JP2007259061A - Acoustic characteristic correction apparatus and acoustic reproduction system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acoustic characteristic correction apparatus for correcting the effect of reflection faces in a space wherein speakers are arranged and excellently correcting a sound field characteristic cost-effectively at less expense in a job load of a user and to provide an acoustic reproduction system using the acoustic characteristic correction apparatus. <P>SOLUTION: When distances between the respective reflection faces and the speakers existing in the space wherein the speakers are arranged are respectively a first distance, a second distance, and a third distance, a control section determines a combination of characteristic values of a parametric equalizer of a signal processing section on the basis of a first distance value, a second distance value, and a third distance value entered to an operation section corresponding to the first distance, the second distance, and the third distance. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an acoustic reproduction system that reproduces an audio signal, and more particularly, to an acoustic characteristic correction device that corrects the influence of a reflecting surface in a space in which speakers are arranged, and an acoustic reproduction system using the same.

  In a sound reproduction system that reproduces sound from a speaker placed in an indoor space, the ceiling, floor, or wall surface becomes a sound wave reflecting surface depending on the boundary conditions around the speaker, that is, the location and height of the speaker. It is known that the output from the power supply changes and affects the frequency characteristics of the sound reproduction system (Non-Patent Document 1). For example, when the speaker approaches the wall surface, the reproduction level at the low frequency range tends to increase, and the bass sound of the reproduced sound tends to be emphasized. Such an effect of reflection by the wall surface is sometimes referred to as sound field characteristics or room gain. The magnitude of the gain of the sound field characteristic and the frequency at which the gain changes depends on the number of wall surfaces close to the speaker and the distance from each wall surface.

Roy F. Allison, `` The Influence of Room Boundaries on Loudspeaker Power Output '', JOURNAL OF THE AUDIOENGINEERING SOCIETY, June 1974, Volume 22, Number 5, p.314-320

  In order to avoid the influence of such a sound field characteristic, conventionally, there has been an acoustic characteristic correction device that attempts to flatten the sound field characteristic by increasing or decreasing the level of a specific frequency range such as a graphic equalizer or a parametric equalizer. is there. The acoustic characteristic correction apparatus is connected between a reproduction apparatus that reproduces an audio signal and an amplifier that drives a speaker, and gives the audio signal a substantially reverse characteristic of the sound field characteristic on the frequency characteristic. For example, some acoustic characteristic correction apparatuses include a microphone that measures sound field characteristics and controls the correction characteristics (Patent Document 1). In addition, some acoustic characteristic correction apparatuses attempt to correct sound field characteristics by changing the tone control means by inputting the speaker height from the floor surface on which the speakers are installed (Patent Document 2). . In addition, there is a speaker that changes a predetermined frequency characteristic of 30 Hz to 50 Hz by including a detection unit that detects a speaker installation height (Patent Document 3).

JP-A-6-53767 (FIG. 1) JP-A-6-105390 (FIGS. 4 and 5) JP-A-2002-112371 (FIGS. 1 and 2)

  However, the conventional acoustic characteristic correction apparatus and the acoustic reproduction system using the same have a problem that the correction of the sound field characteristic is not sufficient. When the microphone for measuring the sound field characteristic is provided, there is a problem that the cost and the work burden on the user increase, such as the necessity of preparing the microphone and reproducing the measurement signal. Further, when the sound field characteristics are corrected by inputting or detecting the speaker height, the tone control means is not sufficient as a substantially inverse characteristic of the sound field characteristics, and in addition, the frequency range to be corrected is 30 Hz to 50 Hz. The frequency is not sufficient as a correction range. Even if a graphic equalizer or a parametric equalizer is prepared, it is difficult for a user who does not have knowledge of “frequency” to make adjustments.

  The present invention has been made to solve the above-described problems of the prior art, and an object thereof is an acoustic characteristic correction apparatus that corrects the influence of a reflecting surface in a space where a speaker is arranged, and is used at a low cost. An object of the present invention is to provide an acoustic characteristic correction apparatus that can correct a sound field characteristic satisfactorily and a sound reproduction system using the same.

