Patent Publication Number: US-2022238094-A1

Title: Active sound effect generating device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-008744 filed on Jan. 22, 2021, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an active sound effect generating device. 
     Description of the Related Art 
     JP 2019-128378 A discloses an active sound effect generating device. The active sound effect generating device generates a plurality of ordered acoustic signals. Each of the ordered acoustic signals is an acoustic signal of an ordered frequency of a fundamental frequency set according to a vehicle speed. The active sound effect generating device generates an acoustic signal of a sound effect by adding a plurality of generated ordered acoustic signals. 
     SUMMARY OF THE INVENTION 
     In order to make the sound effect harmonic, it is necessary to set the ratio of each ordered frequency to a predetermined value. For this reason, there is a problem in that the degree of freedom of tone adjustment of sound effects is low and characteristic sound effects cannot be generated. 
     An object of the present invention is to solve the aforementioned problem. 
     According to one aspect of the present invention, an active sound effect generating device generates a sound effect in a vehicle compartment of a vehicle, and includes a vehicle speed acquisition unit configured to acquire a vehicle speed, a fundamental frequency setting unit configured to set a fundamental frequency that changes in accordance with the acquired vehicle speed, a tone adjusting unit configured to set a plurality of different sub-fundamental frequencies by multiplying the fundamental frequency by coefficients; tone signal generating units provided corresponding to the respective sub-fundamental frequencies, and each configured to generate a tone signal including a plurality of ordered frequency components that are obtained by multiplying each of the sub-fundamental frequencies by predetermined values, and a sound effect signal generating unit configured to generate a sound effect signal that causes a speaker to output the sound effect, based on the tone signal generated by each of the tone signal generating units. 
     According to the present invention, it is possible to increase the degree of freedom of tone adjustment of a sound effect. 
     The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which a preferred embodiment of the present invention is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a configuration of an active sound effect generating device; 
         FIG. 2  is a graph showing a fundamental frequency with respect to the vehicle speed; 
         FIG. 3  is a block diagram showing a configuration of the first tone signal generating unit; 
         FIG. 4  is a graph showing the change of each ordered frequency with respect to the speed; 
         FIG. 5  is a block diagram showing a configuration of a second tone signal generating unit; 
         FIG. 6  is a block diagram showing a configuration of a third tone signal generating unit; 
         FIG. 7  is a block diagram showing the configuration of a fourth tone signal generating unit; 
         FIG. 8  is a map of the gain of each tone signal; 
         FIG. 9  is a vehicle speed gain map; 
         FIG. 10  is an accelerator degree of opening gain map; 
         FIG. 11  is an acceleration gain map; 
         FIG. 12  is a graph showing the fundamental frequency with respect to the vehicle speed; and 
         FIG. 13  is a graph showing the change of each ordered frequency with respect to the vehicle speed. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     First Embodiment 
       FIG. 1  is a block diagram showing a configuration of an active sound effect generating device  10 . The active sound effect generating device  10  is a device that causes a speaker  12  to output sound effects changing according to a vehicle speed. The speaker  12  is provided in a vehicle compartment of a vehicle such as an automobile. 
     The active sound effect generating device  10  includes a vehicle speed acquisition unit  14 , an accelerator degree of opening acquisition unit  18 , an acceleration calculating unit  20 , a fundamental frequency setting unit  22 , a tone adjusting unit  24 , a first tone signal generating unit  26 , a second tone signal generating unit  28 , a third tone signal generating unit  30 , a fourth tone signal generating unit  32 , a tone signal gain adjusting unit  34 , a sound effect signal generating unit  36 , a vehicle speed gain setting unit  38 , an accelerator degree of opening gain setting unit  40 , an acceleration gain setting unit  42 , and a sound effect signal amplifying unit  44 . 
