TITLE 35: ENVIRONMENTAL PROTECTION

CHAPTER I: ILLINOIS POLLUTION CONTROL BOARD
1. Section
  1. Section 910.102 Instrumentation
    1. Section 910.106 Protocols for Determination of Sound Levels
      - Table 1
    2. 910.TABLE A. Daytime long-term background ambient Leq level
      - Background Category

TITLE 35: ENVIRONMENTAL PROTECTION

SUBTITLE H: NOISE

CHAPTER I: ILLINOIS POLLUTION CONTROL BOARD

MEASUREMENT PROCEDURES FOR THE ENFORCEMENT

OF 35 ILL. ADM. CODE 900 & 901

910.100 General

910.102 Instrumentation

910.103 Definitions

910.104 Measurement Techniques for 35 Ill. Adm. Code 900

910.105 Measurement Techniques for 35 Ill. Adm. Code 901

910.106 Protocols for Determination of Sound Levels

910.107 Measurement Techniques for Highly-Impulsive Sound Under 35 Ill. Adm. Code

910.APPENDIX A Tables of Long-Term Background Ambient Noise

910. TABLE A Daytime long-term background ambient Leq levels in decibels by land use

categories and 1/3 octave-band level

910. TABLE B Nighttime long-term background ambient Leq levels in decibels by land

use categories and 1/3- octave-band level

910. TABLE C Daytime long-term background ambient Leq levels in decibels by land use

categories and octave-band level

910. TABLE D Nighttime long-term background ambient Leq levels in decibels by land

use categories and octave-band level

AUTHORITY: Implementing and authorized by Sections 25 and 27 of the Environmental

Protection Act [415 ILCS 5/25 and 27]

SOURCE: Adopted in R03-9 at 30 Ill. Reg. 5594, effective March 10, 2006.

Section 910.100 General

This Part specifies the instrumentation to be used when conducting acoustical noise

measurements and sets forth the specific acoustical measurement techniques to be employed

when conducting time-averaged sound level (Leq) measurements. The instrumentation

requirements and measurement techniques as more specifically set forth in this Part must be used

in determining whether a noise source is in compliance with 35 Ill. Adm. Code 900 and 901.

Section 910.102 Instrumentation

a) Sound Measuring Equipment

1) An integrating sound level meter used alone or used in conjunction with

an octave-band or 1/3 octave-band filter set or a real-time sound analyzer

(octave-band or 1/3 octave-band) must conform with the following

standards incorporated by reference at 35 Ill. Adm. Code 900.106:

A) ANSI S1.4 – 1983 (R2001) “American National Standard

Specification for Sound Level Meters”, and ANSI S1.4 A-1985

“Amendment to ANSI S1.4-1983.”

B) ANSI S1.11 - 1986 (R1998) “American National Standard

Specifications for Octave-Band and Fractional-Octave-Band

Analog and Digital Filters.”

C) ANSI S1.6 – 1984 (R2001) “American National Standard

Preferred Frequencies, Frequency Levels, and Band Numbers for

Acoustical Measurements.”

D) ANSI S1.8 - 1989 “American National Standard Reference

Quantities for Acoustical Levels.”

E) International Electrotechnical Commission, IEC 804-2000

Integrating/Averaging Sound Level Meters.

2) A magnetic tape recorder, graphic level recorder or other indicating device

used must meet the requirements of the Society of Automotive Engineers

(SAE) Recommended Practice J184 “Qualifying a Sound Data Acquisition

System,” November 1998, incorporated by reference at 35 Ill. Adm. Code

3) The laboratory calibration of instrumentation used for acoustic

measurement must be traceable to the National Bureau of Standards, and

must be performed no less often than once every 12 months.

4) For outdoor measurement, a windscreen must be attached to the

b) Weather Measuring Equipment

1) An anemometer and compass or other devices must be used to measure

wind speed and direction in accordance with the manufacturer's

recommended procedures.

2) A thermometer, designed to measure ambient temperature, must be used in

accordance with the manufacturer's recommended procedures.

