JP4545234B1 - Transmitter - Google Patents

Abstract

There is provided a transmission device capable of making it difficult for human ears to perceive sound waves for transmitting information in an environment where information is transmitted as sound waves.
A transmitting device is a device that converts various encoded information into a sound wave of an audible sound band and transmits the sound, and a microphone that inputs an environmental sound of a place where the sound wave is transmitted as an environmental sound signal. And a peak frequency detector 107 for detecting a peak frequency mainly constituting the environmental sound from the environmental sound signal, and a carrier wave for generating a carrier wave having a plurality of frequencies capable of obtaining a masking effect on the environmental sound based on the peak frequency. A generation unit 108 and a modulation unit 115 that modulates a plurality of carrier waves with a baseband signal are provided.
[Selection] Figure 2

Description

  The present invention relates to an information providing system for providing various types of information to a terminal using sound waves, and more particularly to a transmitting device of such an information providing system.

  Systems for providing various types of information to terminals have been conventionally provided. For example, in radio or television broadcasting, character codes, graphic information, information on programs, etc. are superimposed (multiplexed) on broadcast signals, and various information is provided to television receivers and radio receivers in addition to normal program contents. Character multiplex broadcasting is performed.

  However, in the text multiplex broadcasting system, it is necessary to superimpose digital information on the radio waves of TV and radio, so large broadcasting station facilities are indispensable, costly, and information is easily provided to terminals. Can not do it. Also, the method of taking a QR code using a camera of a mobile phone cannot be used with a terminal not equipped with a camera, and is very difficult for beginners and people unfamiliar with machines.

  In view of such problems, a new information providing method has been developed that provides various types of information to a terminal as a sound wave using air as a medium. For example, these are disclosed in Patent Documents 1 to 4 below. . Thus, if it is a method of transmitting information as a sound wave, it is possible to easily transmit information at low cost by using an existing speaker and a microphone mounted on the terminal.

  Patent Document 1 discloses that information to be transmitted is transmitted as sound through an input / output interface of an acoustic device that handles existing sound by using an information encoding device that converts the information to be transmitted into sound. The information transmission system reproduces the transmission target information based on the voice received by the information decoding apparatus. Further, in Patent Document 1, an encoding method is employed that aims to produce comfortable music in which sounds including encoded information can be actively heard by humans.

  In addition, the information providing systems disclosed in Patent Documents 2 and 3 were developed by the present inventors and encode various information as data frames in milliseconds including a preamble for synchronizing timing. Thus, information is provided as sound waves.

  The information providing system disclosed in Patent Document 4 was also developed by the present inventors, and when transmitting various types of information as sound pressure vibration information, the transmission frequency is defined as the gap between the sounds of the average rate scale. This is the frequency.

JP 2003-186500 A Japanese Patent No. 3822224 Japanese Patent No. 3833579 Japanese Patent No. 4295781

  Here, when using a system for transmitting information as a sound wave, as disclosed in Patent Documents 2 to 4, the sound wave for transmitting information is an audible sound. May be heard. In this case, when a sound wave for transmitting information is transmitted in the store, there is a possibility that a customer who feels uncomfortable may leave the store.

  The present invention has been made in view of such a problem, and in an environment where information is transmitted as sound waves, a transmission device capable of making it difficult for human ears to perceive sound waves for transmitting information. The purpose is to provide.

  In order to solve the above-described problems, a transmitting device according to the present invention is a transmitting device that converts various encoded information into sound waves in an audible sound band and transmits the sound. A microphone input as a sound signal, a peak frequency detector for detecting a peak frequency mainly constituting the environmental sound from the environmental sound signal, and a masking effect on the environmental sound based on the peak frequency can be obtained. A carrier generation unit that generates a carrier wave having a plurality of frequencies, and a modulation unit that modulates the plurality of carrier waves with a baseband signal.

  The transmission program according to the present invention is a transmission program for causing a computer to convert various encoded information into sound waves of an audible sound band and transmitting the sound from a speaker. The sound waves input via a microphone are transmitted. A peak frequency detecting step for detecting a peak frequency mainly constituting the environmental sound from a signal of the environmental sound at a place to be performed, and a plurality of frequencies for obtaining a masking effect on the environmental sound based on the peak frequency. A carrier generation step for generating a carrier wave and a modulation step for modulating the plurality of carrier waves with a baseband signal are executed by the computer.

