JP3191897B2 - Alarm sound generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a warning sound generator for use in emergency vehicles and the like, and more particularly to improvement of directivity.

[0002]

2. Description of the Related Art
In a vehicle 2 such as an emergency car, two fingers are usually used as shown in FIG. 7A.
Directional speaker S ₁, S_TwoSide by side to generate one signal
The device is driven simultaneously to generate an alarm sound. this
As a result, at sufficiently distant places, the characteristics of B and C in FIG. 7 were multiplied.
Sound waves are generated with such directivity.
Figure B is by driving two speakers with the same signal
FIG. C shows the directivity of the speaker. However
However, its directional characteristics are not enough.

[0003] An object of the present invention is to provide an alarm sound generating apparatus having directivity as sharp as possible.

[0004]

A resolution means for (1) the alarm sound generating device according to claim 1, toward the vehicle both forward, and a plurality of speakers arranged in the vehicle is shifted in the longitudinal direction, of those speakers And a signal generator for distributing an alarm signal to a predetermined part in the front row (or the last row) of the speaker and the apparatus, and the phase of the alarm signal distributed and supplied from the signal generator is time-averaged with sound waves in front of the vehicle. In order to maximize the power , for each speaker except the front row (or last row) speaker ,
Their create a respectively control signal composed of a phase shifter input to each speaker.

[0005] (2) In the alarm sound generating apparatus according to the above (1), the phase shift section may switch the front row (or last row) of the plurality of speakers. A voltage-controlled oscillator section for inputting an alarm signal to each of the speakers except for the first row (or the last row) of the input signals of each of the speakers except for the first row (or the last row) of speakers;
A phase difference setting unit that sets each phase difference with respect to the input signal of the speaker according to the traveling speed such that the time average power of the sound wave in front of the vehicle is maximized, and the input signal of each speaker and the front row ( Or the last row), and compare the phase with the input signal of the loudspeaker.
A phase comparison unit that controls the voltage-controlled oscillator unit so as to match the value set by the phase difference setting unit.

(3) In the invention according to claim 3, in the alarm sound generating device according to the above (1), the speakers are a first speaker in a front row (or a last row) to a first speaker in a last row (or a front row). , and the signal generator includes a first frequency f ₁ , a second frequency f ₂ ,.
1) switching and generating an alarm signal of a frequency f _n-1 (where f ₁ > f ₂ ...> F _n-1 ), wherein the phase shift unit is distributed and supplied from the signal generation unit; A signal in which the phases of the alarm signals of the first to (n-1) th frequencies are deviated for each of the second to n-th loudspeakers corresponding to the alarm signals is generated and input to each loudspeaker.

(4) The invention according to claim 4, wherein in the alarm sound generating device according to the above (3), the phase shift section is configured to be the second
A voltage-controlled oscillator for inputting an alarm signal to each of the first to n-th speakers, and a phase difference between each of the input signals of the second to n-th speakers with respect to the first to (n-1) th frequency alarm signals. A phase difference setting unit, and input signals of the second to n-th speakers and the first to (n-
1) comparing a phase with an alarm signal of a frequency, and a phase comparison unit that controls the voltage-controlled oscillator unit so that a phase difference with respect to the latter is equal to a value set by the phase difference setting unit. It is composed of

(5) In the invention of claim 5, in the alarm sound generating device according to any one of the above (1) to (4), the frequency of the alarm signal, the respective speakers and the front row (or last The distance between the front and rear speakers
The time average power of the sound wave behind the vehicle is set to be substantially minimum. (6) In the invention according to claim 6, in the alarm sound generating device according to any one of (1) to (5), the speed measuring unit includes a measuring signal generating device and an output of the generating signal. And a sounding body that emits sound toward the front of the vehicle, and a first sound source that is disposed in front of and near the sounding body.
And a second microphone, a time difference measuring unit for measuring a time difference between a sound wave emitted from the sounding body and a sound wave received by the first and second microphones, and A traveling speed measuring unit that measures the traveling speed of the vehicle.

(7) In the invention of claim 7, in the alarm sound generating device according to any one of the above (1) to (6), the speed measuring section measures a sound speed together with a running speed of the vehicle, The phase shifter controls the phase of each speaker input signal according to the measured traveling speed and sound speed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is characterized in that a plurality of loudspeakers are displaced in the front-rear direction of a vehicle, and a sharp directivity is provided by controlling the phases of generated sound waves. At that time, the Doppler effect depending on the traveling speed of the vehicle or the like is also taken into consideration. FIG. 5 shows an example of a speaker arrangement according to the present invention. The speaker is disposed so as to be shifted in the front-rear direction of the vehicle 2. The interval is approximately 1/4 of the wavelength of the generated sound
The degree is a guide. The greater the number of speakers, the stronger the directivity can be provided.