3) A hygrometer must be used in accordance with the manufacturer's

recommended procedures to measure the relative humidity.

4) A barometer must be used in accordance with the manufacturer's

recommended procedures to measure the barometric pressure.

Section 910.103 Definitions

he definitions contained in 35 Ill. Adm. Code 900.101 apply to this Part.

Section 910.104 Measurement Techniques for 35 Ill. Adm. Code 900

Sound pressure level measurements are not required to establish a violation of 35 Ill. Adm. Code

900.102 (nuisance noise). However, sound pressure level measurements may be introduced as

corroborating evidence when alleging a violation of 35 Ill. Adm. Code 900.102. If sound

pressure level measurements are collected, manufacturer’s instructions must be followed for the

equipment used and 35 Ill. Adm. Code 910.105 may be used as guidance in gathering data.

Section 910.105 Measurement Techniques for 35 Ill. Adm. Code 901

Sound pressure level measurements must be obtained in accordance with the following

measurement techniques to determine whether a noise source is in compliance with 35 Ill. Adm.

a) Site Selection

1) Measurements may be taken at one or more microphone positions within

the appropriate receiving land. Measurement instruments must be set up

outdoors within the boundaries of the receiving land for the purpose of

determining whether a noise source is in compliance with 35 Ill. Adm.

2) Measurement instruments must be set up not less than 25 feet (7.6 meters

(m)) from the property-line-noise-source. The 25-foot (7.6 m) setback

requirement is from the noise source and not the property line unless the

noise source is contiguous to the property line.

3) Other measurement locations may be used for investigatory purposes such

as, but not limited to, the following:

A) Determining the extent of noise pollution caused by the source of

B) Determining the ambient; and

C) Analyzing those acoustical parameters that describe the sound

4) For measurements of sound sources with no audible discrete tones,

microphones should not be set up less than 25 feet (7.6 m) from any

reflective surface that may affect data. If measurements must be taken

within 25 feet (7.6 m), the effect, if any, of the reflective surface on the

measured data must be determined.

5) For measurements of sound sources with audible discrete tones,

microphones must not be set up less than 50 feet (15.2 m) from any

reflective surface that may affect data. If measurements must be taken

within 50 feet (15.2 m), the effect, if any, of the reflective surface on the

measured data must be determined.

6) Objects with small dimensions (trees, posts, bushes, etc.) must not be

within 5 feet (1.5 m) of the microphone position. If measurements must

be taken within 5 feet (1.5 m) of such objects, the effect, if any, on the

measured data must be determined.

b) Instrumentation Set Up

1) A tripod must be set at the chosen site. The tripod must be extended to a

height between 3 feet 8 inches (1.12 m) and 4 feet 10 inches (1.47 m)

2) A microphone must be attached to the appropriate end of a 5-foot (1.5 m)

or longer cable and must be affixed to the top of the tripod. The other end

of the cable must be connected to the measuring instrument.

3) The angle of incidence of the microphone must be adjusted to yield the

flattest frequency response in accordance with the manufacturer’s

specifications.

4) The measuring instrument must be separated from the microphone so as to

minimize any influence on the measurements. The cable movement must

be minimized during the measurement period.

c) Measurement Site Operation and Instrument Calibration

1) Before taking sound pressure level measurements, measure and record

(near the measurement site):

A) Wind speed and direction;

B) Ambient temperature;

C) Relative humidity; and

D) Barometric pressure.

2) Turn the measuring instrument on and allow the instrument to stabilize.

Monitor and record the battery condition of the calibrator and all

measuring instruments.

3) Turn the calibrator on at its appropriate frequency. Allow the calibrator to

stabilize and calibrate the measuring system according to the

manufacturer's specifications. After the measuring system has been

calibrated, remove the calibrator and attach a windscreen to the

4) Adjust the microphone to the angle of incidence that will yield the

frequency response in accordance with the manufacturer's specifications.