  An acoustic characteristic correction apparatus according to the present invention includes a signal input unit to which an audio signal is input, a signal processing unit including a plurality of parametric equalizers that perform signal processing on the audio signal output from the signal input unit, and a signal processing unit A signal output unit that receives the audio signal output from the speaker and outputs the audio signal to the speaker, a control unit that controls the signal input unit, the signal processing unit, and the signal output unit, and an operation unit that is connected to the control unit. In the acoustic characteristic correcting device, when the distance between each of the reflecting surfaces existing in the space where the speaker is arranged and the speaker is the first distance, the second distance, and the third distance, respectively, the control unit Characteristics of the parametric equalizer of the signal processing unit based on the first distance value, the second distance value, and the third distance value input to the operation unit corresponding to the first distance, the second distance, and the third distance. To determine the combination.

  Preferably, in the acoustic characteristic correcting device of the present invention, the first distance value and the second distance corresponding to the first distance and the second distance are used when the speaker is an embedded speaker embedded in the reflecting surface. Based on the values, a combination of characteristic values of the parametric equalizer of the signal processing unit is determined.

  Preferably, in the acoustic characteristic correction apparatus of the present invention, the signal processing unit is configured by at least two series-connected parametric equalizers PEQ1 and PEQ2, and PEQ1 has, as its characteristic values, a center frequency F1, a center gain G1, and The resonance sharpness Q1 and the PEQ2 have the center frequency F2, the center gain G2 and the resonance sharpness Q2 as their characteristic values, and the control unit sets the characteristic values of the PEQ1 and PEQ2 to the first It is determined based on an approximate polynomial including at least one of the first distance value, the second distance value, and the third distance value.

  In the acoustic characteristic correction apparatus of the present invention, the two serially connected parametric equalizers PEQ1 and PEQ2 of the signal processing unit are set so that the center frequency F1 of PEQ1 is in the range of 20 Hz to 100 Hz, and the center frequency F2 of PEQ2 Is set in the range of 100 Hz to 600 Hz.

  Further, an acoustic reproduction system of the present invention includes the above-described acoustic characteristic correction device, a reproduction device that reproduces an audio signal and inputs it to a signal input unit, an amplification device that amplifies the audio signal output from the signal output unit, And a speaker to which an output signal from the amplifying device is input.

  The operation of the present invention will be described below.

  An acoustic characteristic correction apparatus according to the present invention includes a signal input unit to which an audio signal is input, a signal processing unit including a plurality of parametric equalizers that perform signal processing on the audio signal output from the signal input unit, and a signal processing unit A signal output unit that receives the audio signal output from the speaker and outputs the audio signal to the speaker, a control unit that controls the signal input unit, the signal processing unit, and the signal output unit, and an operation unit that is connected to the control unit. An acoustic reproduction system including the acoustic characteristic correction device includes a reproduction device that reproduces an audio signal and inputs the audio signal to a signal input unit, an amplification device that amplifies the audio signal output from the signal output unit, and an output signal from the amplification device. Including a speaker. This speaker is an embedded speaker that is disposed in an indoor space whose ceiling, floor, or wall surface is a reflective surface, and is embedded in the reflective surface in some cases.

  Here, the parametric equalizer is an equalizer process that changes a center level and a center frequency with a band pass characteristic or a band eliminate characteristic. The parametric equalizer is defined by its characteristic values, that is, the center frequency, the center level, and the sharpness (Q) of resonance. Specifically, the parametric equalizer may be an analog circuit composed of an element such as a coil, a capacitor, or a transistor, but a secondary or higher order IIR is provided inside a digital signal processing circuit such as a DSP (digital signal processor). It is preferably realized by a filter. This is because the characteristic value of the parametric equalizer can be freely set by changing the coefficient of the IIR filter.

