Conference 7.286::digital

    Since anything that generates a steady masking sound can be considered
    a "white noise" generator, fans and blowers fall into this category.
    I like to have fans going, or a loud blower, for the very reasons
    you mentioned.  However, everyone doesn't agree with this philosophy.
    I have worked in two places where co-workers complained strongly
    about the sound of fans, coming from either PCs or personal fans
    in high-heat areas.
    
    You might check with the people in your area before installing such
    a device.  As far as installing the WCRB system: it has to be approved
    by your cost center manager, and they install their own
    signal-receiving equipment.  I understand the cost is quite high
    (for a private budget).

    My father works in a building that has such a system (don't know
    if it's WCRB).  The system was considered somewhat of a joke, but
    then they already had carpets, etc.  All in all, people don't really
    think it helps.
    
    Charlie

    There are 5 components to speech privacy:
    	1. Source level - how loud is the noise that you don't want
    to hear?
    	2. Barrier effectiveness - height and freedom from holes/gaps
    	3. Cieling reflectivity - absorption coefficient of cieling
    tiles.
    	4. Distance between source and listener
    	5. Ambient level at listener position - this is what the masking
    system works on.
    General: Masking systems can make the difference between a poor
    situation and a good one.  They can not go from horrible to great.
    For high privacy, you need either long distances between positions,
    or walls.  
    Masking systems: work best when installed without listener knowledge
    and are brought up to full level gradually - over a period of weeks.
    Over a certain level (about NC 50) they are often judged to be 
    intrusive. The spectrum must be carefully shaped or it will be judged
    too hissy. It does need very high levels of low frequency noise
    to mask rumbly sounds.  The current state of the art is to mount
    the speakers just above the cieling tiles pointed upward so the
    image source is higher. This results in less variation (less ability
    to locate sources) in levels.  - Chris     

I recall hearing about a year ago about an experimental system
that monitored noise and generated the appropriate
sound waves to eliminate the noise via destructive interference.

I bet we can find enough computes around here to do this!  I don't
know what kind of microphones and loudspeakers are needed, though,
nor whether the necessary programs are public domain.

    re: .4--I doubt that such a system could be made effective
    over an extended area.  Ignoring the computational problems,
    the controlled noise sources would have to generate waves
    that exactly cancelled the uncontrolled noise sources, but
    this could only be effective at the single point where they
    were exactly 180� out of phase.  Because noise is random,
    they would not be exactly out of phase at any other point.
    
    If you tried to overcome this problem by having a controlled
    noise source for each person you would magnify the problem
    tremendously, since the controlled noise for one person would
    be effectively uncontrolled for every other person.  You would
    end up with a spiral of contending noise, likely getting louder
    until reaching some kind of limit: speakers, microphones, or,
    more likely, people's tolerence.
        John Sauter

Re .4,.5:

One of the short stories in Arthur C. Clarke's anthology "Tales of [from?]
the White Hart" deals with exactly this idea.  A protagonist mumbles about
why such a device wouldn't work in the background, while a B.S. story which
pretends to explain how the device ultimately failed (for the wrong
reason) transpires in the foreground.  It is a good story (in a good
anthology).


I can imagine constructing a device which would in theory cancel the noise
exactly if the environment it operated in had perfect bilateral symmetry;
however the device would likely fail miserably in practice, to the point of
making the noise appear twice as loud at it is without correction.


The idea is more believable than perpetual motion machines, but I wouldn't
invest my money in the former any more than I would the latter.
				/AHM

    Such a masking device would probably fail, because it would have
    to generate the countering wave at *exactly* the moment that the
    real wave was created.  We would need a precognative-bus, something
    like Arthur Dent's prescient doors.  ("I hate doors...")
    
    However, such devices do exist for sound that is regular and
    predictable.  I don't know if they are still in use, but I remember
    a steam-powered electricity plant near my home in to '50s that used
    just such a system to mask the sound of the turbine.  The device
    broke one day, and we were treated to several hours of high-intensity
    whine before they fixed it.

  Conceptually, you don't need the prescience.  Since any wave 
  phenomenon moves at a finite speed, you could monitor it at 
  one point and interfere with out farther out in its travels. 
  In open space, where the wavefront is spherical, that 
  probably starts to require many other radiators, especially 
  if your processing takes a long time, but it theoretically 
  could be done.  (It also depends on the wavelengths you're 
  trying to cancel.)  In a more limited context (say, some
  linear conduit in which the wavefront travels) its probably
  quite practical.

