KR102479068B1 - Multi-channel sound system for each performer and multiple audiences in a small concert hall - Google Patents

Abstract

Provided is a multi-channel sound system, which is provided in a rectangular live concert hall defined by a front wall on which a stage is installed, a rear wall opposite to the front wall, and left and right sidewalls extending between the front wall and the rear wall, and provides a performer sweet spot for a performer on the stage and a plurality of audience sweet spots for respective audiences seated on a plurality of seats. The multi-channel sound system comprises: a seating sensor installed in each of the plurality of seats; a microphone provided to the performer, and having a position sensor for sensing the movement of the performer; a plurality of tweeter boxes at least disposed on each of the rear wall and the left and right sidewalls, excluding the front wall, among the four walls of the live concert hall; a plurality of mid boxes arranged at the four corners of the live concert hall, respectively; at least one woofer box embedded in a ceiling area of the live concert hall; a DSP for receiving an audio signal from an audio source, and transmitting an individually processed analog signal to each of tweeters installed in the plurality of tweeter boxes, mid speakers installed in the plurality of mid boxes, and woofer speakers installed in the woofer box; a first controller for controlling the directional angle of the tweeters; a second controller for controlling turn on or off of the mid speakers; and a MCU for controlling the DSP and the first and second controllers, based on the movement of the performer sensed by the microphone so that the performer sweet spot faces the performer, and controlling the DSP and the first and second controllers, based on the position of each of the audiences sensed by the seating sensors so that each of the plurality of audience sweet spots faces each of the audiences. Therefore, the multi-channel sound system can increase the immersion level of the audiences with respect to auditory appreciation.

Description

Multi-channel sound system for performers and multiple audiences in small live venues {MULTI-CHANNEL SOUND SYSTEM FOR EACH PERFORMER AND MULTIPLE AUDIENCES IN A SMALL CONCERT HALL}

The present invention relates to a multi-channel sound system for performers and spectators in a small live venue.

In small live venue sound systems such as concert halls, audition stages, and live cafes, it is very important for performers to hear themselves accurately and comfortably. This is because if you cannot hear yourself clearly during a performance, it is no different than talking with your ears closed. In particular, it is more important than anything else for vocalists, wind instruments, and string instruments, whose volume is relatively low, to hear their own sound clearly due to the sound pouring out of numerous speakers in a large or small venue. However, in reality, it is very difficult for each individual to hear their own sound properly even in a large performance with an engineer. In particular, when the main performance starts, the performers have to pay more attention to the sound that the audience hears, so the performers perform without monitoring their own sound, which is one of the causes of deteriorating the quality of the performance.

Moreover, due to the characteristics of a small concert hall where the distance between the speaker and the listeners is relatively short, the existing audio system has a limitation in that it is impossible to form a sweet spot by localization in all spaces in the concert hall.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a sweet spot for each of the performers and spectators in a small live venue so that the performers can faithfully monitor their own sound and the audience can hear It is an object of the present invention to provide a multi-channel sound system capable of increasing the degree of immersion of the audience.

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

In order to solve this problem, according to an embodiment of the present invention, the front wall on which the stage is installed, the rear wall facing the front wall, and the left and right side walls extending between the front wall and the rear wall. A multi-channel sound system provided in a rectangular live performance hall defined by and providing a performer sweet spot for performers on the stage and a plurality of spectator sweet spots for each of the spectators seated in a plurality of spectator seats, wherein the plurality of Seating sensors installed in each of the spectator seats; a microphone provided to the performer and equipped with a position sensor for sensing the movement of the performer; a plurality of tweeter boxes disposed on each of the rear wall and left and right side walls of the four walls of the live performance hall, excluding the front wall; a plurality of mid boxes disposed at each of the four corners of the live venue; at least one woofer box embedded in a ceiling area of the live performance hall; DSP (digital) that receives audio signals from audio sources and transmits individually processed analog signals to the tweeters installed in the plurality of tweeter boxes, the mid speakers installed in the plurality of mid boxes, and the woofer speakers installed in the woofer box, respectively. signal processor); a first controller for controlling beam angles of the tweeters; a second controller for controlling on/off of the midspeakers; and controlling the DSP and the first and second controllers based on the movement of the performer sensed by the microphone so that the performer's sweet spot faces the performer, wherein each of the plurality of spectator sweet spots is directed to each of the spectators. Based on the position of each of the spectators sensed by the seating sensor so as to face the DSP and the first and second controllers MCU (Micro Controller Unit); including, a multi-channel sound system is provided. .