     The active sound effect generating device  10  includes a computer equipped with one or more operational processing devices (not shown) and one or more storage units. The operational processing device includes, for example, a processor such as a central processing unit (CPU) or a microprocessing unit (MPU), and a memory such as a ROM or a RAM. The storage unit is, for example, a recording medium such as a hard disk or a solid state drive (SSD). The active sound effect generating device  10  need not necessarily include a storage unit. In this case, the active sound effect generating device  10  may transmit and receive data to and from a storage unit on the cloud through communications. Each of the vehicle speed acquisition unit  14 , the accelerator degree of opening acquisition unit  18 , the acceleration calculating unit  20 , the fundamental frequency setting unit  22 , the tone adjusting unit  24 , the first tone signal generating unit  26 , the second tone signal generating unit  28 , the third tone signal generating unit  30 , the fourth tone signal generating unit  32 , the tone signal gain adjusting unit  34 , the sound effect signal generating unit  36 , the vehicle speed gain setting unit  38 , the accelerator degree of opening gain setting unit  40 , the acceleration gain setting unit  42 , and the sound effect signal amplifying unit  44 , is realized by the operation processing unit executing programs stored in the storage unit. 
     The vehicle speed acquisition unit  14  acquires a vehicle speed v from an in-vehicle network  16  of the vehicle. The accelerator degree of opening acquisition unit  18  acquires the accelerator degree of opening θ from the in-vehicle network  16 . The acceleration calculating unit  20  calculates an acceleration Aa of the vehicle from the vehicle speed v acquired by the vehicle speed acquisition unit  14 . 
     The fundamental frequency setting unit  22  sets a fundamental frequency f0 in accordance with the vehicle speed v.  FIG. 2  is a graph showing the fundamental frequency f0 with respect to the vehicle speed v. As shown in  FIG. 2 , the fundamental frequency f0 is set so as to increase exponentially from a lower limit frequency Fmin to an upper limit frequency Fmax as the vehicle speed v increases. When the fundamental frequency f0 has reached the upper limit frequency Fmax, the fundamental frequency f0 is returned to the lower limit frequency Fmin. The fundamental frequency f0 is set so as to increase exponentially from the lower limit frequency Fmin to the upper limit frequency Fmax again as the vehicle speed v increases. The fundamental frequency f0 can be obtained by the following expressions. 
     
       
         
           
             
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     In the expressions, the character n denotes the number of time steps. The active sound effect generating device  10  performs signal processing in a predetermined cycle. The time step indicates a length of the cycle. The number of time steps indicates how many times the signal processing is performed. In the expression, Fmax indicates the upper limit frequency. In the expressions, Fmin indicates the lower limit frequency. In the expressions, ΔV indicates the amount of change in the vehicle speed v when the frequency changes from the lower limit frequency Fmin to the upper limit frequency Fmax. The character k indicates a frequency change rate adjusting coefficient. The character k indicates an interval of the vehicle speed at which the fundamental frequency f0 change from the lower limit frequency Fmin to the upper limit frequency Fmax. As a result, the fundamental frequency setting unit  22  can set the fundamental frequency f0 to be approximate to a Shepherd tone (or Shepherd infinite scale) that changes according to the vehicle speed. 
     The tone adjusting unit  24  multiplies the fundamental frequency f0 by tone setting coefficients rm (r1, r2, r3, r4 . . . ), whereby the tone adjusting unit  24  sets a plurality of different sub-fundamental frequencies fm (f1, f2, f3, f4 . . . ). In the present embodiment, the tone setting coefficients r1, r2, r3, and r4 are set to the following values. 
         r 1=1 
         r 2=1.25 
         r 3=1.5 
         r 4=1.2 
     The tone adjusting unit  24  multiplies the fundamental frequency f0 by the tone setting coefficients r1, r2, r3, and r4. As a result, the tone adjusting unit  24  sets four different sub-fundamental frequencies f1, f2, f3, and f4. It is sufficient that the tone adjusting unit  24  may set a plurality of different sub-fundamental frequencies fm. The number of set sub-fundamental frequencies fm need not necessarily be limited to four. 