5) Measure the sound pressure level data within the limitations of subsection

(d) and according to the manufacturer's recommended procedures. Other

sound pressure levels may be used for investigatory purposes such as, but

not limited to, the following:

A) Determining the extent of noise pollution caused by the source of

B) Determining the ambient; and

C) Analyzing those acoustical parameters that describe the sound

6) While sound measurements are being taken, the operator must be

separated from the microphone so as to minimize any influence on the

7) While measurements are being taken, visual and aural surveillance of

extraneous sound sources and varying wind conditions must be made to

insure that the conditions of measurement are accurately known. Record

any variations in these parameters that may affect data. The number and

basis for affected data block must be recorded. When using a tape

recorder, voice commentary concerning conditions will be recorded on the

8) To minimize wind effects on the microphone, sound measurements must

not be taken when the wind velocity is greater than 12 miles per hour

(5.4 m/second) at the microphone position.

9) For the purposes of data correction, the ambient sound at the measurement

site must be determined by means of measurement or analysis.

10) After taking sound pressure level measurements, remove the windscreen

and attach the calibrator to the microphone. Turn the calibrator on at its

appropriate frequency. After allowing the calibrator to stabilize, monitor

and record the measuring system response. When the measuring system

response varies by more than + 0.5 dB from the most recent field

calibration, the sound pressure level measurements obtained since such

most recent field calibration cannot be used for enforcement purposes.

11) Before removing the calibrator from the microphone, turn the calibrator

off. If the ambient sound has not been determined by means of

measurement, determine the noise floor of the measuring system. If the

noise floor is within 10 dB of the measured sound pressure level data, such

noise floor measurements must be recorded.

12) At the end of the sound survey, monitor and record the battery condition

of the calibrator and all measuring instruments. Near the measurement

site, measure and record:

A) Windspeed and direction;

B) Ambient temperature;

C) Relative humidity; and

D) Barometric pressure.

13) Record the physical and topographical description of the ground surface

within the vicinity of the measurement site, survey site location, a

description of the sound source, a diagram of the area, the location of

reflective surfaces near the microphone, and the approximate location of

the noise source relative to the microphone position.

14) A magnetic tape recorder may be used to preserve the raw data.

Calibration signals must be recorded at the beginning and end of each tape

as well as at intermediate times such as when relocating to a new

measurement site. Voice commentary concerning local conditions and

affected data blocks must be recorded on the cue track. The original tape

recording must be preserved for subsequent evaluation. Laboratory

analyses may be performed on magnetic tape recorded field data. A

description of the laboratory instrumentation and procedures must be

recorded. Analyses used in the laboratory must be correlated to field

measurement techniques.

d) Limiting Procedures for Specific Types of Data Acquisition

1) For measurements of non-impulsive sound with audible discrete tones, 1/3

octave-band sound pressure levels must be obtained in determining

whether a noise source is in compliance with 35 Ill. Adm. Code 901.106.

2) For measurements of non-impulsive sound with no audible discrete tones,

octave-band sound pressure levels must be obtained in determining

whether a noise source is in compliance with 35 Ill. Adm. Code 901.102

e) Correction Factors

If necessary, correction factors rounded to the nearest 1/2 decibel must be applied

to sound pressure level measurements. The correction factors applicable to the

measurement system may include, but are not limited to, corrections for

windscreen interference and the sound pressure level difference between

consecutive field calibrations. Such calibration correction factors must only be

used to make negative corrections (subtraction from the field data). In no case

must such calibration correction factors be added to the measured sound pressure

levels so as to raise the sound pressure level field data. The correction factors

applicable to the measurement site may include, but are not limited to, corrections

for reflective surfaces and ambient sound.

