Conference napalm::commusic_v1

    Damage to the ear increases with sound level and with duration of
    exposure.  Therefore, longer sustained noises, such as a rock band,
    do far greater permanent damage in a couple hours if it's loud enough
    than a short <1second exposure to the same level.  You might say
    7200 times as much damage.
    
1 ! tom janzen 9-22-87  5-3-88 for commusic conference use VAX BASIC
2 ! digital equipment corporation for internal use only
10 print "So, do you know the "
11 print "voltages/currents (1)"
12 print "           powers (2)"
13 print "               dB (3)"
20 input which
30 if which=2 goto powers
   end if
40 if which=3 goto db
   end if
45 print "OK, swell.  You know 2 voltages or 2 currents."
50 print "What's the first one";
60 input v1
70 print "What's the second one";
80 input v2
90 print "The power ratio in dB is: ",20*log10(v1/v2)
100 goto 570
200 powers:
210 print "OK, you know 2 powers in watts."
220 print "What's the first power";
230 input p1
240 print "What's the second power";
250 input p2
260 print "Fine.  The power ratio in dB is: ",10*log10(p1/p2)
270 goto 570
300 db:
310 print "OK fine.  Enter the db: ";
320 input decibel
330 print "Fabulous!  The power ratio is: ";10**(decibel/10)
340 print "Wonderful!  The voltage or current ratio is: ";10**(decibel/20)
570 !stop
580 end
    
    Tom

Edd, SPL doubles every 3db. So 100db is 16.67 times louder than 50 db.

dbii

>    Edd, SPL doubles every 3db. So 100db is 16.67 times louder than 50 db.

    I think that's actually 2 to the 16.67 power, a heck of a difference
    (about 64000!!!). Decibels are logarithmic, to a base of 10. 

    Using db's logic, 130 dbs should be over 8X as loud as 120...
    
          L=volume
    
                  120= 1L
                  123= 2L
                  126= 4L
                  129= 8L 
    
    I don't know how to do logs to use Brian's logic...
    
    Which is right?
    
    Edd

    the reason decibels are so useful is that they are logarithmic and
    the ear is pretty much logarithmic.  The scale was adopted for general
    electronics, but I think they should have stuck with nepers.
    anyway, 50 dB is a power ratio of 100000 and the voltage 316.
    I think intensity follows voltage.  However, the ear hears like
    dB almost.  I think that 10dB is twice as loud to the ear until
    sensory fatigue sets in, which is very fast for the ear.  This is
    a reason loud sounds are dangerous; they don't sound loud after
    a few minutes, and your ear is damaged by the mechanical excitement
    that you ignore because the ear is lying to you about how loud it is.

    So 50dB difference might seem 32 times louder, I think.
    Although it seems about as subjective as color.
   
    120dB difference would be 1000000 times more intense and I guess
    4096 times as loud.  
    So if the ear has 120dB range, how come we don't have 19-20 bit
    d-a convertors in synthesizers? because it's too hard to make such
    low noise analog paths, mixers, amps, and speakers.  If your line
    level peak was 1volt, your noise peak should be less than 1 microvolt.
    Too difficult for midi jockeys.
    Tom

    _Apparent_ loudness doubles approximately every 3dB.
                                      
    A whisper becomes barely understandable (rather than noticeable)
    at about 20 to 40 dB.
    
    Normal indoor conversation is about 80 dB.  
    
    Acoustic instruments in concert (say, playing Beethoven's 9th) peak
    at about 120 dB.
    
    Threshold of pain is about 130 dB.
                                            

    a nit - there are two kinds of dBs - relative dBs and absolute dBs.
    Unadorned "dB" usually means relative dB, and absolute levels are
    represented by "dBA".
    
    len.
    

	Then there are also the two other db's, the one from New Hampshire, and 
the one from Maine.  I don't believe they are relatives, either.

	Dan

    According to Reference Data for Radio Engineers, SAMS, ITT,
    
    Threshold of pain 130
    Airplane, 1600 rpm, 18 feet, 121dB (above 10E-16 watt/centimeter^2)
    subway , local station, express passing 102dB (1.58microwatts/cm2)
    Noisiest spot at niagara falls 92db (.158 uw/cm2, so 10dB is 1/10
    	intensity)
    average automobile 15 feet 70db
    average conversational speech, 3.25 feet 70db
    average office 55db
    average residence 40db
    quiet whisper 5 feet 18db
    reference 0db
  Tom

    From The Tuning of the World by R. Murray Schafer (autographed)
    stema engine: 85dbA
    printing works 87dba
    diesole-electric generator house 96dBA
    screw-heading machine 101dBA
    weaving shed 104dBA
    sawmill chipper 105dBA
    metalwork grinder 106dBA
    wood-planing machine 108dBA
    metal saw 110dBA
    rock band 115 dBA
    boiler works, hammering 118dBA
    jet taking off 120dBA
    rocket launching 160dBA
    Streets of Bombay, Ghatbopar districts at midnight: 47dBA
Tom

    from Music, Physics, and Engineering, by Harry F. Olson
    
    Loudness is measured in Sones.  40dB above the listener's threshold
    is called 1 sone.  The oudness of a sound judged to be n times greater
    than that is n sones loud.
    