  For example, when the parametric equalizer is configured by a digital signal processing circuit, typically, the signal input unit includes an A / D converter, the signal processing unit includes a DSP, and the signal output unit includes a D / A converter. The control unit includes a microcomputer and is connected to an operation unit configured by a switch operated by a user. Based on first distance values, second distance values, and third distance values, which will be described later, input to the operation unit. The combination of characteristic values of the parametric equalizer of the signal processing unit is determined.

  The control unit includes a first distance value, a second distance value, and a third distance corresponding to the first distance, the second distance, and the third distance with respect to the respective reflecting surfaces in the space where the speaker of the sound reproduction system is disposed. Based on the values, a combination of characteristic values of the parametric equalizer of the signal processing unit is determined. For example, when a speaker is installed near a corner in a rectangular parallelepiped indoor space, the first distance, the second distance, and the third distance are the three surfaces approaching the speaker (for example, the ceiling, the front wall, and the side surface). The distance between the combination of the wall) and the speaker. That is, when the output from the speaker changes depending on the boundary conditions around the speaker and the sound field characteristics that affect the frequency characteristics of the sound reproduction system are determined, the first distance, the second distance and the simplest boundary conditions, The inverse characteristic of the sound field characteristic is calculated from the third distance, and the combination of the characteristic values of the parametric equalizer of the signal processing unit is determined.

  The sound field characteristic determined by the boundary condition is calculated by Roy F. Allison (Non-patent Document 1, hereinafter referred to as Allison), and the correction characteristic of the acoustic characteristic correction device uses the inverse characteristic of the calculation formula of Allison. . Since Allison's formula is a complex one with a Bessel function, the combination of the characteristic values of the parametric equalizer of the signal processing unit is set to the first distance in order to realize an acoustic characteristic correction apparatus that corrects the sound field characteristics satisfactorily. , And an approximate polynomial calculated from the second distance and the third distance. That is, the approximate polynomial is obtained by the control unit by using the parametric equalizer characteristic values (center frequency, center level and resonance sharpness (Q)) as the first distance value corresponding to the first distance, the second distance, and the third distance. , Using the second distance value and the third distance value. Therefore, an acoustic characteristic correction apparatus that can correct the sound field characteristic satisfactorily is realized.

  Preferably, the signal processing unit includes at least two series-connected parametric equalizers PEQ1 and PEQ2, and PEQ1 has a center frequency F1, a center gain G1, and a resonance sharpness Q1 as its characteristic values. PEQ2 has, as its characteristic values, center frequency F2, center gain G2, and resonance sharpness Q2, which are determined based on the first distance value, the second distance value, and the third distance value. The As for the characteristic values of the two parametric equalizers PEQ1 and PEQ2 connected in series, a preferable combination is calculated from the approximate polynomial of the control unit. Therefore, in determining the correction characteristic of the acoustic characteristic correction apparatus, the user can determine the first distance value, the second distance value, and the third distance corresponding to the first distance, the second distance, and the third distance based on the boundary condition of the speaker. It is only necessary to input a value to the operation unit. Without preparing a microphone or the like, an acoustic characteristic correction apparatus that easily corrects the sound field characteristic can be realized easily at low cost with less work burden on the user.

  The correction characteristic realized by the signal processing unit of the present invention is approximately 20 Hz to approximately 20 Hz, although it varies depending on the distance between the speaker and the wall surface, etc., even when it is constituted by two serially connected parametric equalizers PEQ1 and PEQ2. The frequency characteristics are complicatedly waved between 1 kHz. That is, with a small input value from the user, a highly accurate correction characteristic can be obtained over a wide frequency band from the low sound range to the mid sound range. Therefore, a better acoustic characteristic correction apparatus is realized as compared with the case where a simple tone control means as in the prior art is used or when the frequency of 30 Hz to 50 Hz which is a low sound range is corrected.

