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FreeFieldHRTF

FreeFieldHRTF SOFA convention

Since R2023b

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    Description

    The FreeFieldHRTF object stores SOFA data following the FreeFieldHRTF convention. This convention is an extension of SimpleFreeFieldHRTF. It considers more complex data sets described in spatially continuous representation. Each head-related transfer function (HRTF) direction corresponds to an emitter, and a consistent measurement for a single listener and all directions is described by a set of the emitter positions. FreeFieldHRTF considers both spatially discrete and continuous HRTF representations.

    Use sofaread and sofawrite to read and write SOFA files with this convention.

    Creation

    Create a FreeFieldHRTF object using sofaconvention.

    s = sofaconvention("FreeFieldHRTF");

    Properties

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    Data

    Measurements in frequency response form, specified as a complex M-by-R-by-N-by-E array, where M is the number of measurements, R is the number of receivers, N is the frequency response length, and E is the number of emitters. The number of receivers is typically equal to 2 in this convention.

    Frequency vector, in hertz, corresponding to the frequency response, specified as a vector.

    This property is read-only.

    Type of data in the file, returned as a string.

    Listener

    Listener position in Cartesian or spherical coordinates, specified as a 1-by-3 or M-by-3 matrix, where M is the number of measurements.

    For more information, see Spatial Data Representations.

    Listener position type, specified as "cartesian" or "spherical".

    This property is read-only.

    Listener position units, returned as "meter" if ListenerPositionType is "cartesian" or "degree, degree, meter" if ListenerPositionType is "spherical".

    Listener view direction, specified as a 1-by-3 or M-by-3 matrix, where M is the number of measurements. This property defines the direction of the positive x-axis of the local listener coordinate system.

    Listener view type, specified as "cartesian" or "spherical".

    This property is read-only.

    Listener view units, returned as "meter" if ListenerViewType is "cartesian" or "degree, degree, meter" if ListenerViewType is "spherical".

    Listener up direction, specified as a 1-by-3 or M-by-3 matrix, where M is the number of measurements. This property defines the direction of the positive z-axis of the local listener coordinate system.

    Listener short name, specified as a string. This property defines the ID of the subject from the database.

    Receiver

    Receiver positions in Cartesian or spherical coordinates, specified as a 2-by-3 matrix or 2-by-3-by-M array, where M is the number of measurements and 2 represents the number of receivers. The default value assumes the head has a radius of 0.09 meters.

    For more information, see Spatial Data Representations.

    Receiver position type, specified as "cartesian" or "spherical".

    This property is read-only.

    Receiver position units, returned as "meter" if ReceiverPositionType is "cartesian" or "degree, degree, meter" if ReceiverPositionType is "spherical".

    Source

    Source position in Cartesian or spherical coordinates, specified as a 1-by-3 or M-by-3 matrix, where M is the number of measurements.

    For more information, see Spatial Data Representations.

    Source position type, specified as "cartesian" or "spherical".

    This property is read-only.

    Receiver position units, returned as "meter" if SourcePositionType is "cartesian" or "degree, degree, meter" if SourcePositionType is "spherical".

    Source view direction, specified as a 1-by-3 or M-by-3 matrix, where M is the number of measurements. This property defines the direction of the positive x-axis of the local source coordinate system.

    Source view type, specified as "cartesian" or "spherical".

    This property is read-only.

    Source view units, returned as "meter" if SourceViewType is "cartesian" or "degree, degree, meter" if SourceViewType is "spherical".

    Source up direction, specified as a 1-by-3 or M-by-3 matrix, where M is the number of measurements. This property defines the direction of the positive z-axis of the local source coordinate system.

    Emitter

    Emitter positions in Cartesian coordinates, spherical coordinates, or spherical harmonics, specified as a 1-by-3 matrix, E-by-3 matrix, or E-by-3-by-M array, where M is the number of measurements. If EmitterPositionType is "cartesian" or "spherical", E is the number of emitters. If EmitterPositionType is "spherical harmonics", E is the number of spherical-harmonic coefficients.

    For more information, see Spatial Data Representations.

    Emitter position type, specified as "cartesian", "spherical", or "spherical harmonics".

    This property is read-only.

    Emitter position units, returned as "meter" if EmitterPositionType is "cartesian" or "spherical harmonics". If EmitterPositionType is "spherical", the units are returned as "degree, degree, meter".

    Metadata

    This property is read-only.

    Name of the SOFA convention, returned as a string.

    Name of the database that this data belongs to, specified as a string.

    This property is read-only.

    Version of the SOFA AES69 specifications, returned as a string of the format "x.y" where x is the version major and y is the version minor.

    This property is read-only.

    Name of the API that created or edited the SOFA file, returned as a string.

    This property is read-only.

    Version of the API that created or edited the SOFA file, returned as a string of the format "x.y" or "x.y.z" where x is the version major and y and z are the version minors.

    This property is read-only.

    Version of the SOFA AES69 convention set, returned as a string of the format "x.y" where x is the version major and y is the version minor.

    Title containing a succinct description of the file contents, specified as a string.

    Contact information of the author (for example, an email address), specified as a string.

    Name of the organization of the author, specified as a string.

    Legal license under which the data is provided, specified as a string.

    Name of the application that created or edited the file, specified as a string.

    Version of the application that created or edited the file, specified as a string.

    Comment that can contain miscellaneous information about the data or methods used to produce the data, specified as a string.

    History defining the audio trail for modifications to the original data, specified as a string.

    Published or web-based references that describe the data or the methods used to produce the data, specified as a string.

    Origin, specified as a string representing the method used for creating the original data. In the case of model-generated data, the origin should name the model and its version. In the case of observed or measured data, the origin should characterize the data and, where possible, name the measurement method.

    This property is read-only.

    Date and time of the creation of the file, returned as a string in ISO 8601 format "YYYY-MM-DD hh:mm:ss". This property is set when a new file is created.

    This property is read-only.

    Date and time of the last file modification, returned as a string in ISO 8601 format "YYYY-MM-DD hh:mm:ss". This property is updated when a file is saved.

    Object Functions

    writeWrite SOFA file
    validateValidate SOFA data

    Examples

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    Open Live Script

    Create a SOFA template object following the FreeFieldHRTF convention for storing emitter-dependent frequency response measurements.

    s = sofaconvention("FreeFieldHRTF");

    Generate mock frequency response data to store in the file. Initialize the FrequencyResponse property to store 512-point frequency responses for 25 measurements, five emitters, and two receivers corresponding to the ears. Use freqz to get the complex frequency responses from random Butterworth filters.

    M = 25;
R = 2;
N = 512;
E = 5;

s.FrequencyResponse = complex(zeros(M,R,N,E));
fs = 44100;

for m = 1:M
    for e = 1:E
        [b1,a1] = butter(5,rand);
        [b2,a2] = butter(5,rand);

        [h1,f] = freqz(b1,a1,N,fs);
        s.FrequencyResponse(m,1,:,e) = h1;
        [h2,f] = freqz(b2,a2,N,fs);
        s.FrequencyResponse(m,2,:,e) = h2;
    end
end

s.FrequencyVector = f;

    Generate random spherical coordinates for each of the emitters.

    s.EmitterPositionType = "spherical";
azimuth = 360*rand(E,1);
elevation = -90 + 180*rand(E,1);
radius = ones(E,1);

s.EmitterPosition = [azimuth elevation radius];

    Save the data to a SOFA file.

    sofawrite("mockFreqResponseData.sofa",s);

    More About

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    Version History

    Introduced in R2023b

    See Also

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    External Websites