KR102077472B1 - An Improved Audio Signal Processing Method And Device For Ultra Directional Speaker - Google Patents

Abstract

The present invention relates to an improved audio signal processing method for an ultrasound speaker, which comprises: a first step of removing a low-frequency component of an inputted audio signal and correcting response characteristics for each frequency band with an equalizer; a second step of comparing a level value of the audio signal, whose response characteristics are corrected for each frequency band, with a level value of an external noise signal to select and apply a dynamic range control characteristic graph to the corrected audio signal so as to control an output audio signal level; and a third step of ultrasound-modifying the level-controlled audio signal. According to the present invention, a sound quality improvement method is appropriate to the characteristics of an ultra-directional ultrasound speaker, thereby providing an effect of transferring an audio signal with improved sound quality to a listener. Moreover, an audio signal level of the ultra-directional ultrasound speaker facing the listener, who is placed in a predetermined position, is controlled in accordance with an external noise level, thereby providing an effect of transferring a clear audio signal to the listener.

Description

An improved audio signal processing method and device for ultra directional speaker

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic speaker device that provides superdirectionality to a sound wave propagation direction through ultrasonic modulation, and more particularly, to an improved audio signal processing method of a superdirectional ultrasonic speaker device and a superdirectional ultrasonic speaker device having the same. .

Typical speakers transmit sound waves in all directions in the air. However, there may be cases where you want to deliver sound waves only in certain directions. In this case, there is a method using parabolic dishes, in which a speaker is installed 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. In order to make up for such drawbacks, super-directional ultrasonic speaker technology using the linearity of ultrasonic waves and the nonlinear medium characteristics of air media has been recently implemented. As the research on sonar, which is an underwater radar technology, has been developed, the super-directional ultrasonic speaker has been studied in earnest by discovering that ultrasonic waves in the air can emit sound like beams. Since then, many scientists have studied the physical principles of super-directional ultrasonic speakers and how to send existing voices to them. However, commercialization of superdirectional ultrasonic speakers was not easy, and it wasn't until after 2000 that superdirectional ultrasonic speakers using ultrasonic modulation technology began to be commercialized.

The superdirectional ultrasonic speaker system utilizes the nonlinear interference phenomenon that ultrasonic waves cause with air in the air. In theory, the audible signal demodulated in air is proportional to the second time derivative of the square of the envelope of the amplitude modulated signal. Accordingly, referring to FIG. 13, the conventional ultrasonic speaker system modulates the square root of the dual-integrated input audio signal before amplitude modulation, and emits the air to the air through the ultrasonic speaker. This method is limited in reducing distortion because the frequency spectrum of the bandwidth-constrained original audio signal is shown on an almost infinite bandwidth by a nonlinear operation called the square root. Meanwhile, ATC of the United States has proposed an iterative error compensation method without increasing the bandwidth in the US patent US 6,584,205.

However, these prior art documents were only concerned with eliminating the nonlinear interference caused by ultrasonic waves and air, and even signal processing to provide clearer sound quality from the listener's point of view or signal processing considering the noise environment around the listener. It is not presented.

If the sound quality improvement method suitable for the characteristics of the super-directional ultrasonic speaker is not applied, the audio signal transmitted due to the nonlinear interference caused by the ultrasonic wave and air is transmitted to the listener with unnatural sound quality.

In addition, the superdirectional ultrasonic speaker can transmit sound waves only to the listener at a specific position, but if there is external noise around the listener and the noise level is higher than the audio signal output level of the ultrasonic speaker, the listener may not be able to transmit the signal through the superdirectional ultrasonic speaker. There is a problem that can not be delivered properly.

Republic of Korea Patent Publication No. 10-2014-0087926 (2014.07.09.) Republic of Korea Patent Publication No. 10-0622078 (2006.09.01.)

The present invention is to propose a signal processing method for providing a more clear sound quality to the listener in view of the above problems, in particular to improve the sound quality of the listener by applying a sound quality improvement method suitable for the characteristics of the super-directional ultrasonic speaker When the audio signal is transmitted and the external noise level around the listener is higher than the audio signal output level of the ultrasonic speaker, and the audio signal of the ultrasonic speaker is relatively small to the listener, the audio signal output level is adjusted so that the listener can see the audio signal. The present invention provides an improved audio signal processing method and a superdirectional ultrasonic speaker device having the same.

