SimpleFreeFieldHRIR

Description

This conventions essentially defines the setup used to measure HRTFs in free field. The measured HRTFs are represented as FIR filters, with a single HRTF set of a listener per file. We defined this conventions to describe data from databases like ARI, LISTEN, FIU, CIPIC, and others.

In SimpleFreeFieldHRIR version 0.2, we used ListenerRotation to describe the different measurement directions, and the source was assumed to be in the center of the measurement setup. This, however, limited the use of SimpleFreeFieldHRIR, thus, in version 0.3, we assume the listener being in the center of the measurement setup, and the source moving around the listener in order to represent the different HRTF directions. Further, the apparent position vector, APV, can be used to more simple provide the apparent position for each measured HRTFs. Note that with SimpleFreeFieldHRIR version 0.3, more complex data can be described where the tilt of the head is varied, or the listener is not exactly in the center of the measurement setup.

Proposed for version 0.3

File:SimpleFreeFieldHRTF 0.3.png

This conventions essentially defines the setup used in the ARI, LISTEN, FIU, CIPIC, and other similar HRTF databases. The measurements are done in free field with a single excitation source assuming an omnidirectional loudspeaker. Human listeners are considered and thus, the number of receivers is two. Note that usually, only the apparent azimuth and elevation angles are provided and this information is modeled as the variation of the source position. This conventions can, however, also be used to describe more complex data where the tilt of the head is varied or the listener is not exactly in the center of the measurement setup. The measured HRTFs are represented as FIR filters, with a single HRTF set of a listener per file.

• General attributes: SOFAConventions: SimpleFreeFieldHRIR, Datatype: FIR, RoomType: free field, other general attributes...

• Listener: The listener is in the origin of the setup, facing in the direction of the y-axis. Thus, for default values, ListenerPosition=[0 0 0], ListenerView=[1 0 0], ListenerUp=[0 0 1], all given in cartesian coordinates.
• Receivers: Two receivers (=ears) on a head with radius H (in meter, default: 0.09): ReceiverPosition=[0 -H 0; 0 +H 0].
• Source: Source consists of a single emitter. For default values, EmitterPosition=[0 0 0] in cartesian coordinates. SourcePosition (in spherical coordinates!) varies corresponding to the different azimuth and elevation angles of the measurement directions. For default, SourcePosition=[0 0 1] (azimuth 0°, elevation 0°, distance 1 m). SourceUp, SourceView, and SourceRotation are not considered and optional.
• Further, the different azimuth and elevation angles of the measurement are described by the apparent position vector, APV, in spherical coordinates (azimuth, elevation, radius).

Name	Default	Flags	Dimensions	Type	Comment
GLOBAL_Conventions	SOFA	rm			Must be always SOFA
GLOBAL_Version	0.4	rm			Describes the SOFA version
GLOBAL_SOFAConventions	SimpleFreeFieldHRIR	rm			Describes the SOFA Conventions
GLOBAL_SOFAConventionsVersion	0.3	rm			Describes the version of the Conventions
GLOBAL_APIName		rm			Insert the API Name here
GLOBAL_APIVersion		rm			Insert the API Version here
GLOBAL_AuthorContact		m
GLOBAL_License	No license provided, ask the author for permission	m
GLOBAL_Organization		m
GLOBAL_RoomType	free field	m
GLOBAL_DataType	FIR	rm
GLOBAL_History		m
GLOBAL_Source		m			The method of production of the original data. If it was model-generated, source should name the model and its version, as specifically as could be useful. If it is observational, source should characterize it.
GLOBAL_Title		m			A succinct description of what is in the dataset
GLOBAL_References		m			Published or web-based references that describe the data or methods used to produce it
GLOBAL_Comment		m
GLOBAL_TimeCreated		m			will be updated when saving and not existing or empty
GLOBAL_TimeModified		m			will be updated each time when saving
ListenerPosition	[0 0 0]	m	IC, MC	double	Listener is assumed to be in the center of the measurement setup
ListenerPosition_Type	cartesian	m
ListenerPosition_Units	meter	m
ReceiverPosition	[0 -0.09 0; 0 0.09 0]	m	rCI, rCM	double
ReceiverPosition_Type	cartesian	m
ReceiverPosition_Units	meter	m
SourcePosition	[0 0 1]	m	IC, MC	double	Source position is assumed to vary for different directions/positions around the listener
SourcePosition_Type	spherical	m
SourcePosition_Units	degree, degree, meter	m
EmitterPosition	[0 0 0]	m	eCI, eCM	double
EmitterPosition_Type	cartesian	m
EmitterPosition_Units	meter	m
GLOBAL_ApplicationName		m
GLOBAL_ApplicationVersion		m
GLOBAL_DatabaseName		m			name of the database to which these data belong
GLOBAL_SubjectID		m			ID of the subject from the database
ListenerUp	[0 0 1]	m	IC, MC	double
ListenerView	[1 0 0]	m	IC, MC	double
APV	[0 0 0]	m	IC, MC	double	Apparent Position Vector: HRTF position/direction as the interpretation of the geometry for applications
APV_LongName	apparent position vector	m
APV_Type	spherical	m
APV_Units	degree, degree, meter	m
Data.IR	[1 1]	m	mRn	double
Data.SamplingRate	48000	m	I	double
Data.SamplingRate_Units	hertz	m
Data.Delay	[0 0]	m	IR, MR	double

