Agenda for the 23rd session of the Task Force on Vehicles Sound on 20 October 2026. The session will cover adoption of the agenda and report of the 22nd session, exchange of information on national and international requirements including presentations on quiet communities and noise sensitivity analysis, cross-matrix comparison of sound traffic modelling approaches with presentations on noise modelling and CNOSSOS-FR parameters, any other business, and arrangement of the next meeting in February 2027.

Proposal to restructure para. 4.4. by dividing it into paras. 4.4.1. through 4.4.8., add a new para. 4.4.7. permitting acceptance of measurements of RD-ASEP leading to operation conditions outside the control range when agreed by the manufacturer and authority, modify the heading of para. 3.6.1. to reference a selected reference v-t-e ratio, update references to v-t-e ratio terminology throughout para. 3.6.1.1., add a provision that negative acceleration values be set to zero in para. 4.5.4.1., restructure para. 2.2.1.2. by renumbering into paras. 2.2.1.2.1. and 2.2.1.2.2., and modify the reference vehicle speed parameter designation from vTEST to vPP,CRS.

Considerations by TF Data Analysis on revising the AVAS term in the RD-ASEP Sound Expectation Model to align with UN R138.02 specifications for electric and hybrid electric vehicles. The document presents two options: Option 1 implements UN R138.02 specifications for constant speed conditions; Option 2 extends Option 1 with an additional term to reflect paragraph 6.2.8 requirements for accelerated conditions. A revised AVAS term formula is proposed applicable only for vehicle speeds up to 50 km/h.

Document presents considerations on amendments to the RD-ASEP Sound Expectation Model SEM concerning calculation of the dynamic base and dynamic load addon. The dynamic sound increase of a vehicle is covered by a dynamic term aggregating all dynamics. A minimum threshold is proposed to be specified as max(0.25; ΔL_dyn) to ensure the function does not become zero or negative due to measurement uncertainties. The value 0.25 is selected to deliver comparable results as the current 10 dB minimum dynamic specification. In combination with a restriction of factor x to an area of 10 to 90 for ICE, the model becomes very robust with fluent transients and no unsteady steps.

Proposal to amend Annex 7, para. 2.3.1 to constrain the factor x determined by discrete coast-down measurement to a minimum of 10 and a maximum of 90 for internal combustion engine and hybrid electric vehicles, or 95 for electric vehicles, ensuring the Sound Expectation Model remains robust against measurement variations in tyre rolling sound and powertrain mechanic sound splitting.

Agenda for the Task Force Data Analysis meeting of 29 September 2026. Discussion topics include amendments to factor x for improved model robustness, consideration on LDYN with amendments on factor x, considerations on the AVAS term to match UN R138, amendments to reference acceleration, temperature correction, indoor testing, simplified model for electric vehicles with integrated AVAS approach and amendments from Supplement 11, and considerations on slopes in the RD-ASEP model. The Task Force will prepare proposals for wording on issues identified in the editing task force list and address a clarification request regarding the phrase ‘but no more than 2.0 m/s’ in para. 3.1.2.1.4.3. concerning vehicles with only one gear ratio.

Document presents suggested revisions to test procedures in Annex 7 and Annex 7 Appendix 1:

• Renumber para. 4.4. into paras. 4.4.1. through 4.4.8. to structure target operation conditions,
• Insert new para. 4.4.7. to permit acceptance of measurement runs outside the control range when agreed by manufacturer and authority,
• Modify para. 3.6.1.1. to define maximum reference acceleration for a selected reference v-t-e ratio and clarify determination procedures,
• Add provision that in case calculated acceleration is negative, the value is set to zero,
• Restructure para. 2.2.1.2. to introduce subsections 2.2.1.2.1. and 2.2.1.2.2. for parameters from acceleration and constant speed tests respectively, and modify parameter definitions including use of vPP,CRS instead of fixed 50 km/h reference speed.

Considerations by TF-Data Analysis regarding tyre slopes, power train slopes, and part load model for the RD-ASEP Sound Expectation Model. Tyre slopes α = 40 and β = 20 are confirmed as appropriate for UN R117 approved tyres. Power train slopes are confirmed as well-framed to normal vehicle behaviour and consistent with Annex 7 ASEP Slope-Assessment principles. For part load model, the function is confirmed for ICE vehicles and HEV in ICE mode, while for EVs and HEVs in EV mode the part load area may require reworking, but the part load model should be applied uniformly to all vehicle techniques.

