Datum Files for
Signals and Systems Laboratory EE422G

 

This page contains downloads for data files to be used in class examples and laboratory experiments.

 

mozart-1.wav – This wave file is a 5 second excerpt of lively classical music by Mozart, 1 channel, sampled at 44.1 kHz with 16 bits per sample.

 

oldwoman.wav – This wave file is a 2.5 second sample of speech from an adult female, 1 channel, sampled at 8 kHz with 16 bits per sample.

 

lab5nde.mat – This mat-file contains sampled ultrasonic A-scans.  The A-scans were obtained from three 2-in diameter stainless steel rods that were heat treated to obtain various grain sizes. A flaw was simulated in each specimen by drilling a flat-bottom hole of 4.22-mm diameter. The samples were placed in a water bath and scanned with a U2-H KB-Aerotech Alpha transducer with a center frequency of 5 MHz and a Gaussian-shaped spectrum with a 4 MHz bandwidth. The received echoes were digitized at a sampling rate of 100 MHz, and each measurement was then averaged 200 times in a LeCroy 9400 digital oscilloscope to reduce time varying noise. Average grain sizes for the difference samples were 86, 106, and 160 pm.   This data can be loaded into your Matlab workspace with the load command (i.e. if labtnde is in current directory, simply type load lab5nde.mat).  Once loaded, type whos and the workspace should contain the following vectors and parameters:

Name                        Size                 Bytes               Class     Attributes

  a1                            2000x1           16000               double             

  a1_posmm              1x1                 8                       double             

  a2                            2000x1           16000               double              

  a2_posmm              1x1                 8                       double             

  c                              1x1                 8                       double             

  fs                             1x1                 8                       double             

  nfa1                                    2000x1           16000               double             

  nfa1_posmm           1x1                 8                       double             

  nfa2                                    2000x1           16000               double             

  nfa2_posmm           1x1                 8                       double             

  nfa3                                    2000x1           16000               double             

  nfa3_posmm           1x1                 8                       double


The vectors a1 and a2 are the sample A-scans that really do not need filtering to make the flaw echo stronger than the grain.  The vectors nfa1, nfa2 and nfa3 are A-scans that need filtering in order for the flaw to be detectable (i.e. be stronger than the grain echoes).  The parameters are as follows:

c                            => is the speed of sound in stainless steel.

fs                           => is the sampling rate.

a1_posmm             => is position of the flaw in millimeters for a1

a2_posmm             => is position of the flaw in millimeters for a2

nfa1_posmm         => is position of the flaw in millimeters for naf1

nfa2_posmm         => is position of the flaw in millimeters for naf2

nfa3_posmm         => is position of the flaw in millimeters for naf3

 

lab5test.mat – This mat-file contains 3 sampled ultrasonic A-scans.  The A-scans were obtained from three 2-in diameter stainless steel rods that were heat treated to obtain various grain sizes. A flaw was simulated in each specimen by drilling a flat-bottom hole of 4.22-mm diameter. The samples were placed in a water bath and scanned with a U2-H KB-Aerotech Alpha transducer with a center frequency of 5 MHz and a Gaussian-shaped spectrum with a 4 MHz bandwidth. The received echoes were digitized at a sampling rate of 100 MHz, and each measurement was then averaged 200 times in a LeCroy 9400 digital oscilloscope to reduce time varying noise. Average grain sizes for the difference samples were 86, 106, and 160 pm.   This data can be loaded into your Matlab workspace with the load command (i.e. if lab5test.mat is in current directory, simply type load lab5test.mat).  Once loaded, type whos and the workspace should contain the following vectors and parameters:

Name                          Size            Bytes                    Class     Attributes

                  c                                  1x1                 8                       double             

                  fs                                 1x1                 8                       double             

                  ta1                                           2000x1        16000                  double             

                  ta2                                           2000x1        16000                  double             

                  ta3                                           2000x1        16000                  double             
The vectors ta1, ta2, and ta3 are the sample A-scans that contain flaws.  The other scalars are as follows:

c                            => is the speed of sound in stainless steel.

fs                           => is the sampling rate.

 

 

 

sqwaveINnoise.mat – This mat-file contains simulated signals of 3 second durations.  Each signal contains a single period square wave corrupted with increasing levels of AWGN.  The signals were sampled at 10kHz.  The square wave (positive values precede negative) was generated with period 0.01 seconds, and occurred at various places within the 3 second received signals. Once loaded into the workspace, the “whos” command displays the following information:


Name                          Size                 Bytes               Class     Attributes
  fs                               1x1                      8                  double             
  sigmat                        12x30000            2880000      double             
  snra                            1x12                    96                double             
  tax                             1x30000             240000         double


 
The scalar variable fs is the sampling rate of the received signals stored in rows of matrix sigmat, in which each row has a square wave signal located in it.  The SNR values corresponding to each row is stored in the vector snra, and the vector tax is the time axis in seconds associated with each row of the signal matrix sigmat.

 

mfopt.wav – This wave file contains a mono speech signal recorded with good quality and sampled at 48 kHz.  The speech consists of an adult male speaking, “The matched filter is the optimal filter for detecting a deterministic signal in uncorrelated random noise.”

 

twNspec.wav – This wave file contains a mono speech signal recorded with good quality and sampled at 48 kHz.  The speech consists of an adult male speaking, “The amplitudes of the time waveform show its energy distribution over time.  The spectral magnitude (derived from the Fourier transform) shows its energy distribution over frequency.”

 

impNtrans.wav – This wave file contains a mono speech signal recorded with good quality and sampled at 48 kHz.  The speech consists of an adult male speaking, “The Laplace transform of a system’s impulse response is its transfer function.”