27 Feb
2007
27 Feb
'07
6:39 p.m.
On Tue, Feb 27, 2007 at 10:40:46PM +0100, Arnold Krille wrote:
We are talking about music-production for the
mainstream and PA, not
musicians amps. :-)
But you said "or with a professional PA". Surely you know that
commonly installed public address systems are capable of far more than
my puny 800 watt bass amp with its two 12" speakers?
A typical 300 capacity club here in NY will have 5000 watts or so
driving a 3-way system with the midrange drivers less than a meter
from the closest audience members. 120 dB at 1 meter would be about
108 dB at 4 meters, still plenty dangerous...
I haven't seen anyone firing his home equipment to
have 120dB and
sitting 1m or less away from it...
You never said anything about distance :-)
and i see that every time I go out to a club.
<snip>
I got my numbers from http://en.wikipedia.org/wiki/Decibel#Safety but
obviously their numbers represent some sort of typical examples; I
been in a number of discotheques (here in the US we can't pronounce
that so we just say "clubs") that had sound levels far above 100 dB.
The amount of time the ear can be exposed to a given sound pressure
level before sustaining permanent damange clearly varies a lot from
person to person. But government standards are probably a good
guideline to start with, eg. OSHA table G-16:
http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&…
TABLE G-16 - PERMISSIBLE NOISE EXPOSURES (1)
______________________________________________________________
|
Duration per day, hours | Sound level dBA slow response
____________________________|_________________________________
|
8...........................| 90
6...........................| 92
4...........................| 95
3...........................| 97
2...........................| 100
1 1/2 ......................| 102
1...........................| 105
1/2 ........................| 110
1/4 or less................| 115
____________________________|________________________________
Footnote(1) When the daily noise exposure is composed of two or
more periods of noise exposure of different levels, their combined
effect should be considered, rather than the individual effect of
each. If the sum of the following fractions: C(1)/T(1) + C(2)/T(2)
C(n)/T(n) exceeds unity, then, the mixed exposure should be
considered to exceed the limit value. Cn indicates the total time of
exposure at a specified noise level, and Tn indicates the total time
of exposure permitted at that level. Exposure to impulsive or impact
noise should not exceed 140 dB peak sound pressure level.
--
Paul Winkler
http://www.slinkp.com
120 dB dynamic range is an incredible amount, it
corresponds roughly
to the difference between whispering and a rifle fired at 1 meter.
Even the humble CD can capture the difference between whispering and a
chainsaw.
120dB is the difference between just loud enough to be heard by your
ear (1dB) and the loudness when the bones in your ear bow to protect
it. At higher levels (>120dB) your ear aches but it will recover if
the noise isn't permanent. At least thats the definition I learned...