  The acoustic characteristic correction apparatus of the present invention can correct the influence of the reflecting surface in the space where the speaker of the sound reproduction system is arranged, and can correct the sound field characteristic with a low cost and a low work burden on the user. And

  The acoustic characteristic correction apparatus of the present invention is a low-cost, low work burden on the user, and an acoustic characteristic correction apparatus that corrects sound field characteristics satisfactorily, and an acoustic reproduction system using the same. A signal input unit to which a signal is input, a signal processing unit composed of a plurality of parametric equalizers that perform signal processing on the audio signal output from the signal input unit, and a speaker that receives the audio signal output from the signal processing unit An acoustic characteristic correction apparatus comprising: a signal output unit that outputs an audio signal to a signal; a control unit that controls the signal input unit, the signal processing unit, and the signal output unit; and an operation unit that is connected to the control unit. When the distance between each reflecting surface and the speaker existing in the arranged space is the first distance, the second distance, and the third distance, respectively, the control unit performs the first distance and the second distance. And a combination of characteristic values of the parametric equalizer of the signal processing unit based on the first distance value, the second distance value, and the third distance value input to the operation unit corresponding to the third distance. .

  Hereinafter, an acoustic characteristic correction apparatus and an acoustic reproduction system using the same according to preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

  FIG. 1 is a diagram for explaining the arrangement of speakers constituting a sound reproduction system according to a preferred embodiment of the present invention. The speaker 1 is installed at one corner so as to reproduce sound into an indoor space surrounded by wall surfaces. In FIG. 1A, a speaker 1 including a tweeter 3 and a woofer 4 attached to a speaker cabinet 2 is installed on a floor surface 6 via a stand 5. The woofer 4 that reproduces the low sound range is separated from the floor surface 6 by a distance z, separated from the side wall surface 7 by a distance x, and separated from the rear surface 8 by a distance y. The influence of the room gain due to the reflection surface increases as the speaker 1 approaches the reflection surface, that is, as the distances x, y, and z become shorter than the wavelength of the reproduced sound wave. Since there is an influence from three boundaries of the side wall surface 7, the rear surface 8, and the floor surface 6, such a case is referred to as the Allison three boundary.

  FIG. 1B is a diagram illustrating a case where the speaker 1 is an embedded speaker embedded in the ceiling surface 9. In this case, the room gain is a case of two boundaries affected by the side wall surface 7 separated by a distance x and the rear surface 8 separated by a distance y. Of course, the speaker 1 may be a full-range speaker as shown, or a multi-way speaker as shown in FIG. Even in the case of FIG. 1A, if the distance to any one of the distances x, y, and z is significantly larger than the distance to the other boundary, the influence of the boundary is ignored. In that case, it becomes the case of the 2 boundary of Allison. Similarly, when only the reflection surface at the closest distance affects, it is the case of one boundary of Allison.

  FIG. 2 is a diagram illustrating the sound reproduction system 20 according to a preferred embodiment of the present invention. The acoustic reproduction system 20 includes a reproduction device 21 such as a CD (compact disc) player, an acoustic characteristic correction device 10 to which a signal from the reproduction device 21 is input, and an amplifier to which an audio signal from the acoustic characteristic correction device 10 is input. 22 and the speaker 1 connected to the amplifier 22. The acoustic characteristic correction apparatus 10 includes an A / D converter 11 that converts an analog audio signal into a digital signal, a DSP (digital signal processor) 12, and a D / A converter that converts audio signal data output from the DSP 12 into an audio signal. 13 and so on. The acoustic characteristic correction apparatus 10 includes a microcomputer 15 that configures the control unit 14 and a memory 16 that stores coefficients used by the DSP 12, and further includes an operation including a switch 17 and a display circuit 18 that are operated by a user. Part 19.

FIG. 3 is a diagram for explaining a parametric equalizer that the DSP 12 configures. As shown in FIG. 3A, this is configured by connecting at least two parametric equalizers PEQ1 and PEQ2 in series. The parametric equalizers PEQ1 and PEQ2 have PEQ1 having a center frequency F1, a center gain G1, and a resonance sharpness Q1 as characteristic values, and PEQ2 has a center frequency F2, a center gain G2, And resonance sharpness Q2. Specifically, as shown in FIG. 3B, the two parametric equalizers PEQ1 and PEQ2 are each realized by a second-order IIR filter. The IIR filter includes a multiplier that is multiplied by coefficients a _{0 to} a ₂ and coefficients b _{1 to} b ₂ , a delay device, and an adder. The coefficients of the IIR filter are determined from the sampling frequency at which the IIR filter operates and the characteristic values of the parametric equalizers PEQ1 and PEQ2.

