Speech synthesis apparatus having prosody generator with user-set speech-rate- or adjusted phoneme-duration-dependent selective vowel devoicing

• US 6,470,316 B1
• Filed: 03/03/2000
• Issued: 10/22/2002
• Est. Priority Date: 04/23/1999
• Status: Expired due to Term

• Current Assignee: Rakuten, Inc. (Rakuten Group, Inc.)
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Chihara, Keiichi
• Primary Examiner(s): SMITS, TALIVALDIS IVARS
• Application Number:
  US09/518,275
• Time in Patent Office: 963 Days
• Field of Search: 704/260, 704/267
• US Class Current: 704/267
• CPC Class Codes: G10L 13/033 Voice editing, e.g. manipulating the voice of the synthesiser

Abstract

The speech synthesis apparatus according to the present invention includes a text analyzer operable to generate a phonetic and prosodic symbol string from text information of an input text; a word dictionary storing a reading and accent of a word; a voice segment dictionary storing a phoneme that is a basic unit of speech; a prosody generator operable to generate synthesizing parameters including at least a phoneme, a duration of the phoneme and a fundamental frequency for the phonetic and prosodic symbol string, the prosody generator including a vowel devoicing determining means operable to determine whether or not a vowel devoicing process is to be performed and a duration modifying means operable to modify the duration of the phoneme depending on a speech rate set by a user, the vowel devoicing determining means determining that the vowel devoicing process is not performed when the set speech rate is slower than a predetermined rate; and a waveform generator operable to generate a synthesized waveform by making waveform overlap-adding referring to the synthesizing parameters generated by the prosody generator and the voice segment dictionary.

Claims

1. A speech synthesis apparatus comprising:

a text analyzer operable to generate a phonetic and prosodic symbol string from character information of an input text;

a word dictionary storing a reading and accent of a word;

a voice segment dictionary storing a phoneme that is a basic unit of speech;

a prosody generator operable to generate synthesizing parameters including at least a phoneme, a duration of the phoneme and a fundamental frequency for the phonetic and prosodic symbol string, the prosody generator including a vowel devoicing determining means operable to determine whether or not a vowel devoicing process is to be performed and a duration modifying means operable to modify the duration of the phoneme depending on a speech rate set by a user, the vowel devoicing determining means determining that the vowel devoicing process is not devoiced when the set speech rate is slower than a predetermined rate; and

a waveform generator operable to generate a synthesized waveform by making waveform-overlap-adding referring to the synthesizing parameters generated by the prosody generator and the voice segment dictionary.

2. A speech synthesis apparatus according to claim 1, wherein the vowel devoicing determining means comprises:

a first determining means operable to make a first determination of devoicing a vowel using the input text such as a character-type and the accent, as a standard; and

a second determining means operable to make a final determination of devoicing the vowel based on a result of the determination by the first determining means and the speech rate set by the user.

3. A speech synthesis apparatus according to claim 1, wherein a threshold value used by the vowel devoicing determining means for determining that the vowel devoicing process is not performed can be set by the user.

4. A speech synthesis apparatus according to claim 1, wherein a threshold value used by the vowel devoicing determining means for determining that the vowel determining process is not performed is half of a normal speech rate.

5. A speech synthesis apparatus comprising:

a text analyzer operable to generate a phonetic and prosodic symbol string from character information of an input text;

a word dictionary storing a reading and accent of a word;

a voice segment dictionary storing a phoneme that is a unit of speech;

a prosody generator operable to generate synthesizing parameters including at least a phoneme, a duration of the phoneme and a fundamental frequency for the phonetic and prosodic symbol string, the prosody generator including a vowel devoicing determining means operable to determine whether or not a vowel devoicing process is performed and a duration modifying means operable to modify the duration of the phoneme depending on a speech rate set by a user and a result of the determination by the vowel devoicing determining means, wherein the duration modifying means does not stretch the duration of the phoneme for a voiceless sound beyond a predetermined limitation value; and

a waveform generator operable to generate a synthesized waveform by making waveform-overlap-adding referring to the synthesizing parameters generated by the prosody generator and the voice segment dictionary.

6. A speech synthesis apparatus according to claim 5, wherein the duration modifying means has a changeable limitation value depending on a type of the voiceless consonant.

7. A speech synthesis apparatus according to claim 5, wherein the duration modifying means has a changeable limitation value depending on a length of the phoneme stored in the voice segment dictionary.