TimeFrequency Analysis Software
(Wigner/Wavelet /STFT)
DS0230 

The DS0230 timefrequency analysis
software is intended to perform shorttime Fourier
transform, Wavelet transform, the Wigner distribution
analysis, and other data processing of the timeaxis data
(with a file extension of .dat or .prn) which is recorded
using the software of the DS2000 Series or FFT analyzers
(CF6400/CF5000/CF4200 Series, etc.) from Ono Sokki.
Overview of each data processing and comparison is shown
below. 
Items 
Wigner distribution 
Wavelet transform 
STFT
Shorttime Fourier transform 
Time resolution 
High 
High
frequency: High
Low frequency: Low 
Constant 
Frequency resolution 
High 
High
frequency: Low
Low frequency: High 
Constant 
Feature 
High
resolution up to the physical limit 
Balanced
time and frequency resolutions 
Stable
result through extended FFT 
Problem 
Existence of cross terms,
negative energy 
Result
for approximate number of frequencies 
Neither
time nor frequency resolutions are so high 
Application 
Abnormal
vibration analysis of rotational drum of photo copy machine 
Voice
analysis, image communications 
Usual
time, frequency analysis 
■ Wigner Distribution
The Wigner distribution is a new analysis method which
enables simultaneous analysis of temporal fluctuation and spatial transition
of sudden or unsteady sound and vibration and other complicated waveforms.
The Wigner distribution was advocated in quantum mechanics by Dr. E.Wigner
in 1932. Then, it was applied to sound analysis by Dr. T.Classen and Dr. Q.
Mecklenbraker. In recent year, it has been expected as an analysis method
for unsteady state signals. The Wigner distribution with the energy
dimension offers high time and frequency resolutions. Therefore, that makes
it possible to capture characteristics of transient signals more efficiently
than conventional methods. However, negative energy and cross terms appear
in many cases which require expertise for interpretation. With the use of
the time and frequency distributions of unsteady state signals provided by
the Wigner distribution function, the Wigner distribution method is expected
as an effective analysis tool for impact sound, abnormal sound, and
transient characteristics of audio equipment
Timeaxis resolution 
200 points 
Frequency resolution 
256 points
(displayed 200 points out of them.) 
Length of rag window 
1 to 257 points
(odd number) can be setup arbitrarily. 
Analysis time frame length 
16384 points
max 
3D plot 
3D plot of
amplitude (dB) in 64 colors 
Data reading 
By the search
point 
Cross section display 
By the search
cursor 
■ Wavelet transform
The Wavelet transform is a new analysis method which
enables simultaneous analysis of temporal fluctuation and spatial transition
of sudden or unsteady sound and vibration and other complicated waveforms.
It is still evolving as a new analysis method. Since an engineer of oil
exploration introduced the Wavelet transform as the analysis way of
artificial earthquake wave, many academians such as physical scientists,
mathematicians, and engineers have tried to apply the Wavelet transform
analysis with mathematical basis to various fields
With the Wavelet transform, as the term “wavelet” (small
waves existing locally) implies, one function is prepared which is existing
locally (practically) in terms of time and frequency, the scale transition
and shift transition are applied to it, then an obtained set of functions is
used as basis functions. The Wavelet transform is a natural analysis method
which uses long temporal data in low frequencies (slow fluctuation) and
short temporal data for high frequencies (quick variations). Therefore, it
is expected as an analysis method for diverse transient phenomena. The
distribution of the absolute square value of the Wavelet transform result is
called scalogram. The Wavelet transform, DS0230 timefrequency analysis
software, makes it possible to display the signal spectrum as 2D or 3D color
image on the timefrequency plane respectively.
Mother wavelet 
Gabor function 
Timeaxis resolution 
200 points 
Frequency resolution 
256 points
(Displayed 200 points out of them.) 
Length of rag window 
1 to 257 points
(odd number) can be setup arbitrarily. 
Analysis time frame length 
16384 points
max. 
3D plot 
3D plot by
amplitude (dB) in 64 colors. 
Data reading 
By search
points 
Cross section display 
By search
cursor 
■ STFT (Shorttime Fourier
Transform)
The shorttime Fourier transform is an data processing
which cuts out signal in shorttime intervals and performs the Fourier
Transform in order to capture timedepended fluctuation of frequency
component of the unsteady state signal. The STFT method is the simplest and
easytouse analysis method of unsteady state signals. However, in order to
improve the accuracy with respect to timedependent variation (time
resolution), it is necessary to shorten the cutout time period. The
accuracy with respect to the frequency (frequency resolution) becomes worse
with decreasing cutout time period. Therefore, the DS0230 timefrequency
analysis software is provided with the function to improve the time
resolution while maintaining the required frequency resolution by setting
the cutout time window length and the Fourier transform length separately.
The distribution of the absolute square value of the shorttime Fourier
transform result is called spectrogram.
Time resolution 
8192 points
max. 
Frequency resolution 
2048 points
max. 
Analysis time frame length 
16384 points 
FFT frame length 
4096 points
max. 
3D plot 
3D display by
amplitude (dB) in 64 colors. 
Data reading 
By search
points 
Crosssection display 
By search
cursor 
●
Descriptions and specifications are
subject to change without prior notice. 
