So How Do We Hear This Stuff?
Our perception of sound is so easy, so seamless, so unequivocal and clear, that it doesn’t seem like there is much to it. Guy/gal makes a cool noise, we hear it. Cool! What could be simpler?
Naturally, when we try to make a recording of said guy/gal’s sound and play it back out of loudspeakers we run into a little trouble, as you may have noticed. Guy/gal makes a cool noise, we record it, play it back. Not quite so cool. Why is that? The obvious answer that most of us like to fall back on is that our equipment isn’t good enough. And so there’s a lot of blather about accuracy going around these days, and we worry about our gear. We reason that if the gear was “really accurate,” why, it’d sound exactly like that soprano digeridoo we’re trying to overdub!
There is another explanation, however. What we perceive isn’t exactly what went in our ears. In fact, it isn’t like what went in our ears at all! What we consciously “hear” is far removed from the physical stimulus called “sound waves” that entered our ears. And because there is such a huge metamorphosis between our ears and our mind, it isn’t reasonable to assume that just because we’d like to think that we’ve made a really physically “accurate” recording of that soprano digeridoo, that in fact we have made a recording that is accurate for our perception.
Just because we’ve used “really accurate” microphones, consoles, recorders and speakers doesn’t guarantee a whole lot, it turns out. We need to consider our hearing mechanism in a little more detail, and understand a bit more about what it is doing. And, along the way, perhaps we need to redefine what we mean by “accurate.”
So, I’d like to devote a couple of articles over the next several months to the human auditory system and how “the way it works” affects our work as recording engineers and producers. As I mentioned earlier, most people get their emotional hits from music and sound at a pre-conscious level. And that gives us some powerful mojo. If we can get control of the raw sonic materials that generate those emotions, why, we can really get our listeners going and they’ll never even have a clue as to why! Maybe we can even come to rule the world!
COMMENTS
River Vale, NJ Jun 16, 2006 01:25 PM
Excellent overview of what goes on in the most sophisticated piece of audio processing gear any of us will ever have the opportunity to use! Since I am a doctoral-candidate audiologist, and an auditory researcher at Columbia University, I can tell you it gets much more fascinating (and even weirder!) than anything you have touched upon here. But that is a topic for another day.
I first wish to thank you for giving our sense of hearing the well-deserved respect and mention that it so deserves. It is an often-overlooked component of the signal chain in our discussions of gear and signal processing. Unfortunately, it is also too often abused. Everyday I see the effects of the noisy world we live in on the human ear. I am referring not only to the loss of hearing sensitivity, but also the loss of frequency specificity in the cochlea (think psychophysical tuning curves here) resulting from inner hair cell damage, which is very difficult to rehabilitate.
Hearing loss is easy to prevent, yet once the damage has been inflicted, there is (usually) no going back. It is simply gone. There is some promising early work in the area of hair-cell regeneration (at least 20 years off even by the most optimistic estimates) as well as various therapies centered on the concept of pharmacologic prophylaxis, including N-acetylcysteine, and the more mundane vitamin C. However, the pharmacological therapies are still unproven, and are very controversial.
As audio professionals, part of your overall healthcare should include annual hearing tests, including Distortion-Product Otoacoustic Emissions (DPOAEs), even if your audiogram is “normal.” Up to 25% of your outer hair cells can be obliterated before a hearing loss will be evident on a basic audiogram, and DPOAEs are highly sensitive to this early damage. Early detection is the key concept here. Also, try to monitor at conservative levels (less than 85 dB SPL is good), and whenever this is not possible use custom – molded musician’s earplugs (especially for live sound work).
Dean Mancuso MS CCC-A
Winter Park, FL Aug 29, 2006 06:46 PM
Did you finish the article? You have me on the edge of my seat! Please, don't let me fall off!! Where are the answers to those great questions you had??
Groton, MA Aug 30, 2006 08:03 AM
Oops! Thanks for bringing this to my attention! We're missing a couple of pretty good articles.
The next article in the series is The Audio Window, which is here. Following that are two articles: "Hearing: the Highs and Lows of It" and "Hearing: the Louds and Softs of It." I will get webguy to get these included ASAP. In the meantime, you can download these from
http://moultonlabs.com/berklee/
I hope this helps.
Best regards,
Dave
davemoulton
Winter Park, FL Aug 30, 2006 02:03 PM
Thanks for the quick reply. =)
It will take me a while to get through everything, but I'm sure it will time well spent. Awesome.