Speech signal modification and concatenation method by gradually changing speech parameters

• US 6,591,240 B1
• Filed: 09/25/1996
• Issued: 07/08/2003
• Est. Priority Date: 09/26/1995
• Status: Expired due to Fees

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Abe, Masanobu
• Primary Examiner(s): Dorvil, Richemond
• Assistant Examiner(s): Opsasnick, Michael N.
• Application Number:
  US08/721,577
• Time in Patent Office: 2,477 Days
• Field of Search: 704/258, 704/265, 704/266, 704/268, 704/269
• US Class Current: 704/278
• CPC Class Codes: G10L 13/033 Voice editing, e.g. manipulating the voice of the synthesiser

Abstract

A speech signal modification and concatenation method is provided, in which spoken messages having different voice characteristics can be concatenated without causing a sense of incompatibility, and it is possible to efficiently perform addition or modification of spoken messages. In the speech signal modification and concatenation method, when two speech signals having different voice characteristics are concatenated, the speech signals are concatenated by modifying a parameter indicating a character of speech signals in a manner such that the parameter is gradually changed from a value indicating a feature of one of the speech signals to a value indicating a feature of the other speech signal over a predetermined period. Accordingly, a time-scaled change of a feature amount of spoken sounds can be performed; thus, even if two speech signals of different speakers are concatenated, it is possible to avoid an abrupt change of voice characteristics in the concatenation section, and thus possible to concatenate speech signals without causing a sense of incompatibility to listeners.

Claims

1. A speech signal modification and concatenation method for concatenating two spoken speech signals having different speaker individuality, each spoken speech signal consisting of a plurality of phonemes and communicating a predetermined message including a plurality of words, said method comprising the step of:

concatenating the speech signals by modifying a parameter indicating a characteristic of the speech signals in a manner such that the parameter is gradually changed from a value indicating a feature of one of the speech signals to a value indicating a feature of the other speech signal over a predetermined period, the concatenated signal having a first section corresponding to the one of the speech signals, a second section corresponding to said predetermined period, and a third section corresponding to the other speech signal, wherein a listener listening to a spoken message including a plurality of words hears said first, second, and third sections in turn.

2. A speech signal modification and concatenation method as claimed in claim 1, wherein the modification of the parameter is performed by using two kinds of speech data, the data being obtained by making two speakers who have the different voice characteristics read the same text aloud over the predetermined period for the change of the parameter.

3. A speech signal modification and concatenation method as claimed in claim 1, wherein the two speech signals having different voice characteristics are obtained by vocalizations of speech-synthesis devices.

4. A speech signal modification and concatenation method as claimed in claim 1, wherein one of the two speech signals having different voice characteristics is obtained by vocalizations of a human and the other speech signal is obtained by vocalizations of a speech-synthesis device.

5. A speech signal modification and concatenation method as claimed in claim 1, wherein the parameter is a spectrum of spoken sounds, and the spectrum is gradually changed over the predetermined period.

6. A speech signal modification and concatenation method as claimed in claim 5, wherein the change of the spectrum comprises the steps of:

in a phoneme which corresponds to the two speech signals, determining each pitch correspondence between the two signals;

generating a spectrum, for every corresponding pitch, by combining, with respect to a boundary frequency, a portion above the boundary frequency among the spectrum of one speech signal and a portion below the boundary frequency among the spectrum of the other speech signal, and determining the generated spectrum as a spectrum at the relevant pitch; and

with respect to the generation of spectra, changing the boundary frequency for each unit time.

7. A speech signal modification and concatenation method as claimed in claim 6, wherein the change of the boundary frequency is performed such that the boundary frequency increases by a fixed amount for each unit time.

8. A speech signal modification and concatenation method as claimed in claim 6, wherein the change of the boundary frequency is performed such that:

the boundary frequency gradually increases from a value at the start of change to a value at the end of change; and

the rate of change is lower in a stage of relatively low boundary frequencies near the start of change, while the rate of change is higher in a stage of relatively high boundary frequencies near the end of change.

9. A speech signal modification and concatenation method as claimed in claim 1, wherein the parameter is a fundamental frequency of spoken sounds, and the fundamental frequency is gradually changed in the predetermined period.

10. A speech signal modification and concatenation method as claimed in claim 9, wherein the change of the fundamental frequency comprises the steps of:

calculating an average fundamental frequency of each speech signal;

determining a frequency value to be changed per unit time for the fundamental frequency, based on the difference between the two average fundamental frequencies and the predetermined period for the change of the parameter; and

with the determined value as a unit of the amount of change, changing the fundamental frequency for each unit time such that the fundamental frequency is modified from the average fundamental frequency of one speech signal to that of the other speech signal.

11. A speech signal modification and concatenation method as claimed in claim 1, wherein each of a spectrum of spoken sounds and a fundamental frequency of spoken sounds is used as the parameter, and:

the change of the spectrum comprises the steps of;

in a phoneme which corresponds to the two speech signals, determining each pitch correspondence between the two signals;

generating a spectrum, for every corresponding pitch, by combining, with respect to a boundary frequency, a portion above the boundary frequency among the spectrum of one speech signal and a portion below the boundary frequency among the spectrum of the other speech signal, and determining the generated spectrum as a spectrum at the relevant pitch; and

with respect to the generation of spectra, changing the boundary frequency for each unit time, and

the change of the fundamental frequency comprises the steps of;

calculating an average fundamental frequency of each speech signal;

determining a frequency value to be changed per unit time for the fundamental frequency, based on the difference between the two average fundamental frequencies and the predetermined period for the change of the parameter; and

with the determined value as a unit of the amount of change, changing the fundamental frequency for each unit time such that the fundamental frequency is modified from the average fundamental frequency of one speech signal to that of the other speech signal.

12. A speech signal modification and concatenation method as claimed in claim 11, wherein the spectrum of spoken sounds and the fundamental frequency of spoken sounds are changed in parallel.