Abstract:
An audio signal reproducing apparatus includes a storage unit for storing digital audio data of music pieces each having a tempo corresponding to either a first tempo or a second tempo, the second tempo being different from the first tempo, if a walking tempo of a user is either the first tempo or the second tempo, a reproducing circuit for reproducing the digital audio data, a detecting unit for detecting the walking tempos of the user, a calculating circuit for calculating a change in the walking tempo detected by the detecting unit, and a control circuit for retrieving the digital audio data from the storage unit in accordance with the walking tempo detected by the detecting unit and sending the retrieved digital audio data to the reproducing circuit.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]     The present invention contains subject matter related to Japanese Patent Application JP 2005-351581 filed in the Japanese Patent Office on Dec. 6, 2005, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to apparatus and methods for reproducing audio signals.  
         [0004]     2. Description of the Related Art  
         [0005]     Recently, with growing interest in health issues, there have been more and more people who go walking, jogging, or running (hereinafter collectively referred to as “walking”) for the purpose of health maintenance, health promotion, weight reduction, etc. Walking brings about a beneficial effect when a person walks continuously for a sufficient period of time.  
         [0006]     To achieve such an effect of walking, several techniques have been developed. For example, a portable audio reproducing device is known in which a walking tempo of a user (walker) is detected, and a music piece having a tempo corresponding to the walking tempo is reproduced as the walker listens to the music piece while walking. Note that a walking tempo refers to the number of steps per unit time (for example, one minute), and a music tempo refers to the number of beats per minute.  
         [0007]     Referring to diagrams I to III shown in  FIG. 7 , a relationship between a walking tempo of a user and a music tempo of a music piece to be reproduced in such an audio reproducing device mentioned above is illustrated. The diagram I in  FIG. 7  illustrates the walking tempo of the user. In a period T 1 , the user walks at a tempo VA that is normal to the user (normal speed). In a period T 2 , the user walks at a tempo VB that is slower than the tempo VA in the period T 1 , and then walks at the tempo VA again in a period T 3 .  
         [0008]     In this case, as illustrated in diagrams II and III in  FIG. 7 , the audio reproducing device reproduces a music piece A 1  of the tempo VA that is equal to the walking tempo VA during the period T 1 . During the period T 2 , the device reproduces a music piece B 1  of the tempo VB that is equal to the walking tempo VB, and then reproduces a music piece A 2  of the tempo VA again that is equal to the walking tempo VA during the period T 3 .  
         [0009]     When the walking tempo of the user matches the tempo of a music piece, as described above, the user can walk with a rhythm. Thus, the audio reproducing apparatus allows the user to continue walking enjoyably.  
         [0010]     An example of such a technique described above is disclosed in Japanese Unexamined Patent Application Publication No. 2005-156641.  
         [0011]     However, if the a music piece having a music tempo suddenly changes into another music piece having a different music tempo in response to a change in the walking tempo of the user, as illustrated in  FIGS. 7B and 7C , the user may feel discomfort at the other music piece and its tempo.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention has been made in view of the above circumstance.  
         [0013]     Accordingly, an audio signal reproducing apparatus according to an embodiment of the present invention includes a storage unit for storing digital audio data of music pieces each having a tempo corresponding to either a first tempo or a second tempo, the second tempo being different from the first tempo, if a walking (including running, hereinafter the same) tempo of a user is either the first tempo or the second tempo at any given time, a reproducing circuit for reproducing the digital audio data, a detecting unit for detecting the walking tempos of the user, a calculating circuit for calculating a change in the walking tempo detected by the detecting unit, and a control circuit for retrieving the digital audio data from the storage unit in accordance with the walking tempo detected by the detecting unit and sending the retrieved digital audio data to the reproducing circuit. In this audio signal reproducing apparatus, when the walking tempo is the first tempo or the second tempo, the control circuit retrieves the digital audio data of the music piece whose tempo corresponds to the first tempo or the second tempo, respectively, and sends the retrieved digital audio data to the reproducing circuit. When the walking tempo of the user changes from the first tempo to the second tempo and the change exceeds a predetermined threshold value, the control circuit changes the digital audio data to be sent from the storage unit to the reproducing circuit, after a predetermined time period has elapsed since the change of the walking tempo, from the digital audio data of a music piece whose tempo corresponds to the first tempo to the digital audio data of a music piece whose tempo corresponds to the second tempo. In addition, when the walking tempo of the user changes from the second tempo to the first tempo and the change exceeds a predetermined threshold value, the control circuit changes the digital audio data to be sent from the storage unit to the reproducing circuit, at the time point when the change of the walking tempo occurs, from the digital audio data of a music piece whose tempo corresponds to the second tempo to the digital audio data of a music piece whose tempo corresponds to the first tempo.  