Legend:

• Name: the name of the metadata
  • An underscore (_): the metadata is an attribute
    • GLOBAL_: the metadata is a global attribute
    • X_Y: the metadata is an attribute Y of the variable X
  • No underscore: the metadata is a variable
  • Data.X: the metadata is structured within the data
• Default: default value for the metadata
  • An asterisk (*): special handling required, mentioned in the column Comment
• Flags:
  • r: read-only, must be the default value
  • m: mandatory, must be saved in the file
• Dimensions: dimensions of the metadata (see SOFA specifications for more explanations)
  • lower case: the variable size in that dimension determines the dimension size in the file
  • upper case: variable must be of that dimension (or one of these dimensions)

Stable (version 0.2)

File:SimpleFreeFieldHRTF.png

This conventions essentially defines the setup used in the ARI, LISTEN, FIU, CIPIC, and other similar HRTF databases. The measurements are done in free field with a single excitation source assuming an omnidirectional loudspeaker. Human listeners are considered and thus, the number of receivers is two. Azimuth and elevation angles are varied and the tilt of the head is not considered during the measurement. The measured HRTFs are represented as FIR filters, with a single HRTF set of a listener per file.

• General attributes: SOFAConventions: SimpleFreeFieldHRIR, Datatype: FIR, RoomType: free field, other general attributes...
• Source: Source is in the origin of the setup and consists of a single emitter. For default values, SourcePosition: (0 0 0), and EmitterPosition: (0 0 0). SourceUp, SourceView, and SourceRotation are not considered and optional.
• Listener: The listener is in the measurement distance X (in meter) from the source, facing the source. For default values, we consider a single distance X, thus, ListenerPosition: (X 0 0), ListenerView: (0 0 0), ListenerUp: (X 0 1).
• Receivers: Two receivers (=ears) on a head with radius H (in meter): ReceiverPosition: (0 -H 0; 0 +H 0).
• The different azimuth and elevation angles of the measurement are described by the ListenerRotation as [M 3] matrix (in degrees). The coordinate type is DIN 9300.

Name	Default	Flags	Dimensions	Type	Comment
GLOBAL_Conventions	SOFA	rm
GLOBAL_Version	0.4	rm
GLOBAL_SOFAConventions	SimpleFreeFieldHRIR	rm
GLOBAL_SOFAConventionsVersion	0.2	rm
GLOBAL_APIName		rm			Insert the API Name here
GLOBAL_APIVersion		rm			Insert the API Version here
GLOBAL_AuthorContact		m
GLOBAL_License	No license provided, ask the author for permission	m
GLOBAL_Organization		m
GLOBAL_RoomType	free field	m
GLOBAL_DataType	FIR	rm
GLOBAL_History		m
GLOBAL_Source		m
GLOBAL_Title		m
GLOBAL_References		m
GLOBAL_Comment		m
GLOBAL_TimeCreated		m			will be updated when saving and not existing or empty
GLOBAL_TimeModified		m			will be updated each time when saving
GLOBAL_ApplicationName		m
GLOBAL_ApplicationVersion		m
GLOBAL_DatabaseName		m
GLOBAL_SubjectID		m
ListenerPosition	[1 0 0]	m	IC, MC	double
ListenerPosition_Type	cartesian	m
ListenerPosition_Units	meter	m
ListenerUp	[0 0 1]	m	IC, MC	double
ListenerView	[-1 0 0]	m	IC, MC	double
ListenerRotation	[0 0 0]	m	IC, MC	double
ListenerRotation_Type	din9300	m
ListenerRotation_Units	degrees	m
ReceiverPosition	[0 -0.09 0; 0 0.09 0]	m	rCI, rCM	double
ReceiverPosition_Type	cartesian	m
ReceiverPosition_Units	meter	m
SourcePosition	[0 0 0]	m	IC, MC	double
SourcePosition_Type	cartesian	m
SourcePosition_Units	meter	m
EmitterPosition	[0 0 0]	m	eCI, eCM	double
EmitterPosition_Type	cartesian	m
EmitterPosition_Units	meter	m
Data.IR	[1 1]	m	mRn	double
Data.SamplingRate	48000	m	I	double
Data.SamplingRate_Units	hertz	m
Data.Delay	[0 0]	m	IR, MR	double

