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DESCRIPTION JP2013205478

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DESCRIPTION JP2013205478
Abstract: A sound pressure of a notification sound can be adjusted by correcting the level of each
frequency constituting a synthetic sound signal individually. A control unit (10) specifies shift
frequencies obtained by shifting frequencies of a plurality of frequency components constituting
a synthetic sound signal according to a vehicle speed of a vehicle (S102), and the signal levels of
the specified shift frequencies. Are individually corrected to adjust the sound pressure of the
notification sound (S104, S106). [Selected figure] Figure 1
Vehicle approach notification device
[0001]
The present invention relates to a vehicle approach notification device that causes a speaker
mounted on a vehicle to output a notification sound based on a synthetic sound signal composed
of a plurality of frequency components to notify the approach of the vehicle.
[0002]
In an electric vehicle equipped with only an electric motor as a drive source for traveling, the
traveling noise at low speed traveling is extremely quiet.
Further, in a hybrid vehicle provided with an electric motor and an internal combustion engine as
a driving source for traveling, the traveling noise is extremely quiet when traveling with only the
driving force of the motor at low speed traveling. For this reason, a pedestrian etc. may not notice
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the approach of the said vehicle.
[0003]
Therefore, in such a low noise vehicle, a notification sound signal whose frequency changes
according to the vehicle speed is generated, and a notification sound based on the generated
notification sound signal is generated toward the outside of the vehicle, and the vehicle is present
around the vehicle. There has been proposed a vehicle approach notification device for notifying
a pedestrian or the like (see, for example, Patent Document 1).
[0004]
Further, there is a system in which a pseudo engine sound or a pseudo motor sound is generated
as a synthetic sound (harmonic sound) composed of a plurality of frequency components as a
notification sound.
Furthermore, in order to allow a pedestrian or the like to recognize the speed of the vehicle, there
is a system in which the frequencies constituting the synthetic sound are changed little by little
with changes in the vehicle speed (see, for example, Patent Document 2).
[0005]
However, when changing each frequency that composes the synthesized sound little by little with
the change of the vehicle speed, the sound pressure of a part of the frequency components that
compose the synthesized sound with the change of the vehicle speed is The sound pressure of
other frequency components may fall or rise. Therefore, the sound pressure of the notification
sound may increase with the increase of the vehicle speed, the sound pressure of the notification
sound may decrease with the increase of the vehicle speed, or the sound pressure of the
notification sound may significantly fluctuate with the change of the vehicle speed. As a result,
there is a problem that it is difficult for a pedestrian or the like to notice the approach of the
vehicle, and a problem that a notification sound is felt as noise.
[0006]
JP, 5-213112, A JP, 2012-17071, A
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[0007]
Therefore, the pitch of the notification sound signal is changed according to the vehicle speed,
and the output level of the notification sound is changed according to the pitch of the notification
sound signal, so that the sound pressure of the notification sound is constant even if the vehicle
speed changes. There is a vehicle approach notification device configured to do this (for example,
Japanese Patent Application No. 2010-275763).
[0008]
However, although such a vehicle approach notification device can change the output level of the
notification sound so that the sound pressure of the notification sound becomes constant, the
level of each frequency constituting the synthetic sound signal is individually determined. It is
not configured to control and adjust the sound pressure of the notification sound.
For this reason, for example, the sound pressure of a part of frequency components constituting
the synthetic sound increases with the change of the vehicle speed, and the sound pressure of
other frequency components decreases, so that the balance of the chord of the notification sound
is broken. As a result, there is a problem that a pedestrian or the like may feel uncomfortable.
[0009]
Further, the vehicle has a frequency band which is easy to transmit into the vehicle interior and a
frequency band which is hard to transmit into the vehicle interior due to the performance of the
soundproof material, the structure of the vehicle body and the like.
Therefore, the sound pressure of the frequency band easily transmitted to the vehicle interior is
reduced when a part of the frequency components constituting the synthetic sound is included in
the frequency band easily transmitted to the vehicle interior as the vehicle speed changes. It is
conceivable that the quietness of the vehicle interior is improved by
[0010]
However, the vehicle approach notification device as described in the above-mentioned Japanese
Patent Application No. 2010-275763 is configured to adjust the sound pressure of the
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notification sound by individually controlling the level of each frequency constituting the
synthesized sound signal. Also, since the sound pressure in the frequency band that easily
penetrates into the vehicle compartment can not be reduced to improve the quietness of the
vehicle interior.
