Importing Measurement Data

REW can import frequency response and impedance measurement data from other applications, including the ETF5 measurement system (http://www.acoustisoft.com). Most ETF5 export formats are supported, along with generic comma, space or TAB-delimited text files. Note that when making measurements with ETF5 it is best to use the calibrated SPL option to allow level comparisons between channels.

ETF *.pcm Format Impulse Responses

Full range ETF measurements allow the impulse response to be exported in a .pcm raw data format, using the File → Write Impulse As *.pcm option. Use REW's File → Import Impulse Response command to load these files. Importing the impulse response allows REW's Spectral Decay and Waterfall plots to be generated from the data (this is not possible when importing frequency response text files). REW loads the first 128k samples from the file (approx 2.73s at 48k sampling).

WAV or AIFF Format Impulse Responses

The File → Import Impulse Response command can also be used to load impulse responses that have been saved as .wav or .aiff format. REW loads the first 256k samples from the file (approx 5.46s at 48k sampling), if the file contents are shorter than 1 second the response is padded out to 1 second with zeroes.

Frequency Response and Impedance Text Files

The File → Import Frequency Response and File → Import Impedance Measurement commands accept text files with extension .txt, .frd, .dat or .zma. If the extension is .zma the data is always treated as impedance, otherwise it is treated as SPL if loaded via Import Frequency Response or impedance if loaded via Import Impedance Measurement. The following formats are accepted:

• Generic comma, TAB, space or semicolon delimited files
  • Data must be presented as freq, magnitude (SPL or impedance) and (optionally) phase in degrees, one set of values per line
  • Samples can be at arbitrary frequency spacing, but each line must have a higher frequency than the one before and there must be at least 5 data entries
  • Only lines which begin with a number are imported, others are ignored
  • In comma-delimited files there must be at least one space after the comma
  • Spaces before values are ignored
  • To add a comment on a data line put a tab, comma or space after the last value
• ETF5 Export Data option for the Low Frequency Room Response window
• ETF5 Export Bode Response option
• ETF5 Export Data option for the Logarithmic Frequency Response window
  
  • Cubic spline interpolation is used between sample points

Comma-delimited File Format

Here is an example of a valid format for comma-delimited SPL data without phase:

            SPL measurements acquired by REW V3.08
            Source: D:\REW\test files\testfile.txt
            Format: Comma delimited data
            Dated: 05-Mar-2005 17:53:56
            Channel: Left, Bass limited 80Hz

            20.0, 65.01
            21.0, 65.77
            22.0, 67.50
            23.0, 67.93
            24.0, 68.22
            25.0, 67.88
            26.0, 67.92
            27.0, 68.31, this line has a comment
            28.0, 69.14
            29.0, 69.16
            30.0, 69.29
        

If comma is used as the decimal delimiter in your locale it is best for clarity to use TAB, space or semicolon as the separator.

Space-delimited File Format

Here is some impedance data in space-delimited format, with phase

            * Measurement data saved by REW V5.00
            * Source: Line (ESI MAYA44 Audio), no input selected, Right channel, volume: no control
            * Format:   1M Log Swept Sine, 1 sweep at -30,0 dBFS
            * Dated: 31-Dec-2010 11:26:49
            * Sense Resistor: 100.0
            * Lead resistance: 0.000
            * Calibration factor: 1.0028
            * Note: horizontal
            * Measurement: SPH170 horz
            * Frequency Step: 0.36621094 Hz
            * Start Frequency: 1.8310547 Hz
            *
            * Freq(Hz) Z(Ohms) Phase(degrees)
            1.831 6.423 5.392
            2.197 6.444 6.426
            2.563 6.481 7.302
            2.930 6.522 8.049
            3.296 6.558 8.714
            3.662 6.586 9.368
            4.028 6.609 10.076
            4.395 6.632 10.864
            4.761 6.664 11.706
            5.127 6.705 12.549
            5.493 6.753 13.346
            5.859 6.803 14.082
            6.226 6.851 14.777
            6.592 6.896 15.467
            6.958 6.939 16.180
            7.324 6.985 16.919
            7.690 7.034 17.669
            8.057 7.089 18.409
            8.423 7.147 19.126
            8.789 7.207 19.822
            9.155 7.269 20.505
            9.521 7.332 21.181
            9.888 7.398 21.851