Section 910.106 Protocols for Determination of Sound Levels

a) The raw data collection procedures for the determination of equivalent continuous

sound pressure level (Leq) are described in this Section using as an example the

determination of a 1-hour Leq corrected for ambient. The following procedures

1) Using small blocks:

A) The 1-hour interval is divided into many small blocks of time so

that corruption of the data from short-term background transient

sound and loss of data can be limited to the corrupted or bad

blocks. The block duration in seconds must remain fixed for any

measurement hour. The duration must be neither less than 10

seconds nor greater than 100 seconds. For example, if the block

duration is chosen to be 60 seconds (1 minute), then the data

collection proceeds for 60, 1-minute periods of measurement.

B) The collected data for each block represents a block duration Leq

(or sound exposure level (SEL)) in octave-bands (or 1/3 octave-

bands if prominent discrete tones may be present).

C) Data for any block corrupted by one or more short-term

background transient sounds must be deleted.

After deleting corrupted data blocks, there will be a fixed number

of “good” data blocks remaining. This number is designated as

NPLNS, where PLNS stands for Property-Line-Noise-Source.

These remaining “good” blocks must be numbered consecutively.

The subscript i is used to denote the numbering of the blocks in

time order after corrupted data blocks have been deleted.

The data for the NPLNS remaining blocks are time averaged on an

energy basis by octave (or 1/3 octave-band) using Equation 1

below. In this equation, two subscripts are used, i to designate

time and j to designate the specific frequency, either an octave-

band or 1/3 octave-band. The raw, 1-hour Leq in the

band is given by:

where Leq is the Leq in the

th frequency band for the

deleted data block.

In terms of SEL, the raw SEL in the

th frequency band is given

The raw, 1-hour Leq in the

th frequency band is given in terms of

the corresponding SELj by:

Where T is the block duration in seconds, NPLNS is the number of

non-discarded data blocks, and 3600 is the number of seconds in

The measuring instrument must be adjusted to continuously

measure sound pressure and accumulate Leq for each block of time.

For convenience, the hour may be split into several smaller blocks

such as 10, 6-minute blocks or 4, 15-minute blocks, etc.

A switch on the measuring instrument must be available to inhibit

data collection whenever a short-term background transient sound

occurs. This switch shall be used to prevent short-term

background ambient sounds from corrupting the data.

Data collection must proceed for one hour. The energy average of

the several measured Leqij each weighted by the number of seconds

actually accumulated during the

th block results in the raw, 1-hour

Leq in each frequency band given by:

Where Leqij is the Leq in the jth frequency band for the

block. Ti is the actual number of seconds of “good” data

accumulated in the

th block of time (e.g., 6 to 15 minutes); and

Minimum data collection requirements:

The property-line-noise-source

measurements must proceed initially for one hour. Because of

correction for short-term background transient sounds, actual

reported data collection time T, in seconds, may be less than 3600

seconds (one hour).

If small blocks of data are used for data collection, then the

total measurement duration in seconds, TPLNS, is given by

NPLNS T, where T is the length of each block in seconds and

NPLNS is the number of non-discarded blocks. If data

inhibition is used for data collection, then TPLNS is the

number of non-inhibited seconds during the measurement

hour. In either case, TPLNS must be no less than 900

If very few blocks were used for data collection, then the

duration of each block, T, may be too long and should be

For either data collection method, sounds considered to be

short-term transient may actually be part of the long-term

background ambient and should be so redefined.

B) Extended Measurement Duration. If TPLNS is less than 900 seconds

during the first hour of measurements, the raw data collection

procedures must be appropriately modified and new measurements

must proceed for an additional hour. If TPLNS after combining the

first and the second hour of measurements is also less than 900

seconds, then the raw data collection must continue using the data

inhibition method or method employed during the second hour

until TPLNS is greater than or equal to 900 seconds.