  Therefore, the characteristic value of the parametric equalizer can be freely set by changing the coefficient of the IIR filter. When the parametric equalizers PEQ1 and PEQ2 can display respective characteristic values on the display circuit 18 of the acoustic characteristic correction apparatus 10, the respective characteristic values can be directly set by the switch 17 operated by the user. The microcomputer 15 calculates the coefficient of the IIR filter from the characteristic values of the parametric equalizers PEQ1 and PEQ2.

  On the other hand, the user may directly input the distances x, y, and z into the operation unit 19. The microcomputer 15 determines a combination of the characteristic values of the parametric equalizer of the DSP 12 based on the distances x, y, and z input from the operation unit 19, and gives the DSP 12 coefficients of the digital filter. In the following, a method for determining a combination of characteristic values of a parametric equalizer will be described taking the case of the Allison two boundary of FIG. 1B as an example.

For example, when the speaker 1 is an embedded speaker, “z = 0” is input from the operation unit 19 and the combination of the characteristic values of the parametric equalizer of the DSP 12 is determined based on the remaining parameter distances x and y. . Alternatively, the operation unit 19 may select the case of the Allison two boundary. The ratio of the sound source output W to the sound source output Wf in the free space in the case of Allison's two boundaries, that is, the room gain of the two boundaries is expressed by the following equation when the wavelength is λ. Note that j ₀ (a) = Sin (a) / a spherical Bessel function.

W / Wf = 1 + j ₀ (4πx / λ) + j ₀ (4πy / λ) + j ₀ (4π (x ² + y ² ) ^1/2 / λ)

  FIG. 4A shows the frequency characteristics of the room gain when the distance x is 20 cm and the distance y is changed to 20, 30, 40, 50, and 60 cm in the case of the Allison two boundary. It is a graph. The frequency characteristics change as shown by the arrows in the graph in the order of increasing the distance y from 20 cm to 60 cm. If the distance y is lengthened, the room gain level is lowered, and the acting frequency is also lowered. On the other hand, FIG. 4B is a graph showing the frequency characteristics of an ideal correction inverse filter that corrects the room gain shown in FIG. Contrary to the room gain, the frequency characteristic must be changed as shown by the arrow in the graph in the order of increasing the distance y from 20 cm to 60 cm.

  Similarly, FIG. 5 (a) shows the distance x = 30 cm for the Allison 2 boundary, while the distances y = 20, 25, 30, 35, 40, 45, 50, 55, 60, and 65 cm. It is a graph showing the frequency characteristic of the room gain when changing to. The frequency characteristics change as shown by arrows in the graph in the order of increasing the distance y from 20 cm to 65 cm. If the distance y is increased, the room gain level is lowered and the frequency at which it acts is also the same as in the case of the distance x = 20 cm. On the other hand, FIG. 5B is a graph showing the frequency characteristics of an ideal correction inverse filter that corrects the room gain shown in FIG. As described above, the frequency characteristic of the correction inverse filter also changes as the distance x changes. However, as the distance y increases, the same tendency of change is seen in the arrow direction.

  Although these corrected inverse filters can be obtained based on the above-described equation representing the room gain, they cannot be reproduced as they are by the DSP 12 because they include a spherical Bessel function. Therefore, a room gain correction filter approximating this correction inverse filter is configured by a preferable combination of the characteristic values of the two serially connected parametric equalizers PEQ1 and PEQ2. For example, FIG. 4C is a graph showing the frequency characteristics of a correction filter approximating the ideal correction inverse filter of FIG. The combinations (center frequency, resonance sharpness, center gain) of the characteristic values of the parametric equalizers PEQ1 and PEQ2 at this time are as follows.