         [0014]     According to an embodiment of the present invention, a music piece having a tempo corresponding to the walking tempo of a user is reproduced. In addition, when the walking tempo of the user is shifted from the first tempo to another tempo (for example, the second tempo that is slower than the first tempo), the music piece and its tempo are changed with a delay of a predetermined time period.  
         [0015]     This prevents the user from feeling discomfort at the subsequent music piece and its tempo.  
         [0016]     In addition, the walking temp of the user is shifted from the second tempo to the first tempo, the music piece to be reproduced and its tempo are changed immediately. This allows the user to walk at an appropriate tempo without disturbance. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a system diagram illustrating an embodiment of the present invention;  
         [0018]      FIG. 2  illustrates an example of contents registered in playlists;  
         [0019]      FIG. 3  illustrates an operation according to an embodiment of the present invention;  
         [0020]      FIG. 4  illustrates an operation according to an embodiment of the present invention;  
         [0021]      FIG. 5  is a flowchart illustrating an embodiment of the present invention;  
         [0022]      FIG. 6  is a flowchart illustrating an embodiment of the present invention; and  
         [0023]      FIG. 7  illustrates an operation according to a known technique. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0000]     [1] Circuit Configuration  
         [0024]      FIG. 1  illustrates an example of a configuration of a circuit of a reproducing apparatus  10  for reproducing an audio signal, according to an embodiment of the present invention. The reproducing apparatus  10  can be used as a walking aid device as well as a general portable player. Thus, the reproducing apparatus  10  has a size and a shape (not shown) that allow the user to carry the reproducing apparatus  10  in his or her pocket or the like while walking.  
         [0025]     The reproducing apparatus  10  includes a microcomputer  20  as a system control circuit. The microcomputer  20  has a CPU (Central Processing Unit)  21  for executing a program, a ROM (Read-only Memory)  22  having various programs recorded therein, a RAM (Random Access Memory)  23  used as a work area, and a non-volatile memory  24 . Each of these memories  22  to  24  is connected to the CPU  21  via a system bus  29 . In this case, the non-volatile memory  24  can be a flash memory, for example, and serves to store various information on the reproducing apparatus  10  and a user. The programs recorded in the ROM  22  will be described below.  
         [0026]     The reproducing apparatus  10  further includes a storage unit  31 . The storage unit  31  serves to store various music data (digital music data) to be reproduced as music pieces. Thus, the storage unit  31  can be a large-capacity flash memory or a small hard disk unit.  
         [0027]     The storage unit  31  is connected to the system bus  29 . The system bus  29  is connected to an interface circuit  32  so that music data is loaded from an external personal computer  51  to the microcomputer  20  through an input connector  33  and the interface circuit  32  and then stored in the storage unit  31 . The music data to be stored in the storage unit  31  can be digital audio data which has been compressed into a MP3 (MPEG (Motion Picture Experts Group)-1/Audio Layer  3 ) format or the like.  
         [0028]     The reproducing apparatus  10  also includes a reproducing circuit  34 , which is connected to the system bus  29 . The reproducing circuit  34  has a decoder for expanding the compressed music data into digital audio data, a digital to analog (D/A) converter for converting the digital audio data into an analog audio signal, and an output amplifier. When the music data is fetched from the storage unit  31 , the music data is expanded and converted into an analog audio signal. The analog audio signal is output to a headphone jack  35  to which a headphone  52  is connected.  
         [0029]     Various operation keys  36  are connected to a system bus  29 . In addition, a display device, for example, an LCD (Liquid Crystal Display)  38  is connected to the system bus  29  through a display control circuit  37 . In this case, the operation keys  36  serves to allow a user to select whether the reproducing apparatus  10  is applied as a portable player or as a walking aid device, to select an operation mode in each of the applications, to select a music piece, and to perform various setting operations. The LCD  38  serves to display a result of an operation of the operation keys  36  and information on a music piece being played.  
