KR20100119114A - Signal processing apparatus for high efficiency ultrasonic speaker system and method thereof - Google Patents

Abstract

PURPOSE: An apparatus and a method for processing a signal for a superdirectivity sound-wave transmitting system are provided to improve the sound quality of a speaker by adopting the grid filter coefficient value of a current input signal. CONSTITUTION: A double integral part(100) double integrates an audio input signal. An envelope curve calculating part(110) calculates the envelope curve of a double integrated signal. An energy calculating part(130) calculates the energy of the calculated envelope curve of the double integrated signal. A control part(140) controls the gain of an ultrasonic amplifier according to the calculated energy.

Description

SIGNAL PROCESSING APPARATUS FOR HIGH EFFECTIVE SOUND TRANSMISSION SYSTEMS

TECHNICAL FIELD The present invention relates to a superdirectional sound wave transmission system, and more particularly, to a signal processing technique in a superdirectional sound wave transmission system.

In general, speakers deliver sound in the air in all directions. But in places such as exhibitions and exhibitions where sound needs to be delivered in a specific direction, sound directivity is needed. In addition, the development of high-direction speakers is essential for sound attack or fleet remote voice communication for military purposes.

The use of parabolic dishes is well known in connection with the development of super-directional sound wave transmission systems. This is done by placing a normal speaker at the focal point of the dish so that the sound output is reflected by the dish and goes straight. However, this method requires a very large diameter plate, has a short range of sound, and has a disadvantage of poor sound quality due to mutual interference of reflected signals.

Recently, ultrasonic speaker technology using nonlinear propagation characteristics of an air medium has been implemented to compensate for these disadvantages. However, the signal processing method according to the known ultrasonic speaker technology outputs a filtered signal regardless of the presence or absence of an input signal, and as a result, amplifies and outputs noise in the system, thereby degrading sound quality. In addition, there is a disadvantage that the power efficiency is lowered because the power amplifier continuously consumes power.

An object of the present invention is to provide a signal processing apparatus and method capable of improving the power efficiency of a super-directional sound wave transmission system.

Furthermore, it is an object of the present invention to provide a signal processing apparatus and method for enabling high quality and high sound quality of a super-directional sound wave transmission system.

The signal processing device constituting the super-directional sound wave transmission system for achieving the above-described technical problem includes a double integrator that double-integrates an audio input signal, an envelope calculator that calculates an envelope signal of the double-integrated signal, and a calculated envelope signal. An energy calculating unit for calculating the energy of the, and a control unit for controlling the gain of the ultrasonic amplifier according to the calculated energy value.

The signal processing apparatus further includes a filter unit for applying a filter coefficient to the calculated envelope signal and outputting the modulated signal, and a modulator for modulating an output signal of the filter unit.

The filter unit includes a lattice filter unit which applies the lattice filter coefficients determined for the previous input signal to the signal output from the delay unit. Furthermore, the filter unit receives the envelope signal output from the envelope calculator and calculates a square root signal to calculate a square root signal, an error calculator that calculates an error between an output signal of the grid filter unit and a square root signal of the square root operator, and an output from the error calculator. The apparatus further includes a lattice filter coefficient calculator for calculating a lattice filter coefficient from the error signal and outputting the lattice filter coefficient to the lattice filter unit.

The signal processing apparatus further includes a delay unit for delaying the envelope signal output from the envelope calculator and outputting the envelope signal to the filter unit.

The signal processing apparatus further includes a switch for applying an output signal of the filter unit to the modulator, and the controller controls the switch to be turned on only when the calculated energy value is greater than or equal to a threshold.

On the other hand, the method for processing the input audio signal in the signal processing device constituting the super-directional sound wave transmission system for achieving the above technical problem, the step of double integration of the audio input signal; Calculating an envelope signal of the double integrated signal, calculating energy of the calculated envelope signal in units of predetermined frames, and activating the ultrasonic amplifier when the calculated energy value is greater than or equal to the threshold and deactivating the threshold value.

By generating and outputting signals based on the energy activation of the audio input signal, high-quality audio output can be generated, and the power amplifier can be powered with high efficiency, resulting in an economical high-direction speaker system.

