Abstract:
Herein disclosed a speech synthesis apparatus for and a speech synthesis method of synthesizing a speech in accordance with text data inputted therein to output a speech consisting of recorded speech portions and synthesized speech portions with reverberation properties identical to those of the recorded speech portions in which the synthesized speech portions with reverberation properties is substantially greater in the amplitude than the recorded speech portions to reduce a feeling of strangeness due to the difference in sound quality between the recorded speech portions and the synthesized speech portions.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a speech synthesis apparatus for and a speech synthesis method of synthesizing a speech in accordance with text data inputted therein, and more particularly, to a speech synthesis apparatus for and a speech synthesis method of synthesizing a speech in accordance with text data inputted therein to output a speech consisting of recorded speech portions and synthesized speech portions with reverberation properties identical to those of the recorded speech portions to reduce a feeling of strangeness due to the difference in sound quality between the recorded speech portions and the synthesized speech portions.  
           [0003]    2. Description of the Related Art  
           [0004]    In recent years, there have been developed and used various kinds of speech synthesis apparatuses for synthesizing a speech in accordance with text data inputted therein. The speech synthesis apparatus of this type, in general, comprises a database, and is operative to divide a speech in a certain language into a plurality of speech segments each including at least one phoneme in the language, disassemble each of the speech segments into a plurality of pitch waveforms, associate the pitch waveforms with each of the speech segments, and then store each of the speech segments associated with the pitch waveforms in the database. The pitch waveforms thus stored in association with each of the speech segments in the database are used when the speech is synthesized.  
           [0005]    On of such conventional speech synthesis apparatus is disclosed, for example, in Japanese Patent Application Laid-Open Publication No 27789/1993.  
           [0006]    Referring to FIG. 5 of the drawing, there is shown a conventional speech synthesis apparatus  500  comprising text inputting means  501 , text judging means  502 , synthesizing method selecting means  503 , synthesizing means  504 , reproducing means  505 , speech overlapping means  506 , and outputting means  507 .  
           [0007]    The text inputting means  501  is adapted to input text data. The text judging means  502  is adapted to disassemble the text data, for example, “this is a pen” inputted by the text inputting means  501  into a plurality of text data elements, for example, “this”, “is”, “a”, and “pen”, and analyze each of the text data elements. The synthesizing method selecting means  503  is adapted to select a synthesizing method for each of the text data elements on the basis of the analysis made by the text judging means  502  from among a synthesizing method and a reproducing method. The synthesizing method selecting means  503  is then operated to output text data elements, for example, “a” and “pen” selected for the synthesizing method to the synthesizing means  504  and text data elements, for example, “this”, and “is” selected for the reproducing method to the reproducing means  505 . The synthesizing means  504  is adapted to generate synthesized speech portions in accordance with the text data elements, i.e., “a” and “pen” inputted from the synthesizing method selecting means  503 . The reproducing means  505  is adapted to reproduce recorded speech portions in accordance with the text data elements, i.e., “this” and “is” inputted from the synthesizing method selecting means  503 .  
           [0008]    The speech overlapping means  506  is adapted to input and overlap the waveforms of, the synthesized speech portions generated by the synthesizing means  504  and the recorded speech portions reproduced by the reproducing means  505  to output a speech “this is a pen” consisting of the recorded speech portions representative of “this” and “is” and the synthesized speech portions representative of “a” and “pen”. The outputting means  507  is adapted to output the speech inputted from the speech overlapping means  506  to an external device such as a speaker, not shown.  
           [0009]    The conventional speech synthesis apparatus  500  thus constructed can synthesize a speech consisting of recorded speech portions and synthesized speech portions in accordance with text data inputted therein. Furthermore, the conventional speech synthesis apparatus  500  mentioned above in part reproduces the recorded speech portions, for example, “this” and “is”, which are recorded natural voices, thereby making it possible to synthesize a speech similar to a natural speech, which is articulate to a listener.  
