I am quite aware of the dangers of hearing loss. Some are unavoidable (infantry on the battlefield), so are (listening to music). I've been listening to elevated levels ever since I built my first super power system in the mid 1970s. It sounded awful, too.. Community SRH60 horns.. need I say more?
I refined things a lot by 1982 and ditched the last of my horn-loaded speakers by the mid 1980s, opting for an increase in power and more speakers instead.
Mark makes an interesting and often overlooked point about room reflections increasing the duration of sounds. My listening space is nearly anechoic at the front. The back used to be the live end, but I have too much junk back there now, so it's more dead than live. The point is, listening to music in a reverberant room greatly increases the stress on the ears because brief durations are stretched out, and reflections may actually amplify some frequencies in a manner not totally unlike a laser.
Peak to average ratio is the key here. I have the dbx 4bx, which can take any decent recording and increase both the impact of percussion as well as the dynamic range over three audio bands. It's the first and only processor I've found over the years that does this fairly transparently when used in moderation. No one has replicated it in the digital domain yet, unfortunately. So I still use it to enhance pop music. With the pop of the snare drums a good 10dB louder, it makes a lively enhancement. One thing that disappoints me about live concerts is that the impact is not there. I'd rather listen to music at home, because I can mold it to fit my mental picture of how I would like it to sound. (This applies only to amplified rock/pop music. My approach to Classical is strictly purist, with no enhancements, played at precisely the volume heard in the concert hall.) Live rock concerts don't 'fulfill' me. I once did a recording gig at a Molly Hatchet concert. I found the levels to be rather mundane, buy the lead singer in the opening band said he felt it was 'crazy loud'. I measured 114dB at FoH where my mics were located. I would have wanted more, but we live in the age of OSHA...
Ethan mentioned that I measured the GBS' SPL during a rehearsal. I clocked 105dB during a tympani crescendo. I think that was 4th row. Interestingly it was only 2dB softer in the balcony, but there was more bass up there. I make those measurements so that I know how loud to play my recording back at the studio. Part of high fidelity and being true to the source is matching the playback levels.
RMS power levels are what the ear is sensitive to, and that's been the name of the game in the volume wars. You can get a boombox to play fairly loud with a compressed hip hop CD. But to get an uncompressed recording to play at that apparent level, the peak levels can go into danger land for our ears. Since I use no compression, but in fact often like to use expansion to add another 25dB to the dynamic range of my music when listening to rock or reggae, the situation demands the ability to play even louder.
On the bass end, the purists here are going to castigate me for saying this.. I have a dbx 500 Subharmonic Synthesizer. I use it to replace the missing fundamental in some 70s pop/rock. It does a great job with certain recordings, to build a believable fundamental bass in a recording that sounds like a bass fed through a practice amp that was miked at a distance. Thinking of Average White Band and similar ilk of that era. Less sensibly, I have used it with Reggae music. 60-50Hz dominant music becomes 30-25Hz dominant. It's strange sounding at first, but after a while, you wonder if it sounds better this way.
Until digital came along, I was limited by what my turntable could tolerate. Too high and the system would oscillate/feedback through the turntable at about 6-8Hz. My solution was to dub all my 45s and LPs to reel to reel tape. That's why I have so many reel tapes. When CD came along, I could go louder, but then the CD would skip. Finally, reading music off solid state media through a computer proved to be the solution to the SPL feedback problems.
Now, about the effects of bass on the ears. Really low bass.. My local YMCA has an Olympic sized swimming pool. It's 14' deep at the deep end. When one dives into the deep end, the pressure on the ears is considerable. Now imagine this pressure moving your ear drum in and out about 14-16 times a second. That's what very deep pipe organ pedal fundamentals feel like in the ears when played louder than life.
At lower frequencies, below 10Hz, when the level is set just below the point where the building structure starts to make sympathetic vibratory noise, and low enough to be below the threshold of hearing, when one speaks, it's a bizarre sensation.. one's speech is garbled. The ear is highly non-linear, and this otherwise inaudible sinewave modulates the ear drum and affects the sensitivity to sound within the audible spectrum.
Listening to pop/rock/reggae at high volume.. loud bass over 140dB is quite painful to the ears. And after the music is stopped, all sound the ear hears for about 30 minutes afterwards has a peculiar distortion to it. It's not like tinnitus, although there is a ringing component to it. What I hear during that recovery period is some gross asynchronous distortion whose harmonics are unrelated to the sounds I am hearing. This only happens after an encounter with some very loud bass guitar parts. Since my CEL 201-1 meter redlines at 140dB, I can only guess at what I'm subjecting myself to after the needle smacks into the peg at full scale. But it feels good in the gut. And as one who's no longer a spring chicken and not as regular as I was as a youngster, I must say the laxative effects are .... useful.
One of the saving graces, besides the dynamics of the music, is that I can only do this about once a week. I have to get everyone out of the house and that's not easy. And then it takes me an hour to clean up after a five minute session. The ceiling tiles get sucked out and fall on the floor. Dust falls everywhere. Last week one of the fluorescent tubes exploded in an overhead troffer fixture. I spent an hour vacuuming all the dust that falls all over the room. It literally 'snows' when the dB level gets in the 140+ range, as precipitation becomes dense and visible. I'm constantly experimenting with methods of hardening the room so I have less distractions. Everything in the house has to be Bass Pig-proofed--that means rubber mats on shelves, lips around every shelf to prevent items from sliding off and falling, etc. The house is less refined and more like a rugged mountain lodge, and my approach to anchoring things down is a comprehensive strategy throughout the house.
Bottom line: dynamic aperture. My fireworks video has 85dB of it. Ethan is the only other person on earth with a copy of the Blu-ray disc that I produced last summer, so he's qualified to comment on peak to average ratios and crest factors that can be extreme.