(x20 cm, y20 cm): (82Hz, Q0.5, -6dB), (550Hz, Q2.0, 4.0dB)
(x20 cm, y30 cm): (70Hz, Q0.5, -6dB), (400Hz, Q1.8, 3.0dB)
(x20 cm, y40 cm): (63Hz, Q0.5, -6dB), (325Hz, Q1.6, 2.0dB)
(x20 cm, y50 cm): (60Hz, Q0.5, -6dB), (250Hz, Q1.6, 1.5dB)
(x20 cm, y60 cm): (58Hz, Q0.5, -6dB), (200Hz, Q1.4, 1.3dB)

  Here, a method for determining the characteristic values of the parametric equalizers PEQ1 and PEQ2 will be described. Since the characteristic of the ideal correction inverse filter in FIG. 4B is accompanied by a fine peak dip, the characteristic is simplified to a frequency characteristic that is smoothed by a moving average on the frequency to remove the fine peak dip. Next, this is normalized by setting the frequency band of about 1 kHz or more, which has a flat characteristic by moving average, to 0 dB. Then, PEQ1 is set first, and then PEQ2 is set. The parametric equalizer PEQ1 has a common resonance sharpness Q1 = 0.5 and a center gain G1 = −6 dB, except that the center frequency F1 = 58 Hz to 82 Hz changes. The parametric equalizer PEQ2 is common in that the center frequency F2 = 200 Hz to 550 Hz changes, but the resonance sharpness Q2 is larger than 1.0, and the center gain G2 has a peak of 1.4 dB to 4.0 dB. is there. In this way, in the case of Allison's two boundaries, a set of characteristic values of the parametric equalizers PEQ1 and PEQ2 is determined for the combination of the distance x and the distance y.

  In other words, the above method is a method in which the frequency band is divided into the number of elements of the parametric equalizer connected in series and the characteristic value of the parametric equalizer is determined based on the frequency near the average level in the divided frequency band. For example, the parametric equalizers PEQ1 and PEQ2 may set the center frequency f1 of PEQ1 within a range of 20 Hz to 100 Hz and the center frequency f2 of PEQ2 within a range of 100 Hz to 600 Hz with a frequency of 100 Hz as a boundary.

  Next, among the characteristic values of the parametric equalizers PEQ1 and PEQ2, an approximate polynomial is obtained by curve fitting for the characteristic values that change according to the distance x and the distance y. Specifically, FIG. 6A is a graph in which the center frequency F1 [Hz] of PEQ1 that changes is plotted among the combinations of the characteristic values of PEQ1 and PEQ2 when the distance x = 20 cm. The function F1f (y) is approximated by a cubic polynomial with a distance y [cm]. As described above, the characteristic values (center frequency F1, resonance sharpness Q1, center gain G1) of the parametric equalizer PEQ1 can be uniquely obtained by the distance y when the distance x = 20 cm.

F1f (y) = Af1 * y ³ + Bf1 * y ² + Cf1 * y + Df1
Here, Af1 = −3.3333 * 10 ⁻⁴
Bf1 = 5.7143 * 10 ⁻²
Cf1 = −3.4811
Df1 = 1.3060 * 10 ²

  Similarly, FIG. 6B is a graph in which the center frequency F2 [Hz] of PEQ2 that changes when the distance x = 20 cm is plotted. The cubic F of the distance y [cm] is expressed by the following function F2f (y). It is approximated by a polynomial.

F2f (y) = Af2 * y ³ + Bf2 * y ² + Cf2 * y + Df2
Here, Af2 = −4.1667 * 10 ⁻³
Bf2 = 6.4286 * 10 ⁻¹
Cf2 = −3.8512 * 10 ¹
Df2 = 1.0950 * 10 ³

  Next, FIG. 7A is a graph plotting the resonance sharpness Q2 of PEQ2 that changes when the distance x = 20 cm, and is a cubic polynomial of the distance y [cm] by the following function F2q (y). Approximated.