           [0010]    The conventional speech synthesis apparatus  500 , however, entails such a problem that the recorded speech portions and the synthesized speech portions constituting the same speech are different in sound quality. The difference in sound quality between the recorded speech portions and the synthesized speech portions may cause a listener to be bothered by a feeling of strangeness. The larger the difference in sound quality between the recorded speech portions and the synthesized speech portions becomes, the more the listener is required to carefully listen to the speech, thereby exhausting his or her concentration on comprehending the speech.  
           [0011]    Every natural sound has sounds persisting after the sound source has been cut off because of repeated reflections. The sounds persisting after the sound source has been cut off are hereinlater referred to as “reverberations”. The synthesized speech portions have no reverberations while, on the other hand, the recorded speech portions have reverberations. The aforesaid difference in sound quality partly results from the difference in presence or absence of reverberations between the recorded speech portions and the synthesized speech portions. This means that the difference in presence or absence of reverberations between the recorded speech portions and the synthesized speech portions may cause a listener to be bothered by a feeling of strangeness. The larger the difference becomes, the more a listener is required to carefully listen to the speech, thereby exhausting his or her concentration on comprehending the speech.  
           [0012]    Further, the synthesized speech portions are more inarticulate than the recorded speech portions. The aforesaid difference in sound quality additionally results from the difference in articulation between the recorded speech portions and the synthesized speech portions. This means that the difference in articulation between the recorded speech portions and the synthesized speech portions may cause a listener to be bothered by a feeling of strangeness. The larger the difference becomes, the more a listener is required to carefully listen to the speech, thereby exhausting his or her concentration on comprehending the speech.  
           [0013]    The present invention is made with a view to overcoming the previously mentioned drawback inherent to the conventional speech synthesis apparatus.  
         SUMMARY OF THE INVENTION  
         [0014]    It is therefore an object of the present invention to provide a speech synthesis apparatus for synthesizing a speech consisting of recorded speech portions and synthesized speech portions with reverberation properties identical to those of the recorded speech portions in accordance with text data inputted therein. The speech synthesis apparatus according to the present invention can synthesize a speech in which the difference in reverberations between the recorded speech portions and the synthesized speech portions is significantly reduced, thereby assisting a listener to attentively and comfortably listen to the speech.  
           [0015]    It is another object of the present invention to provide a speech synthesis apparatus for synthesizing a speech consisting of recorded speech portions and synthesized speech portions with reverberation properties in which the synthesized speech portions with reverberation properties is substantially greater in the amplitude than the recorded speech portions. The synthesized speech portions with reverberation properties thus adjusted is improved in the articulation. This means that the speech synthesis apparatus according to the present invention can synthesize a speech in which the difference in articulation between the recorded speech portions and the synthesized speech portions is significantly reduced, thereby assisting a listener to attentively and comfortably listen to the speech.  
           [0016]    It is a further object of the present invention to provide a speech synthesis method of synthesizing a speech consisting of recorded speech portions and synthesized speech portions with reverberation properties identical to those of the recorded speech portions in accordance with text data inputted therein. The speech synthesis method according to the present invention can synthesize a speech in which the difference in reverberations between the recorded speech portions and the synthesized speech portions is significantly reduced, thereby assisting a listener to attentively and comfortably listen to the speech.  
