[1] https://www.hearingtracker.com/hearables/airpods-pro-2

[2] https://hearingreview.com/hearing-products/hearing-aids/psap/apple-airpods-pro-for-people-with-hearing-loss-in-noisy-environments?utm_source=hearingtracker.com

[3] https://bynss.com/apple/1006442.html

[4] https://www.collectornet.net/regency/

[5] https://apps.who.int/iris/handle/10665/339913

[6] https://www.statista.com/statistics/1087388/global-hearing-aid-market-share-by-company/

[7] https://amarillohearing.com/what-is-high-frequency-hearing-loss/

[8] https://www.nytimes.com/2014/05/18/magazine/who-made-that-earbud.html

[9] https://www.fastcompany.com/90779729/fda-over-the-counter-hearing-aids-tech-startups 

[10] https://www.52audio.com/archives/134628.html

[11] https://www.wired.com/story/smartphone-features-deaf-hard-of-hearing/

[12] https://www.sony.com/en/SonyInfo/CorporateInfo/History/sonyhistory-h.html