60dB Normal conversation
85dB Beginning of hearing damage range, earplugs should be worn
100dB Normal average car or house stereo at maximum volume
90dB is the beginning of hearing damage according to OSHA, at least and it's rated at 8 hours time before any significant damage starts. It gets shorter pretty quick for every 3dB above that. But my point is you left out the most important range. 120dB is considered instant damage. 110dB is like about 15 minutes per day exposure maximum. But Dolby Theater levels are supposed to be set to reach their absolute maximum at about 110dB for the loudest explosions, etc. but that should not go on in a movie for very long periods at the absolute maximum (or hardly ever). And a home stereo that can only max out at 100dB is a total POS (oh Bass at those levels is typically NOT harmful which is why all OSHA type measurements are "A-Weighted" which means scaled to human hearing sensitivity ranges. "C-Weighted" is evenly measured sound for all frequencies and is relatively meaningless for hearing measurements which is why nearly all sound meters have a built-in A-weighting scale option. BTW, even a Bose Wave Radio could probably put out 100dB at certain frequencies.
It takes a doubling of power for every 3dB gain. My system can do about 115dB maximum C-weighted and that's with a 180W amp for my ribbons and a 350W amp (both in to 4 ohms) for my 10" woofers on my Carver Ribbon system. Most music I play is in the low to mid 80s average A-weighted for the loudest parts of the music with peaks possibly at 90+ for short periods. Unless one listens all day long, this should be relatively safe. Most people with hearing damage listen to headphones that are turned up to overcome other noises (e.g. on airplanes) and this leads to average volumes that are way too high.
16 bit recordings offer dynamic range of 96 dB, that means for example a range of 10 db to 106 dB. But even that base level of 10 dB is far-fetched for most listening rooms because they usually have some kind of equipment like lighting, air ducts or amplifiers that produce hum of up to 20 dB.
Actually, the typical average house noise level is typically in the 40s to 50s for a "quiet" room. Thus, noise-masking is a significant issue. No one listens to music in an anechoic chamber except scientists for testing so the idea that 96dB dynamic range isn't enough is ludicrous given the masking effects. To hear all 96dB in an average room, you would probably need to be well over 105dB, possibly 110dB or higher for many frequencies. This is very bad for your hearing. Furthermore, probably 99.5% of all recordings don't have ANYWHERE NEAR 96dB dynamic range to begin with, particularly with the trend for louder and louder mastering. Even the BEST classical recordings I've seen may very rarely achieve recorded dynamic range levels around 98-100dB at most and you can actually reproduce that on CD with noise-shaping fairly well. Most humans hardly notice volume differences in the 1-3dB range without constant comparisons anyway. I don't know what's supposed to be "HD" about going from dead silence to Space Shuttle loudness volume changes anyway. Only movies typically even come close to using that much dynamic range and I don't want to hear ANYTHING that might damage my hearing (i.e. 120dB is instant damage) anyway.
Humans cannot hear much if anything over 20kHz even when they're young and most people over 40 would be lucky to hear 15-16kHz reliably at volume levels that aren't obscene. So many audiophiles rave about (analog) LPs on the best record players sounding better than digital music, particularly CDs, but they have a maximum dynamic range perhaps in the mid-70s at best and that's with 12" singles. Typical 12" 33RPM albums around 60-65dB dynamic range, not even CLOSE to CD capable levels and hardly anyone notices that they're missing since MOST recordings (particularly rock ones) don't have anywhere near 65dB dynamic range. In fact, most rock albums average dynamic range between "semi-quiet" sections and "loud" sections are probably less than 10-20dB these days. It's terrible.
But then is "Music" rated on its ability to go soft to loud quickly or is it based on the actual musical pitch/note changing content? Personally, the difference to me between good speakers and bad speakers has more to do with EVEN (e.g. +/- 1dB) and FAST (ability to handle quick transients) frequency response along with good room matching. What is called "detail" comes from being able to hear the frequencies associated with smaller frequency changes at the start of the envelope relative to louder "noises" like the ringing of a long note or overly emphasized bass, etc. Most cheap systems simply cannot put out quality bass or have things like "metallic" sounding highs (over-emphasis of certain high frequencies given an unnatural "crispy metallic" sound to instruments that didn't have them in the recording. NONE of this has a lot to do with really large scale volume changes (dynamic range) or higher frequency response than human hearing allows (>20kHz).
THUS, I'll say what I've said before on this subject one more time. MOST people would do 10x better to get better speakers with enough power to drive them cleanly and/or work on room response problems than to worry about high-end DACS, "HD Music" or any other crap that doesn't matter a bean in hell compared to the least common denominator which is their speakers, most of which are nowhere NEAR the quality that minute tiny tiny differences would even be revealed. In other words, who CARES about 0.05dB difference in a high-end DAC compared to a "low" one (which are the high ones from 10 years ago) when their speakers are +/- 3dB (i.e. up to a 6dB difference between what the frequency is supposed to be and what is coming out of the speaker, let alone the room response which could potentially make that 10-20dB or more for some frequencies, particularly bass where uneven room response and standing wave issues are a BIG problem for typical rooms which were never designed for audio listening.
In short, "HD Audio" is a marketing gimmick that will be used to separate you from your money when you should be spending it on better speakers and room treatments.
I would like to say one final word about iPhones and the like. The REASON many of you get such god-awful audio from your iPhone has to do with two things. One is the cheapy-little op-amp (amplifier on a chip, basically) used in such tiny flat phones. In short, they put out very little clean power. The second is the other end of it which is the headphones used with the iPhone. Whatever headphone you use is going to impact the music both through its frequency response (those tiny ear buds will NEVER sound very good even with all the clean power in the world) and its ability to be driven with a cheap op-amp (low power). The best thing you can do short of buying a headphone amplifier is to get headphones that both have good frequency response AND are very efficient (e.g. the higher the number the better). In other words, if a headphone doesn't need much power to put out a lot of sound then it can be driven cleanly (high quality) with very little power. THAT is what you want with a device that puts out very little power. The same is true with home systems. Something like Klipsch horn-loaded speakers rated at maybe 100dB per 1 watt at one meter will perform as well with 12.5 Watts of power (e.g. maybe a tube amp) as a 91dB rated speaker will perform with 100W of power. This is extremely important in car speaker systems where no dash head unit on earth can put out more than about 14.5 Watts RMS without an outboard amplifier that uses a DC-to-DC power transformer type amplifier. Reducing noise in the environment can make it sound louder at lower volumes as well and save your hearing in the process.
44.1/16 is CD quality and 96(or higher)/24 is HD. All music is done 24bit these days so downsampling is not 2014.
"HD" is a bad label for audio given there is typically ZERO audible difference between 16/44 and 24/96. It is a gimmick on the playback side, but very useful for headroom on the recording side. Sadly, gullible people that believe everything they read or hear from any "news" source will often buy into any snake-oil sale they read about.
