Thursday, October 5, 2017

Fragile Shadetree-Engineered Mess

img1017For much of my life, I’ve said that the human hearing mechanism is evidence that if god is an engineer, he’s one lousy manufacturing engineer. Our ears are one cobbled-together mess of mechanical, hydraulic, electrical, and chemical parts. The two smallest, most delicate bones in our body are the coupling between the outer and inner ear drums. They can be dislodged by the impact of a simple fall at any point in your life. The outer ear drum is plagued with all sorts of infection and perforation opportunities.

Practically all of the information we define as “sound” is made up of complex collections of audio (20Hz to 20kHz, is generally described as the human hearing frequency response) frequencies. There are root, or fundamental, tones and their associated harmonic frequencies; which we often define as “musical signals.” There are noise signals, which often have non-harmonically related frequency content along with more identifiable harmonic content.

6-damaged earThe most delicate of all the components are the cilia, the “hairs,” that line the cochlear. Those tiny hair cells are the devices our hearing uses to convert air waves into specific audio signals to be decoded in our brain. Those tiny sterocilia are the devices required to convert air motion (sound) into electrical signals sent to our brains. Different areas of the cochlea are responsible for different frequency ranges and each of those areas are made up of a collection of rows of cilia which are responsible for very specific frequencies.

cochlearOne of the most typical symptoms of damaged cilia is “tinnitus”: the perception of noise or ringing in the ear. Sometimes, tinnitus means you have done temporary damage, but often it means you have done permanent damage to a specific area of your cochlea. You may have lost the ability to hear the frequencies you are being cursed with “hearing” all of the time. Because those missing or damaged cilia are no longer sending the appropriate auditory nerve signals to your brain and your brain is “cranking up the gain” in an attempt to compensate for the reduced output. In electronic systems, when amplifier gain is increased beyond the point of stability, oscillation occurs: ie. the perception of noise or ringing in the ear.

Unfortunately for us, nothing in nature prepared our hearing mechanism for the abuse we would be subjecting it to in modern life. Outside of landslides, earthquakes, hurricanes and tornados there is nothing in nature as loud as the kind of crap we subject ourselves to every day with vehicles and traffic (loud pipes destroy lives), industrial noise, and modern music from the usual sources: speakers and headphones. The 120dBSPL+ levels we are regularly subjected to is far more than enough to cause permanent damage to practically every fragile area of our hearing mechanism, particularly the cilia.

Twenty years ago, I had reconstructive nasal surgery in an attempt to fix the damage of being my father’s failed student’s punching bag from when I was about 12 until around 17 when I made the decision to make every fight I was forced to participate in into a fight to the death or dismemberment. By then, my nose had been broken so many times, air could not pass through the left side at all and barely squeezed through a convoluted slit in the right side. The surgery was more complicated than the surgeon anticipated and probably needed a second pass. However, about a week after the surgery, a sneeze caused the right side to hemorrhage and I woke up pouring blood from my nose. I went to an emergency room, where a doctor inserted a 4” long piece of stiff absorptive gauze into my nose. Later, my surgeon replaced that with an inflatable device that forced the blood flow into my sinus cavity and nearly burst my ear drum. After a day of intense pain, I deflated the device and decided I’d rather bleed to death than have my hearing destroyed. In the end, I was stuck with an 8kHz ring, tinnitus, in my right ear. Over the years, that noise slowly reduced in volume, but it has been close to intolerable often.

Last night, at a local bar’s open mic, I slipped up and went unprotected, no hearing protection. I sat in the stupidest possible place in that bar, near the FOH speakers, and possibly did permanent damage to my hearing. When I got home, the volume of the tinnitus was the worst I’ve ever experienced in twenty years. I woke up at 4AM the next morning with approximately the same volume of noise. I am desperately hoping that I did temporary damage and it might go away with time. Tinnitus is intolerable for someone who has spent his whole life primarily driven and directed by hearing, sound, and music. I’ve put up with that damn background 8kHz for 20 years. This is not a background noise. It is front-and-center the loudest thing in any room I am in. If you want to know why I am such an opponent of pointless amplification, get into my head for a few hours and you’ll be ready to shoot anyone who fools with a volume control.

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Wirebender Audio Rants

Over the dozen years I taught audio engineering at Musictech College and McNally Smith College of Music, I accumulated a lot of material that might be useful to all sorts of budding audio techs and musicians. This site will include comments and questions about professional audio standards, practices, and equipment. I will add occasional product reviews with as many objective and irrational opinions as possible.