JP6203482B2 - Vehicle approach notification device - Google Patents

Description

  The present invention relates to a vehicle approach notification device that notifies the surroundings that a vehicle is approaching by generating sound from the vehicle.

  In recent years, electric vehicles (EV cars), hybrid cars (HV cars), etc. have structurally low noise, and it is difficult for pedestrians to notice the approach of these vehicles. A vehicle approach notification device that generates a simulated running sound is being mounted to increase the degree of recognition that the vehicle is nearby (see, for example, Patent Document 1). In this vehicle approach notification device, as a sound generation method, data such as PCM (Pulse Code Modulation) stored in the memory of a microcomputer, that is, a voice code converted into a data code, is encoded for each sampling period. A method is used in which sound is generated by being set in a / A converter or PWM output device. The sound generation data used is mainly pseudo engine sound or pseudo motor sound, and the pseudo running sound is generated by repeatedly outputting a certain amount of data (for example, data for 1.5 seconds). This phonetic data is a chord composed of multiple frequency components, and is expressed as a curve drawn by the peak of a sound or electrical waveform, ie, “head emphasis or inflection (fluctuation)” that raises or lowers the sound volume over time. An envelope is added to make it easier for pedestrians to notice the approach of the vehicle.

JP 2005-215544 A JP 2007-38937 A JP 2009-101895 A

  However, since the sound generation data is expressed in a form to which an envelope is added, the amount of time of sound generation data that must be stored, that is, the length of time of the sound generation data increases, and the memory capacity increases. In addition, there is a problem that the envelope of “head emphasis and inflection (fluctuation)” that is desired to be pronounced cannot be sufficiently added due to the time limitation due to the memory capacity of the microcomputer.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a vehicle approach notification device capable of reducing the memory capacity of pronunciation data while adding an envelope to make it easy for a pedestrian to notice the approach of the vehicle. To do.

In order to achieve the above object, according to the first aspect of the present invention, the basic pronunciation data that is generated at each repetition period and the data for setting the volume of the pronunciation, the emphasis and inflection of the head are added, and the vehicle represents the volume change that indicates the approach, the envelope data indicative of the attenuation rate per unit time of the basic sound data which are repeated every unit time, memory means for separately storing the basic sound data stored in the memory means A sound output generator (21, 21b) that generates a sound output of the basic sound data and reads out the voltage value of the output waveform of the sound output of the basic sound output from the sound output generator (21, 21b). A voltage control unit (22) that adjusts based on the data, and a current corresponding to the output waveform that has been adjusted by the voltage control unit (22) is caused to flow through the sound generator (3). (3) at that is characterized in that comprises an amplifier (24) to perform the sound of the vehicle approaching notification sound.

  As described above, the basic sound generation data and the envelope data are stored in the memory means as separate sound generation data. Thereby, based on the envelope data, the peak value of the sound waveform of the basic sound data is adjusted so as to be the volume indicated by the envelope data. By doing so, it is possible to reduce the memory capacity of the pronunciation data while adding an envelope to make the pedestrian easily notice the approach of the vehicle.

  Specifically, as described in claim 2, the basic sound generation data is a basic sound waveform of a chord including each frequency component divided by unit time, and the envelope data is a vehicle approach of one unit of the envelope unit. Attenuation per unit time when the notification sound is represented by a waveform that is obtained by multiplying the basic pronunciation data divided by unit time by the decay rate per unit time that traces the envelope curve of the vehicle approach notification sound for one unit. The data indicates the rate.

  In the invention according to claim 3, the memory means and the sound output generator (21b) are provided in the microcomputer (21), and the microcomputer (21) has a voltage provided outside the microcomputer (21). The control unit (22) is provided with a control signal output unit (21a) for outputting a control signal for adjusting the voltage value of the output waveform of the sound output of the basic sound data based on the envelope data. The unit (22) adjusts the voltage value of the output waveform from the sound output unit (21b) provided in the microcomputer on the basis of the control signal transmitted from the control signal output unit (21a). It is characterized by expressing the vehicle approach notification sound for a unit.

  Thus, for example, the memory means, the sound output output generator (21b), and the control signal output unit (21a) are provided in the microcomputer (21), and the power controller (22) provided outside the microcomputer (21). The voltage value of the output waveform of the sound output of the basic sound data can be adjusted.