In order to solve the above problems, the present invention provides an improved audio signal processing method of an ultrasonic speaker device, the method comprising: removing a low frequency component of an input audio signal and correcting a response characteristic for each frequency band by using an equalizer 220; ; A second step of selecting a dynamic range control characteristic graph by comparing the level value of the audio signal whose response characteristic is corrected for each frequency band with the level value of the external noise signal and controlling the output audio signal level by applying the dynamic range control characteristic graph to the corrected audio signal; And a third step of ultrasonically modulating the level controlled audio signal. The first step may include a step 1-1 of removing low frequency components of an audio signal input using the high pass filter 210; First and second steps of correcting a response characteristic of each frequency band by using the equalizer 220 to remove the low frequency component; Adjusting the sound pressure level of the signal whose response characteristic is corrected for each frequency band; In order to prevent clipping of signals that may occur in steps 1-2 and 1-3, a fourth step of controlling the signal size does not increase by a specific level or more using the limiter 240. The second step may include a step 2-1 of determining a level value of the audio signal after removing the DC component of the audio signal whose response characteristic is corrected for each input frequency band; A step 2-2 of receiving an external noise signal through an input device, removing a DC component, and then determining a level value of the noise signal; A second step of selecting a dynamic range control characteristic graph by comparing the level value of the audio signal from which the DC component is removed with the level value of the noise signal; And a second to fourth step of controlling the output audio signal level by applying the selected dynamic range control characteristic graph to the audio signal whose response characteristic is corrected for each frequency band.

The present invention also provides an ultrasonic speaker device comprising an improved audio signal processing unit,

The audio signal processor removes low frequency components of the input audio signal and improves the response characteristics for each frequency band by using the equalizer 220; and the level of the audio signal whose response characteristics are corrected for each frequency band. The dynamic range control unit 300 to control the output audio signal level by selecting a dynamic range control characteristic graph by comparing the value with the level value of the external noise signal and applying the same to the corrected audio signal; Ultrasonic modulator for modulating; and Ultrasonic transducer for outputting the ultrasonically modulated signal to the air. The sound quality improving unit 200 may include a high pass filter 210 for removing low frequency components of an input audio signal, and an equalizer 220 for correcting response characteristics for each frequency band from which low frequency components are removed; and for each frequency band. Sound pressure level correction unit 230 for adjusting the sound pressure level of the signal whose response characteristics are corrected; and the signal size is greater than a certain level in order to prevent clipping of signals that may occur in the equalizer 220 and sound pressure level correction unit 230. Limiter 240 for controlling not to increase. The dynamic range controller 300 may include: an audio signal level determiner configured to determine a level value of an audio signal after removing a direct current component of an audio signal whose response characteristic is corrected for each input frequency band; and input an external noise signal through an input device. A noise signal level determination unit for determining a level value of the noise signal after removing the DC component; and selecting a dynamic range control characteristic graph by comparing the level value of the audio signal from which the DC component is removed with the level value of the noise signal. A dynamic range control characteristic graph application unit 330 for controlling the output audio signal level by applying the selected dynamic range control characteristic graph to the audio signal whose response characteristic is corrected for each frequency band; Include.

According to the improved audio signal processing method of the present invention and the superdirectional ultrasonic speaker device having the same, an audio signal processing method suitable for the characteristics of the superdirectional ultrasonic speaker can be applied to deliver an improved and clear audio signal to the listener. .

1 is a view showing the overall configuration of an ultrasonic speaker device including an improved audio signal processor according to an embodiment of the present invention.
2 is a view for explaining an improved audio signal processing method according to an embodiment of the present invention.
3 is a view for explaining a sound quality improvement unit of the improved audio signal processor according to an embodiment of the present invention.
4 is a view for explaining a sound quality improvement method in the improved audio signal processing according to an embodiment of the present invention.
5 is a view for explaining a high pass filter according to an embodiment of the present invention.
6 is a view for explaining the characteristics of the equalizer according to an embodiment of the present invention.
7 is a view for explaining the characteristics of the sound pressure level correction unit according to an embodiment of the present invention.
8 is a view for explaining the characteristics of the limiter according to an embodiment of the present invention.
9 is a diagram illustrating a dynamic range controller of an improved audio signal processor according to an exemplary embodiment of the present invention.
10 is a view for explaining a dynamic range control method in improved audio signal processing according to an embodiment of the present invention.
11 is a diagram for explaining dynamic range compression according to an embodiment of the present invention.
12 is a diagram illustrating a dynamic range control characteristic graph according to an embodiment of the present invention.
FIG. 13 is a diagram illustrating a conventional superdirectional ultrasound system. FIG.
14 is a view for explaining the effect of the equalizer according to an embodiment of the present invention.