  ADVANTAGE OF THE INVENTION According to this invention, the transmitter which can transmit the sound wave for transmitting information as a sound which is hard to be perceived by a human ear can be provided.

FIG. 1 is a schematic diagram schematically showing a configuration of an information providing system according to the present embodiment. FIG. 2 is a block diagram showing a conceptual circuit for realizing a function of generating a sound code in the transmission device according to the present embodiment. FIG. 3 is a diagram for explaining the masking effect on the sound code by the environmental sound according to the present embodiment. FIG. 4 is a block diagram showing a conceptual circuit for realizing a function of receiving a sound code in the mobile phone according to the present embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The information providing system according to the present embodiment transmits various information such as messages and URLs as sound waves using air as a medium from the transmitting device to the receiving device, and the transmitting device transmits and receives sound waves from the speaker. The device recognizes the transmitted information by receiving and decoding the sound wave with the microphone.

  In the present embodiment, the environmental sound existing at the place where the transmitting device and the receiving device are installed, that is, the place where sound pressure vibration information (hereinafter referred to as “sound code”) is transmitted is considered. A sound code is transmitted using a carrier wave. Here, the environmental sound is sound around a place where a system such as ambient noise such as car or train sound or wind sound, human voice or music is installed.

  FIG. 1 is a diagram schematically showing a configuration of an information providing system 1 according to the present embodiment. As shown in the figure, the information providing system 1 includes a transmitting device 10 that transmits various information as a sound code, and a mobile phone 20 as a receiving device that receives the sound code.

The transmitter 10 includes a PC (personal computer) main body 11, a display 12 as a display means, an input device 13 including a mouse and a keyboard, a speaker 15 for transmitting a sound code as sound, and a microphone for inputting environmental sound. 16 is provided. The PC body 11 includes an arithmetic device such as a processor for performing various calculations, an HDD (Hard Disc Drive) for storing various information such as programs, and a RAM (Random) used as a work area for arithmetic processing.
Access memory) is built in.

  The cellular phone 20 includes a microphone 21 for picking up a sound code transmitted from the speaker 15 and a display 22 for displaying various information. In addition, the mobile phone 20 has a built-in memory that stores various types of information such as an arithmetic device such as a processor for performing various calculations and a program, and is used as a work area for arithmetic processing.

  The transmission device 10 of the information providing system 1 described above is installed in a commercial facility such as a department store, a supermarket, a shopping street, a movie theater, an amusement park, an amusement facility, or the like. In the present embodiment, the mobile phone 20 that is a receiving device is assumed to be a terminal owned by a user who has visited such a facility. Information can be obtained.

  As various types of information, for example, messages regarding products, events, facility guidance, etc., and text information such as URLs of related Internet home pages are provided to the terminal. Customers visiting the facility can obtain more information by accessing the Internet using the terminal without entering characters using the input key, if the URL is obtained from the terminal via the sound code, You can read detailed product descriptions.

  Of course, the place where the transmitting device 10 is installed is up to the information provider and may be installed in other places as appropriate. The content of the provided information is not limited to character information, and image information or the like may be provided.

Next, the process of generating a sound code to be transmitted to the mobile phone 20 in the transmission device 10 will be described in detail. FIG. 2 is a block diagram showing a conceptual circuit for realizing a function of generating a sound code in the transmission device according to the present embodiment. In this embodiment, OFDM (Orthogonal Frequency Division)
A modulated wave is generated by a Multiplexing method.

  Note that the function of each unit shown in FIG. 2 is realized by software by the calculation means of the transmission device 10 executing a program stored in the storage device, but it is dedicated for performing such processing. A circuit may be provided and realized in hardware.

As shown in the figure, the transmitting device 10 includes an A / D converter 103, an FFT (Fast
Fourier transform) section 104, peak frequency detection section 107, carrier wave generation section 108, modulation section 115, and D / A conversion section 120.

  The A / D converter 103 converts the analog electrical signal of the environmental sound 101 input from the microphone 16 of the transmission device 10 into a digital signal. The environmental sound 101 is a sound that exists in the environment where the transmission device 10 is installed. For example, noise such as a train, a car, and a wind sound corresponds to the environmental sound.

  The FFT unit 104 converts a signal on the time axis into a signal on the frequency axis by fast Fourier transform. The peak frequency detection unit 107 detects the frequency having the highest sound pressure level from the components on the frequency axis of the environmental sound signal, and determines the peak frequency fp mainly constituting the environmental sound.