F2q (y) = Aq2 * y ³ + Bq2 * y ² + Cq2 * y + Dq2
Here, Aq2 = 4.4929 * 10 ⁻¹⁸
Bq2 = 2.429 * 10 ⁻⁴
Cq2 = −3.2143 * 10 ⁻²
Dq2 = 2.5600

  Finally, FIG. 7B is a graph in which the gain G2 of PEQ2 that changes when the distance x = 20 cm is plotted, and is approximated by a second order polynomial of the distance y [cm] by the following function F2g (y). (Third-order coefficient Ag2 = 0).

^{F2g (y) = Ag2 * y} 3 + Bg2 * y 2 + Cg2 * y + Dg2
Here, Ag2 = 0
Bg2 = 1.5000 * 10 ⁻³
Cg2 = −1.8900 * 10 ⁻¹
Dg2 = 7.2200

  Therefore, the characteristic values (center frequency F2, resonance sharpness Q2, center gain G2) of the parametric equalizer PEQ2 can also be uniquely determined by the distance y when the distance x = 20 cm.

  As shown in FIG. 5, as in the case of the distance x = 20 cm, among the characteristic values of the parametric equalizers PEQ1 and PEQ2 even when the distance x = 30 cm, the characteristic values that change according to the distance x and the distance y are: An approximate polynomial can be obtained by curve fitting. Of course, the same applies to other distances x, and it is also possible to obtain an approximate polynomial using the distance x as a variable with the distance y fixed. As a result, for a plurality of discretely set distances x and distances y, approximate polynomial coefficients that directly calculate the characteristic values of the parametric equalizers PEQ1 and PEQ2 from the distances x and y are obtained.

Therefore, in the acoustic characteristic correction apparatus 10, the memory 16 included in the control unit 14 holds the coefficients of these approximate polynomials, and the microcomputer 15 inputs the distance x and the distance y input by the user, and these approximate polynomials. based on, to calculate the characteristic value of PEQ1 and PEQ2, finally coefficients of the IIR filter (coefficients _a 10 _{~a 12} and the coefficient _b 11 _{~b 12,} the coefficient _a 20 _{~a 22} and the coefficient _b 21 _{~b 22)} Can be calculated. Actually, for example, when the frequency obtained by the function F1f (y) is about 79 Hz, the frequency is rounded to a discrete frequency value of 80 Hz that can be set by the parametric equalizer PEQ1, and this value of 80 Hz is used. The coefficient of the IIR filter is obtained. Since the memory 16 holds the coefficients of the IIR filter of the parametric equalizer corresponding to the discrete frequency values according to the sampling frequency, these coefficients may be used.

Of course, in addition to the coefficients stored in the memory 16, the coefficients of the IIR filter calculated by the microcomputer 15 may be used. For example, if the gain G1 of the parametric equalizer PEQ1 is −6 dB as in the above embodiment, 0.5 is set to the coefficients a _{10 to} a ₁₂ of the IIR filter having a gain of 1.0 held in the memory 16. and integrating the coefficients, using as coefficients _b 11 _{~b 12} memory 16 holds may be set parametric equalizer PEQ1. Thus, the microcomputer 15 calculates the coefficient of the IIR filter, so that the coefficient to be held by the memory 16 can be reduced.

  When the microcomputer 15 loads the DSP 12 with the coefficients of the IIR filter, as a result, the embedded speaker 1 is attached to the ceiling surface 9, and the distance x in the case of Allison's two boundaries having the distance x and the distance y of the reflection surface In addition, the acoustic characteristic correction apparatus 10 that corrects the room gain satisfactorily only by inputting the distance y is realized. Since the work load on the user is small, even an operator who does not have specialized knowledge, for example, even a person who does not even have the concept of “frequency”, can correct the sound field characteristics of the room gain well. An apparatus can be obtained and a sound reproduction system can be obtained in which any user can obtain good acoustic characteristics.

  The memory 16 provided in the control unit 14 preferably holds coefficients of approximate polynomials corresponding to discrete major distances x, y and z. It is sufficient that the distances x, y, and z cover a range of 5 cm to about 2.0 m, and when the distance is longer than that, the influence of the reflecting surface becomes small. Therefore, even in the case of Allison's three boundaries, if it includes a reflective surface of a long distance, it can be approximated to the case of Allison's two or one boundary. The distance between the discrete major distances is also appropriate from the capacity of the memory 16 that the distance of about 5 cm or 10 cm holds, and as the distances x, y, and z take larger values, the distance between the discrete distances is also increased. You may enlarge it.