In addition, by comparing the signal processing method due to the calculation of energy in the frame unit with the grid filter coefficient and the input signal, the grid filter coefficient value of the current input signal is calculated and applied. The sound quality of the incense speaker can be improved.

In addition, the use of a lattice filter allows various lattice filter signal processing methods such as gradient adaptive lattice (GAL), least square lattice (LSL), and QR-decomposition lattice (QRD-Lattice).

In addition, by varying the frame length for the energy calculation of the input signal, it is possible to implement a directional speaker system that can ensure signal generation and system performance in various channel conditions.

In addition, by generating an inverse filter model of the ultrasonic transducer applied to the system and applied to the SSB modulated signal, it is possible to improve the sound quality by minimizing distortion during the ultrasonic conversion of the modulated signal.

The foregoing and further aspects of the present invention will become more apparent through the preferred embodiments described with reference to the accompanying drawings. Hereinafter, the present invention will be described in detail to enable those skilled in the art to easily understand and reproduce the present invention.

1 is a block diagram of a signal processing device configuring a super-directional sound wave transmission system according to an embodiment of the present invention.

The double integrator 100 double-integrates the audio input signal s (t) to calculate the double-integrated signal i (t) and outputs it to the envelope calculator 110. The envelope calculating unit 110 calculates an envelope signal E (t) with respect to the double integrated signal i (t). In general, the envelope signal E (t) may be calculated through Equation 2.

i´ (t) = k + m × i (t)

Where m is the modulation index and k is the offset value.

The delay unit 120 receives the envelope signal i '(t) output from the envelope calculator 110. The input envelope signal i '(t) is delayed for a predetermined time as shown in Equation 2 and output. The envelope signal delayed for a certain time is called E (t).

E (t) = i´ (t-N)

Here, N refers to a time value required for energy calculation by the energy calculator 130. That is, the delay unit 120 serves to delay the output of the envelope signal by the energy calculation time of the energy calculator 130.

The energy calculator 130 calculates energy of the envelope signal i ′ (t) generated by the envelope calculator 110. In an exemplary embodiment, the energy calculator 130 calculates a frame energy p (t) by squaring and summating signals in a frame in units of a predetermined length with respect to the envelope signal i ′ (t).

The controller 140 receives the frame energy p (t) calculated by the energy calculator 130. The controller 140 determines whether the input frame energy p (t) is greater than or equal to a predetermined threshold value and generates a signal g (t) for adjusting the gain of the ultrasonic amplifier 180 according to the determination result. Output to the ultrasonic amplifier 180. Thereby, the gain of the ultrasonic amplifier 180 is adjusted. Here, the threshold means a value for distinguishing whether the input signal is an actual audio input signal or a silent signal or a noise level input signal.

In one embodiment, when the frame energy p (t) is greater than or equal to the threshold, the controller 140 determines that the audio input signal is normally input, and adjusts the gain so that the ultrasonic amplifier 180 sufficiently performs its role. do. On the contrary, when the frame energy p (t) is less than the threshold value, the controller 140 determines that the input signal is the silent section or the noise level and adjusts the gain to minimize the power consumption of the ultrasonic amplifier 180. The gain control of the controller 140 is repeatedly performed in units of frames.

The filter unit 150 receives the envelope signal E (t) output from the delay unit 120 for a time delay. The filter unit 150 reflects the filter coefficients to the envelope signal E (t) and outputs them to the modulator 160. According to an aspect of the present invention, the filter unit 150 includes a lattice filter unit 151, and further includes a square root operator 152, an error operator 153, and a lattice filter coefficient calculator 154 according to an additional aspect. Include. The grating filter unit 151 applies the grating filter coefficient w (t) calculated for the previous stage input signal E (t-1) to the current input signal E (t), and then applies the signal y in the following equation (3). output (t)

y (t) = E (t) ^T w (t)

Where T is the transpose matrix, E (t) is a vector of M delayed input signals, ie [E (t-1) ... E (tM)], and w (t) is of length M [w (1) ... w (M)] means the vector.

The square root calculator 152 performs a square root on the envelope signal E (t) which is an output signal of the delay unit 120 as shown in Equation 4.