[0011]
SUMMARY OF THE INVENTION The present invention has been made in view of the above
problems, and has as its object to adjust the sound pressure of a notification sound by
individually correcting the level of each frequency constituting a synthetic sound signal.
[0012]
In order to achieve the above object, the invention according to claim 1 generates a synthetic
sound signal composed of a plurality of frequency components, and outputs a notification sound
based on the synthetic sound signal from a speaker mounted on a vehicle. A vehicle approach
notification device for notifying approach of a vehicle, comprising: shift frequency specifying
means for specifying each shift frequency obtained by shifting the frequency of a plurality of
frequency components constituting the synthesized sound signal according to the vehicle speed
of the vehicle; And a level correction means for adjusting the sound pressure of the notification
sound by individually correcting the signal level of each shift frequency specified by the
specifying means.
[0013]
According to such a configuration, each shift frequency obtained by shifting the frequency of the
plurality of frequency components constituting the synthesized sound signal is specified
according to the vehicle speed of the vehicle, and the signal level of each specified shift
frequency is individually corrected. The sound pressure of the notification sound is adjusted.
That is, it is possible to adjust the sound pressure of the notification sound by correcting the level
of each frequency constituting the synthesized sound signal individually.
[0014]
Also, in the invention according to claim 2, the level correction means individually separates the
signal level of each shift frequency specified by the shift frequency specification means so that
the balance of the plurality of frequency components included in the notification sound becomes
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constant. It is characterized by correcting to.
[0015]
According to such a configuration, the signal level of each shift frequency specified by the shift
frequency specifying means is individually corrected so that the balance of the plurality of
frequency components included in the notification sound becomes constant. It is possible to
prevent the balance of the chords from being broken and giving the pedestrian or the like an
uncomfortable feeling.
[0016]
In the invention according to claim 3, the correction magnification of the signal level of each shift
frequency specified by the shift frequency specifying means is set for each shift frequency so
that the balance of the plurality of frequency components contained in the notification sound
becomes constant. The level correction means is characterized in that the level correction means
individually corrects the signal level of each shift frequency specified by the shift frequency
specifying means using the correction rate specification table.
[0017]
In this way, a correction magnification definition table that defines the correction magnification
of the signal level of each shift frequency identified by the shift frequency identification means
for each shift frequency so that the balance of the plurality of frequency components included in
the notification sound becomes constant. The signal level of each shift frequency specified by the
shift frequency specifying means can be individually corrected with high accuracy.
[0018]
Also, in the invention according to claim 4, when the level correction means includes a part of
each shift frequency specified by the shift frequency specification means in a transmission
frequency band which is likely to be transmitted into the vehicle compartment in the vehicle, It is
characterized in that the signal level of each shift frequency specified by the shift frequency
specifying means is individually corrected so as to lower the signal level of the shift frequency
contained in the transmission frequency band which can be easily transmitted to the room.
[0019]
According to such a configuration, the level correction means transmits light into the vehicle
compartment of the vehicle when a part of each shift frequency specified by the shift frequency
specifying device is included in the transmission frequency band which is likely to be transmitted
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into the vehicle compartment of the vehicle. Since the signal level of each shift frequency
specified by the shift frequency specifying means is individually corrected so as to lower the
signal level of the shift frequency included in the easy transmission frequency band, the silence
in the vehicle compartment is improved. Can.
[0020]
According to the fifth aspect of the present invention, the signal level of each shift frequency
specified by the shift frequency specifying means is set to lower the signal level of the shift
frequency included in the transmission frequency band which is easy to penetrate into the
vehicle compartment of the vehicle. And the level correction means reduces the level of the shift
frequency included in the transmission frequency band that is likely to be transmitted into the
vehicle compartment of the vehicle using the correction magnification definition table. Thus, the
present invention is characterized in that the signal level of each shift frequency specified by the
shift frequency specifying means is corrected.
[0021]
According to such a configuration, the correction magnification of the signal level of each shift
frequency specified by the shift frequency specifying means is set so as to lower the signal level
of the shift frequency included in the transmission frequency band easily transmitted into the
vehicle compartment in the vehicle. Of each shift frequency specified by the shift frequency
specifying means so as to reduce the level of the shift frequency included in the transmission
frequency band which is likely to be transmitted into the vehicle compartment of the vehicle
using a correction magnification definition table which defines The level can be corrected
accurately.