  The detection of the peak frequency fp by the peak frequency detection unit 107 is performed prior to the transmission of the sound code 150, and in this embodiment, the sound pressure level is obtained by repeatedly acquiring environmental sounds 10 times in units of 10 ms and integrating them. To detect the peak frequency fp. The carrier wave generation unit 108 generates a plurality of carrier waves by a PLL (Phase locked Loop) circuit based on the peak frequency fp.

  The modulation unit 115 performs modulation by the OFDM method, and modulates the plurality of carrier waves generated by the carrier wave generation unit 108 with a baseband signal subjected to parallel conversion to generate an original signal of the sound code 150. Specifically, the modulation unit 115 modulates each carrier by QPSK (Quadrature phase shift keying) based on each parallel transmission bit of the parallel bit stream, and then performs fast inverse Fourier transform (IFFT), thereby modulating the carrier. Generate a signal. As for the data frame structure, four packets of about 10 to 100 ms are arranged in one frame, and the data amount is 1,024 bits in one frame.

  The D / A conversion unit 120 converts the modulation signal from the modulation unit 115 into an analog signal and transmits the analog signal to the speaker 15. This analog signal is transmitted from the speaker 15 as a sound code 150 that is a sound wave.

  In such a configuration, when transmitting the sound code 150, first, the environmental sound 101 input from the microphone 16 is digitally converted by the A / D conversion unit 103. The digital signal of the environmental sound 101 is fast Fourier transformed in the FFT unit 104, and the signal on the time axis is converted into a signal on the frequency axis.

  The peak frequency detection unit 107 detects the frequency having the highest sound pressure level from the components on the frequency axis of the environmental sound signal, and sets it as the peak frequency fp that mainly constitutes the environmental sound. Subsequently, the carrier wave generation unit 108 uses a frequency in the vicinity of 100 Hz out of 1 / n (n is a natural number) of the peak frequency fp as a fundamental frequency, which is 64 times a natural number multiple (1 to 64 times) of the fundamental frequency. Subcarriers (carrier waves) are generated.

  For example, a case where the peak frequency fp is 1 kHz will be described as an example. First, among the 1 / n frequencies of 1,000 Hz, the frequency closest to 100 Hz is 100 Hz which is 1/10 of 1,000 Hz. Therefore, the carrier wave generation unit 108 determines the fundamental frequency as 100 Hz, and generates a carrier wave having a frequency of 4 to 67 times, that is, frequencies of 400 Hz, 500 Hz, 600 Hz, 700 Hz,..., 6,600 Hz, 6,700 Hz.

  Subsequently, the modulation unit 115 modulates the plurality of carrier waves with a baseband signal that has been subjected to parallel conversion, and generates a modulated signal. This modulated signal is converted into an analog signal by the D / A converter 120 and transmitted as a sound code 150 from the speaker 15. As a communication method, for example, CDMA (Collision Detection Multiple Access) may be used.

  The transmitting device 10 that transmits the sound code 150 has been described in detail above. However, the plurality of carrier waves of the sound code 150 have a frequency that is a natural number multiple of the fundamental frequency, and thus are orthogonal to each other. Therefore, it can be decomposed into carrier waves on the receiving device side. Further, the frequency interval of the plurality of carrier waves is 100 Hz, and a sufficient number of carrier waves can be used in the audible sound band.

  In the present embodiment, the peak frequency fp of the environmental sound is detected, and a plurality of carrier waves are generated based on the peak frequency fp, and the sound code 150 composed of such carrier waves is superimposed on the environmental sound. As a result, the sound is difficult to perceive by the human ear due to the masking effect by the environmental sound.

  In addition, when the environmental sound is music such as a musical instrument performance, even if the sound code is superimposed, the environmental sound only changes the timbre, so that the listener who is listening to the music feels uncomfortable due to the sound code flowing. Almost never give.

  The plurality of carrier waves exist over a wide range (400 to 6,700 Hz) of the audible sound band at 100 Hz intervals, and the sound code 150 has frequency components such as white noise. Therefore, the sound of the sound code 150 is a sound that is easy to adjust to the environmental sound and is difficult to perceive by the human ear.

  Here, the masking effect on the sound code 150 by the environmental sound will be described in more detail. FIG. 3 is a diagram for explaining the masking effect on the sound code by the environmental sound according to the present embodiment. In the figure, the horizontal axis indicates the frequency [kHz], and the vertical axis indicates the masking amount [dB]. The solid line in the figure shows the amount of masking with pure tone with a frequency of 400 Hz and a sound pressure level of 80 dB SPL. The audible limit is expressed as a sensory level when there is no masking sound.

