The present document documents investigations on test methodologies for immersive audio systems. Audio is a key component of an immersive multimedia experience and 3GPP systems are expected to deliver immersive audio with a high Quality of Experience. 3GPP needs to characterize the performance of immersive audio systems, as part of the IVAS_Codec [1], VRStream [2] and FS_CODVRA [3] work and study items, have prompted the investigations on the present document.

The present document aims to:

1. Identify a minimum set of relevant perceptual audio quality attributes (e.g. timbre, localization, overall quality, etc.) for the assessment of immersive audio systems relevant to 3GPP.
2. Identify available test methodologies for the perceptual audio quality attributes of interest and their applicability in the context of immersive audio systems relevant to 3GPP.
3. Document subjective and objective test methodologies for assessing the capturing, coding, transmission and rendering blocks of immersive audio systems.
4. Document the diverse considerations for the testing of immersive audio systems such as:
   1. Impacts of audio rendering systems
   2. Impacts of Head Related Transfer Functions (HRTFs)
   3. Impacts of simultaneous video presentation to the perceived audio quality / psychophysical response
   4. Use of naïve and/or experienced listeners
   5. Appropriate statistical methods for data analysis and reporting
   6. Repeatability and reproducibility

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.

• References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.