Specific structural or functional descriptions of the embodiments according to the inventive concept disclosed herein are provided only for the purpose of describing the embodiments according to the inventive concept. It may be implemented in various forms and is not limited to the embodiments described herein.

Embodiments according to the inventive concept may be variously modified and have various forms, so embodiments are illustrated in the drawings and described in detail herein. However, this is not intended to limit the embodiments in accordance with the concept of the present invention to specific embodiments, and includes modifications, equivalents, or substitutes included in the spirit and scope of the present invention.

Terms such as first or second may be used to describe various components, but the components should not be limited by the terms. The terms are only for the purpose of distinguishing one component from another component, for example, without departing from the scope of the rights according to the inventive concept, the first component may be called a second component, Similarly, the second component may also be referred to as the first component.

When a component is said to be “connected” or “connected” to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may exist in the middle. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that no other component exists in the middle. Expressions describing relationships between components, such as "between" and "immediately between," or "neighboring to," and "direct neighboring to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “include” or “have” are intended to designate that the stated feature, number, step, operation, component, part, or combination thereof exists, but one or more other features, numbers, steps It is to be understood that the present invention does not exclude, in advance, the possibility of the addition or the presence of any operation, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and are not construed in ideal or excessively formal meanings unless expressly defined herein. Do not.

Hereinafter, a sound quality improvement method of a superdirectional ultrasonic speaker device and a superdirectional ultrasonic speaker device having the same will be described with reference to the accompanying drawings.

As shown in FIG. 13, the conventional super-directional ultrasonic system modulates the square root of the double-integrated input audio signal prior to amplitude modulation and sends it out into the air through the ultrasonic speaker. This method is limited in reducing distortion because the frequency spectrum of the bandwidth-constrained original audio signal is shown on an almost infinite bandwidth by a nonlinear operation called the square root. On the other hand, ATC of the United States has proposed an iterative error compensation method without increasing the bandwidth in the US patent US 6,584,205, but in this case, similar distortions will appear.

However, as a result of experiments by the inventors of the present invention, it has been found that the magnitude of the harmonic component generated by the nonlinear distortion is almost 20 dB smaller than that of the original signal, so that it is hardly heard in general voice and audio signals. In addition, in order to compensate for nonlinear distortion, the linear distortion of all systems must be measured perfectly.If the measurement is not accurate, the distortion increases, so that the linear distortion can be corrected as much as possible and the intelligibility can be improved at the same time. We found that it is more advantageous for the listener to apply the sound quality improvement method.

Therefore, the sound quality improvement method of the improved audio signal processing method according to the present invention is to reduce the distortion and to deliver a clearer audio signal from the listener's point of view.

In addition, the dynamic range compressor will be described before the dynamic range control of the improved audio signal processing.

Dynamic range refers to the range of the difference between the strongest and the weakest sounds in decibels (dB) when handling or transmitting sound signals. When multiple sound signals are input When the dynamic range of each sound signal is different, a sound signal having a relatively low level is hard to be heard. Therefore, a sound signal over a certain level needs to compress the signal strength. In this case, the dynamic range compressor (DRC), which is a device used, reduces the output when an input of a predetermined level or more is input.

FIG. 11 is a graph showing the operating characteristics of a dynamic range compressor. Referring to this, the horizontal axis represents the level of an input signal and the vertical axis represents the level of an output signal. It shows that the input signal is output to the output level up to -20dB, but the input signal level is set to reduce the compression of the output signal level if the input signal level is above -20dB. The reason for this is to protect the equipment from excessive peaks in the input signal and to reduce the excessive dynamic range to make it easier for the listener to listen to the audio. The threshold level defines the level at which the input signal begins to be compressed. The level is usually expressed in decibels (dB). When an input of more than the level (dB) set as the threshold level is input, the compressor is operated to compress the sound.