           [0017]    It is a still further object of the present invention to provide a speech synthesis method of synthesizing a speech consisting of recorded speech portions and synthesized speech portions with reverberation properties in which the synthesized speech portions with reverberation properties is substantially greater in the amplitude than the recorded speech portions. The synthesized speech portions with reverberation properties thus adjusted is improved in the articulation. This means that the speech synthesis apparatus according to the present invention can synthesize a speech in which the difference in articulation between the recorded speech portions and the synthesized speech portions is significantly reduced, thereby assisting a listener to attentively and comfortably listen to the speech. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    The features and advantages of a speech synthesis apparatus and a speech synthesis method according to the present invention will more clearly be understood from the following description taken in conjunction with the accompanying drawings in which:  
         [0019]    [0019]FIG. 1 is a block diagram of a first embodiment of the speech synthesis apparatus  100  according to the present invention;  
         [0020]    [0020]FIG. 2 is a flowchart showing a speech synthesis method performed by the speech synthesis apparatus  100  shown in FIG. 1;  
         [0021]    [0021]FIG. 3 is a block diagram of a second embodiment of the speech synthesis apparatus  200  according to the present invention;  
         [0022]    [0022]FIG. 4 is a flowchart showing a speech synthesis method performed by the speech synthesis apparatus  200  shown in FIG. 3; and  
         [0023]    [0023]FIG. 5 is a block diagram of a conventional speech synthesis apparatus  500 .  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    Referring to the drawings, in particular FIGS. 1 and 2, there is shown a first embodiment of the speech synthesis apparatus  100  for synthesizing a speech in accordance with text data inputted therein embodying the present invention. The first embodiment to the speech synthesis apparatus  100  thus shown in FIG. 1 comprises text storage means  101 , speech portion storage means  102 , speech segment storage means  103 , text inputting means  104 , judging means  105 , dividing means  106 , recorded speech loading means  107 , speech synthesizing means  108 , reverberation property imparting means  109 , speech overlapping means  110 , and speech outputting means  111 .  
         [0025]    The text storage means  101  is adapted to store a plurality of recorded text data elements therein, which will be described later. The speech portion storage means  102  is adapted to store a plurality of recorded speech portions respectively corresponding to the recorded text data elements therein. The speech segment storage means  103  is adapted to store a plurality of speech segments. Here, a speech segment is intended to mean a segment of a speech including at least one phoneme. The text inputting means  104  is adapted to input the text data.  
         [0026]    The judging means  105  is adapted to input the text data from the text inputting means  104  and disassemble the text data into a plurality of text data elements. Here, a text data element is intended to mean a component unit of text data.  
         [0027]    The judging means  105  is then operated to judge whether or not the text data elements are identical to any one of the recorded text data elements stored in the text storage means  101  one text data element after another. The dividing means  106  is adapted to divide the text data elements into two text portions consisting of a recorded text portion including recorded text data elements identical to the text data elements stored in the text storage means  101  and a non-recorded text portion including non-recorded text data elements identical to the text data elements not stored in the text storage means  101  on the basis of the results made by the judging means  105 .  
         [0028]    The recorded speech loading means  107  is adapted to input the recorded text portion including the recorded text data elements identical to the text data elements divided by the dividing means  106 , and selectively load recorded speech portions respectively corresponding to the recorded text data elements of the recorded text portion from among recorded speech portions stored in the speech portion storage means  102 .  
         [0029]    The speech synthesizing means  108  is adapted to input the non-recorded text portion including the non-recorded text data elements identical to the text data elements divided by the dividing means  106 , and synthesize the speech segments stored in the speech segment storage means  103  in accordance with the non-recorded text data elements of the non-recorded text portion to generate synthesized speech portions.  
         [0030]    The reverberation property imparting means  109  is adapted to impart reverberation properties identical to those of the recorded speech portions stored in the speech portion storage means  102  to the synthesized speech portions generated by the speech synthesizing means  108  so as to construct synthesized speech portions with the reverberation properties.  
         [0031]    The speech overlapping means  110  is adapted to overlap the recorded speech portions loaded by the recorded speech loading means  107  and the synthesized speech portions with the reverberation properties constructed by the reverberation property imparting means  109  to generate a speech consisting of the recorded speech portions and the synthesized speech portions with reverberation properties.  
         [0032]    The speech outputting means  111  is adapted to output the speech consisting of the recorded speech portions and the synthesized speech portions with reverberation properties thus overlapped by the speech overlapping means  110 .  
         [0033]    The operation of the speech synthesis apparatus  100  will then be described with reference to FIG. 2.  