[0022]
Further, as in the invention according to claim 6, the level correction means further individually
corrects the level of each frequency shifted by the shift frequency specifying means so that the
sound pressure of the notification sound becomes constant. Can.
[0023]
It is a figure which shows the structure of the vehicle approach notification apparatus which
concerns on 1st Embodiment of this invention.
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It is a figure which shows the relationship between the vehicle speed and the pitch-up amount
which shifts each frequency component F1-F4 which comprises a synthetic sound signal to the
high frequency side.
It is a figure which shows the sound pressure-frequency characteristic example of a speaker.
It is a figure which shows the relationship between the frequency component of a synthetic
sound signal, and a sound pressure.
It is a flowchart of the control part of the vehicle approach notification apparatus which concerns
on 1st Embodiment.
It is a figure for demonstrating a pitch up frequency-correction | amendment magnification
selection table.
It is a flowchart of the control part of the vehicle approach notification apparatus which concerns
on 2nd Embodiment.
[0024]
First Embodiment FIG. 1 shows the configuration of a vehicle approach notification device
according to a first embodiment of the present invention.
The vehicle approach notification device 1 is mounted on an electric vehicle equipped with only
an electric motor as a power source for traveling, or a hybrid vehicle equipped with an electric
motor and an internal combustion engine as a power source for traveling.
The vehicle approach notification device 1 generates a synthetic sound signal composed of a
plurality of frequency components, outputs a notification sound based on the synthetic sound
signal from the speaker 20, and reports the approach of the vehicle.
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[0025]
The vehicle approach notification device 1 includes a control unit 10, a low pass filter
(hereinafter referred to as an LPF) 11, a mixer 12, and a power amplifier 13.
A vehicle speed signal corresponding to the vehicle speed is input to the control unit 10 from a
vehicle speed sensor 30 mounted on the vehicle.
Further, the power amplifier 13 is connected to, for example, a speaker 20 which is disposed in a
front bumper of a vehicle and emits a notification sound toward the outside of the vehicle.
[0026]
The control unit 10 is configured as a microcomputer including a CPU, a RAM, a ROM, a flash
memory, an I / O and the like, and the CPU performs various processes in accordance with a
program stored in the ROM.
A vehicle speed signal corresponding to the vehicle speed is input to the control unit 10 from a
vehicle speed sensor 30 mounted on the vehicle.
[0027]
The ROM of the control unit 10 stores a plurality of sound source data constituting a synthesized
sound signal. Specifically, the four sound source data having the first frequency F1 = 230 Hz
(Hz), the second frequency F2 = 350 Hz, the third frequency F3 = 620 Hz and the fourth
frequency F4 = 1800 Hz as the reference frequency are the control unit 10 Is stored in the ROM.
The control unit 10 generates a synthesized sound signal using the four sound source data stored
in the ROM.
[0028]
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In addition, the control unit 10 in the present embodiment gradually increases the frequencies of
the four frequency components constituting the synthesized sound signal such that the pitch of
the notification sound gradually increases as the vehicle speed increases. At this time, the signal
levels of the four frequency components are individually corrected so that the balance of the four
frequency components is kept constant.
[0029]
FIG. 2 shows the relationship between the vehicle speed and the pitch-up amount for shifting the
frequency components F1 to F4 constituting the synthesized sound signal to the high frequency
side. As shown in the figure, the control unit 10 specifies a pitch-up amount for shifting the four
frequency components F1 to F4 constituting the synthesized sound signal to the high frequency
side as the vehicle speed increases, and uses this pitch-up amount. Pitch-up frequencies F1 ′ to
F4 ′.
[0030]
The LPF 11 removes high frequency noise components such as harmonics included in each
signal output from the control unit 10. The LPF 11 in the present embodiment is configured by
four low pass filters corresponding to four frequency components that constitute a synthetic
sound signal.
[0031]
The mixer 12 mixes four frequency component signals input from the control unit 10 via the LPF
11. The power amplifier 13 also amplifies the signal input from the mixer 12 and outputs the
amplified signal to the speaker 20.