Side tweeter boxes disposed on the left and right side walls of the plurality of tweeter boxes are driven to form the spectator sweet spot, and side tweeter boxes disposed on the rear side wall of the plurality of tweeter boxes are driven to form the spectator sweet spot. Characterized in that it is driven to form a performer sweet spot.

Each of the plurality of tweeter boxes includes a semi-cylindrical main frame; a first beam angle rail extending in a horizontal direction along a semicircular circumference of the main frame; a first tweeter chamber installed on the first beam angle rail so as to be rotatable in a horizontal direction; a first tweeter mounted in the first tweeter chamber; a second beam angle rail extending in a horizontal direction along the circumference of the semi-cylindrical column and vertically spaced apart from the first beam angle rail; a second tweeter chamber installed on the second beam angle rail so as to be rotatable in a horizontal direction; and a second tweeter mounted in the second tweeter chamber, wherein each of the plurality of mid boxes includes first and second mid-speakers that can be individually turned on and off, and the DSP converts the audio signal into a first A first high-pass signal obtained by high-pass filtering of a frequency domain equal to or higher than the -1 crossover frequency is transferred to the first tweeter, and a second high-pass signal obtained by high-pass filtering of a frequency domain equal to or higher than the 1-2 crossover frequency is transmitted to the first tweeter. is transmitted to the second tweeter, and a first bandpass signal obtained by performing band pass filtering in the frequency domain from the second crossover frequency lower than the 1-1st crossover frequency to the 1-1st crossover frequency. is transmitted to the first midspeaker, and a first bandpass signal obtained by bandpass-filtering a frequency domain from the second crossover frequency to the 1-2 crossover frequency is transmitted to the second midspeaker; A low pass signal obtained by low pass filtering of a frequency domain below a second crossover frequency is transmitted to the woofer speaker, and the gain of each of the first and second high pass signals is first and second. It is calculated based on the distance between each of the 2 spectators and each of the first and second tweeters, and is applied to the 1-1 and 1-2 crossover frequencies and the first and second high-pass signals, respectively. The filter type and filter order (i.e., crossover slope) are calculated based on the distances between the first and second spectators and the first and second midspeakers, respectively, and the first controller A beam angle of each of the first and second tweeter chambers is controlled so that the first tweeter faces the first spectator and the second tweeter faces the second spectator, and the second controller controls the position of the first spectator. and controlling the on/off of the first and second mid-speakers in consideration of both the position of the spectator and the second spectator.

When the distance between the first spectator and the first midspeaker is equal to or greater than the first reference distance, the first high-pass signal is filtered with a second order (-12dB/oct) Bessel filter, and the first spectator and the first midspeaker are filtered. When the distance from the first midspeaker is less than the first reference distance, the first high-pass signal is filtered with a 3rd order (-18dB/oct) Chebyshev filter, and the 1-1 crossover frequency is as follows It is characterized in that it is calculated according to Equation 1.

[Equation 1]

(Here, the F_cut is the 1-1 crossover frequency [Hz], the D_mid is the distance between the first spectator and the first mid speaker [cm], the D_ref is the first reference distance [cm], The G_mid represents the average decibel [dB] of the first mid speaker at the position of the first spectator, and G_tw represents the average decibel [dB] of the first tweeter at the position of the first spectator.)

According to the embodiments of the present invention, by providing a sweet spot for each of the performers and spectators in a small live venue, the performer can faithfully monitor his or her own sound, and the audience can increase the degree of auditory immersion. .