         [0034]    It is assumed that the text inputting means  104  is operated to input text data, “this is a pen”, the judging means  105  is operated to disassemble the text data “this is a pen” into a plurality of text data elements, “this”, “is”, “a”, and “pen”, and the text data elements, “this” and “is” are already stored in the text storage means  101  for the purpose of simplifying the description and assisting in understanding about the whole operation of the speech synthesis apparatus  100 . The text data, however, is not limited to “this is a pen”, nor are the text data elements limited to “this is a pen”, and “this”, “is”, “a”, and “pen” according to the present invention.  
         [0035]    In the step S 201 , the text inputting means  104  is operated to input text data, i.e., “this is a pen”. The step S 201  goes forward to the step S 202  in which the judging means  105  is operated to input the text data, “this is a pen”, from the text inputting means  104  and disassemble the text data into a plurality of component units of text data elements, i.e., “this”, “is”, “a”, “pen”. The judging means  105  is then operated to judge whether or not the text data elements are identical to any one of the recorded text data elements stored in the text storage means  101  one text data element after another. In this embodiment, as mentioned above, the text data elements, “this” and “is” are stored in the text storage means  101 . The judging means  105  is, therefore, operated to judge that the text data elements, “this” and “is” are identical to any one of the recorded text data elements stored in the text storage means  101 . The dividing means  106  is operated to divide the text data elements, “this is a pen” into two text portions consisting of a recorded text portion including recorded text data elements identical to the text data elements, “this” and “is” stored in the text storage means  101  and a non-recorded text portion including non-recorded text data elements identical to the text data elements, “a” and “pen” not stored in the text storage means  101  on the basis of the results made by the judging means  105 . This means that the recorded text data portion includes recorded text data elements, “this” and “is” and the non-recorded text data portion includes non-recorded text data elements “a” and “pen” at this stage.  
         [0036]    The operation performed in the step S 202  will be described in detail.  
         [0037]    In the step  202 , the judging means  105 , for example, judges that a text data element, for example, “this” is identical to any one of the recorded text data element stored in the text storage means  101 , the dividing means  106  is then operated to divide the text data element “this” into a recorded text portion including recorded text data element identical to the text data element “this” stored in the text storage means  101  on the basis of the results made by the judging means  105 , and output the recorded text data element “this” to the recorded speech loading means  107 .  
         [0038]    The judging means  105 , on the other hand, judges that a text data element, for example, “a” is not identical to any one of the recorded text data element stored in the text storage means  101 , the dividing means  106  is then operated to divide the text data element “a” into a non-recorded text portion including non-text data element identical to text data element “a” not stored in the text storage means  101  on the basis of the results made by the judging means  105 , and output the non-recorded text data element “a” to the speech synthesizing means  108 .  
         [0039]    In the step S 203 , the recorded speech loading means  107  is operated to input the recorded text potion including the recorded text data elements, i.e., “this” and “is” divided by the dividing means  106 , and selectively load recorded speech portions respectively corresponding to the recorded text data elements, i.e., “this” and “is” of the recorded text portion from among recorded speech portions stored in the speech portion storage means  102 .  
         [0040]    In the step S 204 , the speech synthesizing means  108  is operated to input non-recorded text portion including the non-recorded text data elements, i.e., “a” and “pen” divided by the dividing means  106 , and synthesizing the speech segments stored in the speech segment storage means  103  in accordance with the non-recorded text data elements, i.e., “a” and “pen” of the non-recorded text portion to generate synthesized speech portions.  
         [0041]    The following description will be directed to the operation of the speech segment storage means  103  and the speech synthesizing means  108 .  
         [0042]    The speech segment storage means  103  is operative to store a plurality of speech segments each including at least one phoneme, and divisible into a plurality of pitch waveforms. In the speech segment storage means  103 , the speech segments are respectively associated with the pitch waveforms with respect to the phonemes. The speech synthesizing means  108  is operated to synthesize the speech segments thus stored in the speech segment storage means  103  by superimposing the pitch waveforms associated with the speech segments with respect to the phonemes in accordance with the non-text data elements, i.e., “a” and “pen” of the non-recorded text portion divided by the dividing means  106  to generate synthesized speech portions representative of the text data elements, i.e., “a” and “pen”.  