  In that case, for example, as described in claim 4, a PWM output device (21b) that generates a PWM output as a sound output of basic sound data can be used as the sound output output unit. As the control signal output unit (21a), a PWM output device or a digital analog converter (hereinafter referred to as DAC) can be applied.

  In the invention according to claim 5, the memory means, the sound output generator and the voltage controller are provided in the microcomputer (21), and in the microcomputer, the voltage controller is the voltage value of the output waveform of the sound output generator. By adjusting, the vehicle approach notification sound for one unit of envelope unit is expressed.

  Thus, the memory means, the sound output generator and the voltage controller are provided in the microcomputer (21), and the voltage controller adjusts the voltage value of the output waveform of the sound output generator in the microcomputer (21). A vehicle approach notification sound for one unit of envelope unit may be expressed.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

1 is a block diagram of a vehicle approach notification system including a vehicle approach notification device according to a first embodiment of the present invention. It is the flowchart which showed the action | operation of the vehicle approach notification system. It is a waveform diagram when the amplitude of the sound waveform indicated by the basic sound data is changed based on the envelope data. (A) is the wave form diagram which showed the sound generation waveform by the vehicle approach notification system concerning this embodiment, (b) is the figure which expanded a part of sound generation waveform shown to (a). It is the figure which showed the production | generation image of the vehicle approach notification sound for 1 unit of an envelope unit. (A) is a waveform diagram of conventional sound generation data, (b) is a partially enlarged view of (a). It is the wave form diagram which extracted a part of the conventional pronunciation data. It is a block diagram of the vehicle approach notification system containing the vehicle approach notification apparatus demonstrated by other embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
FIG. 1 is a block diagram of a vehicle approach notification system including a vehicle approach notification device according to the present embodiment. With reference to this figure, the vehicle approach notification system including the vehicle approach notification apparatus according to the present embodiment will be described.

  As shown in FIG. 1, the vehicle approach notification system includes a vehicle speed sensor 1, a vehicle approach notification device 2, and a speaker 3. In the vehicle approach notification system, the vehicle approach notification device 2 reports the vehicle approach from the speaker 3 that is a sounding body during low speed traveling (for example, 20 km / h or less) based on the vehicle speed detection signal transmitted from the vehicle speed sensor 1. By generating a simulated running sound such as a simulated engine sound or simulated motor sound as a sound, the approach of the vehicle is notified to surrounding pedestrians and the like. Here, the vehicle approach notification device 2 is separated from the speaker 3, but the speaker 3 may be integrated with the vehicle approach notification device 2.

  The vehicle speed sensor 1 outputs a vehicle speed detection signal as a vehicle running state detection signal. For this reason, the vehicle approach notification device 2 inputs a vehicle speed detection signal from the vehicle speed sensor 1, acquires the vehicle speed, and controls sound generation according to the vehicle speed while the vehicle is traveling at a low speed. Here, sound generation is performed according to the vehicle speed, but sound generation control may be performed according to the traveling state of the vehicle, for example, the accelerator opening.

  The vehicle approach notification device 2 includes a microcomputer 21, a voltage control unit 22, a low-pass filter (hereinafter referred to as LPF) 23, and a power amplifier (hereinafter referred to as AMP) 24.

  The microcomputer 21 has a memory corresponding to a memory means (not shown) and an arithmetic unit corresponding to a control means, and also includes a PWM output device 21a and a PWM output device 21b corresponding to a sound output unit. Yes. The memory stores pronunciation control programs, pronunciation data such as PCM data representing vehicle approach notification sounds such as simulated engine sounds and simulated motor sounds, and data for setting a sampling cycle and volume. The microcomputer 21 outputs the PWM output waveform corresponding to the sounding data desired to be sounded from the PWM output device 21b by reading the sounding data for each sampling period and setting it in the PWM output device 21b. Independent of the PWM output from the PWM output device 21b, a PWM output waveform is generated as a control signal for controlling the sound volume (sound pressure level) to be generated from the PWM output device 21a.

  For example, the microcomputer 21 stores, in a memory, a pitch increase amount or volume table associated with the vehicle running state such as the vehicle speed and the accelerator opening, and the vehicle speed when the vehicle is running at low speed. And a pitch up amount and a volume corresponding to the traveling state such as the accelerator opening. For example, the pitch-up amount can be increased as the vehicle speed is increased, and the volume can be increased as the accelerator opening is increased. Then, sound generation data is read at every sampling period corresponding to the calculated pitch up amount and set in the PWM output device 21b to generate a PWM output, and the PWM output waveform corresponding to the calculated volume is output to the PWM output device 21a. Output from. By setting it as such a structure, a pitch and a sound volume can be varied now according to the driving | running | working state of a vehicle.