4) Correction for Long-Term Background Ambient Sound:

A) The raw 1-hour Leq must be corrected for long-term background

ambient sound. Subsection (b) of this Section describes methods to

obtain the long-term background ambient sound level in the jth

frequency band. The correction is dependent on the difference (in

decibels) between the raw, 1-hour, jth band property-line-noise-

source: Leqj and corresponding jth band long-term background

ambient sound level. The correction to be applied is as follows:

i) If the difference between the raw 1-hour Leq and the

long-term background ambient sound is larger than

10 decibels, then the correction must be set to 0.

ii) If the difference between the raw 1-hour Leq and the

long-term background ambient sound difference is

less than 3 decibels, then the

th frequency-band

level, Leqj, must be set equal to 0.

iii) If the difference between the raw 1-hour Leq and the

long-term background ambient sound is between 3

and 10 decibels, then the correction given in Table

1 below must be subtracted from the raw, 1-hour

property-line-noise-source Leqj

Corrections in dB for long-term

background ambient sound

B) The long-term background ambient corrected level must be the

property-line-noise-source Leqj reported for the jth frequency band.

b) Obtaining the background ambient sound level:

1) The background ambient must be measured for the purposes of this

Section during a 10-minute interval.

2) Long-term background ambient measurement procedures are similar to

procedures to measure the property-line-noise-source itself. Eliminating

short-term background ambient transient sounds from the measurement of

average long-term background ambient sound proceeds in a manner

similar to the measurement of the property-line-noise-source emissions

themselves. The two methods for measurement are: to divide the 10-

minute measurement into short blocks of data, or inhibit data collection

when short-term background transient sounds occur. The same method

must be used for gathering both the property-line-noise-source data and

the corresponding long-term background ambient data. The measurement

procedures for each method are given in subsections (b)(3), (b)(4) and

(b)(5) of this Section:

3) Using Small Blocks of Data

A) The 10-minute measurement of long-term background ambient

must be divided into short measurement blocks. The duration of

these blocks must remain constant during the entire measurement,

both when measuring the long-term background ambient and when

measuring the property-line-noise-source. The duration of this

measurement block in seconds, T, must divide exactly (without

remainder) into 600 and must be neither greater than 100 seconds

nor less than 10 seconds.

B) All data for any measurement block corrupted by one or more

short-term ambient transient sounds must be discarded. The

number of remaining, non-discarded measurement blocks is

designated NBA, where

stands for background ambient.

C) The Leq for each octave-(or 1/3 octave-) band are time-averaged on

an energy basis over the NBA remaining measurement blocks to

obtain average long-term background ambient Leq per band.

Equation 1 (see subsection (a) (1) (E) of this Section) is used for

this calculation with NBA replacing NPLNS as the number of

elemental blocks to be summed. The total duration of the

measurement in seconds, TBA, is given by NBA multiplied by T.

4) Continuous Data Collection

A) The measuring instrument must be adjusted according to

manufacturer’s instructions to continuously measure sound

pressure and accumulate (i.e. record) Leq. A switch must be

available to inhibit data collection whenever a short-term

background transient sound occurs, (and on some instruments, a

button may be available to delete the most recent, previous data).

B) The switches or buttons must be used to prevent short-term

background ambient sounds from corrupting the data.

C) Data collection must proceed for 10 minutes. The result is the 10-

minute, long-term background ambient Leq in each band.

D) TBA is the number of non-inhibited measurement seconds during

the 10-minute measurement period.

5) The minimum duration, for either method, TBA must be no less than 150

seconds. If TBA is less than 150 seconds, then the measurement of the

long-term background ambient must continue beyond the original 10

minutes and until TBA for the total long-term background ambient

measurement is greater than or equal to 150 seconds.

6) Measurement Alternatives. The long-term background ambient noise

should ideally be measured at the potential violation site just before

measurement of the property-line-noise-source emissions. However,

turning off the property-line-noise-source may not always be possible. The

following are a hierarchical order of five procedures for obtaining the long-

term background ambient noise. The first four procedures involve direct

measurement; the fifth procedure provides for use of tables of values

obtained from extensive measurements. These are not equivalent

procedures but are ordered from what is considered to be the most accurate

to what is considered to be the least accurate procedure.

A) Direct Measurement Procedure –1: With the property-line-noise-

source (PLNS) turned off, measure the long-term background

ambient noise within the hour before or within the hour after

measurement of the PLNS emissions at the location where the

PLNS measurements are being taken and with the measurement

equipment used for the PLNS measurements.

