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Acoustic Associates,

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102003

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lATE OF

ILLINO

Specialists inHearing andAcoustics

1-Oliutlon

Control Board

Thomas

Thunder, MA, FAAA,

INCE

Principal

Roger Harmon, BSEE, PB

Acoustical Engineer

Regina Dziewior, MA,

CCC

Audiologist

Peter Straus, AAS

Field Technician

Illinois Pollution Control Board

J.R. Thompson Center

—

Suite 11-500

100 West Randolph

Chicago, Illinois

60601

RE:

Comments on the first-notice of the Noise RuleUpdate

Proposed Amendments to

ILL. ADMCODE 900 and 903

R03-8 NOISE RULEMAKING

I appreciate the opportunity to comment on the subject rulemaking. Here are my comments:

Add

definition for “reference time.”

I suggest the following definition:

“the

time period over which the Leq average is measured or

determined.” In 1987, the Board amended 900.103 to require that noise measurements be based on

Leq averaging andthat the referencetime forthis averaging be 1-hour. If the Board intended this to

be a

1-hour measurement time, then with some sound level meters, measurements for all nine octave

bands could take nine hours. By definingreference time as suggested here, the 1-hour Leq could be

projectedbased on shorter measurement periods whichwould greatly reduce the time required forthe

vast majority of situations.

For example, ifthe noise were steady (as defined inthe regulation), there would be no need to

measure fora full hour. In such cases, a 1-minute Leq would yield the same results as a 1-hour Leq. If

the noise were intermittent, then a measurementtaken while the source was

on would be sufficient

to projecta 1-hour Leq when the on/offproportion (duty cycle) is known or assumed. Only in cases

where the noise were non-steady or the source had no repetitive cycle, such as

loading dock

operations, would a full 1-hour measurementbe required.

Finally, ifacomplainant was willing to assume ~

contribution from the noise source for the

unmeasured duration of the 1-hour reference time, the Boardshould not insist on afull 60 minutes of

measurement to support anumerical violation of the regulation, For example, if 30 minutes of

representative sampling was all that a complainant could obtain, for whatever reason, then the

projected 1-hour Leq with ~

assumed contribution from the sourcefor the remaining 30 minutes

might still exceed the State’s limits. In this regard, the definition suggested above for “reference time”

should be amended with: “For purposes of showing

noncompliance with these regulations, 0

of contribution can

be assumed for

the unmeasured portion of the reference time.”

305

E. Northwest Highway, Palatine, illinois

60067

Office:

847-359-1068

•

Fax:

847-359-1207

Website:

wvw.AcousticAssociates.corn

E-mail:

tthunder@concentric.net

February 7, 2003

Dear Board Members:

Acoustic Associates, Ltd.

Page

Illinois Pollution Control Board

—

Noise Rulemaking

February 7,2003

The American National Standard

ANSI S12.9-l993fPart 3, “Short-Term Measurements

with an

Observer Present” should be added as a referencestandard under Section 900.101.

ANSI

12.9-1993/Part

hasalready been added in the Notice.’ However, since this standard only

deals with definitions for standard quantities, I recommend its companion standard,

Part

3, also be

added sincethis is the most relevant American National Sthndard dealing with the type of

measurements and procedures related to this Regulation.

In the definition for

“Background

Sound Level”

—

delete “A-weighted sound.”

The regulation is written to measure the octave band Leq, not the A-weightedLeq. Better yet, the

definition should be made congruent with the definition under ANSI S 12.9. Specifically I recommend

the following language: “all-encompassing sound associated with a given environment-without

contributions from the source or sources ofinterest. When the background noise consists of discrete,

intrusive events (e.g., dog barking, carhorns, train horns, etc.), then~either:

1) the data from these

events must be subtracted from the sample, or2) a statistical analysis must be performed to determine

the level exceeded 90

ofthetime.” The Board should note that ANSI S

12.9/Part

3, as referenced in

item ~2, describes the actual task required to correct for the background noise.

It may, therefore, wish

to refer to this standard to addressthe issue ofbackground noise corrections.

In the definition ofLeq,

add “...the measure

is a time-averaged sound level during

a stated time-

interval,

T.”

This addition is necessary to be consistent with currentANSI terminology per ANSI S 1.1.

The definition “Period ofobservation” should be replaced with “Measurement period.”

This change is consistent with current

ANSI terminology per ANSI S 12.9. An observation period

would be the time a field person observed source operations:andbackground noise conditions. But the

measurement period refers to the actual sampling duration.-Furthermore,I recommend a-minimum

measurement period of 10 minutes. As explained above, the 1-hour Leq could be reliably projected

from a 10-minute measurement ifthe sound was steady

and

continuous.

And

ifthe sound was

intermittent,

but

steady when the source was operating during the 10-minute measurement, the

1-hour

Leq could still be projected with a

known

or assumed on/off proportion. Only forfluctuating sound

would a full 60-minute measurement period be needed. In any case, a complainant ought to be able to

assume 0 dB contribution for the remaining 50 minutes ofthe reference time to show noncompliance

with the numerical portions ofthe State’s limits. Of course, for a respondent to show compliance for a

non-steady noise, a full 60-minute measurement duration would be required.

Sincere~~~

Thomas Thunder, AuD,

FAAA

Licensed Audiologist

—

State ofIllinois

Board Certified

Institute ofNoise Control Engineering

cc: Howard Chinn

AcousticAssociates, Ltd.

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