Effects according to the technical spirit of the present disclosure are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

1 is a schematic diagram for explaining the configuration of a multi-channel sound system according to some embodiments of the present invention.
2 and 3 are diagrams conceptually showing a small-scale live performance hall in which a multi-channel sound system according to some embodiments of the present invention is installed.
4 is a diagram for exemplarily explaining a method of processing an audio signal into a high-pass signal by a DSP of a multi-channel sound system according to some embodiments of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention, and methods of achieving them, will become clear with reference to the detailed description of the following embodiments taken in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms, only the present embodiments make the disclosure of the present invention complete, and common knowledge in the art to which the present invention belongs. It is provided to completely inform the person who has the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numbers designate like elements throughout the specification.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used in a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless explicitly specifically defined.

Also, in this specification, the singular form may also include the plural form unless otherwise specified in the phrase. As used herein, "comprises" and/or "comprising" means that a stated component, step, operation, and/or element is present in the presence of one or more other components, steps, operations, and/or elements. or do not rule out additions.

1 is a schematic diagram for explaining the configuration of a multi-channel sound system according to some embodiments of the present invention, and FIGS. 2 and 3 show a small live venue in which a multi-channel sound system according to some embodiments of the present invention is installed. These are diagrams conceptually shown, and FIG. 4 is a diagram for illustratively explaining how a DSP of a multi-channel sound system processes an audio signal into a high-pass signal according to some embodiments of the present invention.

1 to 4, the multi-channel sound system 1 provided in a rectangular small-scale live performance hall R is provided with seating detection sensors 110 installed in each of a plurality of seats for spectators, and provided to the performers. A microphone 120 equipped with a position sensor for sensing the movements of performers, a plurality of speaker boxes (TBx, MBx, WBx) installed and provided in the small-scale live performance hall (R), and operations for operating and controlling the speakers includes a control unit. The operation control unit includes an RF antenna 210 for performing wireless communication with the mobile terminal 100, a source device 220 for supplying a sound source to be output to a speaker, and processing audio signals from the source device to each speaker. A digital signal process (DSP) 230, a microcontroller unit (MCU) 240 that controls the DSP and the first and second controllers 251 and 252, and a power supply unit that supplies power to drive the control unit and the speaker. s 261 and 262 may be included.

The seat detection sensor 110 may be provided in each of a plurality of spectator seats in order to implement a sweet spot to a seat where the spectator is seated among a plurality of spectator seats provided in the performance hall. The seat detection sensor may be implemented as, for example, a pressure sensor for determining whether a spectator is seated through the weight of a spectator, but is not limited thereto.

The microphone 110 may serve to determine the position of a performer carrying the microphone on stage. To this end, various types of position detection sensors may be applied to the microphone. For example, a location of a performer on stage may be determined through a communication module such as an inertial measurement unit (IMU) or a beacon built into a microphone.

In some other embodiments, the microphone can detect the spectator's viewing position through its own function without a separate sensor. Specifically, when inaudible reference signals are emitted from at least four or more speakers among a plurality of speaker boxes (TBx, MBx, WBx) arranged to be spaced apart from each other in a small-scale live venue to be described later, the wireless terminal 100 receives each non-audible By collecting the delay time of arrival of the reference signal, the position of the performer on stage can be calculated in real time. For example, the MCU 240 generates a microphone based on a difference in arrival time between the inaudible reference signals from the first and second tweeter boxes TB1 and TB2 and the first and second mid boxes MB1 and MB2, respectively. location can be ascertained. Here, the reason why the inaudible reference signal is used is that it interferes with the audience's auditory appreciation when using the audible signal. To this end, each speaker box is provided with a non-audible signal generating unit, and a microphone It can be configured to have receivable performance.

In addition, the microphone may additionally serve as a real-time analyzer (RTA) microphone for monitoring sound characteristics experienced by the corresponding performer.

Specifically, the microphone may collect frequency characteristics and reception sensitivity at the current performer's position, and the MCU 240 determines whether a normal monitoring environment is given to the current performer through the collected frequency characteristics and reception sensitivity, and correction is performed. Corrections can be made if necessary. The correction may be, for example, mid-speaker on/off adjustment and individual output adjustment of a specific mid box, or tweeter filtering adjustment of a tweeter box.

The RF antenna 210 may receive information sensed from the occupancy detection sensor 110 and the microphone 120 and transfer the received information to the MCU 240 .