  By the way, a good example of cancellation of regular pulses
  that's closer to home and dearer to more peoples' hearts is
  any engine with either tuned induction or a tuned exhaust.
  There, the pressure wave from one cylinder is used to help
  charge other cylinders.  That uses part of the energy that 
  would otherwise be emmitted as pressure waves (sound).

  Anyway...

  (I resisted this yesterday, but today I'm weak :-)

  What about "THE CONE OF SILENCE"  (Tee-Hee) ?

                                   Atlant

    How about ear-muffs or 'walkperson' or 'discperson'?  Although it might
    be interesting to justify the discperson on your expense voucher :-) 
    
- Vikas

I can see a valid safety issue with wearing headphones in certain environments,
such as while walking along a corridor where there are also powered vehicles.

But at your place of work, sitting at your desk, if your job doesn't require
you to respond to audible signals that won't get through the headphones, there
is no way a manager can restrict this aspect of your personal freedom.

Take it up the ladder if s/he does.

/john

  Using headphones is a good alternative for someone who wants to
listen to a radio or tapes in their office without disturbing other
people. In fact, if someone in the next office can hear the music
from a Walkman while the headphones are in place, it means the user
is damaging his ears. 
  However, the main problem in my office area is conversation and
"impact" noise, not radios. 

    Isn't there a policy against personal use of radios during business
    hours?
    
    Steve Kallis, Jr.
    

re .14

Find it.

/john

The tape players/CD players and radios cause a worse form of noise pollution,
even when used with headphones. That pollution is caused by amiable, cheery
people who like to sing along with the music (which no-one else can hear). I'd
name culprits, but I promised Dick ASD:: Binder that I wouldn't embarrass
him further   :-).


		Nigel

    re: .15
    
    I don't have a copy of the personnel policies, so I can't rise directly
    to the challenge.  However, I do specifically remember that when
    I joined DEC (back when the earth's crust was cooling), one of the
    policies mentioned in a handout was that radios or other music-making
    devices were specifically excluded.  Walkmans weren't available
    then (yes, something other than crystal sets were available!), so
    the policy may have been altered because of these devices.

    re: .0
    
    I know this reply is several months old, but I thought I'd let you
    know that the facility I am in (LAO - Los Angeles District Office)
    has had "white noise" ever since we moved into this facility
    approximately 5 years ago.  It does sound like air blowing, and
    comes out of speakers that are placed above the ceiling tiles.  Since
    I am so used to hearing it, I tune it out.  However, it is turned
    off after 7-8:00 in the evenings and then it is *real* quiet!

    i find the most noise in my cube comes from the disk drive connected
    to my workstation, it is an external one, and the SCSI cable from
    the disk to the workstation they made it too short, so i have to put 
    the disk on the desk and it is noisy, i tried putting little box on top 
    of it, that helps but very little.

    one way to cut noise in cubes too is to use the ear plugs, those
    sponge like things, you can get from the health office down in
    ZKO1 second floor, they are really good, after i put them in i also
    put the ears headphone things on top of my ears and the noise is all 
    almost gone, but i can still hear my boss if he comes screaming at me , 
    so there is no logistical problems with it.  
    
    i think it is very important  to have quite cubes, i can not think well 
    with noise that is why i try to do my thinking between 1:00 and 5:00 am. 
    when things are very quite, iam sure many DECees share my feelings on this. 
    
    i think our buildings should be like the library, i have been in DEC 
    for 3.5 years and I have not seen one "please be quite" sign any where 
    around. 

    hope this helps.
    \buy
    \nasser


    

    re .-1
    
    >i think it is very important  to have quite cubes, i can not think well 
    >with noise that is why i try to do my thinking between 1:00 and 5:00 am. 
    
    1:00 to 5:00 am, when most people are asleep, This could explain a lot
    about Nasser's thinking processes...
    
    :-)
    

    No need of noise masking here.  This place is quiet as a tomb this
    morning.
    

Geez, Nassar, I can't believe what you've done in only 3.5 years!  You've
developed quiet the reputation...8-o