In the graph of FIG. 11, the threshold level is set to -20 dB, and an output signal of -20 dB or more forms a gentle slope. Compression ratio (Ratio) is the ratio of compression. If the compression ratio is 1: 1, it means that the level of the input signal and the output signal are the same, and the operation of the dynamic range compressor is turned off. If the compression ratio is set to 4: 1, an input signal level of -16dB, a 4dB increase from -20dB, can produce an output signal level of -19dB by raising only 1dB from -20dB. If the compression ratio is set to an infinity (∞) of 10: 1 or more, the same effect as the limiter 240 may be obtained by preventing the level of the output signal level from exceeding the threshold level.

12 is a graph illustrating dynamic range control characteristics according to an embodiment of the present invention, which enables various compression ratios to be set. The configuration of selecting the dynamic range control characteristic graph by comparing the level value of the audio signal and the noise signal described later means selecting the control characteristic graph having various compression ratios of FIG. 12.

The superdirectional ultrasonic speaker device may use the superdirectional characteristic to transmit an audio signal only for the listener at a specific position. However, if there is other external noise in the space where the listener is located and the level of the noise is higher than the audio signal level from the ultrasonic speaker device, the listener may not be able to listen normally. As a countermeasure, a dynamic range control method according to an embodiment of the present invention has been proposed. In particular, if a dynamic range control characteristic graph having various compression ratios is provided and a dynamic range control characteristic graph having an appropriate compression ratio is selected and applied to an input audio signal according to the level of external noise, the listener may have a higher level from the ultrasonic speaker when the external noise is loud You will be able to listen to the audio signal of, and if there is little external noise, you will be able to comfortably listen to the audio signal below the threshold level.

Hereinafter, an improved audio signal processing method and an ultrasonic speaker device having the same according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, the ultrasonic speaker device according to the present invention includes an improved audio signal processor 120. The audio signal processing unit 120 removes low frequency components of the input audio signal and uses the equalizer 220 to improve the sound quality of the response characteristics for each frequency band, and the audio for which the response characteristics are corrected for each frequency band. Dynamic range control unit 300 for controlling the output audio signal level by selecting the dynamic range control characteristic graph by comparing the level value of the signal with the level value of the external noise signal and applying it to the corrected audio signal, and the level controlled audio. An ultrasonic modulator 100 for ultrasonically modulating the signal, and the ultrasonic transducer 110 for outputting the ultrasonically modulated signal to the air.

The audio signal input device may be any audio signal input device such as a general MP3 player, a microphone, and a sound source playback device. The external noise input device refers to a device capable of converting external noise such as a microphone into an electrical signal, but is not limited to the microphone. The external noise signal input device may be installed near the listener, or may be installed integrally with the ultrasonic speaker device to receive the overall ambient noise.

Referring to FIG. 3, the sound quality improvement unit 200 may include a high pass filter 210 for removing low frequency components of an input audio signal; and a signal for which low frequency components have been removed by passing through the high pass filter 210 for each frequency band. Equalizer 220 for correcting the characteristic; and Sound pressure level correction unit 230 for adjusting the sound pressure level of the signal whose response characteristics are corrected for each frequency band; and Signals that may occur in the equalizer 220 and sound pressure level correction unit 230 And a limiter 240 that controls the size of the signal not to increase by more than a certain level to prevent clipping of the signal.

The high pass filter 210 is to remove low frequency components included in the input audio signal. The ultrasonic speaker is difficult to reproduce low frequency components due to the physical limitations of the ultrasonic transducer 110. Therefore, the first to remove the low-frequency band difficult to reproduce in the ultrasonic speaker through the high pass filter 210 (HPF) to secure the head-room required for signal amplification, and to improve the loudness (loudness) at low power It is essential to secure.

The high pass filter 210 used in the present invention is implemented as a second-order IIR filter 210 (Infinite Impulse Response Filter), as shown in Figure 5, the cutoff frequency (cutoff frequency) used ultrasonic transducer 110 This can be set based on the output performance of). The output performance of the ultrasonic transducer 110 can be grasped by confirming an audible frequency signal reproducing a single tone signal. In the present invention, the ultrasonic transducer 110 confirms that effective reproduction is possible from about 150 Hz, and the cutoff low frequency component is 150 Hz or less based on this. Meanwhile, in the present invention, the high pass filter 210 employs a secondary IIR filter structure for ease of implementation, but the present invention is not limited thereto, and a person having ordinary skill in the art may employ a high pass filter 210 having various structures as necessary. Is self-explanatory.