The speaker boxes may include a tweeter box (TBx) with tweeters for tracking treble reproduction, a mid box (MBx) with mid- and mid-bass speakers installed, and a woofer box (WBx) with woofer speakers for bass reproduction. can

As shown in FIG. 2, the tweeter boxes are disposed on at least one rear wall and left and right side walls, excluding the front wall, among the four walls of the small-scale live venue, and the mid boxes are arranged on the small-scale live venue. Arranged at each of the four corners of the live venue, the woofer box may be buried in a ceiling area of the small-scale live venue. That is, the tweeter box, the mid box, and the woofer box each play a role of reproducing different frequency bands.

Each of the plurality of tweeter boxes includes a semi-cylindrical main frame, a beam angle rail (LLx) extending horizontally along the semicircular side circumference of the main frame, and a tweeter installed on the beam angle rail so as to be rotatable in the horizontal direction. A chamber TCx and a tweeter TWx mounted in the tweeter chamber may be included, but the beam angle rail, the tweeter chamber, and the tweeter may be arranged in a plurality of sets spaced apart in a vertical direction as shown. Each set can be reproduced with a beam angle for each spectator, ie facing each spectator. For example, a first tweeter may direct a first spectator along a beam angle rail, and a second tweeter may direct a second spectator along a beam angle rail. To this end, the first controller 251 may control a corresponding servo motor so that the tweeter chamber rotates along the beam angle rail.

Each of the plurality of mid boxes MBx may include first and second mid speakers MRx that can be individually turned on and off. For example, as shown in FIG. 3 , the first to third mid-speakers MR1, MR2, and MR3 may be provided in the first mid box MB1. The second controller 252 may control on/off of individual midspeakers in the box by comprehensively considering the positions of a performer and a plurality of spectators. The second controller 252 may control on/off of the midspeakers based on the frequency characteristics and reception sensitivity collected by the wireless terminal.

The DSP 230 receives raw audio signals from the audio source 220 and transmits them to the tweeters installed in the plurality of tweeter boxes, the mid speakers installed in the plurality of mid boxes, and the woofer speakers installed in the woofer box, respectively. It plays a role in transmitting individually processed analog signals.

The MCU 240 controls the DSP and the first and second controllers based on the movement of the performer sensed by the microphone so that the performer's sweet spot faces the performer, and each of the plurality of spectator sweet spots is The DSP and the first and second controllers may be controlled based on a position of each of the spectators sensed by the seating sensor to face each of the spectators.

Specifically, the DSP 230 transfers a high-pass signal obtained by high-pass filtering the audio signal to a frequency domain equal to or higher than the first crossover frequency to the tweeter, and transmits a second crossover frequency lower than the first crossover frequency. Transmits a bandpass signal obtained by band pass filtering of the frequency domain from to the first crossover frequency to the midspeaker, and low pass filtering of the frequency domain below the second crossover frequency Low pass A signal may be transmitted to the woofer speaker. Here, the DSP 230 may transfer individual (that is, different) high-pass signals to all tweeters and, in some cases, transfer different band-pass signals to some midspeakers. That is, different crossover frequencies (1-1 and 1-2 crossover frequencies) may be applied to the first and second midspeakers, respectively.

For example, the DSP transfers a first high-pass signal obtained by high-pass filtering the audio signal in a frequency domain equal to or higher than a 1-1 crossover frequency to a first tweeter, and converts a frequency domain equal to or higher than a 1-2 crossover frequency to a first tweeter. Passing the high-pass filtered second high-pass signal to the second tweeter, band-pass filtering the frequency range from the second crossover frequency lower than the 1-1 crossover frequency to the 1-1 crossover frequency A first bandpass signal is transferred to the first midspeaker, and a first bandpass signal obtained by bandpass filtering a frequency domain from the second crossover frequency to the 1-2th crossover frequency is transmitted to the second midspeaker. can be forwarded to

Here, it is preferable that the first crossover frequency is about 1 kHz to 2 kHz, and the second crossover frequency is about 50 Hz to 300 Hz.

Meanwhile, the DSP 230 may change the gain of each of the first and second high-pass signals, and the type and order of the high-pass filter applied to each in real time. Specifically, the gain of each of the first and second high-pass signals is calculated based on the distance between each of the first and second spectators and the first and second tweeters, and -2 crossover frequencies, and the filter type and filter order (ie, crossover slope) applied to each of the first and second high-pass signals are the first and second spectators respectively and the first It can be calculated based on the respective distances of the first and second midspeakers.