  Further, the memory 16 included in the control unit 14 may hold the characteristic values of the parametric equalizers PEQ1 and PEQ2 that directly correspond to the discrete main distances x, y, and z as they are. The input distances x, y, and z are rounded off and rounded to discrete retained main distances x, y, and z, and the characteristic values of the parametric equalizers PEQ1 and PEQ2 may be approximated.

  The acoustic characteristic correction apparatus and the sound reproduction system using the same according to the present invention are not limited to the above-described embodiments, and can be applied to the case of correcting the room gain of a speaker disposed in a narrower vehicle interior space.

It is a figure explaining arrangement | positioning of the speaker which comprises the sound reproduction system by preferable embodiment of this invention. Example 1 It is a figure explaining the sound reproduction system of this invention. Example 1 It is a figure explaining the parametric equalizer which DSP12 comprises. Example 1 It is a graph showing the frequency characteristics of a room gain and a correction filter. It is a graph showing the frequency characteristics of a room gain and a correction filter. It is a graph which shows the change of the characteristic value of a parametric equalizer. It is a graph which shows the change of the characteristic value of a parametric equalizer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Speaker 2 Speaker cabinet 3 Tweeter 4 Woofer 5 Stand 6 Floor surface 7 Side wall surface 8 Back surface 9 Ceiling surface 10 Acoustic characteristic correction apparatus 11 A / D converter 12 DSP
13 D / A converter 14 Control unit 15 Microcomputer 16 Memory 17 Switch 18 Display circuit 19 Operation unit 20 Sound reproduction system

Claims (5)

A signal input unit to which an audio signal is input, a signal processing unit including a plurality of parametric equalizers that perform signal processing on the audio signal output from the signal input unit, and an audio signal output from the signal processing unit An acoustic characteristic correction comprising: a signal output unit that receives and outputs an audio signal to a speaker; a control unit that controls the signal input unit, the signal processing unit, and the signal output unit; and an operation unit that is connected to the control unit A device,
When the distance between each reflecting surface present in the space where the speaker is placed and the speaker is the first distance, the second distance, and the third distance,
The control unit performs the signal processing based on the first distance value, the second distance value, and the third distance value that are input to the operation unit corresponding to the first distance, the second distance, and the third distance. Determine the combination of the characteristic values of the part parametric equalizer,
Acoustic characteristic correction device. When the speaker is an embedded speaker installed embedded in the reflecting surface, based on the first distance value and the second distance value corresponding to the first distance and the second distance, Determine the combination of characteristic values of the parametric equalizer of the signal processor
The acoustic characteristic correction apparatus according to claim 1. The signal processing unit is composed of at least two serially connected parametric equalizers PEQ1 and PEQ2.
The PEQ1 has a center frequency F1, a center gain G1, and a resonance sharpness Q1 as its characteristic values.
The PEQ2 has, as its characteristic values, a center frequency F2, a center gain G2, and a resonance sharpness Q2.
The control unit determines the characteristic values of the PEQ1 and the PEQ2 based on an approximate polynomial including at least one of the first distance value, the second distance value, and the third distance value;
The acoustic characteristic correction apparatus according to claim 1. Two serially connected parametric equalizers PEQ1 and PEQ2 of the signal processing unit are:
The center frequency F1 of the PEQ1 is set in a range of 20 Hz to 100 Hz, and the center frequency F2 of the PEQ2 is set in a range of 100 Hz to 600 Hz.
The acoustic characteristic correction apparatus according to claim 3. 5. The acoustic characteristic correction device according to claim 1, a reproduction device that reproduces an audio signal and inputs the audio signal to the signal input unit, and an amplification device that amplifies the audio signal output from the signal output unit; And a speaker to which an output signal from the amplifying device is input.

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