  The voltage control unit 22 changes the voltage level of the PWM output waveform of the PWM output device 21b based on the PWM output waveform transmitted from the PWM output device 21a, and the PWM output waveform of the PWM output device 21a serving as a control signal is instructed. The voltage level of the PWM output waveform of the PWM output device 21b is changed to the voltage level to be applied. Therefore, for example, the lower the sound pressure level that is generated, the smaller the voltage level of the PWM output waveform is outputted from the voltage control unit 22.

  The LPF 23 corresponds to filter means, and removes high frequency noise components and generates an output corresponding to the output of the PWM output device 21 b transmitted via the voltage control unit 22. For example, the LPF 23 stores a voltage corresponding to the output of the voltage control unit 22 in a built-in capacitor and outputs it to the AMP 24.

  The AMP 24 supplies a current corresponding to the output of the LPF 23 to the speaker 3 based on voltage application from a constant voltage source (not shown). The sound pressure generated by the speaker 3 is determined according to the magnitude (amplitude) of the current supplied from the AMP 24, and the magnitude of the current supplied from the AMP 24 is determined by the output waveform of the LPF 23 corresponding to the PWM output. For this reason, the current flowing through the AMP 24 can be changed based on the adjustment of the voltage level in the voltage control unit 22.

  With the configuration as described above, a vehicle approach notification system including the vehicle approach notification device according to the present embodiment is configured. In the vehicle approach notification system configured as described above, pronunciation data such as PCM data is converted into basic pronunciation data that becomes a repetitive pattern, and “sound-head emphasis or inflection (fluctuation)” that is to be pronounced, that is, an envelope that indicates volume change・ It is divided into data, and these are stored separately in the memory. Envelope data is data that can sufficiently add “emphasis emphasis and inflection (fluctuation)”, and is data representing a volume change that a pedestrian is likely to notice when approaching a vehicle.

  Specifically, the entire vehicle approach notification sound that is sounded by the vehicle approach notification device is configured by repeating the number of units corresponding to the sound generation time with the vehicle approach notification sound having a predetermined envelope as one unit. That is, the entire vehicle approach notification sound is configured by repeating the vehicle approach notification sound for each envelope. Conventionally, since the vehicle approach notification sound for one unit of envelope unit is stored as sounding data, the memory capacity of the microcomputer is increased, or conversely, due to the time limitation from the memory capacity, the envelope is sufficiently Could not be added.

  On the other hand, the present inventors indicate that the vehicle approach notification sound is composed of chords of a plurality of frequency components, and the vehicle approach notification sound for one unit of the envelope unit is further divided into “frequency components divided by unit time”. It has been found that it can be decomposed or approximated to a “basic pronunciation waveform” of a chord including it. In other words, vehicle approach notification sounds such as all simulated engine sounds and simulated motor sounds are basically composed of repetition of “basic pronunciation waveform” of chords including each frequency component divided by unit time. By changing the volume of each repeated “basic pronunciation waveform”, it is possible to express the vehicle approach notification sound for one unit of the envelope unit, and by repeating it for the number of units corresponding to the pronunciation time, I found that I can express it.

  For this reason, in this embodiment, “basic pronunciation waveform” of a chord including each frequency component divided by unit time is used as basic pronunciation data, and the basic pronunciation data for a plurality of periods is repeated, By changing the volume of the basic pronunciation data, the vehicle approach notification sound for one unit of the envelope unit is expressed. When changing the volume of the basic sound data, the “basic sound waveform” represented by the basic sound data may be multiplied by an attenuation factor corresponding to the envelope curve. In other words, the vehicle approach notification sound for one unit of envelope unit is traced per unit time for tracing the envelope curve such as “head emphasis, inflection (fluctuation)” based on the basic pronunciation data divided by unit time. It can be expressed as an array of waveforms multiplied by the attenuation rate. And the whole vehicle approach notification sound can be expressed by repeating the vehicle approach notification sound for one unit of the envelope unit by the number of units corresponding to the sounding time.

