algorithm was tested across a variety of skin types and tones to ensure that sensor platform adjustments for skin tone were sufficient in the context of the...

https://www.apple.com/jp/healthcare/docs/site/Apple_Watch_Arrhythmia_Detection.pdf

Tones are played at various frequencies, starting with 1000Hz, with incremental increases and decreases in tone decibels hearing level (dBHL) based on the u...

https://www.apple.com/jp/health/pdf/Hearing_Health_Features_on_AirPods_Pro_2_October_2024.pdf