Document presents considerations on amendments to the RD-ASEP Sound Expectation Model SEM. A simplified approach for electric vehicles is proposed based on Supplement 11 to UN R51.03, using a tyre rolling sound curve with slopes identical to internal combustion engine and hybrid electric vehicles, plus an acceleration term from UN R51.03 Supplement 11 as an additional term, and the AVAS term from Option 1, without other parts of the SEM.

Document presents considerations on revising the AVAS term in the RD-ASEP Sound Expectation Model to align with UN R138.02 specifications for electric and hybrid electric vehicles. Two options are discussed: Option 1 implements only constant speed specifications from UN R138.02, while Option 2 extends this with an additional term to reflect interpretation of paragraph 6.2.8 for accelerated conditions. A revised AVAS term formula applicable for vehicle speeds up to 50 km/h is proposed.

Proposal to amend the determination of reference acceleration aREF by introducing a theoretical calculation formula based on PMR, rated engine speed S, and vehicle mass mro, with a correction function accounting for transmission losses, virtual mass increase, tyre slip, and turbo delay, and to allow manufacturers to alternatively determine reference acceleration by discrete measurements.

Document presents considerations on factor x used in the Sound Expectation Model to split constant speed test results into tyre rolling sound and power train mechanic references. Factor x values are concentrated between 80 and 99, indicating tyre dominance. Small variations in measurements cause disproportional variability in the minor sound source when one source dominates. Two options are proposed: Option 1 requires factor x determined during type approval to be reported and used for subsequent assessments, with any redetermination not exceeding the type approval value; Option 2 requires the power train reference from type approval to be used for all further assessments regardless of measurement variations.

The Task Force Data Analysis meeting scheduled for 15 September 2026 will discuss database pilot documents covering amendments to factor x, reference acceleration, AVAS term considerations, simplified EV models, and RD-ASEP model slopes. The task force will prepare proposals based on draft UN R51.04 for items 13–19 from the Editing TF issues list and address a question regarding the phrase “but no more than 2.0 m/s” in paragraph 3.1.2.1.4.3 concerning acceleration values for vehicles with single gear ratios.

The agenda includes a review of Terms of Reference from GRBP 78th Session (GRBP-78-13), report of Data Analysis Task Force, review of issues list, review of draft text, and discussion of UN R51 matters. Dates and locations of 2027 meetings will be determined.

The 15th RD-ASEP informal group session will be held at Nissan Technical Center Europe Spain in Barcelona. The venue is located 11 minutes walk from Mercabarna Metro Station Line 9S. Participants should make hotel reservations independently; options include areas near metro line L9S or city center near metro line L5, which connects with L9S. Participants must provide last name, first name, phone number, company name, and email in advance.

Rationale for Figure Part B.5 of GRBP-84-36-Rev.1

Proposal to amend para. 6.2.1.1. to permit testing of vehicle sound either indoors or outdoors with equivalent results, add new Annex 11 specifying indoor testing provisions, amend Annex 1 to insert para. 8.5. and 8.5.1. requiring documentation of test method selected, amend Annex 3 para. 1. to specify sound level meter requirements for indoor testing per IEC 651 and IEC 61672-3, amend Annex 3 para. 1.1.1. to provide calibration procedures for indoor testing per IEC 942:1988, amend Annex 3 para. 1.3. to exempt wind speed monitoring for indoor facilities, amend Annex 3 para. 2.1. and add para. 2.1.4. to specify outdoor and indoor test site requirements per ISO 362-3:2022 and ISO 26101, add para. 2.1.5. specifying indoor ambient conditions, add para. 2.2.7. addressing test mass for indoor dynamometer testing, amend Annex 3 para. 3. to specify outdoor and indoor test procedures per ISO 362-3:2022 Variant A, amend Annex 3 para. 3.1.1. to clarify outdoor testing microphone placement, add para. 3.1.1.4. defining virtual lines and simulated vehicle speeds for indoor testing, and renumber former paras. 3.1.1.4. and 3.1.1.5. as 3.1.1.5. and 3.1.1.6.