B) Direct Measurement Procedure-2: With the PLNS turned off,

measure the long-term background ambient during a similar time

period in terms of background ambient sound level, within one to

24 hours before, or within one to 24 hours after measurement of the

PLNS emissions at the location where the PLNS measurements are

being taken and with the measurement equipment used for the

C) Direct Measurement Procedure- 3: With the PLNS turned off,

measure the long-term background ambient during some other

acoustically similar period within one to 30 days before, or within

one to 30 days after measurement of the PLNS emissions. This

alternate long-term background ambient measurement time might

be a Saturday night or anytime during a Sunday or holiday. The

measurements would be made at the location where the PLNS

measurements are being taken and with the measurement

equipment (or like equipment) used for the PLNS measurement.

D) Direct Measurement Procedure-4: With the PLNS turned off,

measure the long-term background ambient noise during some

other acoustically similar period within 30 to 90 days before, or

within 30 to 90 days after measurement of the PLNS emissions.

These measurements would be made at the location where the

PLNS measurements are being taken and with the measurement

equipment (or like equipment) used for the property-line-noise-

source measurements.

E) Tables of Long-Term Background Ambient Noise. Where none of

the alternatives can be used, use the applicable long-term

background ambient data taken from Tables A through D in

Appendix A of this Part. These tables are organized by

predominant land use and time of day (daytime or nighttime).

There are separate tables for octave- and 1/3- octave-bands. The

background environments presented in the table are based on

extensive measurements conducted in the Chicago area and are

divided into the five categories given below in accordance with

G.L. Bonvallet, “Levels and Spectra of Traffic, Industrial, and

Residential Area Noise,” Journal of the Acoustical Society of

America, 23 (4), pp 435-439, July 1951; and Dwight E. Bishop and

Paul D. Schomer, Handbook of Acoustical Measurements and

Noise Control, Chapter 50, Community Noise Measurements, 3

Edition, Cyril M Harris, Editor, McGraw-Hill Book Co., New York

i) Category 1: Noisy Commercial and Industrial Areas. Very

heavy traffic conditions, such as in busy downtown

commercial areas, at intersections of mass transportation

and other vehicles, including the Chicago Transit Authority

trains, heavy motor trucks and other heavy traffic, and

street corners where motor buses and heavy trucks

ii) Category 2: Moderate Commercial and Industrial Areas,

and Noisy Residential Areas. Heavy traffic areas with

conditions similar to subsection (b)(6)(E)(i) of this Section

but with somewhat less traffic, routes of relatively heavy or

fast automobile traffic but where heavy truck traffic is not

extremely dense, and motor bus routes.

iii) Category 3: Quiet Commercial and Industrial Areas, and

Moderate Residential Areas. Light traffic conditions where

no mass transportation vehicles and relatively few

automobiles and trucks pass, and where these vehicles

generally travel at low speeds. Residential areas and

commercial streets and intersections with little traffic

comprise this category.

iv) Category 4: Quiet Residential Areas. These areas are

similar to Category 3 in subsection (b)(6)(E)(iii) of this

Section but, for this group, the background is either distant

traffic or is unidentifiable.

v) Category 5: Very Quiet, Sparse Suburban or Rural Areas.

These areas are similar to Category 4 subsection

(b)(6)(E)(iv) of this Section but are usually in

unincorporated areas and, for this group, there are few if

any near neighbors.

Section 910.107 Measurement Techniques for Highly-Impulsive Sound Under 35 Ill. Adm.

a) Measurement of highly-impulsive sound under 35 Ill. Adm. Code 901.104 can be

made in two distinct and equally valid ways, namely the general method and the

controlled test method.

b) General Method: The general method is to measure the 1-hour, A-weighted Leq

(not the octave- or 1/3 octave-band levels) using essentially one of the two

procedures described in Sections 910.105 and 910.106.