  Therefore, in the range below the solid line shown in FIG. 3, the second sound is masked and only the first sound (pure sound) can be heard. On the other hand, the alternate long and short dash line in the figure shows the masking amount when the masking sound is 80 dB narrowband noise (noise) having a bandwidth of 90 Hz with 410 Hz as the center frequency.

  Here, it is considered that sound having a certain bandwidth is generated in a normal environment such as outdoors where the sound code transmitting device 10 is installed. Therefore, looking at the masking amount indicated by the alternate long and short dash line when the first sound is narrow band noise, the masking effect is obtained in a wide range of both low and high sounds from the center frequency of the noise. Therefore, as in the present embodiment, a sufficient masking effect can be obtained even with a plurality of carrier waves that exist over a wide range of the audible sound range.

  Further, when looking at the masking amount indicated by the solid line when the first sound is a pure sound, the masking effect is increased in the vicinity of the frequency (overtone) that is a natural number multiple of the first sound (pure sound). Therefore, as in this embodiment, if 1 / n of the peak frequency of the environmental sound is a basic frequency and a carrier wave having a frequency 1 to 64 times that is used, a harmonic with a large masking effect (a natural number multiple of the peak frequency) (Sound of frequency) is used as a carrier wave, and a larger masking effect can be obtained.

  The configuration of the transmitting device described above can be variously modified without departing from the gist of the present invention. For example, the fundamental frequency obtained by setting the peak frequency to 1 / n is not limited to the vicinity of 100 Hz, and maintains the interval between carriers capable of multi-carrier and the required number of bands over a certain range in the audible sound band. Any frequency that can secure a carrier wave may be used. In order to satisfy such a condition, the fundamental frequency is preferably in the range of 30 to 260 Hz.

  In this embodiment, the carrier wave is generated using the PLL circuit, but may be generated by a circuit other than the PLL circuit. In addition, the number of carrier waves can be changed as appropriate according to the amount of data to be transmitted. When pilot signals or the like are input, the number of carrier waves may be further increased. However, it is desirable that the frequency of the carrier wave be in the range of 400 Hz to 12 kHz in consideration of the frequency characteristics of the speaker 15 and the microphone 22.

  The peak frequency fp does not necessarily have to be the frequency of the maximum sound pressure. The peak frequency fp has a certain size among the frequency components constituting the environmental sound, and is a frequency mainly constituting the environmental sound together with other frequency components. I need it. This is because, if the fundamental frequency is determined based on the frequency components mainly constituting the environmental sound, a sufficient masking effect can be obtained. Further, the detection timing and the number of times of the peak frequency fp by the peak frequency detection unit 107 can be changed as appropriate.

  If it is difficult for the peak frequency detection unit 107 to detect the peak frequency fp of the environmental sound, a preset frequency may be set as the peak frequency. For example, 880 Hz (ra sound) and 1,047 Hz (fa sound) may be used as the set frequency.

  The modulation scheme in the modulation unit 115 is not limited to QPSK, and other modulation schemes such as BPSK, 8PSK, OQPSK (Offset QPSK), 16QAM, and 64QAM can be used. However, in order to maintain the orthogonality of a plurality of carriers and suppress the error rate, it is desirable to use phase displacement modulation (PSK).

  In the present embodiment, the case where the PC main body 11 and the speaker 15 are installed at the same place has been described. However, the speaker 15 may be installed at a place away from the PC main body 11. In this case, the microphone 16 needs to be installed at the same location as the speaker 15 in order to measure the environmental sound where the sound code 150 is transmitted.

  In addition to the processing shown in FIG. 2, other processing may be performed as necessary. For example, when assigning parallel transmission bits to each carrier wave, scramble processing or the like may be performed as necessary.

  Next, processing for receiving a sound code in a mobile phone will be described in detail. FIG. 4 is a block diagram showing a conceptual circuit for realizing a function of receiving a sound code in the mobile phone according to the present embodiment. Note that the function of each unit shown in FIG. 4 is realized by software by the calculation means of the mobile phone 20 executing a program stored in the storage device, but for performing such processing. A dedicated circuit may be provided and realized in hardware.

  As shown in the figure, the mobile phone 20 includes an A / D conversion unit 203, an FFT unit 204, an environmental sound storage unit 210, an environmental sound subtraction unit 213, and a demodulation unit 215. The environmental sound accumulation unit 210 accumulates an environmental sound signal in a state where no sound code exists for a predetermined time.