Legend:

• Name: the name of the metadata
  • An underscore (_): the metadata is an attribute
    • GLOBAL_: the metadata is a global attribute
    • X_Y: the metadata is an attribute Y of the variable X
  • No underscore: the metadata is a variable
  • Data.X: the metadata is structured within the data
• Default: default value for the metadata
  • An asterisk (*): special handling required, mentioned in the column Comment
• Flags:
  • r: read-only, must be the default value
  • m: mandatory, must be saved in the file
• Dimensions: dimensions of the metadata (see SOFA specifications for more explanations)
  • lower case: the variable size in that dimension determines the dimension size in the file
  • upper case: variable must be of that dimension (or one of these dimensions)

Stable (version 0.1)

Name	Default	Flags	Dimensions	Comment
GLOBAL_Conventions	SOFA	rm
GLOBAL_Version	0.3	rm
GLOBAL_SOFAConventions	SimpleFreeFieldHRIR	rm
GLOBAL_SOFAConventionsVersion	0.1	m
GLOBAL_APIName	*	rm		Insert the API Name here
GLOBAL_APIVersion	*	rm		Insert the API Version here
GLOBAL_ApplicationName		m
GLOBAL_ApplicationVersion		m
GLOBAL_AuthorContact		m
GLOBAL_License	No license provided, ask the author for permission	m
GLOBAL_Organization		m
GLOBAL_DatabaseName		m
GLOBAL_SubjectID		m
GLOBAL_RoomType	free field	m
GLOBAL_DataType	FIR	m
GLOBAL_History
GLOBAL_Comment
GLOBAL_DatabaseTimeCreated	*	m		will be updated when saving and not existing or empty
GLOBAL_DatabaseTimeModified	*	m		will be updated each time when saving
I	1	rm	I
I_LongName	singleton dimension	rm
R	2	rm	R
R_LongName	number of receivers	rm
E	1	rm	E
E_LongName	number of emitters	rm
N	-	m	N
N_LongName	time	m
N_Units	samples	m
M	-	m	M
M_LongName	number of measurements	rm
C	3	rm	C
C_LongName	coordinate triplet	rm
ListenerPosition	[1 0 0]	m	IC, MC
ListenerPosition_Type	cartesian	m
ListenerPosition_Unitsmeter		m
ListenerUp	[1.2 0 1]	m	IC, MC
ListenerUp_Type	cartesian	m
ListenerUp_Units	meter	m
ListenerView	[0 0 0]	m	IC, MC
ListenerView_Type	cartesian	m
ListenerView_Units	meter	m
ListenerRotation	[0 0 0]	m	IC, MC
ListenerRotation_Type	din9300	m
ListenerRotation_Units	degrees	m
ReceiverPosition	[0 -0.09 0; 0 0.09 0]	m	rCI, rCM
ReceiverPosition_Type	cartesian	m
ReceiverPosition_Units	meter	m
SourcePosition	[0 0 0]	m	IC, MC
SourcePosition_Type	cartesian	m
SourcePosition_Units	meter	m
SourceUp	[0 0 1]	m	IC, MC
SourceUp_Type	cartesian	m
SourceUp_Units	meter	m
SourceView	[1 0 0]	m	IC, MC
SourceView_Type	cartesian	m
SourceView_Units	meter	m
EmitterPosition	[0 0 0]	m	eCI, eCM
EmitterPosition_Type	cartesian	m
EmitterPosition_Units	meter	m
Data.IR	[1 1]	m	mRn
Data.SamplingRate	48000	m	I
Data.SamplingRate_Units	hertz	m

Legend:

• Name: the name of the metadata
  • An underscore (_): the metadata is an attribute
    • GLOBAL_: the metadata is a global attribute
    • X_Y: the metadata is an attribute Y of the variable X
  • No underscore: the metadata is a variable
  • Data.X: the metadata is structured within the data
• Default: default value for the metadata
  • An asterisk (*): special handling required, mentioned in the column Comment
• Flags:
  • r: read-only, must be the default value
  • m: mandatory, must be saved in the file
• Dimensions: dimensions of the metadata (see SOFA specifications for more explanations)
  • lower case: the variable size in that dimension determines the dimension size in the file
  • upper case: variable must be of that dimension (or one of these dimensions)