       FIG. 3  is a block diagram showing the configuration of the first tone signal generating unit  26 . The first tone signal generating unit  26  generates three frequency components S 1   c , S 1   d , and S 1   e  for the sub-fundamental frequency component f1. Further, the first tone signal generating unit  26  generates the first tone signal S 1  by adding the frequency components S 1   c , S 1   d , and S 1   e , each of which has been multiplied by the gain. The frequency component Sic is a c-th order component for the sub-fundamental frequency f1. The frequency component Sid is a d-th order component for the sub-fundamental frequency f1. The frequency component S 1   e  is an e-th order component for the sub-fundamental frequency component f1. The c-th order, d-th order and e-th order are power values having the same base α. In the present embodiment, the c-th order is α{circumflex over ( )}0-th, i.e., the 1-th order. The d-th order is α{circumflex over ( )}1-th, i.e., a-th order. The e-th order is α{circumflex over ( )}2-th order. Here, the character “{circumflex over ( )}” indicates a power. 
       FIG. 4  is a graph showing changes of the c-th, d-th, and e-th frequencies for the sub-fundamental frequency f1, with respect to the vehicle speed v. For example, when the vehicle speed v is v1, the d-th order frequency is α times the c-th order frequency, and the e-th order frequency is α{circumflex over ( )}2 times the c-th order frequency. For example, when α=2, the sound of the first tone signal S 1  can be harmonized. 
       FIG. 5  is a block diagram showing a configuration of the second tone signal generating unit  28 . The second tone signal generating unit  28  generates three frequency components S 2   c , S 2   d , and S 2   e  for the sub-fundamental frequency f2. Further, the second tone signal generating unit  28  generates the second tone signal S 2  by adding the frequency components S 2   c , S 2   d , and S 2   e , each of which has been multiplied by the gain. The frequency component S 2   c  is the c-th (=1) order component for the sub-fundamental frequency f2. The frequency component S 2   d  is the d-th (=α) order component for the sub-fundamental frequency f2. The frequency component S 2   e  is the e-th (=α{circumflex over ( )}2) order component for the sub-fundamental frequency f2. When α=2, the sound of the second tone signal S 2  can be harmonized, in a similar manner to the sound of the first tone signal S 1 . 
       FIG. 6  is a block diagram showing the configuration of the third tone signal generating unit  30 . The third tone signal generating unit  30  generates three frequency components S 3   c , S 3   d , and S 3   e  for the sub-fundamental frequency component f3. Further, the third tone signal generating unit  30  generates third tone signal S 3  by adding the frequency components S 3   c , S 3   d , and S 3   e , each of which has been multiplied by the gain. The frequency component S 3   c  is the c-th (=1) order component for the sub-fundamental frequency f3. The frequency component S 3   d  is the d-th (=α) order component for the sub-fundamental frequency f3. The frequency component S 3   e  is the e-th (=α{circumflex over ( )}2) order component for the sub-fundamental frequency f3. When α=2, the sound of the third tone signal S 3  can be harmonized, in a similar manner to the sound of the first tone signal S 1 . 
       FIG. 7  is a block diagram showing a configuration of the fourth tone signal generating unit  32 . The fourth tone signal generating unit  32  generates three frequency components S 4   c , S 4   d , and S 4   e  for the sub-fundamental frequency component f4. Further, the fourth tone signal generating unit  32  generates the fourth tone signal S 4  by adding the frequency components S 4   c , S 4   d , and S 4   e , each of which has been multiplied by the gain. The frequency component S 4   c  are the c-th (=1) order component for the sub-fundamental frequency f4. The frequency component S 4   d  is the d-th (=α) order component for the sub-fundamental frequency f4. The frequency component S 4   e  is the e-th (=α{circumflex over ( )}2) order component for the sub-fundamental frequency f4. When α=2, the sound of the fourth tone signal S 4  can be harmonized, in a similar manner to the sound of the first tone signal S 1 . 
     The active sound effect generating device  10  of the present embodiment includes four tone signal generating units, namely, the first tone signal generating unit  26 , the second tone signal generating unit  28 , the third tone signal generating unit  30 , and the fourth tone signal generating unit  32 . The number of tone signal generating units need not necessarily be four. The number of tone signal generating units may be the same as the number of sub-fundamental frequencies generated by the tone adjusting unit  24 . 