Preferably, when the distance between the first spectator and the first mid-speaker is equal to or greater than the first reference distance, the first high-pass signal is a 2nd order (-12dB/oct, for example, slope 1 in FIG. 4) Bessel (Bessel) filter, and when the distance between the first spectator and the first midspeaker is less than the first reference distance, the first high-pass signal is 3rd order (-18dB/oct, for example Slope 2 of FIG. 4 may be filtered by a Chebyshev filter. More specifically, the 1-1 crossover frequency may be calculated according to Equation 1 below. In Equation 1, the F_cut is the 1-1 crossover frequency [Hz], the D_mid is the distance between the first spectator and the first mid speaker [cm], and the D_ref is the first reference distance [cm] ], G_mid represents the average decibel [dB] of the first mid speaker at the position of the first spectator, and G_tw represents the average decibel [dB] of the first tweeter at the position of the first spectator. The distance value and average decibel value may be measured through the wireless terminal 100 as described above.

For example, if the distance between the first spectator and the first mid-speaker is greater than the first reference distance, the 1-1 crossover frequency (F_cut) has a value greater than 1.5 kHz as shown in cutoff 1-1 in FIG. calculated, and if the distance between the first spectator and the first mid-speaker is less than the first reference distance, the 1-1 crossover frequency (F_cut) is calculated to have a value smaller than 1.5 kHz as shown in cutoff 1-2 in FIG. It can be.

When such a multi-channel sound system (1) is built in a small live venue, it provides a performer's sweet spot (NSS) for performers and individual spectator's sweet spots (SS1-SS3) for each of a plurality of spectators seated in a specific spectator seat. can do. Here, the performer's sweet spot (NSS) may be constructed to have monitoring sound characteristics compared to the audience's sweet spot (SS1 to SS3), and the audience's sweet spot (SS1 to SS3) may have sentimental acoustic characteristics compared to the performer's sweet spot (NSS). can be built to have That is, the performer's sweet spot (NSS) and the audience's sweet spot (SS1 to SS3) may be designed to have different frequency characteristics.

To this end, the side tweeter boxes (TB1, TB2, TB5, TB6) disposed on the left and right side walls of the plurality of tweeter boxes are driven to form the spectator sweet spot, and the plurality of tweeter boxes The side tweeter boxes (TB3, TB4) disposed on the rear side wall of the middle can be driven to form the performer sweet spot, and the tweeters of the tweeter boxes (TB1, TB2, TB5, TB6) and the tweeter boxes The tweeters of (TB3 and TB4) may have different frequency characteristics.

On the other hand, as described above, the reason for directing only the tweeter, that is, the treble speaker, is that when the bass speaker has an individual beam angle, it is necessary to control the mutual interference between the mid-high pitch or between the mid-tone of the first mid-bass speaker and the mid-tone of the second bass speaker. Because difficulties follow. Individual beam angles are adjusted by applying the individually calculated cutoff frequency (F_out) to the tweeter side, but the mid-speaker is placed at the corner end of a small live venue to alternate with the tweeter box, and then only output is controlled within one tweeter box. It is possible to minimize mutual interference between multiple tweeters, maximize the effect of the stage unfolding in front of each of the multiple spectators, and at the same time, enhance consistent auditory appreciation within all viewing routes.

Those skilled in the art related to the present embodiment will be able to understand that it may be implemented in a modified form within a range that does not deviate from the essential characteristics of the above description. Therefore, the disclosed methods are to be considered in an illustrative rather than a limiting sense. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent scope will be construed as being included in the present invention.

