Dr. Toole, in his book, discussed hearing loss resulting from exposure to excessively loud noise. Not surprisingly, the vulnerability of the human ear to noise induced injury is frequency dependent, corresponding to its frequency dependent sensitivity, as illustrated by Fletcher -Munson and other curves. Hence, the rationale for OSHA and other regulatory bodies to offer guidance on allowed time-based exposures to loud noise based on various "weighted" scales, such as dBA, dBC, and so forth, which take into account the ear's sensitivity to different frequencies. In Amir's video he discussed a key difference between occupational noise and music, which I think is useful. He explained that while loud industrial noise is typically continuously loud, music includes occasional, very brief or transient peaks superimposed on longer periods of varying but much lower sound pressure levels. We are more conscious or aware of these longer continuous signals with their correspondingly lower SPLs. We are less aware of the loud transient peaks and less vulnerable to injury from them, as well. And, importantly, most of the energy in music is in the lower frequencies or bass, to which we are less sensitive, and which are attenuated by measuring devices using the dBA scale. Amir measures the SPL of music in actual dB SPL. Thus, measuring the loudness of music in dBA and in dBSPL is like discussing prices in dollars and a different currency. While 100 dB instantaneous may seem "loud" on paper, if its concentrated in the bass, it may be perceived as loud as a 60-70 dB SPL signal at 1,000 Hz. I use the NIOSH app on my i-phone with it's uncalibrated internal microphone, so I realize its hardly a precision device. And as Amir explains, even measuring "peaks" with such a device involves averaging the sound pressure levels over a period of time, thus understating them. Nevertheless, I do like to use it when attending a live performance, and then attempt to achieve a similar loudness level as measured from my listening position at home. Our local symphony orchestra often streams a recording of a live performance a week after a performance, so after attending and recording LC peaks of 108-112 dB SPL, Lmax readings of 88-90 or so, and instantaneous levels bouncing around between say 40-105 dB SPL, I adjust the gain on my system, typically -10 dB, to produce similar levels at my listening position. I'm sure it is not accurate, but close enough for my purposes and fun just the same.