     In the active sound effect generating device  10  of the present embodiment, the first tone signal generating unit  26  generates three frequency components S 1   c , S 1   d , and S 1   e . The first tone signal generating unit  26  may generate two frequency components. The first tone signal generating unit  26  may generate four or more frequency components. 
     The second tone signal generating unit  28  generates three frequency components S 2   c , S 2   d , and S 2   e . The second tone signal generating unit  28  may generate two frequency components. The second tone signal generating unit  28  may generate four or more frequency components. 
     The third tone signal generating unit  30  generates three frequency components S 3   c , S 3   d , and S 3   e . The third tone signal generating unit  30  may generate two frequency components. The third tone signal generating unit  30  may generate four or more frequency components. 
     The fourth tone signal generating unit  32  generates three frequency components S 4   c , S 4   d , and S 4   e . The fourth tone signal generating unit  32  may generate two frequency components. The fourth tone signal generating unit  32  may generate four or more frequency components. 
     The tone signal gain adjusting unit  34  adjusts gains by which the first tone signal S 1 , the second tone signal S 2 , the third tone signal S 3 , and the fourth tone signal S 4  are multiplied. Hereinafter, the gain for the first tone signal S 1  may be referred to as a gain 1. The gain for the second tone signal S 2  may be referred to as a gain 2. The gain for the third tone signal S 3  may be referred to as a gain 3. The gain for the fourth tone signal S 4  may be referred to as a gain 4.  FIG. 8  is a map of the gain 1, the gain 2, the gain 3, and the gain 4. As shown in  FIG. 8 , the gains 1 and 3 are constant values regardless of the vehicle speed v. The gain 2 decreases as the vehicle speed v becomes higher. The maximum value of the gain 2 is equal to the value of the gain 1 and the gain 3. The gain 4 increases as the vehicle speed v increases. The maximum value of the gain 4 is equal to the value of the gain 1 and the gain 3. 
     As a result, when the vehicle speed v is low, the sound effect output from the speaker  12  includes a lot of the first tone signal S 1 , the second tone signal S 2 , and the third tone signal S 3 . The ratio of the fundamental frequency (sub-fundamental frequency f1) of the first tone signal S 1 , the fundamental frequency (sub-fundamental frequency f2) of the second tone signal S 2 , and the fundamental frequency (sub-fundamental frequency f3) of the third tone signal S 3  is r1:r2:r3=1:1.25:1.5. As a result, the sound effect becomes a bright resonance of the major chord. 
     On the other hand, when the vehicle speed v is high, the sound effect output from the speaker  12  includes a lot of the first tone signal S 1 , the fourth tone signal S 4 , and the third tone signal S 3 . The ratio of the fundamental frequency of the first tone signal S 1  (sub-fundamental frequency f1), the fourth tone signal S 4  (sub-fundamental frequency f4), and the third tone signal S 3  (sub-fundamental frequency f3) is r1:r4:r3=1:1.2:1.5. As a result, the sound effect becomes a fantastic sound of the minor chord. 
     The sound effect signal generating unit  36  generates a sound effect signal S by adding a first tone signal S 1 ′, a second tone signal S 2 ′, a third tone signals S 3 ′, and the fourth tone signal S 4 ′. The first tone signal S 1 ′, the second tone signal S 2 ′, the third tone signal S 3 ′, and the fourth tone signal S 4 ′ are signals, each of which has been multiplied by the gain adjusted by the tone signal gain adjusting unit  34 . 
     The vehicle speed gain setting unit  38  sets a vehicle speed gain Gv.  FIG. 9  is a vehicle speed gain map. The vehicle speed gain Gv is a constant value regardless of the vehicle speed v in a low vehicle speed region. The vehicle speed gain Gv increases linearly as the vehicle speed v increases in a middle vehicle speed region and a high vehicle speed region. 