FIG. 1A shows the structure of the first embodiment of the present invention. Here, a sine wave is used as an alarm signal, and the number of speakers is four. The output of the signal generator 4 is directly sent to the front row speaker S ₁ , and the speaker S
Supplied to the ₂ ~S _4. Phase shifter 5 is controlled for each speaker the phase of the alarm signal as a reference input of the phase of the speaker S _1. This can be realized by a PLL control using a VCO and a phase comparator or a method of controlling a delay unit by a controller. As will be described later, the phase adjustment method is determined so as to obtain a desired directivity depending on the interval between the speakers, the frequency of the alarm signal, and the running speed of the vehicle.

FIG. 2 is a diagram showing the configuration of a second embodiment of the present invention. In this example, the phase shift unit 5 includes a VCO unit 8,
It comprises a phase comparing section 9 and a phase difference (offset) setting section 10. The signal generator 4 includes a VCO 4a and a control voltage generator 4b. In this case, the speakers S ₂ and S
_3, prepared voltage-controlled oscillator (VCO) for each S _4, PLL control for controlling the phase so that the phase of each output is the output of the reference signal generator 4 is maintained at a desired phase difference (offset) Is used. Also in this case, the phase difference is set based on the interval between the speakers, the oscillation frequency, and the running speed. In the configuration of FIG. 2, since the control is performed in a closed loop using the output of each oscillator, it is possible to flexibly follow a change in the frequency of the alarm signal and a change in the traveling speed.

FIG. 4 shows a method of measuring the traveling speed v together with the sound speed V. A speaker 21 is prepared separately from the speaker for generating an alarm sound, and driven by a pulse train or M-sequence noise.
The output of the speaker 21 is received by the microphones 22 and 23, and the sound speed V from the time difference Δt ₁ and Δt ₂ between the output M ₁ (t) and M ₂ (t) of each microphone and the speaker drive signal S (t) is obtained. The running speed v is calculated. With the front microphone 21 alone, the difference V−v = L ₁ between the sound speed V and the traveling speed v.
/ Δt ₁ can be measured, but the speed at which they were separated is not known. When the time difference Δt ₂ is measured by placing another microphone 23 behind, the sum V + v = L ₂ / Δt _{2 of} the sound speed V and the traveling speed v can be measured. Where L ₁ , L ₂
Is the distance between the microphones 22 and 23 and the speaker 21. V and v can be measured from the difference and sum of the speeds. The phase difference for each speaker may be controlled using this result. It is also possible to share the speed measurement speaker 21 with the alarm sound generation speaker and superimpose the speed measurement M-sequence signal on the alarm sound. This is because if the alarm sound is a sine wave, the time difference can be measured by removing the component with a filter.

Regarding the method for setting the phase difference, 2
The case of FIG. 5 in which two speakers S ₁ and S ₂ are arranged shifted in front of and behind the vehicle will be described. L is the distance between speakers,
The frequency of the alarm signal is f, and the speaker S after the traveling direction is
A phase difference before the _second input to the input of the speaker S ₁ theta, acoustic velocity and the travel speed respectively V, v, a respective amplitudes of the sound waves from the speakers before and after, when is b, sufficiently far in front The instantaneous power P (t) of the sound wave can be calculated as follows.

P (t) = | asin {2πVft / (V−v)} + bsin [{2πVf (t−L / V) / (V−v)} + θ] | ² (1) Power Pa is Pa = a ² + b ² + 2ab cos [2πf ｛L / (V−v)｝ + θ] (2) Similarly, at a sufficiently distant position, the average power Pa (φ) in the direction of angle φ from the front is Pa (φ). ) = A ² + b ² + 2ab cos [2πf ｛L cos φ / (V−v cos φ)｝ + θ] (3) Note that when φ = 0, the front of the vehicle in the traveling direction, ie, the front of the vehicle assuming that the vehicle goes straight ahead, φ = Π / 2 is right beside, φ =
The time of π corresponds directly behind.