E´ (t) = E (t) ^1/2

The error calculator 153 calculates the error signal e (t) of the output signal y (t) of the grid filter unit 151 and the signal E '(t) calculated by the square root calculator 152. E (t) calculated by the error calculating unit 153 is expressed by Equation 5.

e (t) = E´ (t)-y (t)

The grid filter coefficient calculating unit 154 may include a GAL (Gradient Adaptive Lattice), LSL (Least Square Lattice), QRD-Lattice (QR-Decomposition Lattice) method, and the like. Calculate the grid filter coefficients by applying The method of calculating the lattice filter coefficients from the error signal vector e (t) may be applied to various other methods. The structure of the grating filter is illustrated in FIG. 2. The meaning of each variable in FIG. 2 is as follows. u (n) is the filter input signal at n time point, z ^-1 is one sample delay element, kb _i is i-stage backward adaptive filter coefficient, f _i = u (n-1) * kf _i . Lattice adaptive filter coefficients, kb _i and kf _i Various algorithms can be applied for updating, and detailed derivation and formula are omitted.

The modulator 160 modulates the output signal y (t) of the grating filter unit 151. According to an aspect of the present invention, the modulator 160 is of SSB modulation configuration. Accordingly, the modulator 160 modulates the output signal y (t) of the grating filter unit 151 into an ultrasonic band through upper side or lower side band SSB (Single Side Band) modulation. The transducer inverse filter 170 grasps the frequency characteristics of the ultrasonic transducer 190, estimates the inverse filter, and applies the inverse filter to the modulated signal z (t) generated by the modulator 160. produces (t) The ultrasonic amplifier 180 generates a signal x '(t) obtained by amplifying the output of the converter inverse filter 170 with the gain control signal g (t) of the controller 140 as an input. The ultrasonic transducer 190 emits an ultrasonic wave by using the ultrasonic vibration device to the signal x '(t) amplified by the ultrasonic amplifier 180 to generate the final signal o (t). The ultrasonic signal converted by the ultrasonic transducer 140 is radiated into the air, thereby being demodulated by the nonlinear medium characteristic of the air.

The switch 200 is connected to an output terminal of the grating filter unit 151 and an input terminal of the modulation unit 160, and is switched under the control of the control unit 140 to switch the output signal of the grating filter unit 151 to the modulation unit ( 160) or to block. In this case, the controller 140 determines whether the frame energy p (t) calculated by the energy calculator 130 is greater than or equal to a predetermined threshold value and controls the switch 200 according to the determination result. That is, when the frame energy p (t) is greater than or equal to the threshold value, the controller 140 determines that the audio input signal is normally input, and controls the switch 200 on. On the contrary, when the frame energy p (t) is less than the threshold value, the controller 140 determines that the input signal is the silent section or the noise level and adjusts the gain to minimize the power consumption of the ultrasonic amplifier 180. The control of the switch 200 of the controller 140 is repeatedly performed in units of frames.

In the first embodiment, the controller 140 controls only the gain of the ultrasonic amplifier 180 according to the energy value calculated by the energy calculator 130 and the switch 200 is on regardless of the energy value. Keep it steady. In the second embodiment, the controller 140 controls the on / off of the switch according to the energy value calculated by the energy calculator 130 and maintains the ultrasonic amplifier 180 continuously. In the third embodiment, the controller 140 controls the gain of the ultrasonic amplifier 180 to be activated or deactivated according to the energy value calculated by the energy calculator 130, and simultaneously controls the switch 200. Or turn it off.

3 is an audio input signal processing flowchart of a signal processing device configuring a super-directional sound wave transmission system according to an embodiment of the present invention.

The double integrator 100 calculates a double integral of the audio input signal s (t) (S1). The envelope calculating unit 110 calculates the envelope signal i '(t) by giving a gain and an offset to the double-integrated signal i (t) (S2). The energy calculator 130 calculates a frame energy p (t) by squaring and summing signals in a frame in units of a predetermined length with respect to the calculated envelope signal i '(t) (S8). The controller 140 compares the calculated frame energy p (t) with a threshold value, and if the comparison indicates that the frame energy p (t) is smaller than the threshold value, the controller 140 determines that there is no silence or a signal and that d (t) = 0, g ( t) = 0. On the contrary, if the frame energy p (t) is greater than or equal to the threshold, it is determined that a normal audio signal exists and d (t) = 1 and g (t) = k (S9). It has been described that both d (t) and g (t) are set according to the comparison result of the frame energy p (t) and the threshold, but one value may be fixed and only the remaining value may be newly set.

