Hearing protection

Last week I did a Tailgate talk on hearing protection. Trying to illustrate the weight of a logarithm was a challenge. In the end what I did was to set a 50dB volume as the weight of a pint of water. Then I scaled up the "weight" by factors of ten. By the time I got to 110 dB the "weight" was the same as a redwood. Reducing the "weight" by 30 dB brought it down to an elephant's weight if I remember correctly. I think the point came across better. Before I realized that the dB scale was a log I thought it was like any volume knob on the radio. Not really...
 
It is the same. The volume control is a potentiometer that varies logarithmically. The best way I have found to explain dBs is simply every 3 dB increase is a doubling of power. 10 lbs becomes 20, then 40, then 80. 9dBs increase. It is a ratio, ie 10 watts to 20 watts is 3 dB. 1000 watts to 2000 watts is also 3 dB. Hope that helps. I luv this stuff.
 
Merak,

Respectfully, you're conflating different aspects of measurement. If you had a two-way loudspeaker, you might have the signals to the respective drivers each attenuated 3 dB at the crossover frequency, and the electrical signal would (mostly) sum back to 0 dB to achieve a flat response over the frequency range, so in that sense -3 dB equals half. If you could drive those speakers to only a certain volume level with your 10 Watt amplifier but wanted to double that volume, you'd need 100 Watts to do so; but we're not talking signal level now, but rather power level. Now -10 dB equals half in terms of sound intensity.

I admit now that although I'd thought I had a good recollection of the concepts, I was mistaken earlier. Sound pressure is measured in such a way that -20 dB equals a halving.

We're concerned with sound intensity here, I believe, and for that, 10 dB steps are required to double or halve the results.

Section "2" of this audio FAQ should help make all this clear as mud.

This Web page doesn't directly get into all the differences, but it succinctly states the rule of thumb regarding relative sound intensity levels.

This Web Page has a neat chart, and mentions the relationships between 3 dB and 10 dB increments at the bottom of the page.

Finally, here is a Java demo where you can select different levels of a 250 Hz tone. There is a reference level available, and one each of -3, -6, -10, and -20 dB from which you can select to play over your computer speakers.

(oh, there are [or at least historically where] two different tapers available for potentiometers: linear and audio [logarithmic])

Glen
 
I guess it was myself who was mixing the terminology. Yes, you'll be receiving twice the sound energy with a 3 dB increase, but you'll not perceive it as being much of a difference at all, which I guess is the danger of playing with such toys.

Glen
 
Don't forget that the Richter scale, used for measuring earthquakes, is a logarithm too.

Do you know what significance the "B" in dB has? Without googling first? Say it out loud and then think about it for a bit :)
 
Logs and tree werk

If'n i remember right ancient Greeks found an escalating scale of distance between leaves on the spiral around a branch, that also imitated that in a spiral seashell that started logarithmic scale, on these geometric, spiraling advancing. Much later, circles were calculated in 10,000 parts, and logarithms slid in to handle. Logarithms aren't just for our base 10 either.

i remeber $100 calculators, called electronic sliderules, when Texas Instruments first figured out how to use silicon, as we do now. The real sliderules (the calculators were replacing in classrooms); would just add numbers really on their simple slide, but the numbers they would add, were logs; thus multiplying the numbers printed. Then they would have a multiplied log scale, for then the slide would add those logs together, to give the raise in powers of that number.

So, to me a decibel log is pictured on this same scale, the increasing size of a spiral seashell (like part of the constructionof the ear itself), a geometric, rather than arithmetic stepping from value to value; that multiplys, rather than adds their powers.
 
just to complicate things, I've been using these (since my computer crashed, I lost the US web address, but at least awhile back it was out there): http://www.naturalearplugs.co.uk/
Wait, here ya go: http://www.earplugsonline.com/

These are like putty you pack over the ear canal, and they stick there without exerting pressure on the canal--even with foam, my ears get sore after a long time plugged. When you don't need them, you can just mash them sideways a little and they still stay in there. Over time, they have picked up a little dust and such, but I haven't noticed any detrimental side effects as a result.

The biggest complaint I have is they seem to work TOO well--with foam, I can hear a conversation fairly well, but with these wax kind, I really can't hear you unless you speak loudly.

I bought a 6-pack and found I can make three plugs out of two, turning it into a 9-pack. Been through the laundry a time or two (inside a plastic box), turning a pair into a big blob, but they are easily rehabilitated into two separate plugs.

k
 
When I am sawing for any length of time, I wear both plugs and muffs - I like the leightening muff the best.

Otherwise I stick with muffs only, as they are less of a hassle for me to take on and off...
 
I have used ear plugs similar to these and they work like a charm, but you are right they work so well that they make comunication slightly difficult.

But I recomend anyone who doesnt like earmuffs and dont feel ear plugs work very well to give em a try.

you can get em here In Point at menards, Fleet Farm or Franks.
 
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