In order to maximize the average power Pa ahead of the vehicle in the equation (2), the traveling speed v is set so as to satisfy 2πf {L / (V−v)} + θ = 0 ± 2mπ (4) The phase difference θ may be controlled accordingly. ∴ θ = ± 2mπ−2πfL / (V−v) (4 ′) Further, the average power P behind the vehicle where φ = π in equation (3)
To minimize a, the following must be satisfied: -2πf L / (V + v)｝ + θ = ± π ± 2mπ (5) From equations (4 ′) and (5), f = (1 + 2m) (V ² −v ² ) / 4VL (6) If f and θ are set so as to satisfy equations (4) and (5), then Sound waves can be transmitted to the rear and weak to the rear. However, the equation (5) necessary to minimize the average power Pa at the rear of the vehicle is given by:
Since it is not as important as the expression (4) necessary for maximizing a, it may be approximately established. Then, since V≫v, v is omitted, and a frequency f that satisfies f ≒ (1 + 2m) V / 4L (6 ′) is set.

When the frequency f is a specified constant value, the speaker interval L can be set to L = (1 + 2 m) (V ² −v ² ) / (4f × V) (7) from the equation (6). . By the way, in the equation (7), it is generally impossible to change the speaker interval L according to the traveling speed v.
In many cases, (running speed) v is much lower than sound speed V.
Therefore, if v is ignored and L す (1 + 2m) V / 4f (7 ′), the expression (5) is approximately satisfied. Thus f
Is constant, the intervals L and θ may be determined. Anyway, f and L is set to the rear of the power becomes almost minimum (claim 5).

Note that in both the equations (4) and (5), the right side has a degree of freedom of 2mπ (m is a natural number), and a convenient combination can be selected. However, in this case, in addition to the front, there are m directions having strong directivity in the horizontal direction (see FIG. 5). While this speaker to have described the case of two, in the case of two or more, likewise of the speakers S _i input, a phase difference theta _i for the speaker S ₁ input, the distance L _i between S ₁ What is necessary is just to set by Formula (4) and Formula (5).

The frequency is f ₁ , f ₂ (f ₁
> F ₂ ), at least three speakers are arranged in the front-rear direction of the vehicle as shown in FIGS. 2 and 4B. When the frequency is high (f = f ₁ ), the speaker S having a small interval L ₁ is used. use ₁ and S _2, the desired directivity can be obtained for both frequency with larger speakers S ₁ and S ₃ of the lower frequency (f = f ₂₎ times the interval L _2. If the frequency is (n
-1) In the case of the type, n speakers may be used.

[0020] Figure 1 B is a case of a configuration with PLL controlled by the phase shifter 5 of Figure 1 A and FIG 2 and the VCO 8 and the phase comparator 9 and the phase difference setting unit 10 as well. 5 In the arrangement as and D, the center of the speaker S ₂ and S ₂ arranged in the horizontal direction 'is 5 sets the interval L _1, L ₂ as in the case of B as being on the central axis of the traveling direction Then, the directivity of the front and the rear can be controlled in the same manner. 5 it is possible to further have lateral directivity (the different directivity in the right direction and left direction) in the arrangement of D.

The specific numerical value examples below shows the case of Figure 5 C. When θ is set so as to satisfy the expression (4), the forward power is Pa (0) = a ² + b ² + 2ab... (8), but the backward power is Pa (π) = a ² + b ² + 2ab cos ｛. 4πfVL / (V ² −v ² )｝ (9)

F = 500 (Hz), V = 340 (m /
s) and v = 0 (m / s), L is given by L = (1 + 2m) V / 4f = V / 4f =
If 0.17 (m) (m = 0), θ is given by θ = −2πfL / V = −π / 2 according to the expression (4) or (4 ′).
When the vehicle speed v increases, θ is changed accordingly,
When satisfying the expression (4), the expression (5) is not satisfied, but the power to the rear increases only slightly from the minimum value because V≫v. Also, assuming m = 1, L = 3V / 4f
= 0.51 (m) or m = 2 and L = 5V / 4f =
It may be 0.85 (m). FIG. 6 shows the directional characteristics in these cases.

[0023] Although the foregoing description (also referred to as a speaker serving as a reference) speaker corresponding to the input signal to provide a phase reference while S ₁ is set to those in the front row, the speaker S ₁ is the last row to be the reference However, it is clear that the directivity can be improved by controlling the phase of each speaker input as in the past. In the description so far, the phase shifter 5 determines the traveling speed v of the vehicle measured by the speed measuring unit 7,
Although the phase of each speaker input is controlled, in order to improve the accuracy, the speed measuring unit measures the traveling speed v and the sound speed V (which changes depending on the wind direction, wind speed, and atmospheric pressure, etc.). Accordingly, the phase control may be performed so as to satisfy the expression (4) (claim 7).

[0024]

According to the present invention, a plurality of speakers are arranged so as to be shifted in the front-rear direction of the vehicle, and the phase of each speaker input is changed.
Since the control is performed according to the traveling speed so that the time average power of the sound wave in front of the vehicle is maximized, the directivity of the sound wave in front of the vehicle can be sharper than before.

