Personalized Timbre Optimization for Stereophonic Sound Reproduction via Earphones: Part 2 – Practical Implementation and Validation on Consumer TWS Devices

Hamasaki K, Hara A, Hirai H, Tojo N, Saito S, Hosoo M. Personalized Timbre Optimization for Stereophonic Sound Reproduction via Earphones: Part 2 – Practical Implementation and Validation on Consumer TWS Devices. In: Express Paper. Audio Engineering Society; 2026. Paper 438. Available from: https://aes.org/publications/elibrary-page/?id=23163

@inproceedings{Hamasaki2026_23163,
  author = {Hamasaki, Kimio and Hara, Atsushi and Hirai, Haruto and Tojo, Nao and Saito, Shun and Hosoo, Mitsuru},
  title = {{Personalized Timbre Optimization for Stereophonic Sound Reproduction via Earphones: Part 2 – Practical Implementation and Validation on Consumer TWS Devices}},
  note = {Paper 438},
  year = {2026},
  month = may,
  publisher = {Audio Engineering Society},
  url = {https://aes.org/publications/elibrary-page/?id=23163}
}

TY  - CPAPER
TI  - Personalized Timbre Optimization for Stereophonic Sound Reproduction via Earphones: Part 2 – Practical Implementation and Validation on Consumer TWS Devices
AU  - Hamasaki, Kimio
AU  - Hara, Atsushi
AU  - Hirai, Haruto
AU  - Tojo, Nao
AU  - Saito, Shun
AU  - Hosoo, Mitsuru
M1  - Paper 438
PY  - 2026
DA  - 2026/05/28
UR  - https://aes.org/publications/elibrary-page/?id=23163
PB  - Audio Engineering Society
LA  - en
AB  - This paper presents Part 2 of our study on personalized timbre optimization for stereophonic sound reproduction via earphones, following our previous work [1]. Part 1 established an auditory-model-based framework, hereafter referred to as PTTC-1 (Personalized Timbre Target response Curve), for reproducing the listener's individual reference for natural timbre. However, its practical application was constrained by the need for high-resolution 3D anatomical scanning, individualized HRTF computation by the boundary element method, and controlled listening tests conducted by trained audio engineers. The present paper introduces PTTC-2, a simplified and fully automated implementation for consumer True Wireless Stereo (TWS) earphones, in which a single smartphone image captures the listener's head and outer ear, the directionally averaged HRTFs are estimated by machine learning, and a brief in-app listening test determines a listener-specific weighting coefficient . Two empirical studies are reported. First, the analysis of values selected by 2,850 users, together with a follow-up assessment of 29 listeners, indicates that is a listener-specific parameter that is not strongly biased by program material. Second, a controlled subjective experiment with 24 listeners compared PTTC-1, PTTC-2, and two non-individualized target response curves used in consumer products. PTTC-1 and PTTC-2 did not differ significantly in holistic timbre attributes, and both were preferred over non-individualized target response curves. Principal component analysis further revealed that listener preference is governed by an overall naturalness axis rather than by a high-frequency emphasis axis. These results demonstrate that auditory-model-based timbre personalization can be effectively translated into a practical, consumer-ready technology that preserves the perceptual benefits of the full workflow.
ER  -