https://www.noisemeters.com/help/faq/frequency-weighting.asp
A-weighting assumes how the human ear works in relation to frequency and dB. Real SPL at low frequency is not dependent on how the human ear works WRT decibels and frequency to cause damage. If the SPL is very high at very low frequencies such as 10-60Hz, then most dB meters (let alone SPL meters) will not represent the true SPL. Even dB meters with C-Weighting will miss the mark below roughly 100Hz because they are not linear in that region.
In my experience most dB meters and SPL meters along with OSHA/other regulatory bodies’ recommendations miss the mark when it comes to low frequency dB and SPL measurements.
I know there are more sources out there that back up my claims, but I’m busy with other stuff now.
Maybe I’ll look more later.
I don’t see how to apply that information to designing equipment, providing sound level warnings and selecting appropriate hearing protection.
For most people interested in the topic, they want to know when and where to protect, and how much protection is needed.
I did a fair amount of research in a former business in this area. One day I noticed my left ear had worse hearing than the right. I wondered why. I eventually had a ‘lightbulb moment’ and took my meter for a ride in my rig and checked the SPL with the window down.
Try it sometime. I now keep an earplug in my car for my left ear.