bass-reflex cabinet is measured in order to following method:

In the frequency acoustic analogy circuit of pipeline bass-reflex cabinet, the acoustic impedance Z relevant in the loudspeaker unit with voice coil loudspeaker voice coil _LSRepresent; R _AS, C _AS, M _ASBe respectively acoustic resistance, acoustic compliance and the acoustic mass of speaker vibration system; C _AB, R _ABBe respectively the acoustic compliance and the acoustic resistance of casing; R _ALLeakage acoustic resistance for casing; M _AP, R _APAcoustic mass and acoustic resistance for acoustic conducting pipe;

In the low frequency electrical equivalent circuit of pipeline bass-reflex cabinet, R _E, L _E, L _E1, R _E1The electrical impedance of having formed voice coil loudspeaker voice coil has been considered the eddy current effect of voice coil loudspeaker voice coil, corresponding to the Z in the acoustic analog circuit _LSR _ES, C _MES, L _CESCorrespond respectively to the R in the acoustic analog circuit _AS, M _AS, C _ASL _CEB, R _EBCorrespond respectively to C _AB, R _ABR _EL, C _MEP, R _EPCorrespond respectively to R _AL, M _AP, R _AP

Order: $Z_{\mathrm{VB}}=\frac{s{R}_{\mathrm{EB}}{L}_{\mathrm{CEB}}}{R_{\mathrm{EB}}+s{L}_{\mathrm{CEB}}}----\left(12\right)$

$Z_{\mathrm{VP}}=\frac{1}{\frac{1}{R_{\mathrm{EP}}}+s{C}_{\mathrm{MEP}}}----\left(13\right)$

$Z_{\mathrm{LE}}=R_E+s{L}_E+\frac{{\mathrm{sR}}_{E1}{L}_{E1}}{R_{E1}+s{L}_{E1}}----\left(14\right)$

Electrical impedance so $Z_i=Z_{\mathrm{LE}}+\frac{1}{\frac{1}{R_{\mathrm{ES}}}+s{C}_{\mathrm{MES}}+\frac{1}{s{L}_{\mathrm{CES}}}+\frac{1}{R_{\mathrm{EL}}+Z_{\mathrm{VB}}+Z_{\mathrm{VP}}}}----\left(15\right)$

$\frac{E_0}{E_g}=\frac{Z_i-Z_{\mathrm{LE}}}{Z_i}\frac{Z_{\mathrm{VB}}}{R_{\mathrm{EL}}+Z_{\mathrm{VP}}+Z_{\mathrm{VB}}}----\left(16\right)$

At first measure the electrical impedance of pipeline bass-reflex cabinet under conventional environment, the electric input impedance optimization that utilizes the genetic algorithm basis to record obtains the value of each element in the low frequency electrical equivalent circuit, component value is brought into (15) (16) formula again and is obtained E ₀/ E _g, then (16) formula is brought into (4) formula, as long as know other parameter value in (4) formula again, free field sound pressure level in the time of just can calculating low frequency, thus the non-dead room of realizing frequency response is measured.

6, the non-dead room method of measurement of the loud speaker low frequency frequency response based on electrical impedance as claimed in claim 1: the low frequency frequency response that it is characterized in that sky cone bass-reflex cabinet is measured in order to following method:

In the frequency acoustic analogy circuit of empty cone bass-reflex cabinet, the acoustic impedance Z relevant in the loudspeaker unit with voice coil loudspeaker voice coil _LSRepresent; R _AS, C _AS, M _ASBe respectively acoustic resistance, acoustic compliance and the acoustic mass of speaker vibration system; C _AB, R _ABBe respectively the acoustic compliance and the acoustic resistance of casing; R _ALLeakage acoustic resistance for casing; M _AP, R _AP, C _APAcoustic mass, acoustic resistance and acoustic compliance for empty cone;

In the low frequency electrical equivalent circuit of empty cone bass-reflex cabinet, R _E, L _E, L _E1, R _E1The electrical impedance of having formed voice coil loudspeaker voice coil has been considered the eddy current effect of voice coil loudspeaker voice coil, corresponding to the Z in the acoustic analog circuit _LSR _ES, C _MES, L _CESCorrespond respectively to the R in the acoustic analog circuit _AS, M _AS, C _ASL _CEB, R _EB, R _ELCorrespond respectively to C _AB, R _AB, R _ALC _MEP, R _EP, L _CEPCorrespond respectively to M _AP, R _AP, C _AP

Order: $Z_{\mathrm{PB}}=\frac{s{R}_{\mathrm{EB}}{L}_{\mathrm{CEB}}}{R_{\mathrm{EB}}+s{L}_{\mathrm{CEB}}}----\left(17\right)$

$Z_{\mathrm{PP}}=\frac{1}{\frac{1}{R_{\mathrm{EP}}}+s{C}_{\mathrm{MEP}}+\frac{1}{s{L}_{\mathrm{CEP}}}}----\left(18\right)$

$Z_{\mathrm{LE}}=R_E+s{L}_E+\frac{{\mathrm{sR}}_{E1}{L}_{E1}}{R_{E1}+s{L}_{E1}}----\left(19\right)$

Electrical impedance so $Z_i=Z_{\mathrm{LE}}+\frac{1}{\frac{1}{R_{\mathrm{ES}}}+s{C}_{\mathrm{MES}}+\frac{1}{s{L}_{\mathrm{CES}}}+\frac{1}{R_{\mathrm{EL}}+Z_{\mathrm{PB}}+Z_{\mathrm{PP}}}}----\left(20\right)$

$\frac{E_0}{E_g}=\frac{Z_i-Z_{\mathrm{LE}}}{Z_i}\frac{Z_{\mathrm{PB}}}{R_{\mathrm{EL}}+Z_{\mathrm{PP}}+Z_{\mathrm{PB}}}----\left(21\right)$

At first measure the electrical impedance of sky cone bass-reflex cabinet under conventional environment, the electric input impedance optimization that utilizes the genetic algorithm basis to record obtains the value of each element in the low frequency electrical equivalent circuit, component value is brought into (20) (21) formula again and is obtained E ₀/ E _g, then (21) formula is brought into (4) formula, as long as know other parameter value in (4) formula again, free field sound pressure level in the time of just can calculating low frequency, thus the non-dead room of realizing frequency response is measured.

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