[0032]
In the present embodiment, as the speaker 20, a speaker having a sound pressure-frequency
characteristic as shown in FIG. 3 is used. Specifically, in the low frequency range (for example,
100 Hz to 800 Hz), the sound pressure changes relatively linearly with the change in frequency,
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and in the high frequency range the sound pressure changes relatively non-linearly with the
change in frequency It has the characteristics.
[0033]
FIG. 4 shows the relationship between the frequency component of the synthesized sound signal
and the sound pressure. As shown in the figure, the synthetic speech signal includes frequency
components of a first frequency F1, a second frequency F2, a third frequency F3 and a fourth
frequency F4.
[0034]
As shown in FIG. 3, since the frequency characteristic of the speaker 20 differs depending on the
frequency band, when each frequency component constituting the synthesized sound signal as
shown in FIG. 4 is changed along with the change of the vehicle speed, With the change, the
sound pressure of a part of frequency components constituting the notification sound increases,
and the sound pressure of other frequency components decreases. Therefore, the balance of each
frequency component included in the notification sound is broken, and as a result, there is a
problem that the pedestrian or the like is given a sense of discomfort.
[0035]
So, in the vehicle approach notification apparatus 1 which concerns on this embodiment, the
process which correct | amends the signal level of each frequency component contained in a
report sound separately, and adjusts the sound pressure of a report sound is performed.
[0036]
FIG. 5 shows a flowchart of this process.
The vehicle approach notification device 1 is activated when the ignition switch of the vehicle is
turned on in response to the driver's operation, and the control unit 10 starts the process shown
in the figure.
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[0037]
First, the pitch-up amount is specified from the vehicle speed (S100). The flash memory of the
control unit 10 stores a pitch-up frequency-correction magnification selection table as shown in
FIG. The pitch-up frequency-correction magnification selection table shows the relationship
between the vehicle speed and the pitch-up amount. Here, the pitch-up amount is specified based
on the relationship between the vehicle speed and the pitch-up amount indicated in the pitch-up
frequency-correction magnification selection table. For example, in the case of 0 km / h, the
pitch-up amount is 0%, in the case of 10 km / h, the pitch-up amount is 17.5%, and in the case of
23 km / h The pitch-up amount is 50%.
[0038]
Next, the pitch up frequency is specified (S102). For example, in the case of the first frequency
F1, a portion obtained by multiplying the first frequency F1 = 230 Hz by the pitch-up amount (%)
is added to the first frequency F1 to specify the pitch-up frequency F1 '. In the case of the second
frequency F2, the second frequency F2 = 350 Hz multiplied by the pitch-up amount (%) is added
to the second frequency F2 to specify the pitch-up frequency F2 '. Similarly, in the case of the
third frequency F3, the third frequency F3 = 620 Hz multiplied by the pitch-up amount (%) is
added to the third frequency F3 to specify the pitch-up frequency F3 ′, and the fourth
frequency F4 In this case, the fourth frequency F4 = 1800 Hz multiplied by the pitch-up amount
(%) is added to the fourth frequency F4 to specify the pitch-up frequency F4 ′.
[0039]
Next, the correction magnification for specifying the balance of the chord of the notification
sound is specified (S104). In the pitch-up frequency-correction magnification selection table,
correction magnifications for keeping the balance of the four frequency components constant are
individually defined for each pitch-up frequency.
[0040]
Specifically, in the pitch-up frequency-correction magnification selection table, the sound
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pressure of the speaker 20 at each frequency and the correction magnification are defined for
each frequency, and the sound pressure of the speaker 20 at each frequency is multiplied by the
correction magnification. Then, the correction magnification is defined so as to be the sound
pressure of the reference frequency. For example, in the case of the first frequency F1, the pitchup frequency F1 ′ = 270 (Hz), the sound pressure of the speaker 20 = 65.3 (dB), the correction
magnification = 0.953 at 10 km / h. It has become. Here, when the sound pressure of the speaker
20 = 65.3 (dB) is multiplied by the correction factor = 0.953, it becomes 62.2 (dB), that is, the
sound pressure of the reference frequency, that is, 0 km / h And the sound pressure of the
speaker 20 = 62.2. Similarly, for the second frequency F2 to the fourth frequency F4, by
multiplying the sound pressure of the corresponding speaker 20 by the correction magnification,
the sound pressure of the speaker 20 at a speed of 0 km / h and It can be matched. By
multiplying the signal level of each frequency component by such a correction magnification, it
becomes possible to make the balance of the chord of the notification sound constant.