  The environmental sound subtracting unit 213 extracts the sound code component by subtracting the environmental sound signal accumulated in the environmental sound accumulating unit 210 from the environmental sound on which the sound code is superimposed. That is, the environmental sound accumulation unit 210 and the environmental sound subtraction unit 213 perform adaptive noise reduction processing. The demodulator 215 demodulates each carrier wave that has been Fourier-transformed and decomposed. In this embodiment, the sound code is QPSK-modulated, and the demodulator 215 demodulates using the QPSK method.

  In such a configuration, the sound picked up by the microphone 21 of the mobile phone 20 is sent to the A / D converter 203. The A / D conversion unit 203 samples the input analog signal and converts it into a digital signal, and the digital signal is transmitted to the FFT unit 204. The FFT unit 204 performs fast Fourier transform to convert the digital signal into a component on the frequency axis.

  Here, the environmental sound accumulation unit 210 accumulates the environmental sound signal that is the output of the FFT unit 203 for a predetermined time prior to reception of the sound code. Thereafter, when an environmental sound on which the sound code 150 is superimposed is input, the FFT unit 204 converts it into a signal on the frequency axis. Subsequently, the environmental sound subtracting unit 213 subtracts the environmental sound signal accumulated in the environmental sound accumulating unit 210 from the received signal on the frequency axis, and the sound code component, that is, the signal component transmitted from the transmitting device 10 is obtained. Extracted.

  The sound code component is input to the demodulation unit 215. The demodulator 215 demodulates each carrier wave on the frequency axis by the QPSK method, and converts it into a serial signal in the same order as at the time of transmission. Thereby, a baseband signal, that is, various information can be extracted.

  Although the information providing system according to the present embodiment has been described above, according to the information providing system, the frequency at which the masking effect is obtained for the environmental sound based on the peak frequency of the environmental sound is used as the sound code transmission frequency. The sound code can be avoided from being annoying to the human ear.

  The embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the terminal on the receiving side is not limited to a mobile phone, and any terminal provided with a microphone may be used. For example, it may be a PDA, an IC recorder, a portable radio, a portable television, a notebook computer, a radio cassette, a game machine, or the like. In addition, a dedicated terminal for applying the present invention may be provided.

DESCRIPTION OF SYMBOLS 1 Information provision system 10 Transmission apparatus 11 PC main body 12 Display 13 Input device 15 Speaker 16 Microphone 20 Cellular phone 21 Microphone 22 Display 103 A / D conversion part 104 FFT part 107 Peak frequency detection part 108 Carrier wave generation part 115 Modulation part 120 D / A conversion unit 203 A / D conversion unit 204 FFT unit 210 Environmental sound storage unit 213 Environmental sound subtraction unit 215 Demodulation unit

Claims (5)

In a transmitting device that converts various encoded information into sound waves of an audible sound band and transmits the sound,
A microphone that inputs the environmental sound of the place where the sound wave is transmitted as an environmental sound signal;
A peak frequency detection unit for detecting a peak frequency mainly constituting the environmental sound from the environmental sound signal;
A carrier generation unit that generates a plurality of carrier waves having a masking effect with respect to the environmental sound based on the peak frequency;
A modulation unit that modulates the plurality of carriers with a baseband signal;
A transmitting device comprising: The carrier generation unit generates 1 / n (n is a natural number) of the peak frequency as a fundamental frequency, and generates a carrier wave having a frequency that is a natural number multiple of the fundamental frequency,
The transmitting device according to claim 1, wherein the modulation unit modulates by an OFDM method. The transmission device according to claim 2 , wherein the fundamental frequency is a frequency of 30 to 260 Hz among 1 / n (n is a natural number) of the peak frequency.   4. The transmission device according to claim 1, wherein the plurality of carrier waves include a frequency that is a natural number multiple of the peak frequency. 5. In a transmission program for causing a computer to convert various encoded information into sound waves of an audible sound band and transmit them from a speaker,
A peak frequency detecting step for detecting a peak frequency mainly constituting the environmental sound from a signal of the environmental sound at a place where the sound wave inputted through a microphone is transmitted;
A carrier wave generating step for generating a carrier wave of a plurality of frequencies capable of obtaining a masking effect on the environmental sound based on the peak frequency;
Modulating the plurality of carriers with a baseband signal;
Is transmitted to the computer.

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