1) The procedure using small blocks of time to collect data is as follows:

A) The hour must be divided into small blocks and the A-weighted Leq

must be measured for each of these small blocks of time. Leq must

be measured for the entire hour but data collection must be

inhibited whenever a short-term background transient sound

B) The duration of each block must be held constant during the hour.

This duration in seconds must divide exactly into 900 and must be

neither greater than 100 seconds nor less than 10 seconds.

C) The data for any block corrupted by one or more short-term

background ambient sounds must be discarded.

2) The continuous data collection procedure is as follows:

A) Leq must be measured for the entire hour.

B) Data collection must be inhibited whenever a short-term

background transient sound occurs.

3) Correction for the long-term background ambient must be accomplished

using all of the other procedures and requirements enumerated in Sections

910.105 and 910.106. These requirements must be complied with to

determine an A-weighted, 1-hour, background-ambient-corrected Leq for

the highly impulsive property-line-noise-source under study.

c) Controlled Test Method:

For this method, the following procedures must be used:

1) General Measurement Description

A) The sound exposure per impulse from each separate individual

impulsive source is measured.

B) The total sound exposure per hour from each source is the sound

exposure per event multiplied by the number of events per hour.

C) The grand total sound exposure (SE) per hour is the sum of the

sound exposures per hour from each of the separate individual

D) The reported SEL is obtained from the grand total sound exposure

(SE) per hour using the following:

SEL = 10 log (SE) + 94 [Equation 7]

E) The equivalent level, Leq corresponding to a SEL measured or

predicted for one hour (3600 seconds) is given by:

Leq = SEL - 10 log (3600) [Equation 8]

2) Determination of sound exposure per event must be as follows:

A) The sound exposure per event from each, separate, individual

source must be determined by measuring the total A-weighted

sound exposure for about 10 repetitions of this source. This set of

about 10 measurements may be performed continuously over a

short period of time, or this set of measurements may be performed

over a discontinuous set of measurement periods. In either case,

the total measurement duration must be less than 100 seconds.

B) These separate, individual property-line-noise- source controlled

measurements must be free of any short-term ambient sounds. If

any short-term background transient sounds occur during these

measurements, then the measurement must be repeated until

measurement data, free of any corrupting short-term background

ambient sounds, are obtained.

C) The total measured A-weighted sound exposure for this group of

about 10 repetitions must be corrected for long-term background

ambient by subtracting the A-weighted long-term background

ambient sound exposure. The sound exposure value subtracted

must be the long-term A-weighted background ambient sound

exposure per second multiplied by the number of seconds used to

measure the several source repetitions.

D) The reported Source: A-weighted sound exposure per event must

be the total corrected sound exposure divided by the number of

source repetitions measured.

E) The background ambient must be measured for a short time, at

least 30 seconds as near in time to the source measurements as

possible, but within ½ hour. The total A-weighted long-term

background ambient sound exposure per second is the total

measured long-term background ambient sound exposure divided

by the number of seconds of background ambient measurement.

F) There must be no short-term background ambient sounds present

during the measurement of the long-term background ambient. If

any short-term background transient sounds occur during these

measurements, then the measurements must be repeated until long-

term background ambient measurement data free of any corrupting

short-term background ambient sound are obtained.

910.APPENDIX A Tables of Long-Term Background Ambient Noise

910.TABLE A. Daytime long-term background ambient Leq levels in decibels by land use

categories and 1/3 octave-band level

Background Category

Octave-Band Center

910. APPENDIX A Tables of Long-Term Background Ambient Noise

Nighttime long-term background ambient Leq levels in decibels by land use

categories and 1/3 octave-band level

Background Category

Octave-Band Center

910. APPENDIX A Tables of Long-Term Background Ambient Noise

Daytime long-term background ambient Leq levels in decibels by land use

categories and octave-band level

Background Category

Octave-Band Center

910. APPENDIX A Tables of Long-term Background Ambient Noise

Nighttime long-term background ambient Leq levels in decibels by land use

categories and octave-band level

Background Category

Octave-Band Center