1. Workshop on Standards for Safe Listening Standardized measurements of headphones/earphones Lars Birger Nielsen WP1/12 Chairman SG12 WP1:Terminals and multimedia subjective assessment Geneva, 6 June 2016

2. Agenda Introduction to SG12 WP1 Measurements on headphones/earphones Summary 2Geneva, 6 June 2016

3. Introduction (1 of 2) SG12 WP1 responsibilities covers Objective methods Procedures for measurements of electroacoustic parameters of terminals (handset, hands-free, headsets, headphones and earphones) Physical setups for terminal when they are being tested Ensure reproducibility and a well defined accuracy when using standardized procedures and setups Subjective methods E.g. intelligibility just to mention one 3Geneva, 6 June 2016

4. Introduction (2 of 2) SG12 WP1 responsibilities covers Collaboration with other SDO (standards development organisations) e.g. ITU-T SG, ETSI STQ, IEEE, IEC Recommendations* dealing with test procedures and test setup of headset/headphones/earphones developed by experts: P.58 – HATS (Head and Torso Simulator) P.311 – Wideband Handset and Headset testing P.360 – “Acoustic shock” for handset P.380 – Electroacoustic measurements on headsets P.381 – Headset interface testing *Standards for safe listening devices : situation analysis 4Geneva, 6 June 2016

5. Measurements on headphones/earphones (1 of 5) The following factors determines the sound pressure level produced in a headphone/earphone: Output voltage of the player Level of recorded music Sealing between ear and headphone/earphone Sensitivity of speaker in headphone/earphone 5Geneva, 6 June 2016

6. Measurements on headphones/earphones (2 of 5) For a specific headphone/earphone the variability in sound pressure level is caused by the mounting of the headphone/earphone (sealing) This is true even in the case of using standardized procedures and setups !!! In order to reduce the variation – 5 measurements are performed and the average is used 6Geneva, 6 June 2016

7. Measurements on headphones/earphones (3 of 5) EN-50332-1 (intra-concha) +/- 1dB 7Geneva, 6 June 2016

8. Measurements on headphones/earphones (4 of 5) ITU-T Round Robin test 2003 (insert) +/-10dB 8Geneva, 6 June 2016

9. Measurements on headphones/earphones (5 of 5) Newer studies show similar results as ITU-T Round Robin from 2003 Keith et al 2008 Playback levels ranged from 101 to 107 dBA at maximum volume level. Estimated listener sound levels could vary from 79 to 125 dBA due to the following factors. “Evaluating the maximum playback sound levels from portable digital audio players” Hammershøj et al 2015 shows that the dose estimate proposed by the EN 50332-3 is based on the output voltage of the music player alone, disregarding the sensitivity of the earphones used. The results presented show that this strategy will ignore differences of more than 10 dB. 9Geneva, 6 June 2016

10. Summary (1 of 2) The EN-50332-3 method Are based on measurement of the voltage produced by the player The influence of sealing and sensitivity are excluded in the determination of the actual sound pressure level presented to the user As a consequence the user can potentially be exposed to significantly higher levels before a warning is produced – and as a consequence the risk of hearing damage is increased Alternatively a warning can be produced at too low levels – and as a consequence the risk that the next warning being ignored is increased 10Geneva, 6 June 2016

11. Summary (2 of 2) Proposal for future standardisation activities To further develop the dose model to take into account the sealing and the sensitivity – this could improved the accuracy of estimated sound pressure level the user are exposed to In addition an alternative method that are base on direct measurement of the reproduced sound pressure level – e.g. using a microphone in the headphone/earphone – could be developed 11Geneva, 6 June 2016

12. Other information More information available SG12 info http://www.itu.int/en/ITU-T/studygroups/2013-2016/12/Pages/default.aspx http://www.itu.int/en/ITU-T/studygroups/2013-2016/12/Pages/default.aspx WP1 info http://www.itu.int/en/ITU-T/studygroups/2013-2016/12/Pages/structure.aspx http://www.itu.int/en/ITU-T/studygroups/2013-2016/12/Pages/structure.aspx Recommendations http://www.itu.int/ITU-T/recommendations/index_sg.aspx?sg=12 http://www.itu.int/ITU-T/recommendations/index_sg.aspx?sg=12 Thank you for your attention! Any Questions? 12Geneva, 6 June 2016