         [0030]     The reproducing apparatus  10  also includes a detecting unit  40  for detecting a walking tempo of a user walking carrying the reproducing apparatus  10 . The detecting unit  40  is constituted by a three-dimensional acceleration sensor  41  and an analyzing circuit  42  for analyzing an output of the three-dimensional acceleration sensor  41 . The three-dimensional acceleration sensor  41  detects body movement of the user. Then the analyzing circuit  42  analyzes a result of the detection and outputs a pulse at a tempo synchronized with walking of the user. The output of the detection of the walking tempo is loaded to the microcomputer  20  through the system bus  29 .  
         [0000]     [2] Operation  
         [0000]     [2-1] Storage of Music Data  
         [0031]     Music data of music pieces desired to be stored in the reproducing apparatus  10  is compressed and prepared in the personal computer  51 . Then, the personal computer  51  is connected to the connector  33 , and a predetermined transfer program is executed in the personal computer  51  so that transfer of the music data is instructed. Subsequently, the music data prepared in the personal computer  51  is fed to the reproducing apparatus  10  through the connector  33 . The music data is loaded to the CPU  21  through the interface circuit  32  and stored in the storage unit  31 .  
         [0032]     At this time, the CPU  21  executes a predetermined program such that a tempo of the stored music data is analyzed and registered in one of playlists provided on the basis of categories of music tempos.  
         [0033]     Referring to  FIG. 2 , examples of such playlists and contents registered therein are shown. The walking tempo (walking speed) of a user is categorized into three types: VA (a normal tempo), VB (a tempo slower than VA), and VC (a tempo other than VA and VB). Three playlists PA to PC are provided that correspond to the three types of tempos.  
         [0034]     For example, if the tempo of a music piece is within a range of ±10 percent of the normal tempo VA, the music piece is registered in the playlist PA. If the tempo of another music piece is within a range of, for example, ±10 percent of the tempo VB, the music piece is registered in the playlist PB. A music piece whose tempo corresponds to neither the playlist PA nor the playlist PB is registered in the playlist PC.  
         [0035]     In the example shown in  FIG. 2 , music titles A 1  to Aa of music pieces whose tempos are within ±10 percent of the tempo VA are registered in the playlist PA. Music titles B 1  to Bb of music pieces whose tempos are within ±10 percent of the tempo VB are registered in the playlist PB. Music titles C 1  to Cc of music pieces whose tempos are neither within ±10 percent of VA nor VB are registered in the playlist PC. These playlists PA to PC are stored in the non-volatile memory  24 , for example.  
         [0000]     [2-2] Reproducing Music as Portable Player  
         [0036]     When the reproducing apparatus  10  is used as a general portable player, an operation mode that enables a function of the portable player is selected using the operation keys  36 . When a play key among the operation keys  36  is depressed, music data stored in the storage unit  31  is read out. The read music data is fed to the reproducing circuit  34  so as to undergo data expansion and D/A conversion.  
         [0037]     Thus, an analog audio signal corresponding to the read music data is output from the reproducing circuit  34 . This analog audio signal is supplied to the headphone  52  so that a user can listen to the music piece corresponding to the music data through the headphone  52 . At this time, the title of the music piece being reproduced is displayed on the LCD  38 .  
         [0038]     The music data is read out from the storage unit  31  in accordance with a reproducing mode which has been set in advance, such that reproduction of a single music piece, or sequential or random reproduction of music pieces is executed. In such a manner as described above, the reproducing apparatus  10  can be used as a general portable player.  
         [0000]     [2-3] Reproducing Music as Walking Aid Apparatus (Part 1)  
         [0039]     When the reproducing apparatus  10  is used as a walking aid apparatus, an operation mode that enables a function of the walking aid apparatus is selected using the operation keys  36 . In this case, music pieces to be reproduced and the tempos of the music pieces are controlled in accordance with the walking tempo of a user as illustrated in diagrams I to IV shown in  FIG. 3 .  