The signal from which low frequency components are removed through the high pass filter 210 is input to an equalizer 220 for correcting frequency characteristics for each frequency band. The equalizer 220 is used to correct the frequency response characteristics of the ultrasonic transducer 110, the ultrasonic amplifier AMP, and the air column, and at the same time to enhance the intelligibility.

FIG. 6 shows a characteristic curve of an Infinite Impulse Response (IIR) equalizer 220 (Equalizer) set to a default value. The equalizer 220 is designed not only to smooth the frequency response of the air column, the ultrasonic transducer 110, and the ultrasonic amplifier (AMP) but also to amplify the 4kHz band or more, which is important for speech intelligibility. It is apparent to those skilled in the art that the characteristic curve of the equalizer 220 may be appropriately adjusted as necessary to increase the intelligibility.

14 is a diagram illustrating a frequency response characteristic to which the equalizer 220 is applied. The left diagram of FIG. 14 shows the frequency components of the original sound signal, and the right diagram shows the frequency components of the signal through which the original signal has passed through the equalizer 220. The equalizer 220 has an effect of reducing or eliminating harmonic distortion and compensating for the bass portion.

The signal whose frequency response is adjusted by the equalizer 220 is input to the sound pressure level correction unit 230 that adjusts the sound pressure level. For the purpose of the use of the ultrasonic speaker, it is necessary to maintain the level of the reproduced sound at a desired target level as well as a high directivity to make the sound heard only by a specific user. The sound pressure level correction unit 230 is a configuration necessary for this purpose is to compress the signal of a level (second level) that is too high, and the signal of a certain section level provides a make-up gain for improving the clarity. And a signal of too low a level (first level) is removed to prevent reproduction.

7 shows a characteristic graph of the input / output level of the sound pressure level correction unit 230. According to FIG. 7, in the exemplary embodiment of the present invention, the input / output characteristic of the sound pressure level correction unit 230 is set to about −83 dB or less so that the first level is not reproduced. The second level was set to -7 dB or more to compress the signal, and the other signal level was applied to 4 dB as the make-up gain.

Therefore, the sound pressure level correction unit 230 removes the signal level below the first level (dB) so as not to reproduce, compresses the second level (dB) or more, and other signal levels give a gain of 4dB or more. It is done.

The output of the sound pressure level correction unit 230 is input to the limiter 240. The limiter 240 controls the size of the signal not to increase by more than a certain level in order to prevent clipping of signals that may occur in the equalizer 220 and the sound pressure level corrector 230. This is because clipping of the signal in the time domain, which may occur in the equalizer 220 or the sound pressure level corrector 230, may generate harmonics in the frequency domain and distort the sound. Thus, the limiter 240 is used to ensure that the signal level does not rise above a certain threshold.

8 shows a waveform before applying the limiter 240 and a waveform after applying the limiter 240. When a signal of 0.5 level or more is input to the limiter 240 in the chart on the left side of FIG.

The dynamic range controller 300 controls the dynamic range characteristic of the audio signal by comparing the audio signal level with the external noise signal level. Referring to FIG. 9, the dynamic range controller 300 may include: an audio signal level determination unit configured to determine a level value of an audio signal after removing a DC component of an audio signal whose response characteristic is corrected for each input frequency band; A noise signal level determination unit 320 for removing a DC component of an input noise signal and determining a level value of the noise signal; and selecting a dynamic range control characteristic graph by comparing the level value of the audio signal with the level value of the noise signal Dynamic range control characteristic graph selector 330; Dynamic range control characteristic graph application unit 330 for controlling the output signal level by applying the selected dynamic range control characteristic graph to the audio; It may include a control unit 300.

The audio signal level determination unit 310 and the noise signal level determination unit 320 compare the level values after removing the DC components mixed in each of the audio signal and the noise signal in order to accurately compare the level values. The level value to be compared may be the maximum value of the dynamic range and may be the average value of the maximum value of each signal over a period of time.