  In order to realize this, only basic sounding data for one period is stored here, and envelope data that is a data indicating an attenuation rate of basic sounding data repeated every unit time is stored. doing.

  The operation of such a vehicle approach notification system will be described with reference to FIG. FIG. 2 is a flowchart showing the operation of the vehicle approach notification system. Each process shown in this flowchart is executed at every changing carrier cycle (sampling cycle). This carrier cycle (sampling cycle) is determined by the pitch of the vehicle approach notification sound to be generated. For example, the pitch increase amount is determined according to the traveling state such as the vehicle speed and the accelerator opening, and the pitch of the vehicle approach notification sound is determined by adding the pitch increase amount to a predetermined reference pitch. The carrier period is calculated as a value corresponding to this pitch.

  First, after reading basic sound data (sound data to be set in the PWM output device 21b) stored as sound data in step 100, the basic sound data read in the PWM output device 21b is set in step 105, and the basic sound data is set. Output as output. Subsequently, in step 110, the basic pronunciation data counter is incremented by one. The basic sounding data counter is a counter that is counted every time the basic sounding output is repeated for one cycle, and the number of times it takes for the sounding to repeat for one cycle of the basic sounding data repetition cycle. Counting.

  Then, the process proceeds to step 115 to determine whether or not it is the envelope update timing. Whether or not it is the envelope update timing is determined based on whether or not the basic pronunciation data counter is the final value. As described above, the basic sounding data counter counts the number of times it takes to sound one cycle of the basic sounding data repetition period. The final value of this value is the number of times it takes to complete the sounding of one repetition of the basic sounding data. When the basic sounding data counter reaches the final value, the basic sounding data is returned to the beginning again. Output as pronunciation output. Therefore, if an affirmative determination is made in this step, the process proceeds to step 120 and the subsequent steps, and if a negative determination is made, the process ends.

  In step 120, the basic pronunciation data counter that has been counted up to the final value is returned to the first value. Then, the process proceeds to step 125, and after reading envelope data (sound generation data set in the PWM output device 21a) stored as sound generation data, the envelope data read into the PWM output device 21a is set in step 130, The amplitude (voltage level) of the PWM output waveform of the PWM output device 21b representing the basic sound generation data is changed. As a result, a PWM output waveform for controlling the volume (sound pressure level) indicated by the envelope data is generated. Thereafter, in step 135, the envelope data counter is incremented by one. The envelope data counter is a counter that is counted each time the envelope data repetition period is output, and is output for one cycle of the envelope data pattern repetition period (one unit of envelope unit). Counts the number of times it takes to finish.

  In step 140, it is determined whether or not the envelope data counter is the final value. The envelope data counter counts the number of times it takes to output one envelope data cycle (one envelope unit). The final value of this value is the number of times it takes for one envelope data repetition period (one envelope unit) to be output. When the envelope data counter reaches the final value, it is again. The envelope data is returned to the beginning and output repeatedly. Therefore, if an affirmative determination is made in this step, the process proceeds to step 145, the envelope data counter is returned to the top value, and the process is terminated. If a negative determination is made, the process ends.

  In this way, the peak value of the voltage value of the PWM output waveform output from the PWM output device 21b based on the basic sound generation data is adjusted by the PWM output output from the PWM output device 21a based on the envelope data.

  FIG. 3 is a waveform diagram when the amplitude of the sound waveform indicated by the basic sound data is changed based on the envelope data. FIG. 4A is a waveform diagram showing a sound waveform by the vehicle approach notification system according to the present embodiment, and FIG. 4B is an enlarged view of a part of the sound waveform shown in FIG. It is.

  When the basic sound data stored in the memory is the sound waveform indicated by the solid line in FIG. 3, the sound waveform is adjusted based on the envelope data so that the peak value of the sound waveform is the volume indicated by the envelope data. Is done. In the case of the present embodiment, when a PWM output waveform indicating basic sound generation data is input from the PWM output unit 21b in the voltage control unit 22, the voltage value of the PWM output waveform is output from the PWM output unit 21a based on the envelope data. It is made to change according to the output PWM output. As a result, the sound waveform is adjusted so that the peak value of the sound waveform of the basic sound data becomes the volume indicated by the envelope data.