         [0040]     The diagram I in  FIG. 3  illustrates walking tempos of the user. During a period T 1 , the user walks at the normal tempo VA. Thus, the playlist PA corresponding to the tempo VA is selected in accordance with a detection output of the detecting unit  40 . At the same time, one of the music titles A 1  to Aa that have been registered in the playlist PA (for example, Al in this case) is selected.  
         [0041]     Then, the music data corresponding to the music title Al is read from the storage unit  31  and fed to the reproducing circuit  34 . Accordingly, during the period Ti, the user is to listen to the music piece of the selected music title Al through the headphone  52 , as illustrated in the diagram II and III in  FIG. 3 .  
         [0042]     Specifically, as can be seen from  FIG. 3 , when the user is walking at the normal walking tempo VA, the music piece (title: Al, for example) of the normal tempo VA is reproduced. Thus, while walking, the user is to listen to the music piece (title: A 1 ) of the normal tempo VA that is similar to the current walking tempo VA of the user.  
         [0043]     When the music piece (title: A 1 , for example) ends during the period T 1 , another music title is selected from the playlist PA. The music data corresponding to the music title is read from the storage unit  31  so as to be reproduced. With this arrangement, music pieces having normal tempos are continuously reproduced during the period T 1 .  
         [0044]     Then the walking tempo of the user slows down to the tempo VB in a period T 2  subsequent to the period T 1 . Even in this case, the music piece (title: A 1 ), which has been performed in the period T 1 , is continued to be reproduced for a predetermined period t starting at the beginning of the period T 2  (for example, t=15 seconds).  
         [0045]     However, when the period t has elapsed since the beginning of the period T 2 , the playlist PB corresponding to the tempo VB is selected and the music title B 1 , for example, registered in the playlist PB is selected. Then, the music data corresponding to the music title B 1  is read from the storage unit  31  and fed to the reproducing circuit  34 .  
         [0046]     As can be seen from  FIG. 3 , from the time when the period t has elapsed, the music piece (title: B 1 ) corresponding to the walking tempo VB of the user is subsequently reproduced. That is, even when the user reduces his or her walking tempo, the music piece and the music tempo are not changed immediately. Instead, a music piece of a slower tempo, which corresponds to the slower walking tempo in the period T 2 , starts being reproduced when the period t has elapsed.  
         [0047]     When the user&#39;s walking tempo becomes the normal tempo VA again in a period T 3  subsequent to the period T 2 , the playlist PA corresponding to the tempo VA is selected. At the same time, the music title A 2 , for example, registered in the playlist PA is selected. Then, the music data corresponding to the music title A 2  is read from the storage unit  31  and fed to the reproducing circuit  34 .  
         [0048]     Thus, as can be seen from  FIG. 3 , at the beginning of the period T 3 , the music piece (title: A 2 ), which corresponds to the walking tempo VA, starts being reproduced. That is, when the user walks at the normal tempo VA again, a music piece of the tempo VA immediately starts being reproduced.  
         [0049]     As illustrated by a broken line in the diagram I in  
         [0050]      FIG. 3 , in a case where the user changes his or her walking tempo from the slow tempo VB to the normal tempo VA during the period t, the music piece (title: A 1 ), which has been reproduced in the period T 1  and period t, is continued to be reproduced, as shown in the diagram IV in  FIG. 3 .  
         [0051]     As described above, the reproducing apparatus  10  reproduces a music piece corresponding to a walking tempo of a user. In addition, when the walking tempo of the user changes from the normal tempo VA to the slow tempo VB, such as at the beginning of the period T 2  illustrated in  FIG. 3 , the music piece and the music tempo are changed with a delay of the predetermined period t. This arrangement prevents the user from feeling discomfort at the subsequent music piece and its tempo after the change.  
         [0052]     In addition, when the walking tempo of the user is changed from the slow tempo VB to the normal tempo VA, such as at the beginning of the period T 3 , the music piece and the music tempo are immediately changed. This arrangement prevents a music piece to be reproduced from hindering walking of the user, and thus allows the user to walk appropriately at his or her normal tempo.  