     The accelerator degree of opening gain setting unit  40  sets an accelerator degree of opening gain Gθ.  FIG. 10  is an accelerator degree of opening gain map. The accelerator degree of opening gain Gθ is a constant value regardless of the accelerator degree of opening θ in a small degree of opening region of the accelerator degree of opening θ. The accelerator degree of opening gain Gθ increases linearly as the accelerator degree of opening θ increases from a middle degree of opening region to a large degree of opening region. The accelerator degree of opening gain Gθ is a constant value regardless of the accelerator degree of opening θ in the large degree of opening region of the accelerator degree of opening θ. 
     The acceleration gain setting unit  42  sets an acceleration gain GΔa.  FIG. 11  is an acceleration gain map. The acceleration gain GΔa is a constant value regardless of the acceleration Aa in a low acceleration region. In a middle acceleration region and a high acceleration region, the acceleration gain GΔa increases logarithmically as the acceleration Aa increases. 
     The sound effect signal amplifying unit  44  multiplies the sound effect signal S by the gain G to output the sound effect signal S′. The gain G is obtained from the vehicle speed gain Gv, the accelerator degree of opening gain Gθ, and the acceleration gain GΔa by the following expression: 
     
       
      
       G=Gv×Gθ+GΔα 
      
     
     The sound effect signal S′ is converted into an analog signal by a digital-to-analog converter (not shown) and output to the speaker  12 . A sound effect corresponding to the sound effect signal S′ is output from the speaker  12  into a vehicle compartment. 
     Advantageous Effects 
     The first tone signal S 1  generated by the first tone signal generating unit  26  of the active sound effect generating device  10  includes frequency components having c-th, d-th, and e-th order tone signals. The second tone signal S 2  generated by the second tone signal generating unit  28  includes frequency components having c-th, d-th, and e-th order tone signals. The third tone signal S 3  generated by the third tone signal generating unit  30  includes frequency components having c-th, d-th, and e-th order tone signals. The fourth tone signal S 4  generated by the fourth tone signal generating unit  32  includes frequency components having c-th, d-th, and e-th order tone signals. 
     The d-th order is α times the c-th order, and the e-th order is α times the d-th order. That is, the first tone signal S 1 , the second tone signal S 2 , the third tone signal S 3 , and the fourth tone signal S 4  have the same order of frequency components. The ratio of the order is also constant at α. In order to harmonize the sound effect output from the speaker  12 , the value α is often set to 2 (α=2). Therefore, only by adjusting the orders of the frequency components of the first tone signal S 1 , the second tone signal S 2 , the third tone signal S 3 , and the fourth tone signal S 4 , the degrees of freedom of tone color adjustment of the sound effect are low. As a result, a sound effect specific to each vehicle type cannot be generated. In addition, a sound effect symbolizing a brand cannot be generated. 
     Thus, in the active sound effect generating device  10  according to the present embodiment, the tone adjusting unit  24  generates the sub-fundamental frequencies f1, f2, f3, and f4. The sub-fundamental frequencies f1, f2, f3, and f4 are generated by multiplying the fundamental frequency f0 by the tone setting coefficients r1, r2, r3, and r4, respectively. The first tone signal generating unit  26  generates the first tone signal f1 based on the sub-fundamental frequency S 1 . The second tone signal generating unit  28  generates the second tone signal f2 based on the sub-fundamental frequency S 2 . The third tone signal generating unit  30  generates the third tone signals f3 based on the sub-fundamental frequency S 3 . The fourth tone signal generating unit  32  generates the fourth tone signals f4 based on the sub-fundamental frequency S 4 . The sound effect signal generating unit  36  generates the sound effect signal S based on the first tone signal S 1 , the second tone signal S 2 , the third tone signal S 3 , and the fourth tone signal S 4 . 
     Thus, by arbitrarily setting the tone setting coefficients r1, r2, r3, and r4 used in the tone adjusting unit  24 , a sound effect of an arbitrary tone can be realized. 
     In the active sound effect generating device  10  according to the present embodiment, the first tone signal S 1  generated by the first tone signal generating unit  26  includes the frequency components S 1   c , S 1   d , and S 1   e . The frequency component S 1   c  is the c-th order component for the sub-fundamental frequency component f1. The frequency component Sid is the d-th order component for the sub-fundamental frequency f1. The frequency component S 1   e  is the e-th order component for the sub-fundamental frequency component f1. The d-th order is α times the c-th order, and the e-th order is α times the d-th order. By setting α=2, the sound of the first tone signal S 1  can be harmonized. 
