sofaconvention

Create SOFA convention

Since R2023b

Syntax

s = sofaconvention(convention)

Description

s = sofaconvention(convention) returns a template object following the specified SOFA convention.

Examples

Write SOFA File

Create a SOFA template object following the SimpleFreeFieldHRIR convention.

s = sofaconvention("SimpleFreeFieldHRIR");

Generate mock impulse response data to store in the file. Set the number of measurements M to two and set the impulse response length N to 1024. The number of receivers R is two, corresponding to two ears. Use the fir1 function to create arbitrary FIR filters for the impulse response measurements.

M = 2;
N = 1024;
R = 2;

IR = zeros(M,R,N);
IR(1,:,:) = [fir1(N-1,0.1);fir1(N-1,.2)];
IR(2,:,:) = [fir1(N-1,0.15);fir1(N-1,.25)];

Store the measurements in the SOFA object.

s.Numerator = IR;

Set the ListenerView so the positive x-axis of the local listener coordinate system points up with a 45 degree elevation. Set the ReceiverPosition so the ears are 18 cm apart on the x-axis.

s.ListenerViewType = "spherical";
s.ListenerView = [0 45 0];
s.ReceiverPosition = [0 0 0; 0 0.18 0];

Modify the Title and Comment metadata properties.

s.Title = "My SOFA File";
s.Comment = "This SOFA file contains mock FIR data.";

Save the data to a SOFA file.

sofawrite("myFile.sofa",s);

Write Frequency Response Data to SOFA File

Create a SOFA template object following the SimpleFreeFieldHRTF convention to store measurement data as complex frequency responses.

s = sofaconvention("SimpleFreeFieldHRTF");

Load HRTF data containing impulse response measurements. Initialize the FrequencyResponse property to store 100 measurements in 512-point frequency responses.

load 'ReferenceHRTF.mat' hrtfData sourcePosition sampleRate
M = 100;
N = 512;
R = 2; % 2 ears

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

For 100 of the measurements from the HRTF data, use freqz to get the complex frequency responses from the FIR filters and store them in the SOFA object.

for i = 1:M
    ear1FIR = squeeze(hrtfData(:,i,1));
    ear2FIR = squeeze(hrtfData(:,i,2));
    
    [h1,f] = freqz(ear1FIR,1,N,sampleRate);
    s.FrequencyResponse(i,1,:) = h1;
    h2 = freqz(ear2FIR,1,N,sampleRate);
    s.FrequencyResponse(i,2,:) = h2;
end

s.FrequencyVector = f;

Set the SourcePosition property to store the positional data, in spherical coordinates, corresponding to the selected measurements.

s.SourcePositionType = "spherical";
s.SourcePosition = sourcePosition(1:M,1:3);

Write the data to a SOFA file.

sofawrite("freqResponseData.sofa",s);

Write SOS Data to SOFA File

Create a SOFA template object following the SimpleFreeFieldHRSOS convention to store measurement data as second-order section (SOS) filters.

s = sofaconvention("SimpleFreeFieldHRSOS");

Generate mock SOS data to store in the file. Use designVarSlopeFilter to create an SOS filter to use for both receivers in a single measurement.

M = 1;
N = 4;
R = 2;
s.Numerator = zeros(M,R,N,3);
s.Denominator = zeros(M,R,N,3);

[num,den] = designVarSlopeFilter(24,.2,Orientation="row");
s.Numerator(1,1,:,:) = num;
s.Numerator(1,2,:,:) = num;
s.Denominator(1,1,:,:) = den;
s.Denominator(1,2,:,:) = den;

Save the data to a SOFA file.

sofawrite("mockSOSData.sofa",s);

Input Arguments

convention — SOFA convention

"SimpleFreeFieldHRIR" | "SimpleFreeFieldHRSOS" | "SimpleFreeFieldHRTF" | "GeneralFIR" | ...

SOFA convention from the AES69-2022 standard [3], specified as one of the following values.

• "SimpleFreeFieldHRIR"

• "SimpleFreeFieldHRSOS"

• "SimpleFreeFieldHRTF"

• "GeneralFIR"

• "GeneralSOS"

• "GeneralTF"

• "GeneralTF-E"

• "GeneralFIR-E"

• "FreeFieldHRIR"

• "FreeFieldHRTF"

• "SimpleHeadphoneIR"

• "SingleRoomSRIR"

• "SingleRoomMIMOSRIR"

• "FreeFieldDirectivityTF"

Data Types: char | string

Output Arguments

s — SOFA object

SimpleFreeFieldHRIR object | SimpleFreeFieldHRSOS object | SimpleFreeFieldHRTF object | ...

SOFA object following the convention specified by convention, returned as one of the following objects.

• SimpleFreeFieldHRIR

• SimpleFreeFieldHRSOS

• SimpleFreeFieldHRTF

• GeneralFIR

• GeneralSOS

• GeneralTF

• GeneralTFE

• GeneralFIRE

• FreeFieldHRIR

• FreeFieldHRTF

• SimpleHeadphoneIR

• SingleRoomSRIR

• SingleRoomMIMOSRIR

• FreeFieldDirectivityTF

More About

SOFA Files

Spatially oriented format for acoustics (SOFA) is a file format for storing spatially oriented acoustic data like head-related transfer functions (HRTF) and binaural or spatial room impulse responses. The AES69 standard [3] defines the SOFA file format.

References

[1] Majdak, P., Zotter, F. Brinkmann, F., De Muynke, J., Mihocic, M., and Noisternig, M., “Spatially Oriented Format for Acoustics 2.1: Introduction and Recent Advances.” Journal of the Audio Engineering Society 70, no. 7/8 (July 25, 2022): 565–84. https://doi.org/10.17743/jaes.2022.0026.

[2] Majdak, P., Carpentier, T., Nicol, R., Roginska, A., Suzuki, Y., Watanabe, K., Wierstorf, H., et al., “Spatially Oriented Format for Acoustics: A Data Exchange Format Representing Head-Related Transfer Functions.” In Proceedings of the 134th Convention of the Audio Engineering Society (AES), Paper 8880. Roma, Italy, 2013.

[3] AES69-2022. "AES standard for file exchange - Spatial acoustic data file format." Standard of the Audio Engineering Society. https://www.aes.org/publications/standards/search.cfm?docID=99

Version History

Introduced in R2023b