         [0000]     [2-4] Reproducing Music as Walking Aid Apparatus (Part 2)  
         [0053]     In the following, a case where a playlist PD is added to the playlists PA to PC will be described. In this playlist PD, music titles D 1  to Dd of music pieces whose tempos are slower than the normal tempo VA and faster than the tempo VB (intermediate tempo VD) are registered. For example, if the tempo of a music piece is within a range of ±10 percent of a walking tempo of a user corresponding to the tempo VD, the music piece is registered in the playlist PD.  
         [0054]     In this case, when the walking tempo of the user is changed from the normal tempo VA to the slow tempo VB, the music piece to be reproduced and the music tempo are controlled in accordance with the walking tempo, as illustrated in  FIG. 4 .  
         [0055]     Specifically, as illustrated in the figure, the user is walking at the tempo VA in the period T 1 , similarly to the case illustrated using  FIG. 3 , and the music piece [title: A 1 , for example] of the tempo VA is reproduced.  
         [0056]     However, when the walking tempo of the user slows down to the tempo VB in the period T 2  subsequent to the period T 1 , the playlist PD is selected and the music title D 1  registered in the playlist PD is selected in the predetermined period t starting at the beginning of the period T 2 . Then, music data corresponding to the selected music title D 1  is read from the storage unit  31  and fed to the reproducing circuit  34 . Thus, during the period t, the user is to listen to a music piece whose tempo is intermediate between the normal tempo VA and the slow tempo VB.  
         [0057]     When the period t has elapsed, the playlist PB corresponding to the tempo VB is selected for the period T 2 . At the same time, the music title B 1 , for example, registered in the selected playlist PB is selected. Then, the music data corresponding to the music title B 1  is read from the storage unit  31  and fed to the reproducing circuit  34 .  
         [0058]     Accordingly, as illustrated in  FIG. 4 , from time point when the period has elapsed since the beginning of the period T 2 , a music piece (title: B 1 , for example) corresponding to the current walking tempo VB starts being reproduced. That is, even when the user reduces his or her walking tempo, the music piece and the music tempo are not changed immediately. Instead, after the period t has elapsed, a music piece of a slow tempo corresponding to the walking tempo is reproduced.  
         [0059]     When the walking tempo of the user returns to the normal tempo VB in the period T 3  subsequent to the period T 2 , a music piece (title: A 2 , for example) whose tempo corresponds to the walking tempo VA start being reproduced, similarly to the case illustrated using  FIG. 3 . That is, when the user changed his or her walking tempo back to the normal tempo VA, a music piece corresponding to the tempo VA immediately starts being reproduced.  
         [0060]     As described above using  FIG. 4 , when the walking tempo of the user changes from the tempo VA to the tempo VB, the music piece whose tempo is intermediate between the tempo VA to the tempo VB is subsequently reproduced. This prevents the user from feeling discomfort at the subsequent music piece and music tempo after the change.  
         [0000]     [3-1] Example of Processing Routine (Part 1)  
         [0061]     Referring now to  FIG. 5 , a routine  100  performed by the reproducing apparatus  10  for implementing the processing illustrated using  FIG. 3  is illustrated. This routine  100  is stored in the ROM  22  and executed by the CPU  21 . At STEP  101 , a walking tempo Vi of a user is detected by the detecting unit  40 . Then, at STEP  102 , a difference between the walking tempo Vi detected in STEP  101  and a walking tempo detected at a previous time point, i.e., the change in walking tempo ΔV (ΔV=Vi−(Vi−1)), is calculated.  
         [0062]     At STEP  103 , the absolute value of ΔV calculated in STEP  102  is compared with a predetermined threshold value VTH (for example, the maximum value VTH of variation in walking tempo). If |ΔV|≦VTH, it is assumed that the value ΔV has been changed due to variation in walking tempo, and the routine returns to STEP  101 .  
         [0063]     On the other hand, if |ΔV|&gt;VTH in STEP  103 , it is assumed that the user has intentionally changed his or her walking tempo and the routine proceeds to STEP  111 . At STEP  111 , it is determined whether the ΔV is positive or negative. If ΔV&gt;0, it is indicated that the walking tempo has become faster, as in the beginning of the period T 1  and the period T 3 , and the routine proceeds to STEP  112 .  
