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Format of Amplitude and Phase Tables

Ravi Kochhar
Dept. of Neuroscience
University of Wisconsin - Madison
Nov. 11, 1997
rev. 1.00, Nov. 24, 1997
Programming Note no. 16


This report is based almost entirely on Ref. # 1.

The Calibration Storage File (CSF) is a file on disc that is used for storing the current phone calibrations (ref. 2) for use during experiments.

The CSF is a direct access file that is stored in directory D: with the name CALTAB.DAT. Both the amplitude and phase tables for Phone-1 and Phone-2 are stored in this file. In addition, the CSF also contains all the correction curves for the various probe tubes (see ref. 3).

The first four (4) blocks of the CSF (D:CALTAB.DAT) contain a directory which contains pointers to locations in the CSF where are the various calibration tables are stored. There is room for 8 entries per directory block, thus maximum of 32 calibration tables can be stored in the CSF. Of these, the first eight (8) are reserved for storage of current phone calibrations for use during experiments. At present the DSS has only two output channels, so entries 3 thru 8 of the CSF are unused (reserved for future expansion).

Entries no. 9 thru 32 of the CSF are available for storage of probe tube correction curves.

The program ECAL can be used to view and edit the CSF.

Directory Entries

Each entry in the CSF directory is 16 words (32-bits each) long, and consists of the following:

          Word # (32-bit)    Contents
          ---------------    --------
                1            Busy Flag (=1 if busy)
               2-4           Calibration ID (12 chars.)
               5-6           Date of Expt. (DDMMM-YY)
                7            Low Freq. (Hz) (real)
                8            High Freq. (Hz) (real)
                9            Freq. Increment (Hz) (real)
               10            Location of Amplitude data (Block #)
               11            Location of Phase data (Block #)
               12            Size of table (amp.+phase) (blocks)
              13-16          Unused

The "busy" (or "in use") flag in each entry is set to 1 when when a calibration table is stored in that entry. A value other than 1 indicates a "deleted" or "available" entry.

If the "location" of either the Amplitude or Phase is set to zero then the corresponding table is "missing".

The first block in the directory is reserved for storing the entries for upto 8 phones for use during data collection. Of these, only 2 are typically used since the DSS has only two channels of output at present.

The allocation of entries in the first directory block is as follows:

       Entry #     Word #      Contents
       -------     ------      --------
          1         1-16       Calibration Table for Phone-1
          2        17-32       Calibration Table for Phone-2
          3 ]
          4 ]
          5 }                  Reserved for future use for
          6 }                  phones 3 thru 8
          7 ]
          8 ]

The 2nd, 3rd and 4th blocks of the directory contain room for 24 more entries for the probe tube correction curves.

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Format of Amplitude and Phase Tables

Both Amplitude and Phase tables are stored as real (floating point) numbers. The tables always start at the first word of a block. The first value is that for the low frequency, the next is for low freq plus the increment frequency, then low + 2 *(inc. freq.), and so on.

The size of each table is an integer number of blocks. Word 12 of the directory entry specifies the space occupied by the Table (both amplitude and phase tables, combined).

At present, for the current phone calibrations, the following space is reserved:

Forty (40) blocks each for Amplitude and Phase Tables.

The probe tube correction curves can be of any length.


  1. "Calibration Storage File and Calibration Editor", R. Kochhar, Conversion Report # 12, Feb. 1983.
  2. "NEUCAL - Acoustic Calibration Program", R.Kochhar, Tech.Report # 4, Dept. of Neurophysiology.
  3. "Generating a Probe Tube Correction Curve", R. Kochhar,Programming Note # 13, Feb. 1983.

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Please send feedback/suggestions/questions/complaints to the author via email, at

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This work was done at the University of Wisconsin - Madison under the direction of Dr. W.S. Rhode. Supported in part by a grant from NIH.

(This page last modified on May 21, 2015)

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