    The loudness of a sound in phons, on the other hand, is the same
    as the spl in dB, relative the .0002 dynes/cm^2 of a 1kHz tone equally
    loud.  See figure 7.8.
    0 phon	.001 sone
    8 phon	.01 sone
    20 phon	.1 sone
    40phon	1 sone
    70phon	10 sones
    100phon	100 sones
    
    From Horns, Strings and harmony by Arthur H. Benade:
    It takes 8 radios to sound 5 times louder.
    
    Tom

    Tom, that's exactly the type of thing I'm looking for. Thank you.
    
    I'm still not clear on how to determine what 2X a given dbA is.
    What is "twice as loud"?
    
    Edd

    I'm pretty sure I recall seeing an article on the risk of hearing
    impairment among musicians in some magazine relatively recently
    (like the last 6 months?)  Anybody else with better memory remember
    exactly where?  It had a lot of stuff in it about sound levels of
    standard obnoxious noises and mechanisms of hearing loss etc.
    
    len (dumb but not yet deaf).
     

AUDIO had an article similar to that within the last 6-8 months.  The same
issue had an interview with Mr. Kurzweil.

Chad

    Just a brief ancedote,
    
    This weekend, while we were playing a gig, our singer was getting
    too much volume from one of the amps. When she put an ear plug into
    her left ear she got a surprise,... it didn't make any difference.
    Seems that she had not noticed that she had quite a bit of hearing
    loss in that ear.
    
    The cause was probably the many years of singing in bands, but another
    factor was that she has had two children. I remember reading of
    a study that discovered many parents (especially the primary
    care-givers) developed some hearing loss in one ear. The cause is
    believed to be the crying infants. IE: baby falls down, starts to
    cry,... mom picks it up,... baby winds up and gets a proper lungfull
    of air just as it is put on mom's shoulder, and WAAAAAAA! inches
    from mom's ear. It seems most parents tend to favor holding the
    child on one side or the other, hence the difference in hearing
    loss.
    
    Moral: Use earplugs on stage, and with children!

    Next thing you know, OSHA will require that persons working in a
    day-care center wear hearing protectors...
    
    And since with the hearing protectors on, they won't be able to
    hear a normal baby crying at 15 feet...
    
    So they'll require "backup beepers" on baby diapers...  :-)
    
    	-Bill

    Can someone explain the difference between "A Weighted" and "C
    weighted"?
    
    I was of the impression that "A" was an analysis that was flat across
    the spectrum, while "C" was weighted to more closely mimic the response
    characteristics of the human ear. Am I even close?
    
    Edd

    
    Re: .17
    
    That's essentially it.  The weightings were thought up by Ma Bell
    for evaluating noise over phone lines.  "C" weighting was more
    forgiving of noise since the frequency response of your average
    phone line is pretty piss poor.
    
    Weighting is only of interest when talking broadband information.
    
						Brian

    Edd - there is a somewhat cursory explanation of all this hoo-hah in
    the June '86 issue of Keyboard (page 43?).

    If you're a pack rat, it may have paid off...

-b

    Is that the "Recording" issue with the picture of the tape hubs on
    the cover? I thought I read that article, but the issue got trashed
    during some bathroom remodeling. (That *is* where everyone keeps
    their magazines, right?)
    
    Edd

    re: Edd
    ......
    ...........Only the GOOOOD magazines!!!!!You know the ones with the
    centerfolds..woooo   wooo look at all those keys,,, wow, how many
    notes can she hold? oh my, a full frontal of the MIDI ports!!!!
    
    8^) 
    
    
              Franko

    Uh, I think you have it backwards.
                                  
    	A weighting - ANSI weighting - as in what OSHA uses to establish
    		"dangerous" versus "non-dangerous" hearing loss.  The
    		"A" weight curve looks very much like the bandwidth
    		curve of the older telephone sets - which is no
    		coincidence, because they're both modeled on the 
    		"speech intelligibility" of human ears listening 
    		to human speech.  Think of it as a bell curve that starts
    		at 100 Hz, tapers upward to 300 Hz, is pretty constant
    		till about 2.5 KHz, and then tapers down to zero at
    		5KHz.  It's actually smoother than that, but you get
    		the vague picture.
    
    	C weighting - Constant weighting.  This is essentially flat
    		from 20 Hz to 20 KHz for audio meters, and extends
    		in either direction for those spl meters that can 
    		sense infra/ultrasonic energy.
    
    Many meters can measure either; there's a little switch to select
    which weighting to use.
    
    	-Bill