SimpleFreeFieldHRIR
Description
The SimpleFreeFieldHRIR
object stores SOFA data following the
SimpleFreeFieldHRIR convention. This convention describes a spatially discrete free-field
head-related transfer function (HRTF) measurement for a single subject (a single human
listener or a mannequin head device). The measurements are made in the free field with a
single excitation source assuming an omnidirectional loudspeaker. There are two receivers
representing the ears of the subject. The measured HRTFs are represented as head-related
impulse responses (HRIR).
Use sofaread
and
sofawrite
to read
and write SOFA files with this convention.
Creation
Create a SimpleFreeFieldHRIR
object using sofaconvention
.
s = sofaconvention("SimpleFreeFieldHRIR");
Properties
Data
Numerator
— Head-related impulse responses
[0 0]
(default) | M-by-R-by-N array
Head-related impulse responses in FIR form, specified as a real-valued M-by-R-by-N array, where M is the number of measurements, R is the number of receivers, and N is the impulse response length. The number of receivers is typically equal to 2 in this convention.
Delay
— Impulse response delay
[0 0]
(default) | 1-by-R matrix | M-by-R matrix
Delay of each impulse response in samples, specified as a 1-by-R or M-by-R matrix, where M is the number of measurements and R is the number of receivers. The number of receivers is typically equal to 2 in this convention.
SamplingRate
— Sampling rate (Hz)
48000 (default) | positive scalar
Sampling rate of the data in hertz, specified as a positive scalar.
SamplingRateUnits
— Sampling rate units
"hertz"
This property is read-only.
Sampling rate units, returned as a string.
DataType
— Type of data
"FIR"
This property is read-only.
Type of data in the file, returned as a string.
Listener
ListenerPosition
— Listener position
[0 0 0]
(default) | 1-by-3 matrix | M-by-3 matrix
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.
ListenerPositionType
— Listener position type
"cartesian"
(default) | "spherical"
Listener position type, specified as "cartesian"
or
"spherical"
.
ListenerPositionUnits
— Listener position units
"meter"
| "degree, degree, meter"
This property is read-only.
Listener position units, returned as "meter"
if
ListenerPositionType
is "cartesian"
or
"degree, degree, meter"
if
ListenerPositionType
is "spherical"
.
ListenerView
— Listener view direction
[1 0 0]
(default) | 1-by-3 matrix | M-by-3 matrix
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.
ListenerViewType
— Listener view type
"cartesian"
(default) | "spherical"
Listener view type, specified as "cartesian"
or
"spherical"
.
ListenerViewUnits
— Listener view units
"meter"
| "degree, degree, meter"
This property is read-only.
Listener view units, returned as "meter"
if
ListenerViewType
is "cartesian"
or
"degree, degree, meter"
if ListenerViewType
is
"spherical"
.
ListenerUp
— Listener up direction
[0 0 1]
(default) | 1-by-3 matrix | M-by-3 matrix
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.
ListenerShortName
— Listener short name
""
(default) | string
Listener short name, specified as a string. This property defines the ID of the subject from the database.
Receiver
ReceiverPosition
— Receiver positions
[0 0.09 0; 0 -0.09 0]
(default) | 2-by-3 matrix | 2-by-3-by-M array
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.
ReceiverPositionType
— Receiver position type
"cartesian"
(default) | "spherical"
Receiver position type, specified as "cartesian"
or
"spherical"
.
ReceiverPositionUnits
— Receiver position units
"meter"
| "degree, degree, meter"
This property is read-only.
Receiver position units, returned as "meter"
if
ReceiverPositionType
is "cartesian"
or
"degree, degree, meter"
if
ReceiverPositionType
is "spherical"
.
Source
SourcePosition
— Source position
[0 0 1]
(default) | 1-by-3 matrix | M-by-3 matrix
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.
SourcePositionType
— Source position type
"spherical"
(default) | "cartesian"
Source position type, specified as "cartesian"
or
"spherical"
.
SourcePositionUnits
— Source position units
"meter"
| "degree, degree, meter"
This property is read-only.
Receiver position units, returned as "meter"
if
SourcePositionType
is "cartesian"
or
"degree, degree, meter"
if SourcePositionType
is "spherical"
.
SourceView
— Source view direction
[1 0 0]
(default) | 1-by-3 matrix | M-by-3 matrix
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.
SourceViewType
— Source view type
"cartesian"
(default) | "spherical"
Source view type, specified as "cartesian"
or
"spherical"
.
SourceViewUnits
— Source view units
"meter"
| "degree, degree, meter"
This property is read-only.
Source view units, returned as "meter"
if
SourceViewType
is "cartesian"
or
"degree, degree, meter"
if SourceViewType
is
"spherical"
.
