Real time pitch detection by stream processing

• US 4,486,900 A
• Filed: 03/30/1982
• Issued: 12/04/1984
• Est. Priority Date: 03/30/1982
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: AT&T, Inc.
• Inventors: Cox, Richard V., Crochiere, Ronald E.
• Primary Examiner(s): Kemeny, E. S. Matt
• Application Number:
  US06/363,470
• Time in Patent Office: 980 Days
• Field of Search: 381/38, 381/49, 364/513.5, 364/724, 364/728
• US Class Current: 704/207
• CPC Class Codes: G10L 25/90 Pitch determination of speech signals

Abstract

Continuous stream processing of an input signal to find the autocorrelation function and pitch period is simplied. The input speech signal is sampled at 8 khz, from which the autocorrelation function is formed by multiplying each sample by a stored-delay reduced sequence of up to 30 past samples. The reduced sequence is formed by every fourth sample of input signal gated to storage. Autocorrelation values are sequentially compared by a peak-peaker for maxima, thus further minimizing storage requirements to find the pitch period.

Claims

1. A method for detecting the pitch of a speech pattern, comprising the steps of:

sampling a speech pattern at spaced time intervals to form a series of sample signals representative of the pattern;

gating every Q^th sample, Q between 2 and 6, into a storage device, thereby storing a predetermined number of past samples, and

processing said original samples and said stored Q^th samples to generate a signal representative of the pitch of the speech pattern.

2. The method of pitch detection according to claim 1 wherein said processing step further comprises the steps of

sequentially retrieving said stored sample signals, and

multiplying each sample signal with each one of said stored sample signals to form a product signal.

3. The method of pitch detection according to claim 2 wherein said processing step further comprises the step of generating an autocorrelation function (ACF) estimate signal responsive to said product signals from the first sequence of Q consecutive sample signals.

4. The method of pitch detection according to claim 3 wherein said processing step further comprises the steps of

retrieving the ACF estimate, generated Q sample time intervals ago, and

generating an updated ACF estimate signal responsive to said product signals from the subsequent sequences of Q consecutive sample signals.

5. The method of pitch detection according to claim 4 wherein said processing step further comprises the steps of

(1) multiplying said recomputed ACF estimate by a weighting factor, and

(2) selecting the maximum valued weighted ACF estimate signal.

6. The method of pitch detection according to claim 5 wherein said processing step further comprises the steps of

generating a signal representative of the occurrence of said largest of said weighted ACF estimates, and

producing a signal corresponding to the pitch in response to said representative signal.

7. Apparatus for detecting the pitch of a speech pattern comprising:

means for sampling a speech pattern at spaced time intervals to form a series of sample signals representative of the pattern;

means for gating every Q^th sample, Q between 2 and 6, into a storage device, thereby storing a predetermined number of past samples, and

means for processing said original samples and said stored Q^th samples to generate a signal representative of the pitch of the speech pattern.

8. The apparatus for detecting the pitch of a speech pattern according to claim 7 further comprising

means for sequentially retrieving said stored sample signals, and

means for multiplying each consecutive sample signal with a plurality of said stored sample signals to form a product signal.

9. The apparatus for detecting the pitch of a speech pattern according to claim 8 further comprising means for generating an autocorrelation function (ACF) estimate signal responsive to said product signals from the first sequence of Q consecutive sample signals.

10. The apparatus for detecting the pitch of a speech pattern according to claim 9 further comprising

means for retrieving the ACF estimate, generated Q sample time intervals ago, and

means for generating an updated ACF estimate signal, responsive to said product signals from the subsequent sequences of Q consecutive sample signals.

11. The apparatus for detecting the pitch of a speech pattern according to claim 10 further comprising

means for multiplying said recomputed ACF estimate by a weighting factor, and

means for selecting the largest weighted ACF estimate signal.

12. The apparatus for detecting the pitch of a speech pattern according to claim 11 further comprising

means for generating a signal representative of the occurrence of the largest of said weighted ACF estimates, and

means responsive to said representative signal for producing a signal corresponding to the pitch.