Device extracts average frequency of human speech and produces second, third, and fourth moments of instantaneous frequency about this average. It operates on electrical time representation of input signal, performs statistical analysis on zero-crossing of almost any signal, and does not require specialized personnel to operate it

Stewart, C. H.

English

NASA Technical Reports Server

August 1971	 Brief 71-10276 
NASA TECH BRIEF 
Manned Spacecraft Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a xubscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the. Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
A Real-Time Statistical Time-Series Analyzer 
S(t)	 Sc	 S(T1)	 S(T1')'S	 S(T1')'S 
FREQUENCY5 J DIVIDERINTETRAC-JRT 
T, P F1 DIX CONVERTER	 y	 X	 I 0 
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AMP 
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(S-S) 
(5 -) SUBTRAC TOR	 Y	 fA.P 
NOTES 
SC - CONSTANT AMPLITUDE I	 U:MULTIP)LIER 
- DISTANCE BETWEEN ZERO CROSSINGS  150 LIMITS	 T.	 TLc [III1.-
T: UPPER CUTOFF FREQUENCY 
TLC	 '11F LOWER CUTOFF FREQUENCY fix MULTIPLIER C	 - CONSTANT J'AMP I	 (5_)4
Figure 1. General Block Diagram of Real-Time Statistical Time-Series Analysis 
A relatively inexpensive device operating on the 
electrical time representation of an input signal has been 
conceived. This device will extract the average frequency 
of human speech and produce the second, third and 
fourth moments of instantaneous frequency about this 
average. Because it can be used by personnel who have 
not had specialized training it has significant advantages 
which will appeal to government agencies and industries 
concerned with communications. 
Attempts have been made to simulate the process
of a real-time statistical analysis of the time intervals be-
tween zero axis crossings of a given input signal in the 
past. But these have been confined to the laboratory 
and no self-contained system has been built specifically 
for this purpose. Because the laboratory test sets have 
been limited to a specialized purpose they have had no 
general application. 
This innovation comprises four major compo-
nents: a zero-crossing detector, a frequency-to-amplitude 
converter, an integrator, and a moment generating net-
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19710000275 2020-03-17T02:20:45+00:00Z
work. Figure 1 illustrates the function of the analysis 
operation. The input signal is first passed through the 
zero-crossing detector and the signal zero-crossing signal 
is then converted by the frequency-to-amplitude con-
verter. From here the converted signal frequencies are 
passed through a network to allow the integrator to 
measure the average frequency. This is then subtracted 
from the instantaneous frequency and appropriately 
multiplied to produce the second, third and fourth 
statistical moments of the input signal zero-crossings in 
real-time. 
In general the Analyzer can be used to perform 
statistical analysis on the zero-crossing of almost any sig-
nal. But its main purpose is to analyze human speech. 
The device does this by defining and displaying the first 
fourth central statistical moments of the reciprocal time 
distance between successive zero-crossings. The analysis 
begins by converting the input speech signal to a square 
wave showing variations only in the signal zero-crossing 
points. Then, the time intervals between the varying 
zero-crossing joints are measured, inverted, and con-
verted with relative amplitudes. These amplitudes are 
averaged, and then used to calculate the second, third 
and fourth central statistical moments. When displayed 
on an oscilloscope these moments illustrate the emphasis 
of the transition between phonetic sounds in given 
speech samples.
The advantages of this innovation are that it can 
be operated by non-specialized personnel to provide 
speech analysis without the use of complex ancillary 
equipment such as computers. Moreover, the Statistical 
Time-Series Analyzer has a selectable bandwidth. As 
such it will be of interest to the communications in-
dustry where complex waveforms need to be analyzed. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Manned Spacecraft Center, Code JM7 
Houston, Texas 77058 
Reference: TSP71- 10276 
Patent status: 
Inquiries about obtaining rights for the commer-
cial use of this invention may be made to: 
Patent Counsel 
Mail Code AM 
NASA Manned Spacecraft Center 
Houston, Texas 77058 
Source: Carrington H. Stewart

Manned Spacecraft Center

(MSC-1 2428) 
Brief 71-10276 Category 02


A real-time statistical time-series analyzer

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