[0041]
Next, the signal levels of the four frequency components are individually corrected using the
correction magnification (S106). Specifically, the signal level of each frequency component is
multiplied by the corresponding correction magnification to individually correct the signal level
of each frequency component, and the process returns to S100.
[0042]
Repeat the above process to change each frequency component included in the notification
sound as the vehicle speed increases, and individually correct the signal level of each frequency
component included in the notification sound to obtain the sound pressure of the notification
sound. adjust.
[0043]
According to the configuration described above, each pitch-up frequency is determined by
pitching up the frequencies of the plurality of frequency components constituting the
synthesized sound signal according to the vehicle speed of the vehicle, and the signal level of
each identified pitch-up frequency is individualized. The sound pressure of the notification sound
is adjusted.
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That is, it is possible to adjust the sound pressure of the notification sound by correcting the level
of each frequency constituting the synthesized sound signal individually.
[0044]
In addition, since the signal level of each pitch-up frequency is individually corrected so that the
balance of the plurality of frequency components included in the notification sound becomes
constant, the balance of the chord of the notification sound is lost, and the pedestrian etc. feels
strange. Can be prevented.
[0045]
In addition, a pitch-up frequency-correction magnification selection table (correction
magnification specification table) which defines correction magnifications of signal levels of each
pitch-up frequency for each pitch-up frequency so that balance of plural frequency components
included in notification sound becomes constant. And the signal level of each pitch-up frequency
can be individually and accurately corrected using this pitch-up frequency-correction
magnification selection table.
[0046]
Second Embodiment In the first embodiment, the signal levels of the four frequency components
are individually corrected so that the balance of the four frequency components is maintained
constant. However, in the present embodiment, When a part of the frequency components
constituting the synthesized sound signal is included in a frequency band (for example, 300 Hz to
500 Hz) that easily penetrates into the vehicle compartment as the vehicle speed changes, the
frequency easily penetrates into the vehicle compartment Reduce the sound pressure of the
band.
The description of the same parts as those of the first embodiment is omitted, and the following
description will be focused on different parts.
[0047]
The configuration of the vehicle approach notification device 1 in the present embodiment is the
same as that shown in the first embodiment.
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However, in the pitch-up frequency-correction magnification selection table in the first
embodiment, correction magnifications for keeping the balance of the four frequency
components constant are individually defined for each pitch-up frequency. In the pitch-up
frequency-correction magnification selection table in the present embodiment, the correction
magnification for decreasing the signal level of the pitch-up frequency included in the
transmission frequency band that easily penetrates into the vehicle compartment of the vehicle is
the pitch-up frequency. Each is individually defined.
[0048]
Although the pitch-up frequency-correction magnification selection table according to the
present embodiment is not shown, the correction magnification of the frequency band easily
transmitted into the vehicle compartment is smaller than the pitch-up frequency-correction
magnification selection table shown in FIG. It is defined to be In addition, since the frequency
band easily transmitted into the vehicle compartment differs depending on the type of vehicle,
etc., the signal levels of the four frequency components are individually corrected using the
pitch-up frequency-correction magnification selection table suitable for the sound insulation
characteristics of each vehicle. Is preferred.
[0049]
FIG. 7 shows a flowchart of the control unit 10 of the vehicle approach notification device 1
according to the present embodiment. Since S100 and S102 are the same as the process shown
in FIG. 5, the description thereof is omitted here.
[0050]
In S204, the correction magnification is specified so as to reduce the signal level of the pitch-up
frequency included in the transmission frequency band which is likely to be transmitted into the
vehicle compartment. As described above, in the pitch-up frequency-correction magnification
selection table according to the present embodiment, the correction magnification for reducing
the signal level of the pitch-up frequency included in the transmission frequency band which is
easily transmitted into the vehicle compartment of the vehicle. Are individually defined for each
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pitch-up frequency. Using this pitch-up frequency-correction magnification selection table, the
correction magnification is specified so as to reduce the signal level of the pitch-up frequency
included in the transmission frequency band which is likely to be transmitted into the vehicle
interior.
[0051]
Next, the signal levels of the four frequency components are individually corrected using the
correction magnification (S206). Specifically, the signal level of each frequency component is
multiplied by the corresponding correction magnification to individually correct the signal level
of each frequency component, and the process returns to S100.