Further, by selecting the frequency of the alarm signal and the interval between the speakers, the average power behind the vehicle can be substantially minimized. The present invention can also be applied to a case where alarm sounds of different frequencies are switched and emitted as in an ambulance.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the invention according to claim 1 or 3;

FIG. 2 is a block diagram showing an embodiment of the invention of claim 2;

FIG. 3 is a block diagram showing an embodiment of the invention of claim 4;

FIG. 4 is a block diagram showing an example of a speed measuring unit 7 of FIGS. 1 to 3;

FIG. 5 is a schematic plan view showing an example of disposition of speakers according to the present invention.

FIG. 6 shows a case where the phase difference between the respective inputs of the two speakers is controlled and the frequency of the alarm signal and the speaker interval are selected so that the average power of the sound waves in front of and behind the vehicle is maximized or almost minimized. The figure which shows an example of the directivity characteristic of a sound wave.

FIG. 7A is a principle plan view showing a speaker arrangement of a conventional alarm sound generating device, and FIGS. 7B and 7C are diagrams showing two elements constituting a conventional sound wave directional characteristic.

Claims (8)

(57) [Claims] 1. A front-rear direction of a vehicle with a sounding axis directed forward of the vehicle.
A plurality of speakers arranged in
An alarm signal is sent to the main speaker located in the front row or the last row.
The time-average power of the sound wave in front of the vehicle is maximized
Thus, for each speaker except the main speaker,
A phase shifter for controlling the phase of the alarm signal distributed and supplied to the
An alarm sound generator having: 2. The apparatus according to claim 1 , wherein the phase shifter is a switch other than the main speaker.
Voltage-controlled oscillator section that inputs alarm signals to each speaker
And, of the input alarm signal of each speaker except the main speaker,
Each phase difference with respect to the input alarm signal of the main speaker is
The time average power of the sound wave in both fronts will be the maximum value
And a phase difference setting unit for setting the phase of the input alarm signal of each speaker except the main speaker.
And the difference between the phase of the alarm signal input to the main speaker,
The position for controlling the phase difference so as to correspond to the set phase difference
And a phase comparison unit.
Alarm sound generator. 3. The main speaker is a first speaker.
The other speakers are the second to n-th speakers (n ≧
3), the signal generating portion includes a first frequency f ₁ to the n-1 frequency
f _n-1 alarm signal (where f ₁ > f ₂ >...> f _n-1 )
Respectively, and the phase shift section is distributed and supplied from the signal generation section.
Frequency f ₁ to position of the first n-1 frequency f _n-1 of the alarm signal
The phase is set to each of the speakers from the second speaker to the n-th speaker.
2. The alarm according to claim 1, wherein the control is performed for each of the workers.
Alarm sound generator. 4. The apparatus according to claim 1 , wherein the phase shifter is configured to control the second to n-th speeds.
A voltage-controlled oscillator section for inputting an alarm signal to each of the first to n-th speakers;
Frequency f ₁ to pair to the (n-1) frequency f _n-1 of the alarm signal
A phase difference setting unit for setting a phase difference to be set, a phase of each input signal to the second to n-th speakers,
The alarm signal of the first frequency f _{1 to} the (n−1) _th frequency f _n−1
The voltage- controlled oscillation is performed so that the phase difference is the phase difference.
4. A phase comparison unit for controlling a control unit.
Alarm sound generator. 5. The second to n-th speakers and the main speaker
The distance between the speaker and the front-back direction should be
The alarm signal so that the time average power of the sound wave
The frequency is set according to the frequency of the signal
The alarm sound generator according to any one of claims 1 to 4. 6. A speed measuring unit for measuring a running speed of a vehicle.
The phase shift unit according to the traveling speed.
Controlling the phase of the input signal to the speaker
The alarm sound generator according to any one of claims 1 to 5. 7. The speed measurement section generates a measurement signal.
A signal generator for inputting the measurement signal
A sounding body that emits sound towards the sounding body, and are arranged in front of and behind the sounding body, respectively.
First and second microphones, sound waves emitted from the sounding body, and the first and second microphones
Time difference to measure time difference from sound wave received by lophone
A measuring unit for measuring a traveling speed of the vehicle from the time difference;
7. A speed measuring unit comprising:
Alarm sound generator. Claim 8. The speed measuring unit together with the traveling speed of the vehicle
A sound speed measuring unit for measuring a sound speed, wherein the phase shift unit
Entry into each speaker according to the running speed and the sound speed
8. The method according to claim 7, wherein the phase of the force signal is controlled.
Alarm sound generator.