Meanwhile, the grating filter unit 151 generates an output signal y (t) by applying the grating adaptive filter coefficient vector of the signal E (t-1) of the previous stage to the signal E (t) having undergone the step S3 (S7). ). The error calculator 153 delays and outputs the signal E (t) having passed through the step S3 by the time required for the steps S9 and S10 (S3). The square root calculator 152 generates a signal E (t) ^1/2 by performing a square root operation on the time-delayed output signal E (t) (S4). The error calculating unit 153 calculates the difference between the lattice filter output signal y (t) and E (t) ^1/2 that have passed through step S7 and generates the error signal e (t) (S5). Next, the lattice filter coefficient calculator 154 calculates the lattice adaptive filter coefficients according to the signal e (t) output through the step S5 and outputs the lattice adaptive filter coefficients to the lattice filter unit 151 (S6). Here, GAL, LSL, QRD-lattice adaptation, etc. may be used to calculate the grid adaptive filter coefficients.

The modulator 160 performs SSB modulation on the output signal to which the lattice adaptive filter coefficient is applied in step S7 to generate a modulated signal z (t) (S10). Next, the ultrasonic transducer inverse filter 170 is applied to the SSB modulated signal z (t) (S11). In this case, the inverse filter applied may be calculated through analysis of frequency response characteristics of the ultrasonic transducer 190 used in the system. Next, the ultrasonic amplifier 180 amplifies the output signal x (t) of the converter inverse filter 170 to generate an amplified signal x '(t) (S12). Next, the amplified signal is converted into an ultrasonic signal through the ultrasonic transducer 190 (S13). Finally, the ultrasonic signal is nonlinearly demodulated in air and output as an output signal o (t).

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a signal processing device constituting a superdirectional sound wave transmission system according to an embodiment of the present invention.

2 is an exemplary grid filter.

3 is an audio input signal processing flowchart of a signal processing device configuring a super-directional sound wave transmission system according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: double integration unit 110: envelope calculation unit

120: delay unit 130: energy calculation unit

140: control unit 150: filter unit

151 lattice filter unit 152 square root calculator

153: error calculation unit 154: grid filter coefficient calculation unit

160: modulator 170: converter reverse filter

180: ultrasonic amplifier 190: ultrasonic transducer

200: switch

Claims (21)

