About neuroscience and music (mainly classical). Exploring the relationship of music and the brain based on experience of two careers.

October 8, 2012

Treasure Your Hearing

by Carl Ellenberger, MD

Our sound guy, Jack Nissley, will tell you that I have complained that our jazz concerts are too loud since Adam and Eve. I point out that Allen Krantz’s unamplified guitar can be heard well from any of the 720 seats in the Playhouse, but the next night electric guitars may be played through two 10-foot banks of speakers (destroying directionality because the sound seems to come from the bank nearest you, not from the guitar) through a sound board as large as some pianos. I suspect the same sound level would fill Hershey Stadium. Most recently Jack said that the performers' stage monitors were so loud that he just transmitted their sound to the hall without amplifying it.

Imagine my reaction on a nearby porch after one of these concerts when a neighbor appeared in this T-shirt!

I am indeed old. And I have lost significant hearing over a lifetime playing and attending concerts. I have “presbycusis,” a word that implies (falsely) that hearing loss that comes with aging is ‘normal’ at a certain age or inevitable. Typically, my high frequency sensitivity (>2,000 Hz) is what I have lost, so in some situations, like loud parties, I have trouble understanding speech, distinguishing the sibilant “s” from “f” from “t” unless I watch the speakers’ lips. Fortunately, I don’t have any trouble hearing music (if not painfully loud).

There are two main reasons for progressive age-related hearing loss: 1) the DNA in your inherited genome, and 2) the cumulative effect of a lifetime of exposure to sound. The former you can’t avoid; the latter you can. The pictures help us to understand the reason. Sound (vibration of air) enters the ear and causes the eardrum to vibrate. The vibration is passed by the three “ossicles” (bone) to the cochlea, a small delicate organ embedded in the thick temporal bone (for protection). The ossicle at the end of the chain, the stapes (looks like a horseshoe), acts like a drumhead on the bell-like opening of the cochlea and the sound travels though the bore of the cochlea, as if backwards through a french horn, all the way to the narrow “mouthpiece” end of the coil, stimulating the microscopic hair cells that line the bore as it passes by. 

If you were a hair cell living near the opening of the cochlea it would be like sitting under a drumhead, and these hair cells are the ones that resonate with higher frequency sounds and thus may be the most vulnerable to damage. Loud sounds cause hair cells to disappear, as putting mileage on your car thins the treads on your tires -- very slowly and imperceptibly. You can replace a tire but you can’t replace hair cells and they don’t regenerate. So the number of hair cells you possess at any time in your life is the maximum you will have from then on. You can destroy hair cells with loud sounds during any time of your life but may not notice hearing loss until enough of them are gone. By then it is usually too late because you have permanent hearing impairment.

Early in life we may be cavalier about exposure to anything, especially loud rock music if it is essential to our emerging identity. Some musicians are beginning to be aware of the problem. The next time you ‘see’ an orchestra watch the woodwind players who sit in front of the trumpets and trombones. If there are no sound-blocking baffles behind their chairs, you may see them insert ear plugs when the brass play exuberantly. The orchestra pit may be the most hazardous environment; players are trapped in sounds from all directions.

There is some suggestion that sustained sounds (2-30 minutes, depending on loudness) are more damaging than sound that is periodically interrupted. But it certainly makes sense to avoid loud sounds altogether, if only by carrying a pair of earplugs in your pocket.  Just remember a first sentence in a recent issue of Consumer Reports: “Our shoppers purchased ... 48 hearing aids ... ranging from $1,800 to $6,800 per pair.”  But they don't replace normal hearing and come with their own set of problems, especially for people who enjoy music.

Warning: If your hearing loss is only in one ear, you may have an acoustic neuroma.

1 comment:

  1. Ditto: "What Causes Hearing Loss" by Jane Brody: http://well.blogs.nytimes.com/2013/03/18/faster-recovery-from-hip-surgery/