         [0043]    The step S 204  goes forward to the step S 205  in which the reverberation property imparting means  109  is operated to impart reverberation properties identical to those of the recorded speech portions stored in the speech portion storage means  102  to the synthesized speech portions generated by the speech synthesizing means  108  so as to construct synthesized speech portions with the reverberation properties. The reverberation properties are intended to mean the properties of reverberations inherent to the recorded speech portions. More particularly, the reverberation properties of the recorded speech portions stored in the speech portion storage means  102  have been measured beforehand. The reverberation property imparting means  109  is operated to impart reverberation properties identical to those of the recorded speech portions on the basis of the reverberation properties of the recorded speech portions stored in the speech portion storage means  102  thus measured beforehand, to the synthesized speech portions.  
         [0044]    The step S 203  and the step S 205  go forward to the step S 206  in which it is judged whether all text data has been inputted or not. According to the present invention, the judgment whether all text data has been inputted or not can be made by any appropriate constituent parts such as, for example, the speech overlapping means  110 . It is, for example, judged that all text data has not yet been inputted, the step S 206  returns to the step S 202  and the above processed in the steps from S 202  to S 206  will be repeated for the remaining text data elements one text data element after another.  
         [0045]    It is, on the other hand, judged that all text data has been inputted, the step S 206  goes forward to the step S 207  in which the speech overlapping means  110  is operated to overlap the recorded speech portions thus loaded by the recorded speech loading means  107  and the synthesized speech portions with the reverberation properties thus constructed by the reverberation property imparting means  109  one text data element after another to generate a speech consisting of the recorded speech portions and the synthesized speech portions with reverberation properties. According to the present invention, the speech overlapping means  110  may overlap the recorded speech portions and the synthesized speech portions by superimposing the pitch waveforms associated with the recorded speech portion and the synthesized speech portions in accordance with the text data elements.  
         [0046]    The step S 207  goes forward to the step S 208  in which the speech overlapping means  110  outputs the speech consisting of the recorded speech portions and the synthesized speech portions thus overlapped to the speech outputting means  111 . The speech outputting means  111  is then operated to output the speech consisting of the recorded speech portions and the synthesized speech portions with reverberation properties thus overlapped by the speech overlapping means  110  to an external device such as, for example, a speaker, not shown.  
         [0047]    As will be seen from the foregoing description, it is to be understood that the speech synthesis apparatus  100  according to the present invention makes it possible to synthesize a speech in which the difference in reverberations between the recorded speech portions and the synthesized speech portions is significantly reduced, thereby assisting a listener to attentively and comfortably listen to the speech.  
         [0048]    Referring to the drawings, in particular FIGS. 3 and 4, there is shown a second embodiment of the speech synthesis apparatus  200  for synthesizing a speech in accordance with text data inputted therein embodying the present invention. The second embodiment of the speech synthesis apparatus  200 , as shown in FIG. 3 comprises text storage means  101 , speech portion storage means  102 , speech segment storage means  103 , text inputting means  104 , judging means  105 , dividing means  106 , recorded speech loading means  107 , speech synthesizing means  108 , reverberation property imparting means  109 , noise measurement means  210 , speech overlapping means  110 , and speech outputting means  111 . The reverberation property imparting means  109  further includes amplitude adjusting means  209 .  
         [0049]    The second embodiment of the speech synthesis apparatus  200  is almost the same in construction as the first embodiment of the speech synthesis apparatus  100  except for the amplitude adjusting means  209  and the noise measurement means  210 . The parts same as the first embodiment of the speech synthesis apparatus  100  are not described in detail.  