  When the output of one repetition period of the basic sound data shown in FIG. 3 is completed, as shown in FIGS. 4A and 4B, the basic sound data is again generated based on the next envelope data. The sound generation waveform is adjusted so that the peak value of the waveform becomes the volume indicated by the envelope data. By repeating such an operation, it is possible to realize a sound generation waveform to which a desired envelope is added.

In this way, the vehicle approach notification sound for one unit of envelope unit is multiplied by the decay rate at each time point that traces the curve of the envelope such as “head emphasis, inflection (fluctuation)” based on the basic pronunciation data. Can be represented as a series of waveforms. Therefore, as shown in FIG. 5, if the vehicle approach notification sound for one unit of envelope unit is A and the basic pronunciation data is B, the vehicle approach notification sound A for one unit is converted into the basic pronunciation data B and the envelope sound. It can be expressed based on the data. That is, each time point (each time point from the first value of the envelope data counter to the final value) for each sampling period of the envelope data is t1 to tm (where m is an integer, and the final value of the envelope data counter is and equivalent), each time t1~tm respective damping rate (coefficient to the volume indicated by the envelope data) as n ₁ ~n _m, as follows, the basic sound for each time point t1~tm The vehicle approach notification sound A for one unit can be expressed by a value obtained by adding a value obtained by multiplying the data B by the attenuation rate n _{1 to nm} .

  Therefore, the vehicle approach notification sound A is expressed only by basic sound data and envelope data for one cycle. In the case of the present embodiment, the basic sound generation data to be a repetitive pattern is, for example, 0.128 k in 0.08 seconds of 16 kHz sampling, and the envelope data is, for example, 1.250 k in 10 seconds of 125 Hz sampling. Is 1.378k in total.

  FIG. 6A is a waveform diagram of conventional sound generation data, and FIG. 6B is a partially enlarged view of FIG. 6A. FIG. 7 is a waveform diagram obtained by extracting a part of conventional sound generation data (corresponding to the left half of FIG. 6B).

  As shown in FIG. 6A, in the conventional sound generation data, a repetition cycle in an envelope unit is set as one cycle, and all sound generation data during that period is stored in the memory. That is, as shown in FIG. 6B and FIG. 7, the sound generation data in each period is data with an envelope added, and all data that is different in a long period is stored. For this reason, in the case of conventional sound generation data, the memory capacity is 160 k in 10 seconds of 16 kHz sampling.

  Therefore, when the basic sound data and the envelope data are separated as in the present embodiment, the memory capacity is greatly increased compared to the case where the sound data is provided with an envelope as in the prior art. Can be reduced to

  Thus, in the past, it has been repeated for a long time (for example, 10 seconds) to which an envelope represented as a curve drawn by the peak of a voice or an electric waveform is added, that is, “head emphasis and inflection (fluctuation)” to be pronounced It was necessary to memorize the pronunciation data to be a pattern. On the other hand, in the present embodiment, the basic sounding data and the envelope data are separated into sounding data, so that the sound of the sounding data is added while making the sound easy for the pedestrian to notice the approach of the vehicle by adding the envelope. The memory capacity can be reduced. For example, as described above, the conventional sound generation data requires a memory capacity of 160 k, but the sound generation data in which the basic sound generation data and the envelope data are separated as in the present embodiment is 1.250 k. / 116. For this reason, even if the microcomputer 21 has a very small memory capacity, a vehicle approach notification device capable of reducing the memory capacity of the sounding data while adding an envelope to make it easy for a pedestrian to notice the approach of the vehicle. 2 is possible.

  Here, a case has been described where sound generation with an envelope is performed using basic sound generation data and envelope data. In order to add an envelope, a control signal is output from the PWM output unit 21a to the power control unit 22, and the voltage level of the PWM output waveform of the PWM output unit 21b is adjusted to a voltage level corresponding to the envelope data. In addition to this, the volume can be set according to the traveling state such as the accelerator opening as described above. In this case, the voltage level of the PWM output waveform of the PWM output device 21b is adjusted to a level obtained by multiplying the attenuation rate corresponding to the envelope curve indicated by the envelope data and the volume increase rate corresponding to the running state. Become.

(Other embodiments)
In the above embodiment, the sound volume (sound pressure level) is changed according to the accelerator opening, and the pitch is changed according to the vehicle speed. However, these are merely examples. For example, both the volume and the pitch may be changed according to the vehicle speed or the accelerator opening. In this case, as the vehicle speed or accelerator opening increases, the volume and the pitch increase amount can be increased.

