I appreciate the math and the effort but I think this is potentially very irresponsible. There's a serious mistake being made that, it seems to me, might mislead people into listening at unsafe levels, believing that they are safe.
Originally Posted by d_headshot
but they're using dBA rather than dBSPL so I'm not sure if my findings are meaningful.
A-weighting (dBA) and Sound Pressure Level (SPL) aren't two options from the same list.
A-weighting is entirely in the frequency domain. It takes a full-spectrum sound and applies weights to different frequency bands (roughly according to a human equal-loudness curve at 40-phons) and then adds all the bands up into a single number.
You can have A-weighted SPL (with any time constant, whether slow or fast or whatever), sound power, continuous equivalent level (Leq), Ln, or however you want to measure in the time domain.
And there's the problem I see with the original post. It's mixing different SPL concepts. The SPL that's measured to determine headphone sensitivity is a pure tone at 1000 Hz, measured in the (fake) ear canal. I don't know what time constant is used.
The SPL values that are said to cause hearing damage at such a level and comfortable listening levels and such are A-weighted, full-spectrum SPL ("slow"), and at ear level (not in-ear). This is not directly comparable to the SPL in the sensitivity measurement.
It's possible for different types of music to result in very different A-weighted SPLs, even if they're adjusted so that their 1-kHz levels are the same.
A-weighting can be a useful tool, but it grossly oversimplifies. It's also usually quite incompatible with music. Broadband noise, like machines running or highway traffic can be fairly well characterized with A-weighted figures. But music often has exaggerated low frequency sounds that are effectively ignored by the A-weighting scheme, but still quite able to cause hearing loss.
So please be VERY CAREFUL about telling people certain SPLs are safe when in reality it's very possible that THEY ARE NOT. Please make sure you've got your decibels straight before you post anything that deals with people's health. Make sure you understand the specifics of the dB you are using in both the frequency and the time domain, and make sure you don't equate different types of dB.