Claims (4)

It is provided in a rectangular live performance hall defined by the front wall on which the stage is installed, the rear wall facing the front wall, and the left and right side walls extending between the front wall and the rear wall to provide a performer on the stage. A multi-channel sound system that provides a performer sweet spot for a performer and a plurality of spectator sweet spots for each of spectators seated in a plurality of spectator seats,
Seating sensors installed in each of the plurality of spectator seats;
a microphone provided to the performer and equipped with a position sensor for sensing the movement of the performer;
a plurality of tweeter boxes disposed on each of the rear wall and left and right side walls of the four walls of the live performance hall, excluding the front wall;
a plurality of mid boxes disposed at each of the four corners of the live venue;
at least one woofer box embedded in a ceiling area of the live performance hall;
DSP (digital) that receives audio signals from audio sources and transmits individually processed analog signals to the tweeters installed in the plurality of tweeter boxes, the mid speakers installed in the plurality of mid boxes, and the woofer speakers installed in the woofer box, respectively. signal processor);
a first controller for controlling beam angles of the tweeters;
a second controller for controlling on/off of the midspeakers; and
The DSP and the first and second controllers are controlled based on the movement of the performer sensed by the microphone so that the performer's sweet spot faces the performer, and each of the plurality of spectator sweet spots controls each of the spectators. A Micro Controller Unit (MCU) for controlling the DSP and the first and second controllers based on the position of each of the spectators sensed by the seating sensor so as to face the audience,
Side tweeter boxes disposed on the left and right side walls of the plurality of tweeter boxes are driven to form the spectator sweet spot, and side tweeter boxes disposed on the rear side wall of the plurality of tweeter boxes are driven to form the spectator sweet spot. Driven to form a performer sweet spot,
Each of the plurality of tweeter boxes,
A semi-cylindrical main frame;
a first beam angle rail extending in a horizontal direction along a semicircular circumference of the main frame;
a first tweeter chamber installed on the first beam angle rail so as to be rotatable in a horizontal direction;
a first tweeter mounted in the first tweeter chamber;
a second beam angle rail extending in a horizontal direction along the circumference of the semi-cylindrical column and vertically spaced apart from the first beam angle rail;
a second tweeter chamber installed on the second beam angle rail so as to be rotatable in a horizontal direction; and
A second tweeter mounted in the second tweeter chamber;
Each of the plurality of mid boxes includes first and second mid speakers that can be individually turned on and off,
The DSP transmits a first high-pass signal obtained by high-pass filtering the audio signal in a frequency domain equal to or higher than the 1-1 crossover frequency to a first tweeter, and transmits a frequency domain equal to or higher than the 1-2 crossover frequency. The high-pass filtered second high-pass signal is transferred to the second tweeter, and the frequency range from the second crossover frequency lower than the 1-1 crossover frequency to the 1-1 crossover frequency is band-pass (band pass). pass) The filtered first bandpass signal is transferred to the first midspeaker, and the second bandpass signal obtained by bandpass filtering the frequency domain from the second crossover frequency to the 1-2th crossover frequency is transmitted to the first midspeaker. A low-pass signal obtained by passing a second mid-speaker and low-pass-filtering a frequency domain below the second crossover frequency to the woofer speaker, wherein each of the first and second high-pass signals A gain is calculated based on a distance between each of the first and second spectators and each of the first and second tweeters, the 1-1 and 1-2 crossover frequencies, and the first and second tweeters. The filter type and filter order (i.e., crossover slope) applied to each of the second high-pass signals is based on the distance between the first and second audiences and the first and second midspeakers, respectively. is calculated,
The first controller controls beam angles of the first and second tweeter chambers to direct the first tweeter toward the first spectator and direct the second tweeter toward the second spectator;
The second controller controls on/off of the first and second midspeakers in consideration of both the position of the first spectator and the position of the second spectator;
When the distance between the first spectator and the first midspeaker is greater than or equal to a first reference distance, the first high-pass signal is filtered with a 2nd order (-12dB/oct) Bessel filter,
When the distance between the first spectator and the first midspeaker is less than the first reference distance, the first high-pass signal is filtered with a 3rd order (-18dB/oct) Chebyshev filter,
The 1-1 crossover frequency is characterized in that calculated according to Equation 1 below, the multi-channel sound system.
[Equation 1]

(Here, the F_cut is the 1-1 crossover frequency [Hz], the D_mid is the distance between the first spectator and the first mid speaker [cm], the D_ref is the first reference distance [cm], The G_mid represents the average decibel [dB] of the first mid speaker at the position of the first spectator, and G_tw represents the average decibel [dB] of the first tweeter at the position of the first spectator.)
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