         [0064]     At STEP  112 , a music title corresponding to the current walking tempo Vi (in this case, any one of the music title A 1  to Aa in the playlist PA) is selected. The music data corresponding to the selected music title is read from the storage unit  31  and fed to the reproducing circuit  34 . Then, the routine returns to STEP  101 . At the time when the walking tempo changes from a stop state or the slow tempo VB to the normal tempo VA, a music piece corresponding to the tempo VA starts being reproduced.  
         [0065]     On the other hand, if ΔV≦0, in STEP  111 , it is indicated that the walking tempo has become slower, as in the beginning of the period T 2 , and routine proceeds to STEP  121 . At STEP  121 , a timer TMR for checking the period t is set to 0. At STEP  122 , the timer is incremented by a predetermined amount ΔTMR, and then compared with the value t, at STEP  123 . If ΔTMR≦t, indicating that the period t has not elapsed, the routine proceeds to STEP  124 .  
         [0066]     At STEP  124 , the current walking tempo Vi of the user is detected. Then, at STEP  125 , the change ΔV in the walking tempo is calculated from Vi detected in STEP  124  and a walking tempo (Vi−1) detected at a time point preceding to the detection in STEP  124 .  
         [0067]     Subsequently, at STEP  126 , the absolute value of the change ΔV calculated in STEP  125  is compared with the maximum value VTH of variation in walking tempo. If |ΔV|≦VTH, it is indicated the change is caused by variation in walking tempo, and the routine returns to STEP  122 . Thus, if the walking tempo is maintained at the slow tempo VB during the period t, the processing of STEP  122  to STEP  126  is repeated. During this repetition period, a music piece of the normal tempo VA is reproduced and the timer TMR is incremented at a predetermined rate.  
         [0068]     When the walking tempo is maintained at the slow tempo VB and the value of the timer TMR has been incremented and become greater than t, i.e., the period t ends, the routine proceeds to STEP  127 . At STEP  127 , one of the music titles B 1  to Bb is selected from the playlist PB. Then, the music data corresponding to the selected music title is read from the storage unit  31  and fed to the reproducing circuit  34 . Then, the routine returns to STEP  101 .  
         [0069]     With this arrangement, the music piece of the slow tempo VB is reproduced when the predetermined period t has elapsed after the change of the walking tempo from the normal tempo VA to the slow tempo VB, as in the period T 2 .  
         [0070]     On the other hand, if |ΔV|&gt;VTH in STEP  126 , the routine proceeds to STEP  128 . At STEP  128 , it is determined whether the value ΔV is positive or negative. If ΔV&gt;0, indicating that the walking tempo has changed from the slow tempo VB to the normal tempo VA, and the routine proceeds to STEP  112 . At STEP  112 , one of the music titles A 1  to Aa corresponding to the normal tempo VA is selected from the playlist PA.  
         [0071]     Thus, as illustrated by the broken line in the diagram I in  FIG. 3 , when the walking tempo changes from the slow tempo VB to the normal tempo VA during the period t, reproduction of a music piece of the normal tempo VA is continued.  
         [0072]     When ΔV&lt;0, in STEP  128 , it is indicated that the walking tempo has become slower than the slow tempo VB or the user has stopped walking. In this case, the routine returns to STEP  121 .  
         [0073]     If it is determined that the walking tempo Vi is substantially zero, i.e., the user has stopped walking, a music piece can be selected from the playlist PC, or a music piece can be selected regardless of the walking tempo, since there is no music piece whose tempo is zero.  
         [0074]     Thus, according to this routine  100  described above, the music pieces and music tempos can be changed in accordance with the walking tempo of the user, as illustrated in  FIG. 3 .  
         [0000]     [3-2] Example of Processing Routing (Part 2)  
         [0075]      FIG. 6  illustrates a routine  100  performed by the reproducing apparatus  10  for implementing the processing described above with reference to  FIG. 4 . The routine  100  in this example includes processing of STEP  131  in addition to the routine  100  for described above with using in  FIG. 3 . Specifically, if ΔV&lt;0 in STEP  111  (in the beginning of the period T 2  in  FIG. 4 ), the routine proceeds to STEP  131 .  