     In the active sound effect generating device  10  according to the present embodiment, the second tone signal S 2  generated by the second tone signal generating unit  28  includes the frequency components S 2   c , S 2   d , and S 2   e . The frequency component S 2   c  is the c-th order component for the sub-fundamental frequency f2. The frequency component S 2   d  is the d-th order component for the sub-fundamental frequency f2. The frequency component S 2   e  is the e-th order component for the sub-fundamental frequency component f2. The d-th order is α times the c-th order, and the e-th order is α times the d-th order. By setting α=2, the sound of the second tone signal S 2  can be harmonized. 
     In the active sound effect generating device  10  according to the present embodiment, the third tone signal S 3  generated by the third tone signal generating unit  30  includes the frequency components S 3   c , S 3   d , and S 3   e . The frequency component S 3   c  is the c-th order component for the sub-fundamental frequency f3. The frequency component S 3   d  is the d-th order component for the sub-fundamental frequency f3. The frequency component S 3   e  is the e-th order component for the sub-fundamental frequency component f3. The d-th order is α times the c-th order, and the e-th order is α times the d-th order. By setting α=2, the sound of the third tone signal S 3  can be harmonized. 
     In the active sound effect generating device  10  according to the present embodiment, the fourth tone signal S 4  generated by the fourth tone signal generating unit  32  includes the frequency components S 4   c , S 4   d , and S 4   e . The frequency component S 4   c  is the c-th order component for the sub-fundamental frequency f4. The frequency component S 4   d  is the d-th order component for the sub-fundamental frequency f4. The frequency component S 4   e  is the e-th order component for the sub-fundamental frequency component f4. The d-th order is α times the c-th order, and the e-th order is α times the d-th order. By setting α=2, the sound of the fourth tone signal S 4  can be harmonized. 
     In this embodiment, the tone signal gain adjusting unit  34  adjusts gains to be multiplied by the first tone signal S 1 , the second tone signal S 2 , the third tone signal S 3 , and the fourth tone signal S 4 , in accordance with the vehicle speed v. More specifically, in the present embodiment, the tone signal gain adjusting unit  34  adjusts the gain of the second tone signal S 2  to be a smaller value as the vehicle speed v increases, and adjusts the gain of the fourth tone signal S 4  to be a larger value as the vehicle speed v increases. As a result, the tone of the sound effect can be switched according to the vehicle speed v. 
     Further, in the present embodiment, the fundamental frequency setting unit  22  sets the fundamental frequency f0 so as to repeatedly increase exponentially from the lower limit frequency Fmin to the upper limit frequency Fmax in accordance with an increase in the vehicle speed v. As a result, sound effects corresponding to the vehicle speed v and the acceleration Aa can be generated from the speaker  12  using only sounds of frequencies within a certain frequency range. 
     Second Embodiment 
     In the first embodiment, the fundamental frequency setting unit  22  sets the fundamental frequency f0 so as to increase exponentially as the vehicle speed v increases. On the other hand, the fundamental frequency setting unit  22  may set the fundamental frequency f0 so as to increase linearly as the vehicle speed v increases. 
       FIG. 12  is a graph showing the fundamental frequency f0 with respect to the vehicle speed v. As shown in  FIG. 12 , the fundamental frequency f0 is set so as to increase linearly as the vehicle speed v increases. When the vehicle speed v reaches a predetermined vehicle speed (v1, v2, v3 . . . ), the fundamental frequency f0 is set to 0. Then, the fundamental frequency f0 is set so as to increase again linearly as the vehicle speed v increases. 