In the signal processing device constituting the super-directional sound wave transmission system, A double integrator for double integrating the audio input signal; An envelope calculating unit for calculating an envelope signal of the double integrated signal; An energy calculator configured to calculate energy of the calculated envelope signal; And A control unit controlling a gain of the ultrasonic amplifier according to the calculated energy value; Signal processing apparatus comprising a. The method of claim 1, And the energy calculator calculates a frame energy by squaring and adding the envelope signals by a predetermined frame unit. The method of claim 1, And the controller controls the gain of the ultrasonic amplifier to deactivate the ultrasonic amplifier if the calculated energy value is less than a threshold and to activate the ultrasonic amplifier if it is above a threshold. The method of claim 1, A filter unit which applies a filter coefficient to the calculated envelope signal and outputs the filter coefficient; And A modulator for modulating an output signal of the filter unit; Signal processing apparatus comprising a. The method of claim 4, wherein the filter unit: A lattice filter unit applying a lattice filter coefficient determined with respect to a previous input signal to a signal output from the delay unit; Signal processing apparatus comprising a. The method of claim 5, wherein the filter unit: A square root calculator which calculates a square root signal by calculating a square root by receiving an envelope signal output from the envelope calculator; An error calculator configured to calculate an error between an output signal of the lattice filter unit and a square root signal of the square root calculator; And A lattice filter coefficient calculator for calculating a lattice filter coefficient from the error signal output from the error calculator and outputting the lattice filter coefficient to the lattice filter unit; Signal processing apparatus further comprising a. The method of claim 6, The lattice filter coefficient calculating unit calculates a lattice filter coefficient by applying any one of a method of gradient adaptive lattice (GAL), least square lattice (LSL), and QRD-Lattice (QR-decomposition lattice) to the error signal. Signal processing device. The method of claim 4, wherein The modulator is a signal processing device characterized in that the SSB (Single Side Band) modulator. The method according to any one of claims 4 to 6, A delay unit for delaying the envelope signal output from the envelope calculator and outputting the envelope signal to the filter unit for a predetermined time; Signal processing apparatus further comprising a. 10. The method of claim 9, And the delay unit delays at least the energy calculation time required by the energy calculator. 10. The method of claim 9, And a switch for applying an output signal of the filter unit to the modulator. And the controller controls the switch to be turned on only when the calculated energy value is greater than or equal to a threshold. The method of claim 4, wherein A transducer inverse filter for filtering the signal modulated by the modulator with an inverse filter corresponding to a frequency characteristic of the ultrasonic transducer and outputting the inverse filter to the ultrasonic amplifier; Signal processing apparatus further comprising a. In the signal processing device constituting the super-directional sound wave transmission system, A double integrator for double integrating the input signal; An envelope calculating unit for calculating an envelope signal of the double integrated signal; A delay unit configured to delay the envelope signal output from the envelope calculator and to output the delayed signal for a predetermined time; A filter unit for applying a filter coefficient to the envelope signal output from the delay unit and outputting the filter coefficient; A modulator for SSB modulation of the output signal of the filter unit; A switch for applying an output signal of the filter unit to the modulator; An energy calculator configured to calculate energy of the envelope signal; And A control unit which controls the switch to be turned on only when the calculated energy value is greater than or equal to a threshold; Signal processing apparatus comprising a. The method of claim 13, wherein the filter unit: A lattice filter unit generating an output signal by applying a lattice filter coefficient determined with respect to a previous input signal to the signal output from the delay unit; Signal processing apparatus comprising a. The method of claim 14, wherein the filter unit: A square root calculator which calculates a square root signal by calculating a square root by receiving an envelope signal output from the envelope calculator; An error calculator configured to calculate an error between an output signal of the lattice filter unit and a square root signal of the square root calculator; And A lattice filter coefficient calculator for calculating a lattice filter coefficient from the error signal output from the error calculator and outputting the lattice filter coefficient to the lattice filter unit; Signal processing apparatus further comprising a. The method of claim 15, The lattice filter coefficient calculating unit calculates a lattice filter coefficient by applying any one of a gradient adaptive lattice (GAL), a least square lattice (LSL), and a QR-decomposition (QR-decomposition lattice) scheme to the error signal. Signal processing device. The method of claim 13, A transducer inverse filter for filtering the signal modulated by the modulator with an inverse filter corresponding to a frequency characteristic of the ultrasonic transducer and outputting the inverse filter to an ultrasonic amplifier; Signal processing apparatus further comprising a. In the method for processing the audio signal input from the signal processing device constituting the super-directional sound wave transmission system, Double integrating the audio input signal; Calculating an envelope signal of the double integrated signal; Calculating energy of the calculated envelope signal in units of predetermined frames; Activating an ultrasonic amplifier when the calculated energy value is greater than or equal to a threshold and deactivating the threshold if less than a threshold; Signal processing method comprising a. The method of claim 18, Outputting the output of the calculated envelope signal after a predetermined time delay; Applying a lattice filter coefficient determined for a previous input signal to the signal output after the predetermined time delay; And Outputting a signal to which the lattice filter coefficients are applied to a modulator to perform SSB (Single Side Band) modulation; Signal processing method further comprising. The method of claim 19, Turning on a switch located at the input of the modulator so that the signal to which the lattice filter coefficient is applied is applied to the modulator only when the calculated energy value is greater than or equal to a threshold; Signal processing method further comprising. The method of claim 17, wherein applying the filter coefficients comprises: Calculating a square root of an envelope signal output after the predetermined time delay; Calculating an error between the signal to which the filter coefficient is applied and the square root calculated signal; And Calculating a grating filter coefficient for the calculated error signal; Signal processing method comprising a.

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