4.2.1 Headset Binaural Diffuse-field Receive frequency response for Scene-based audio
26.2603GPPObjective test methodologies for the evaluation of immersive audio systemsRelease 18TS
4.2.1.1 Introduction
This test is applicable to UEs rendering scene-based audio (e.g. First and Higher Order Ambisonics) over a binaural headset.
4.2.1.2 Definition
The Headset Binaural Diffuse-field Receive Frequency Response for Scene-based Audio (for left and right ears) is defined as the transfer function, GL,R (f), between:
a) PL,R(f), the binaurally recorded sound pressure magnitude spectra, obtained when a diffuse field signal in the equivalent spatial domain representation, w(t), is played on the DUT; and
b) Pref L,R(f), the reference sound pressure magnitude spectra, obtained by direct convolution of the diffuse field signal in the equivalent spatial domain representation, w(t) with its corresponding set of HRTFs.
4.2.1.3 Test Conditions
Test environment noise floor
The equivalent continuous sound level of the test environment in each 1/3rd octave band, Leq(f), shall be less than the limits of the NR10 curve, following the noise rating determination procedures in [4].
The set of HRTFs used by the UE shall be documented and available to the test lab.
4.2.1.4 Measurement
Reference sound pressure magnitude spectra
The reference sound pressure magnitude spectra are derived offline. The reference sound pressure magnitude spectra for the left and right ears, Pref L,R (f) is the frequency domain representation of the convolution between the set of equivalent spatial domain signals, w(t), with its corresponding set head related transfer functions h L,R(t), for each direction j in an equivalent spatial domain of order NDUT , i.e.:
The signals wj(t), for 1 ≤ j ≤ (NDUT +1)2, are uncorrelated pink noise signals of 30s length.
Binaurally recorded sound pressure magnitude spectra
The binaurally recorded sound pressure magnitude spectra is obtained as follows:
a) The binaural headset is placed on a HATS.
b) The DUT shall be configured such that the set of HRTFs used for binaural rendering correspond to the HATS used for testing.
c) The DUT volume control (if any) is adjusted for its nominal setting.
d) The binaural time-domain signals are recorded with HATS.
e) The binaurally recorded sound pressure magnitude spectra, PL,R(f) is obtained by taking the Fourier transform of the binaurally recorded time-domain signals.
Calculation of headset binaural diffuse-field receive frequency response for scene-based audio
The headset binaural diffuse-field frequency response for scene-based audio, G(f), is calculated for each supported Ambisonics order NDUT as:
