5.0 MEASUREMENT OF CONSTRUCTION NOISE

5.1 History

While the techniques for measuring noise described in the 1977 Handbook^ref001 remain valid, more sophisticated noise measurement equipment exists three decades later, allowing for more precise measurement of highway and construction-related noise with the likelihood of greater accuracy. For example, the "check-off" method for computing L₁₀ or L_Aeqin the 1977 Handbook is documented in Chapter 3 of the 1973 textbook report titled Fundamentals and Abatement of Highway Traffic Noise^ref085 and was geared to use of the analog-type sound level meters typical of that time period. Current sound level meters are predominantly digital in nature, capable of internally integrating sound level information and providing direct readouts and/or printouts of L_Aeq, L₁₀, and other selected descriptors. Current FHWA guidance related to noise measurements can be found in the FHWA Measurement of Highway Related Noise document^ref006, with specific reference to construction equipment noise measurements found in Chapter 7^ref011 of that document.

No information related to the measurement of non-human noise impacts (effects on wildlife, fish, etc.) was presented in the 1977 Handbook. Since that time, additional research and studies^{ref054
and ref060} have been conducted which have involved measurements of noise in a variety of habitats. Refer to documents listed in the Related Information column of Table 10.1 for the following States and agencies: EPA, Florida, U.S. Army Corps of Engineers, Washington, and West Virginia.

Evaluation of the effects of the operational and construction aspects of highways on non-humans is the responsibility of qualified biologists expert in specific fields of study associated with specific species. While noise analysts may provide acoustical information associated with highway operations and/or construction activities, any studies related to the effects of such operations or activities on non-humans are conducted by the appropriate qualified biologists. The overall results of such studies are typically reported in the sections of environmental documents dealing with biological resources and related environmental consequences.

5.2 Purpose of Noise Measurements

Excluding research projects and studies to address the requirements of OSHA, noise measurements related to highway construction are generally conducted to obtain information needed to identify and predict highway project construction noise impacts and then to evaluate mitigation strategies. While most projects will not require construction noise measurements, those cases where measurements may be required generally relate to the following purposes:

Measurement of existing noise levels to determine baseline (background) conditions;

A noise analyst performs sound level measurements with a sound level meter in a forested area adjacent to a low volume road.

Figure 5.1 Measuring existing noise levels (Photo #1301)

Background noise level measurement, prior to construction activities, are performed with a sound level meter on a residential property.

Figure 5.2 Measuring ambient noise levels in the absence of construction activity (Photo #1291)

Measurement of noise levels associated with individual pieces of construction equipment or construction operations for the purpose of establishing noise emission levels for inclusion in a reference database;

An analyst uses a sound level meter to measure the emission level of a stationary piece of equipment.

Figure 5.3 Measurement of an individual piece of equipment (Photo #693)

Measurement of noise levels associated with individual pieces of construction equipment to relate such levels to prescribed levels or limiting values;
Measurement of the noise levels associated with a particular construction operation for comparison with background levels and/or established limiting values or criteria;

A noise analyst, wearing appropriate safety gear, uses a sound level meter to capture an individual nighttime construction operation.

Figure 5.4 Measuring an individual construction operation (Photo #418)

Measurement of noise levels associated with multiple construction operations for comparison with background levels and/or established limiting values or criteria; and

A construction area adjacent to nearby residences has several pieces of stationary equipment, such as a crane and mixing container, under operation.

Figure 5.5 Several construction operations affecting noise levels at nearby residences (Photo #929)

Measurement of noise levels of indirect activities (such as diverted traffic) associated with the construction of the project for comparison with pre-construction levels.

An individual dump truck in existing automobile traffic in an urban setting with nearby townhomes.

A heavy truck uses side streets en-route to a construction project in a suburban area.

Figure 5.6 Undesignated routes may be used by construction-related traffic (Photos #1179 & #1399)

An orange sign with directional arrow posted on existing sign pole designating a street as a haul route for trucks on the Woodrow Wilson Bridge project in metro DC area.

Figure 5.7 Routes may also be specifically designated for use by construction-related traffic (Photo #560)

In addition to measurements associated with the construction of a highway, certain types of highway project maintenance and/or rehabilitation operations may also require the measurement of construction noise levels. An example could be a bridge painting project where blasting is utilized in the paint removal process in the close proximity of sensitive receptors such as residences, churches, schools, etc. Under such circumstances, noise measurements could be performed at a property adjacent to the bridge, with simultaneous measurements taken close to the blasting zone. In combination, these measurements could then be used to determine source noise emissions and to estimate noise level drop-off rates.

For such a project, measurement of equipment other than the actual blasting nozzles would likely also be performed.

A compressor, vacuum, and paint chip collection equipment located as close to an existing wall to shield noise to nearby receptors.

Figure 5.8 Compressors, vacuums, and paint chip collection equipment associated with paint removal operation (Photo #398)

Monitoring may also be conducted of construction equipment and activities associated with other types of highway maintenance, bridge and pavement rehabilitation, etc.

A worker operates a compressor and bridge cleaning equipment while traffic passes by in the background.

Figure 5.9 Bridge rehabilitation activities (Photo #1490)

A worker operates a concrete saw perpendicular to travel direction with an idling truck in the background.

A heavy truck passes by a construction zone in the left lane while the right lane pavement is under rehabilitation.

Figure 5.10 Pavement rehabilitation project (Photos #1407 & #1397)

5.3 Measuring Existing and Ambient Noise

5.3.1 Establishing Background Levels

Existing (or background) noise levels serve as a reference or benchmark level to which a comparison can be made with noise levels associated with construction operations. Background levels include noise contributions from all sources and may be the result of normal neighborhood activities plus noise generated by traffic on local transportation facilities. If the predominant noise source in an area is traffic on an existing transportation facility, existing noise levels can often be predicted using traffic noise prediction models such as the FHWA Traffic Noise Model^® (FHWA TNM)^ref086or the Federal Transit Administration (FTA) Transit Noise and Vibration Assessment procedure^ref014 (also refer to website links listed under FHWA and FTA in Table 10.1.). In such instances, little or no noise measurements may be required, with the only purpose of performing noise measurements being related to noise model verification or calibration.

Should the predominant existing noise sources be non-transportation related activities, noise measurements may be the only reliable means of establishing background noise levels. In either case, the information on existing noise levels is normally developed in the early stages of project planning, often years before the start of construction. Therefore, it may be necessary to re-evaluate the existing levels prior to the start of construction and/or at various intervals during the construction phase.

Measurement of background noise levels associated with the evaluation of construction noise on non-human species typically considers the habitat features, migration trends, spawning, and nesting characteristics of such species in establishing appropriate measurement periods. Regarding fish and other aquatic species, background noise levels often consider other activities occurring within the species' environment, including recreational activities, commercial fishing operations, boating patterns, etc. While providing links and references to selected material associated with non-human species, the authors of this Handbook suggest that any detailed evaluation of effects on non-humans be conducted by qualified experts in the appropriate field of study.

5.3.2 Selecting Measurement Sites and Periods

For the purposes of evaluating highway construction noise, noise measurement sites generally are selected for the following reasons:

To determine existing noise levels in areas influenced predominantly by non-transportation noise generating sources; and
For purposes of verifying or calibrating the noise model used to calculate existing noise levels generated by highway traffic on existing facilities.

In either of the above conditions, construction noise measurement sites are typically located as close as possible to the location at which noise impact evaluations are planned. It is important to recognize that sites selected for evaluation of potential construction noise impacts may or may not be the same as sites selected for evaluation of noise impacts resulting from the operation of vehicles on the proposed highway. In addition, the noise generated by highway vehicles is typically evaluated using future year traffic conditions that create the highest noise, while construction noise is normally evaluated for the year(s) in which construction is expected to occur and for the period(s) when construction noise is expected to be the highest. These peak construction periods may be in the middle of the night, on weekends, or during other periods that do not coincide with the peak traffic noise hour.

