One last science lesson: Loudness and the corresponding unit, decibel, measure sound pressure level, which relates to amplitude as illustrated in the figure below. Your iPhone is able to internally use the amplitude to calculate the decibel of music volume or any sound output.
In fact, a detailed analysis of sound level is accessible through iOS 13s Health App for iPhone. It can show the headphone audio levels in hours, days, and weeks, as well as a clear summary that people can use to keep track and be aware of their audio level trends (see below). This feature works even better with Apple Watch, as it can measure and send noise notification when the ambient sound levels in the environment is over 80 decibels.
Currently, the noise notification is not available with the headphone audio levels, and this seems like a missed feature that could be crucial to solving hearing loss problems. For instance, my Health App indicates OK, when in fact I was at 90dB for over 30 minutes.
I interviewed three friends to understand if they also cared about their headphone audio levels as much as I did.
- All three were surprised at how often they listened to music over the recommended 85dB.
- All three wanted some form of notification (one described like the battery saving mode notification), and two mentioned that they preferred their iPhones to automatically lower their music to below 85dB.
People want to know when their volume is above 85dB and be able to take action right away to reduce the risk of hearing loss.
Constraints & Assumptions:
- AirPods need to output the sound and calculate the volume accordingly, and thus, we cannot predict and set a limit to the decibel of a sound output. We can only send notification and manually adjust in real-time.
- We will assume that majority of sound outputs like a song generally have the same volume throughout its durations. This means if we lower the volume to below 85dB, the rest of the sound output is assumed to not exceed 85dB.