  Further, the microcomputer 21 uses the PWM output unit 21a as a control signal output unit that outputs a control signal, and generates a PWM output as a control signal for changing the sound pressure from the PWM output unit 21a, thereby generating a voltage control unit 22. The voltage control of the voltage control unit 22 may be performed using a DAC. Similarly, in the microcomputer 21, the PWM output device 21b is used as a sound output unit for generating sound output based on basic sound data, but sound output may be generated by other devices.

  Further, in the first embodiment, the microcomputer 21 is provided with a PWM output device 21b that constitutes memory means and sound output output generation means, and outputs from the PWM output device 21a and DAC that constitute the control signal output unit provided in the microcomputer 21. Based on the control signal, voltage control by the power control unit 22 is performed outside the microcomputer 21. On the other hand, only the microcomputer 21 can generate an output corresponding to the vehicle approach notification sound using the basic pronunciation data and the envelope data. For example, as shown in FIG. 8, the function of the power control unit 22 provided in the first embodiment and the function of the sound output unit configured by the PWM output device 21 b are provided in the microcomputer 21, and each period is included. It is also possible to execute in the microcomputer 21 until the volume control (envelope control) of the basic sound output data read out and output, and the sound output after the sound volume control is directly input to the LPF 23 from the PWM output device 21c.

  In addition, when the time of the above basic sound data, that is, the unit time of the “basic sound waveform of chords including each frequency component divided by unit time” becomes long and the amount of data cannot be reduced as expected. The basic sound generation data at this time may be compressed using a data compression algorithm such as ADPCM and stored in the memory of the microcomputer 21.

1 Vehicle speed sensor 2 Vehicle approach alarm device 3 Speaker 21 Microcomputer 21a, 21b PWM output device 22 LPF
23 AMP

Claims (5)

In a vehicle approach notification device for reporting the approach of the vehicle by generating a vehicle approach notification sound from the sounding body (3) mounted on the vehicle,
Basic sounding data to be sounded at each repetition period and data for setting sounding volume , adding emphasis and inflection of the head and representing a change in sound volume indicating the approach of the vehicle, and repeated every unit time memory means for separately storing the envelope data, the indicating the attenuation rate per unit time of the basic sound data,
A sound output generator (21, 21b) that reads the basic sound data stored in the memory means and generates a sound output of the basic sound data;
A voltage controller (21, 22) for adjusting a voltage value of an output waveform of the sound output of the basic sound data output from the sound output generator (21, 21b) based on the envelope data;
An amplifier that causes the sounding body (3) to sound the vehicle approach notification sound by causing the sounding body (3) to flow a current corresponding to the output waveform after being adjusted by the voltage control unit (22). (24) The vehicle approach notification apparatus characterized by the above-mentioned. The basic sound generation data is a basic sound waveform of a chord including each frequency component partitioned by unit time,
The envelope data is obtained by tracing the envelope curve of the vehicle approach notification sound for one unit in the basic pronunciation data obtained by dividing the vehicle approach notification sound for one unit of envelope unit by the unit time. 2. The vehicle approach notification device according to claim 1, wherein the vehicle approach notification device is data indicating an attenuation rate per unit time when expressed by a waveform obtained by multiplying the attenuation rates. The memory means and the sound output generator (21b) are provided in the microcomputer (21), and the microcomputer has the envelope relative to the voltage controller (22) provided outside the microcomputer. A control signal output unit (21a) for outputting a control signal for adjusting a voltage value of an output waveform of the sound output of the basic sound data based on the data;
The voltage control unit adjusts the voltage value of the output waveform from the sound output unit provided in the microcomputer based on a control signal transmitted from the control signal output unit, so that one unit of an envelope unit is obtained. The vehicle approach notification device according to claim 1 or 2, wherein a vehicle approach notification sound is expressed.   4. The vehicle approach notification device according to claim 3, wherein the sound output generator is a PWM output device (21b) that generates a PWM output as a sound output of the basic sound data.   The memory means, the sound output generator and the voltage controller are provided in a microcomputer (21), and the voltage controller adjusts the voltage value of the output waveform of the sound output generator in the microcomputer. The vehicle approach notification device according to claim 1, wherein a vehicle approach notification sound for one unit of an envelope unit is expressed.

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