5.3.3 Determining Events/Activities to Include/Exclude

In determining the existing background noise levels for use in evaluating construction noise levels, it is important to consider the events and activities which will typically occur during the time period for which construction noise is planned to be evaluated. It is equally important to exclude infrequent noise events such as lawn mowing, neighborhood construction activities, shouting, loud radios, etc.

A noise analyst pauses a background noise measurement when a river tour vehicle passes by; this activity is not representative of the typical background level and must be excluded from the measurement.

Figure 5.11 Excluded events could include vehicles with amplified sound systems (Photo #695)

A neighbor’s dog approaches a noise analyst in the field; the dog’s barks must be excluded from the noise measurement.

Figure 5.12 Influences of neighborhood pets on measurements (Photo #1307)

In cases where a school or a church is to be evaluated, consideration of the following activities may be appropriate in determining the period(s) when noise measurements and analyses are performed:

Periods of classes or services;
Interior classroom activities;
Exterior activities (recess, outdoor classes, after school activities, etc.); and
Noise generated by church or school-related activities, including school bus entry and exit and parking lot noise events.

A noise analysis using a sound level meter outside a church is to establish pre-construction background noise levels; the heating ventilation and air conditioning system is included.

Figure 5.13 Measurements at church; consider also influences of air conditioning units (Photo #1302)

A noise analysis using a sound level meter in a school parking lot to establish pre-construction background noise levels.

Figure 5.14 Measurements in vicinity of schools (Photo #1292)

A commuter rail line pass-by is included in the pre-construction noise measurement of background levels.

Figure 5.15 Influence of train noise on measurement of background levels (Photo #1293)

If construction noise is to be evaluated in the vicinity of a noise-generating source such as an airport, rail line, factory, etc., the consideration of the operational characteristics of that noise source may be appropriate. If aircraft operations were continuous and likely to be occurring during the analyzed period of construction noise, such operations would most likely be included in any background measurements. Conversely, if aircraft operations are infrequent and/or minimal, it may be appropriate to exclude them from any background noise level measurements.

Once again, these considerations emphasize the importance of coordinating proposed measurement times with proposed periods of construction noise evaluation. As discussed above, such considerations also apply when obtaining and providing noise-related information to biologists involved in evaluating project effects on non-human species.

5.3.4 Determining the Appropriate Noise Descriptor

Noise descriptors are discussed in Chapter 3 in terms of their weighting characteristics. In certain instances, it may be necessary to perform frequency-based noise measurements, particularly if such measurements (and subsequent analyses) will be compared to an existing ordinance that contains criteria or noise limits that are expressed in terms of full or one-third octave band noise levels.

5.3.5 Consideration of Meteorological Factors

In most cases, noise measurements are conducted under controlled meteorological conditions based on accepted measurement protocols. Under unique circumstances, noise measurements may be appropriate under other conditions. For instance, if construction noise is being considered in a location which normally has strong winds, a predominant wind direction, snow cover over extended periods of time, etc., it may be appropriate to consider these conditions as the norm in measuring background noise levels and in measuring and analyzing construction noise levels.

Meteorological effects are more significant at larger distances from the noise source. As such, effects of wind speed (even within acceptable ranges), wind speed gradient, wind direction, and temperature lapse rates are factors appropriately considered in the measurement of background levels and construction noise events.

Precipitation or wet roadways, including ice or snow, typically precludes valid measurements due to the effect on noise levels; sometimes wet pavement is a typical condition and adjustments and documentation noting the condition is appropriate.

Figure 5.16 Wet roadways preclude valid noise measurements. Snow cover normally precludes valid measurements, except if a typical condition (Photo #1299)

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