         [0050]    The noise measurement means  210  is adapted to measure a noise level in the environment in which the speech is audibly outputted. The amplitude adjusting means  209  is adapted to adjust the amplitude of the synthesized speech portions with the reverberation properties constructed by the reverberation property imparting means  109  on the basis of the noise level measured by the noise measurement means  210  and the amplitude of the recorded speech portions loaded by the recorded speech loading means  107  to the degree that the synthesized speech portions with the reverberation properties is substantially greater in the amplitude than the recorded speech portions in proportion to the noise level.  
         [0051]    The operation of the speech synthesis apparatus  200  will be described in detail with reference to FIG. 4. The operation of the speech synthesis apparatus  200  is almost the same as that of speech synthesis apparatus  100  except for the step S 210 . The steps same as those of the speech synthesis apparatus  100  are not described in detail.  
         [0052]    In the step S 210 , the noise measurement means  210  is operated to measure a noise level in the environment in which the speech is audibly outputted. The amplitude adjusting means  209  is then operated to adjust the amplitude of the synthesized speech portions with the reverberation properties constructed by the reverberation property imparting means  109  on the basis of the noise level measured by the noise measurement means  210  and the amplitude of the recorded speech portions loaded by the recorded speech loading means  107  to the degree that the synthesized speech portions with the reverberation properties is substantially greater in the amplitude than the recorded speech portions in proportion to the noise level.  
         [0053]    The difference in articulation between the recorded speech portions and the synthesized speech portions is large if the noise level in the environment in which the speech is audibly outputted is high while, on the other hand, the difference in articulation between the recorded speech portions and the synthesized speech portions is small if the noise level in the environment in which the speech is audibly outputted is low.  
         [0054]    This means that the amplitude adjusting means  209  is operated to increase the amplitude of the synthesized speech portions with the reverberation properties to the degree that the amplitude of the synthesized speech portions with the reverberation properties becomes much greater than that of the recorded speech portions so that the synthesized speech portions will be articulate enough for a listener to comprehend in comparison with the recorded speech portions if the noise level is high. The amplitude adjusting means  209 , on the other hand, is operated to increase the amplitude of the synthesized speech portions with the reverberation properties to the degree that the amplitude of the synthesized speech portions with the reverberation properties becomes slightly greater than that of the recorded speech portions so that the synthesized speech portions will be articulate enough for a listener to comprehend in comparison with the recorded speech portions if the noise level is low.  
         [0055]    The step S 203  and the step S 210  goes forward to the step S 206  in which it is judged whether all text data has been inputted or not. It is, for example, judged that all text data has not yet been inputted, the step S 206  returns to the steps S 202  and the above processes in the steps from S 202  to S 206  will be repeated for the remaining text data elements one text data element after another.  
         [0056]    It is, on the other hand, judged that all text data has been inputted, the step S 206  goes forward to the step S 207  in which the speech overlapping means  110  is operated to overlap the recorded speech portions thus loaded by the recorded speech loading means  107  and the synthesized speech portions with the reverberation properties thus adjusted by the amplitude adjusting means  209  one text data element after another to generate a speech consisting of the recorded speech portions and the synthesized speech portions with reverberation properties.  
         [0057]    The step S 207  goes forward to the step S 208  in which the speech overlapping means  110  outputs the speech consisting of the recorded speech portions and the synthesized speech portions thus overlapped to the speech outputting means  111 . The speech outputting means  111  is then operated to output the speech consisting of the recorded speech portions and the synthesized speech portions with reverberation properties thus overlapped by the speech overlapping means  110  to an external device such as, for example, a speaker, not shown.  
         [0058]    As will be seen from the foregoing description, it is to be understood that the speech synthesis apparatus according to the present invention makes it possible to synthesize a speech in which the difference in articulation between the recorded speech portions and the synthesized speech portions is significantly reduced, thereby assisting a listener to attentively and comfortably listen to the speech.  
         [0059]    The many features and advantages of the invention are apparent from the detailed specification, and thus it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope thereof. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described herein, and accordingly, all suitable modifications and equivalents may be construed as being encompassed within the scope of the invention.