[0052]
Repeat the above process to change each frequency component included in the notification
sound as the vehicle speed increases, and individually correct the signal level of each frequency
component included in the notification sound to obtain the sound pressure of the notification
sound. adjust.
[0053]
According to the above configuration, when a part of each pitch-up frequency is included in the
transmission frequency band that is easy to transmit into the vehicle compartment of the vehicle,
the signal of the pitch up frequency included in the transmission frequency band that is easy to
transmit into the vehicle compartment of the vehicle Since the signal level of each pitch-up
frequency is corrected individually so as to reduce the level, the quietness in the vehicle
compartment can be improved.
[0054]
Also, a pitch-up frequency-correction that specifies the correction level of the signal level of each
pitch-up frequency for each pitch-up frequency so as to reduce the signal level of the pitch-up
frequency included in the transmission frequency band that easily penetrates into the vehicle
compartment in the vehicle. It has a magnification selection table (corresponding to a correction
magnification definition table) and uses this pitch-up frequency-correction magnification
selection table to reduce the level of the pitch-up frequency included in the transmission
frequency band which is easily transmitted into the vehicle compartment of the vehicle. Thus, the
signal level of each pitch-up frequency can be corrected accurately, and the quietness in the
vehicle interior can be improved.
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[0055]
Other Embodiments In the first embodiment, the signal level of each pitch-up frequency is
individually corrected using the pitch-up frequency-correction magnification selection table so
that the balance of the plurality of frequency components becomes constant. Instead of using
such a pitch-up frequency-correction magnification selection table, another means is used to
individually correct the signal level of each pitch-up frequency so that the balance of a plurality
of frequency components becomes constant. You may
[0056]
Further, in the first embodiment, the signal level of each pitch-up frequency is individually
corrected so that the balance of the plurality of frequency components becomes constant, but,
further, the sound pressure of the notification sound becomes constant, The signal level of each
pitch up frequency may be corrected to be adjusted overall.
In this case, the correction factor may be defined in the pitch-up frequency-correction factor
selection table such that the balance of the plurality of frequency components is constant and the
sound pressure of the notification sound is constant.
[0057]
Further, in the second embodiment, each pitch-up frequency is reduced so as to lower the signal
level of the pitch-up frequency included in the transmission frequency band which is easily
transmitted into the vehicle compartment of the vehicle using the pitch-up frequency-correction
magnification selection table. Signal level is corrected, but without using such a pitch-up
frequency-correction magnification selection table, the signal level of the pitch-up frequency
included in the transmission frequency band easily transmitted into the vehicle compartment of
the vehicle using another means To reduce the signal level of each pitch-up frequency.
[0058]
Further, in the second embodiment, the signal level of each pitch-up frequency is corrected so as
to lower the signal level of the pitch-up frequency included in the transmission frequency band
which is easily transmitted into the vehicle compartment of the vehicle. The signal level of each
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pitch-up frequency may be corrected to be generally adjusted so that the sound pressure of the
sound is constant.
In this case, the signal level of the pitch-up frequency included in the transmission frequency
band that easily penetrates into the vehicle compartment in the vehicle is reduced, and the sound
pressure of bands other than the transmission frequency band is increased, and the sound
pressure of notification sound is constant The correction magnifications such as the following
should be defined in the pitch-up frequency-correction magnification selection table.
[0059]
In the first and second embodiments, the frequency components included in the synthesized
sound signal are shifted to the high frequency side as the vehicle speed increases. However, the
present invention is not limited to such a configuration. For example, the present invention can
also be applied to a configuration in which each frequency component included in the
synthesized speech signal is shifted to the low frequency side as the vehicle speed increases.
[0060]
In the first and second embodiments, the configuration has been described in which the
notification sound including four frequency components is output from the speaker 20. However,
the number of frequency components is not limited to four, and two frequencies may be used. A
notification sound including a component, three frequency components, and five or more
frequency components may be output from the speaker 20.
[0061]
S100 and S102 correspond to shift frequency specifying means, and S104, S106, S204 and S206
correspond to level correction means.
[0062]
DESCRIPTION OF SYMBOLS 1 Vehicle approach notification apparatus 10 Control part 11 Lowpass filter 12 Mixer 13 Power amplifier 20 Speaker 30 Vehicle speed sensor
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