     In the present embodiment, the first tone signal generating unit  26  generates three frequency components S 1   c , S 1   d , and S 1   e  for the sub-fundamental frequency f1. Further, the first tone signal generating unit  26  generates the first tone signal S 1  by adding the frequency components S 1   c , S 1   d , and S 1   e , each of which has been multiplied by the gain. The frequency component S 1   c  is a c-th order component for the sub-fundamental frequency f1. The frequency component S 1   d  is a d-th order component for the sub-fundamental frequency f1. The frequency component S 1   e  is an e-th order component for the sub-fundamental frequency f1. In the present embodiment, the c-th order is a 1-th order, the d-th order is an α-th order, and the e-th order is a 2α-th order. 
       FIG. 13  is a graph showing changes of the c-th, d-th, and e-th frequencies for the sub-fundamental frequency f1, with respect to the vehicle speed v. For example, the d-th order frequency is α times the c-th order frequency, and the e-th order frequency is 2α times the c-th order frequency. 
     Other Embodiments 
     The active sound effect generating device  10  of the first embodiment includes four tone signal generating units, namely, the first tone signal generating unit  26 , the second tone signal generating unit  28 , the third tone signal generating unit  30 , and the fourth tone signal generating unit  32 . The number of sub-fundamental frequencies f1, f2, f3, and f4 generated by the tone adjusting unit  24  is four. That is, the number of tone signal generation units is equal to the number of sub fundamental frequencies fm. The number of audio signal generating units is not limited to four, but the number of the audio signal generating units may correspond to the number of sub-fundamental frequencies fm. 
     Further, some of the sub-fundamental frequencies fm from among the plurality of sub-fundamental frequencies fm may be the same frequency. In this case, the number of tone signal generating units that generate a tone signal based on the same sub-fundamental frequency fm is counted as one. For example, when the sub-fundamental frequencies f2 and f4 are the same, the number of the two tone signal generating units, i.e., the second tone signal generating unit  28  and the fourth tone signal generating unit  32 , is regarded as one. 
     Technical Invention Obtained from Embodiments 
     A description will be given below concerning technical invention that can be grasped from the above-described embodiments. 
     The active sound effect generating device ( 10 ) generates a sound effect in the vehicle compartment of the vehicle, and includes the vehicle speed acquisition unit ( 14 ) configured to acquire a vehicle speed, the fundamental frequency setting unit ( 22 ) configured to set a fundamental frequency that changes in accordance with the acquired vehicle speed, the tone adjusting unit ( 24 ) configured to set a plurality of different sub-fundamental frequencies by multiplying the fundamental frequency by coefficients, the tone signal generating units ( 26 ,  28 ,  30 ,  32 ) provided corresponding to the respective sub-fundamental frequencies, and each configured to generate a tone signal including a plurality of ordered frequency components that are obtained by multiplying each of the sub-fundamental frequencies by predetermined values, and the sound effect signal generating unit ( 36 ) configured to generate a sound effect signal that causes the speaker ( 12 ) to output the sound effect, based on the tone signal generated by each of the tone signal generating units. 
     The active sound effect generating device according to the present invention may further include the gain adjusting unit ( 34 ) configured to set a gain corresponding to the tone signal generated by each of the tone signal generating units in accordance with the vehicle speed, and multiply each of the tone signals by the set gain corresponding to the tone signal to thereby output each of the resultant tone signals. 
     In the active sound effect generating device according to the present invention, the gain adjusting unit may be configured to set the gain corresponding to at least one of the tone signals so as to increase as the vehicle speed increases, and configured to set the gain corresponding to at least one of the tone signals so as to decrease as the vehicle speed increases. 
     In the active sound effect generating device according to the present invention, the fundamental frequency setting unit may be configured to set the fundamental frequency between the lower limit frequency and the upper limit frequency, set the fundamental frequency so as to increase exponentially from the lower limit frequency to the upper limit frequency in accordance with an increase in the vehicle speed, and set the fundamental frequency so as to return to the lower limit frequency when the fundamental frequency reaches the upper limit frequency, and so as to increase exponentially from the lower limit frequency to the upper limit frequency again in accordance with the increase in the vehicle speed. 
     The present invention is not particularly limited to the embodiments described above, and various modifications are possible without departing from the essence and gist of the present invention.