         [0076]     At STEP  131  one of the music titles D 1  to Dd is selected from the playlist PD. Then, the music data corresponding to the selected music title is read from the storage unit  31  and fed to the reproducing circuit  34 . Then, the routine proceeds to STEP  121 . Thus, the music piece corresponding to the music title registered in the playlist PD is reproduced when the period t begins. Thereafter, the processing of STEP  121  to  126  is executed, similarly to the routine  100  illustrated in  FIG. 5 .  
         [0077]     If the user maintains the slow walking tempo VB after the period t ends, the routine proceeds from STEP  123  to STEP  127 . Thus, any one of the music pieces corresponding to the music titles registered in the playlist PB starts being reproduced at the end of the period t. When the walking tempo is changed before the period t ends so that |ΔV|&gt;VTH is satisfied before the period t ends, the routine proceeds similarly to the case illustrated using  FIG. 5 .  
         [0078]     As described above using  FIG. 6 , the music pieces and music tempos can be changed in accordance with the walking tempo of the user, according to the routine  100  illustrated in  FIG. 6 .  
         [0000]     [4] Other Implementations  
         [0079]     In the foregoing, the case is described in which when the walking tempo of a user changes to a relatively slow tempo, a music piece being reproduced is changed to another music piece of a different tempo with a delay of the predetermined period t. In contrast, however, it can also be configured that when the walking tempo is change to a relatively fast tempo, a music piece being reproduced changes to another music piece having a different tempo with a delay of the predetermined period t.  
         [0080]     In addition, when the walking tempo Vi is detected in each of STEP  101  and STEP  124 , the average walking tempo over several seconds can be obtained. With this arrangement, the influence of disturbance and an instantaneous change in the walking tempo can be reduced or become ignorable. The playlists PA to PD can also be stored in the storage unit  31 . Moreover, the case is described above in which another tempo is applied in the period t as an intermediate tempo between the tempo VA and the tempo VB (i.e., the tempo VD), as illustrated using  FIG. 4 . However, a plurality of such intermediate tempos can also be applied.  
         [0081]     Furthermore, in a case where the user walking at the tempo VA or the tempo VB stops walking, a period similar to the period t illustrated in  FIG. 3  or  FIG. 4  can be provided. In this case, the period starts at the time point when the user stops walking. During the period, a music piece of the tempo VB or a music piece whose tempo is slower than the tempo VB can be reproduced. It can also be configured such that silence is maintained during the period. Moreover, music pieces to be selected from each of the playlists PA and PB can be arranged so as to be reproduced in the order of the titles or at random. These music pieces can also be arranged so that one music piece is repeated. In addition, the user can designate music pieces to be reproduced.  
         [0082]     The acceleration sensor  41  can be provided inside the reproducing apparatus  10 . However, the acceleration sensor  41  can also be separated from the reproducing apparatus  10  and mounted on the headphone  52 , for example. In this case, the detection signal of the acceleration sensor  41  can be sent to the analyzing circuit  42  through a wired or wireless connection. Specifically, a communication unit and the detecting means  40  are stored in a case separated from the storage unit  31 , the reproducing circuit  34 , the microcomputer  20 , etc. Thus, using the communication unit, detection information of the detecting unit  40  can be sent to the microcomputer  20 .  
         [0083]     Instead of the acceleration sensor  41 , a sensing device such as a velocity sensor, a pedometer, a gyro, and a GPS (Global Positioning System) can be employed. Further, the detecting unit  40  is not limited to being mounted on the body of a user. The detecting unit  40  can be carried in a pocket of the user&#39;s clothing or in the user&#39;s bag, as long as the unit can detect the walking tempo of the user.  
         [0084]     It is also possible that music data is incorporated into digital video data. Further, as described in the foregoing, music data is changed to another when the amount of change in the walking tempo exceeds the threshold value VTH. This change can be validated or invalidated by setting of the user. In this case, the user can set an amount of the threshold value VTH. The user can also set a plurality of threshold values VTHs so as to appropriately apply each of the threshold values.  
         [0085]     In the foregoing, the case is described in which the threshold value VTH is set using an absolute value of a walking tempo. However, it is also possible that the threshold value VTH is changed using an absolute value or set as a percentage of a walking tempo. Further, if a step with a predetermined weight is added to each of the procedure from STEP  101  to STEP  103  and the procedure from STEP  122  to STEP  126 , a time interval for the change ΔV can be set to a desired value.  
         [0086]     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.