SourceUp
— Source up direction
[0 0 1]
(default) | 1-by-3 matrix | M-by-3 matrix
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
EmitterPosition
— Emitter position
[0 0 0]
(default) | 1-by-3 matrix | 1-by-3-by-M array
Emitter position in Cartesian or spherical coordinates, specified as a 1-by-3 matrix or 1-by-3-by-M array, where M is the number of measurements and 1 represents the number of emitters.
For more information, see Spatial Data Representations.
EmitterPositionType
— Emitter position type
"cartesian"
(default) | "spherical"
Emitter position type, specified as "cartesian"
or
"spherical"
.
EmitterPositionUnits
— Emitter position units
"meter"
| "degree, degree, meter"
This property is read-only.
Emitter position units, returned as "meter"
if
EmitterPositionType
is "cartesian"
or
"degree, degree, meter"
if EmitterPositionType
is "spherical"
.
Metadata
SOFAConventions
— Name of SOFA convention
"SimpleFreeFieldHRIR"
This property is read-only.
Name of the SOFA convention, returned as a string.
DatabaseName
— Name of database
""
(default) | string
Name of the database that this data belongs to, specified as a string.
Version
— Version of specifications
"2.1"
(default) | 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.
APIName
— Name of API
"Audio Toolbox"
(default) | string
This property is read-only.
Name of the API that created or edited the SOFA file, returned as a string.
APIVersion
— Version of API
"1.0"
(default) | 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.
SOFAConventionsVersion
— Version of convention set
"1.0"
(default) | string
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
— Title
""
(default) | string
Title containing a succinct description of the file contents, specified as a string.
AuthorContact
— Contact information of author
""
(default) | string
Contact information of the author (for example, an email address), specified as a string.
Organization
— Name of organization
""
(default) | string
Name of the organization of the author, specified as a string.
License
— Legal license
""
(default) | string
Legal license under which the data is provided, specified as a string.
ApplicationName
— Name of application
"Audio Toolbox"
(default) | string
Name of the application that created or edited the file, specified as a string.
ApplicationVersion
— Version of application
"3.0.0"
(default) | string
Version of the application that created or edited the file, specified as a string.
Comment
— Comment
""
(default) | string
Comment that can contain miscellaneous information about the data or methods used to produce the data, specified as a string.
History
— History
""
(default) | string
History defining the audio trail for modifications to the original data, specified as a string.
References
— References
""
(default) | string
Published or web-based references that describe the data or the methods used to produce the data, specified as a string.
Origin
— Origin
""
(default) | 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.
DateCreated
— Date created
string
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.
DateModified
— Date modified
string
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
write | Write SOFA file |
validate | Validate SOFA data |
interpolateHRTF | 3-D head-related transfer function (HRTF) interpolation |
findMeasurements | Find measurements in specified plane |
plotGeometry | Plot measurements geometry |
freqz | HRTF frequency response |
impz | Head-related impulse response |
spectrum | HRTF power spectrum |
interauralTimeDifference | Interaural time difference |
interauralLevelDifference | Interaural level difference |
directivity | Frequency directivity |
energyTimeCurve | Compute energy-time curve |
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);
Visualize and Analyze SOFA HRTF Data
Read in a SOFA file containing HRTF measurements.
s = sofaread("ReferenceHRTF.sofa");
Call plotGeometry
to visualize the 3-D locations of the receiver and moving source from the measurements.
figure plotGeometry(s)
Use findMeasurements
to get the indices of measurements in the median plane. Plot the 3-D geometry of the specified measurements.
idx = findMeasurements(s,Plane="median");
figure
plotGeometry(s,MeasurementIndex=idx);
Use freqz
to compute and visualize the frequency response of the first measurement for the first receiver.
figure freqz(s)
Use impz
to compute and visualize the impulse response of the first measurement for the first receiver.
figure impz(s)
Use spectrum
to compute and visualize the power spectrum of the HRTF data in the horizontal plane at zero elevation for the first receiver.
figure spectrum(s)
Compute and visualize the interaural time difference of the HRTF data in the horizontal plane at zero elevation.
figure interauralTimeDifference(s)
Compute and visualize the interaural level difference of the HRTF data in the horizontal plane.
figure interauralLevelDifference(s)
Compute and visualize the directivity of the HRTF data at 750 Hz and 1500 Hz in the horizontal plane.
figure directivity(s,[750 1500])
Compute and visualize the energy-time curve of the HRTF data in the horizontal plane.
figure energyTimeCurve(s)
More About
Spatial Data Representations
In this SOFA convention, you can represent spatial data using Cartesian or spherical coordinate systems with spatially discrete representations.
Each spatial representation stores the position data in numerical triplets (for example,
[0 0 0]
).
Cartesian coordinates contain three orthogonal linear values in the format
[x y z]
. The units of the values are meters.Spherical coordinates contain angular values for azimuth and elevation and a linear value for the radius in the format
[azimuth elevation radius]
. The azimuth angle, in degrees, must be in the range [0, 360). The elevation angle, in degrees, must be in the range [-90, 90]. The units of the linear radius are meters.
Version History
Introduced in R2023b
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