The dynamic range control characteristic graph selector 330 includes control characteristic graph information having one or more various compression ratios. If the noise signal level value is larger than the audio signal level value, the dynamic range control characteristic graph selector 330 may adjust the compression ratio to increase the audio signal listening level of the listener. You can choose from 1 to 1: 1. The control characteristic graph information selected to increase the audio signal level above the threshold level may be transmitted to the dynamic range control characteristic graph application unit 330.

Referring to FIG. 12, various compression ratios may be represented by one or more control characteristic graphs, and the compression ratio may select a compression ratio from ∞: 1 to 1: 1 and may be configured as a plurality of control characteristic graphs at an appropriate ratio as necessary.

The dynamic range control characteristic graph application unit 330 may control the output signal level by applying the selected dynamic range control characteristic graph to the audio signal. In this case, the dynamic range control characteristic graph is a basic function of compressing a signal of a specific level or more, but may be expanded as necessary. Although not shown in the drawing, the stretching ratio becomes 1: 2, 1: 3, so that the control characteristic graph in which the input signal over the grain boundary level is amplified and output can be made.

The ultrasonic modulator 100 may perform ultrasonic amplitude modulation on the audio signal output from the audio signal processor 120 and perform double side band (DSB) or single side band (SSB) amplitude modulation. In addition, the ultrasonic modulator 100 may be configured of an AM (Amplitude Modulation) modulator 100 and an ultrasonic amplifier, as shown in FIG. The ultrasonic transducer 110 outputs the amplitude-modulated ultrasonic signal into the air.

Figure 2 shows a flow diagram of the improved audio signal processing of the ultrasonic speaker apparatus according to an embodiment of the present invention. An improved audio signal processing method of an ultrasonic speaker device includes a first step of removing low frequency components of an input audio signal and correcting response characteristics for each frequency band using the equalizer 220; A second step of selecting a dynamic range control characteristic graph by comparing the level value of the audio signal whose response characteristic is corrected for each frequency band with the level value of the external noise signal and controlling the output audio signal level by applying the dynamic range control characteristic graph to the corrected audio signal; And a third step of ultrasonically modulating the level controlled audio signal.

Figure 4 shows a flow chart of the sound quality improvement method of the first step in the improved audio signal processing of the ultrasonic speaker apparatus according to an embodiment of the present invention. The first step may include a step 1-1 of removing low frequency components of an audio signal input using the high pass filter 210; A second step of correcting a response characteristic for each frequency band by using the equalizer 220 of the signal from which the low frequency component is removed; Adjusting the sound pressure level of the signal whose response characteristic is corrected for each frequency band; In order to prevent clipping of signals that may occur in steps 1-2 and 1-3, steps 1-4 may be controlled by using the limiter 240 so that the magnitude of the signal does not increase more than a certain level. have.

10 is a flowchart illustrating a method of controlling the dynamic range of the second stage in the improved audio signal processing of the ultrasonic speaker apparatus according to an embodiment of the present invention. The second step includes a step 2-1 of determining a level value of the audio signal after removing the direct current component of the audio signal whose response characteristic is corrected for each input frequency band; Step 2-2 of receiving an external noise signal through an input device, removing a DC component, and then determining a level value of the noise signal; Selecting a dynamic range control characteristic graph by comparing the level value of the audio signal from which the DC component is removed with the level value of the noise signal; And a second to fourth step of controlling the output audio signal level by applying the selected dynamic range control characteristic graph to the audio signal whose response characteristic is corrected for each frequency band.

The improved audio signal processing method is different from the super-directional ultrasonic speaker device including the improved audio signal processing unit 120 described above, and thus a detailed description thereof will be omitted.

However, the improved audio signal processing method may be implemented as a computer program that may be executed in a digital signal processor (DSP), or may be implemented as a program such as an app that may be executed in a computer device such as a PC or a mobile phone. In this case, the program may be recorded and stored in a computer readable storage medium and executed in various devices such as a computer and a mobile phone.

In the above, the preferred embodiments of the improved audio signal processing method of the superdirectional ultrasonic speaker device and the superdirectional ultrasonic speaker device having the same have been described. The above-described embodiments are to be understood in all respects as illustrative and not restrictive, the scope of the invention being indicated by the claims that follow, rather than the foregoing detailed description. And it is to be understood that all changes and modifications derived from the equivalent concept as well as the meaning and scope of the claims are included in the scope of the present invention.

