A-Weight vs C-Weight Questions
A-Weight vs C-Weight Questions
(OP)
I need to know the basic differences between A vs C weighting when measuring sound. I am measuring sound for an outdoor event and in my searching I find a lot of stuff for A-Weight, but little on C-Weight.
When measuring sound with the above weighting, when would one use slow vs fast settings?
When is it desirable to switch from A to C? Again the event is an outdoor music concert. Any advice would be appreciated.
Thanks!
Bill
When measuring sound with the above weighting, when would one use slow vs fast settings?
When is it desirable to switch from A to C? Again the event is an outdoor music concert. Any advice would be appreciated.
Thanks!
Bill





RE: A-Weight vs C-Weight Questions
In practice though, the B and C filters don't correlate with subjective response, so most people use A for everything.
Industrial (in EU at least) noise levels are generally based on A-weighted levels.
I would probably use "slow" if wanting a reasonably avereraged reading.
- Steve
RE: A-Weight vs C-Weight Questions
Ftome what Steve has Posted I would thing that A weighting would cover your needs.
Chris
RE: A-Weight vs C-Weight Questions
RE: A-Weight vs C-Weight Questions
As to fast vs slow - fast seems to correlate better for most noises I am familiar with.
To be honest if you really want to do it properly you probably want to be using a more statistical approach like Leq
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: A-Weight vs C-Weight Questions
The sound measurements are to find out the decibel levels, compare them to known db levels and finally try to figure out some upper limit so as to not have a public nuisance with future outdoor concerts.
Thanks!
Bill
RE: A-Weight vs C-Weight Questions
Depending on where you are holding these concerts, you may find there is already legislation in place. Worth a hunt.
- Steve
RE: A-Weight vs C-Weight Questions
I.e., no difference = little or no low-freq content'
large difference = lots of low-freq content.
Believe it or not, this was the method used by a German automotive supplier firm to analyze exhaust tailpipe noise as recently as the late '90s.
- R
RE: A-Weight vs C-Weight Questions
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: A-Weight vs C-Weight Questions
All regulations are written around A-weighted levels. And usually slow response. A-weighted appoximates human ear response, perception of sound.
Ted
RE: A-Weight vs C-Weight Questions
ConsistentAs hydtools post, you would want to measure it consistent with the applicable ordinance in question..
And if the ordinance in question is written to be implementable, it would include a section on sound measurement standards as the ordinance in my county is written below.....
Sec. 16-54. Sound measurement standards.
Standards, instrumentation, and measurement procedures to be used in the measurement of sound as provided for in this article are as follows:
(1) Sound level measurement shall be made with a sound level meter using the "A" weighting scale set on "slow response," except for measurements of impact sound, set on "slow response. Impact sound shall be measured using the fast response of the sound level meter.
(2) The entire sound measurement system shall be serviced and operated as recommended by the manufacturer. Any officer authorized to enforce this ordinance shall be trained in the use of sound level measurement and the operation of sound level meters.
(3) Except in the case where noises are emanating from within multi-family structures and the complainant is a resident of the same multi-family structure, noise measurements shall be taken at the corner of the primary structure of the complainant nearest the noise source but when this location is not practical noise measurements shall be made at the boundary of the public or private right-of-way which adjoins the complainants' property.
(4) In the case of noises emanating from within a multi-family structure and where a complainant is a resident of the same multi-family structure, noise measurements shall be made in the unit of complainant at a height of at least four feet above the floor and at a point approximately equidistant from all walls.
(5) No individual other than the officer operating the meter shall be within ten feet of the meter during the sample period.
(6) The meter shall be calibrated immediately before use and recalibrated after use.
(7) The officer operating the meter shall face the noise source and record the meter's instantaneous response observed at consecutive ten second periods. The sound meter operator may cease taking readings as soon as the readings already taken show a violation of this article. Five readings above the allowed decibel limits as specified in subsection 16-53(b) attributed to the sound source or sources shall constitute prima facie evidence of a violation of the maximum permissible sound levels set in this article.
(Ord. of 6-7-2005, art. IV)
and there will be exceptions.. check the ordinance in your area of interest.. especially if what you are planning is a "permitted" event..
Sec. 16-55. Exceptions.
The following are exempt from the provisions of this article:
(1) Construction operations from 7:00 a.m. to 9:00 p.m. on weekdays and 8:00 a.m. to 9:00 p.m. on weekends for which any required building permits have been issued, provided all equipment is operated according to the manufacturers' specifications and with all standard equipment, manufacturers' mufflers and noise reducing equipment are in use and in proper operating condition.
(2) Noises of safety signals, warning devices, emergency pressure relief valves and church bells or chimes.
(3) Noises resulting from any authorized emergency vehicle when responding to any emergency call or acting in time of emergency.
(4) Nonamplified noises at street activity (such as fairs or parades) where the participants have a permit, if a permit is required by law for such activity.
(5) Agricultural or forestry activities from bona fide farming and forestry operations when equipment or machinery is operated in accordance with manufacturer's specifications and with all standard noise reducing equipment in place and in good working order.
(6) All noises coming from the normal and legal operation of properly equipped aircraft (not including scale model aircraft).
(7) All noises coming from normal operation of motor vehicles properly equipped with a standard mufflers, in good working order and in constant operation, including noises coming from compression release engine or transmission breaking systems when used in emergency circumstances.
(8) Noise from lawful fireworks and noisemakers on holidays.
(9) Lawn mowers, chainsaws and other landscaping equipment used between 7:00 a.m. and 9:00 p.m. when operated with all the manufacturers' standard noise reducing mufflers in use and in proper operating condition.
(10) Nonamplified crowd noise at regularly scheduled athletic events at county parks, and public or private schools.
(11) Nonamplified speeches made from a fixed location in nonresidential property.
(12) Trains and associated rolling stock.
(13) Activities by government personnel in the performance of their duties, including without limitation the armed forces and law enforcement personnel.
(14) Sound or noise emanating from construction or repair work and regulated activities of utilities regulated by the North Carolina Utilities Commission.
(15) Blasting, but only as permitted by state law and county regulations.
(16) Commercial race tracks, as permitted by state law and county regulations.
(17) Discharge of firearms, but only as permitted by state law and county regulations.
(18) Refuse and recycling collection vehicles when operated between the hours of 6:00 a.m. and 9:00 p.m. according to the manufacturer's specifications and with all standard noise reducing equipment in place and in proper condition.
(Ord. of 6-7-2005, art. V)
RE: A-Weight vs C-Weight Questions
"Exceptions" Section 16-55, item no. 7, should refer to engine and transmission "brakes," not "breaks," unless of course it is the noise from the failure of these devices which you wish to except...
RE: A-Weight vs C-Weight Questions
The incorrect wording may well be in the final adopted copy, or it may be that h
This is a private publisher of Codes of Ordinances, Land Use Codes and Charters for local governments. Caveat emptor.
In any event, I have no responsibility for it.
regards
RE: A-Weight vs C-Weight Questions