100: ultrasonic modulator
110: ultrasonic transducer
120: audio signal processor
200: sound quality improvement unit
210: high pass filter
220: equalizer
230: sound pressure level correction unit
240: limiter
300: dynamic range control unit
310: audio signal level determination unit
320: noise signal level determination unit
330: dynamic range control characteristic graph selector
340: dynamic range control characteristic graph application unit

Claims (7)

In the improved audio signal processing method of the ultrasonic speaker device,
Removing a low frequency component of an input audio signal and correcting a response characteristic for each frequency band using an equalizer;
A second step of selecting a dynamic range control characteristic graph by comparing the level value of the audio signal whose response characteristic is corrected for each frequency band with the level value of the external noise signal and controlling the output audio signal level by applying the dynamic range control characteristic graph to the corrected audio signal;
A third step of ultrasonically modulating the level controlled audio signal,
The first step is,
A step 1-1 of removing low frequency components of an input audio signal using a high pass filter;
A step 1-2 of correcting a response characteristic for each frequency band by using an equalizer to remove the low frequency component signal;
Adjusting the sound pressure level of the signal whose response characteristic is corrected for each frequency band;
1 to 4 steps of controlling the signal size does not increase more than a certain level by using a limiter to prevent clipping of the signal that can occur in steps 1-2 and 1-3,
The ultrasonic speaker device may include an ultrasonic modulator and an ultrasonic transducer, and the ultrasonic speaker device may provide hyperdirectionality in a sound wave propagation direction through ultrasonic modulation, and the low frequency component removed in step 1-1 may be 150 Hz or less. An improved audio signal processing method for an ultrasonic speaker device, characterized by the above-mentioned.
delete The method according to claim 1,
The second step,
A step 2-1 of determining a level value of the audio signal after removing a DC component of the audio signal whose response characteristic is corrected for each input frequency band;
Step 2-2 of receiving an external noise signal through an input device, removing a DC component, and then determining a level value of the noise signal;
Selecting a dynamic range control characteristic graph by comparing the level value of the audio signal from which the DC component is removed with the level value of the noise signal;
And a second step of controlling the output audio signal level by applying the selected dynamic range control characteristic graph to the audio signal whose response characteristic is corrected for each frequency band. .
An ultrasonic speaker device including an improved audio signal processor,
The audio signal processor includes: a sound quality improving unit for removing low frequency components of an input audio signal and correcting response characteristics for each frequency band using an equalizer;
A dynamic range controller configured to compare a level value of an audio signal whose response characteristic is corrected for each frequency band with a level value of an external noise signal, select a dynamic range control characteristic graph, and apply the same to the corrected audio signal to control an output audio signal level; Wow,
An ultrasonic modulator for ultrasonically modulating the audio signal whose level is controlled;
And an ultrasonic transducer for outputting the ultrasonically modulated signal to the air.
The sound quality improvement unit,
A high pass filter for removing low frequency components of an input audio signal; and
An equalizer for correcting response characteristics for each frequency band of a signal from which low frequency components have been removed; and,
Sound pressure level correction unit for adjusting the sound pressure level of the signal whose response characteristics are corrected for each frequency band; And,
Includes a limiter for controlling the signal size does not increase more than a certain level in order to prevent clipping of the signal that may occur in the equalizer and sound pressure level correction unit;
The ultrasonic speaker device includes an ultrasonic modulator and an ultrasonic transducer, and the ultrasonic speaker device imparts superdirectionality to the sound wave propagation direction through ultrasonic modulation, and the low frequency component removed from the high pass filter is 150 Hz or less. Ultrasonic speaker device comprising an improved audio signal processing unit characterized in that.
delete The method according to claim 4,
The dynamic range control unit,
An audio signal level determination unit to determine a level value of the audio signal after removing a DC component of the audio signal whose response characteristic is corrected for each input frequency band;
A noise signal level determination unit that receives an external noise signal through an input device, removes a DC component, and then determines a level value of the noise signal;
A dynamic range control characteristic graph selector for selecting a dynamic range control characteristic graph by comparing the level value of the audio signal from which the DC component is removed with the level value of the noise signal;
And a dynamic range control characteristic graph application unit for controlling the output audio signal level by applying the selected dynamic range control characteristic graph to the audio signal whose response characteristic is corrected for each frequency band. Ultrasonic speaker device.
A computer-readable storage medium having recorded thereon a program for performing the method of claim 1.

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