While the techniques for measuring noise described in the 1977 Handbookref001 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 LAeq in the 1977 Handbook is documented in Chapter 3 of the 1973 textbook report titled Fundamentals and Abatement of Highway Traffic Noiseref085 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 LAeq, L10, and other selected descriptors. Current FHWA guidance related to noise measurements can be found in the FHWA Measurement of Highway Related Noise documentref006, with specific reference to construction equipment noise measurements found in Chapter 7ref011 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 studiesref054 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.
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:
Figure 5.1 Measuring existing noise levels (Photo #1301)
Figure 5.2 Measuring ambient noise levels in the absence of construction activity (Photo #1291)
Figure 5.3 Measurement of an individual piece of equipment (Photo #693)
Figure 5.4 Measuring an individual construction operation (Photo #418)
Figure 5.5 Several construction operations affecting noise levels at nearby residences (Photo #929)
Figure 5.6 Undesignated routes may be used by construction-related traffic (Photos #1179 & #1399)
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.
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.
Figure 5.9 Bridge rehabilitation activities (Photo #1490)
Figure 5.10 Pavement rehabilitation project (Photos #1407 & #1397)
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)ref086 or the Federal Transit Administration (FTA) Transit Noise and Vibration Assessment procedureref014 (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.
For the purposes of evaluating highway construction noise, noise measurement sites generally are selected for the following reasons:
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.
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.
Figure 5.11 Excluded events could include vehicles with amplified sound systems (Photo #695)
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:
Figure 5.13 Measurements at church; consider also influences of air conditioning units (Photo #1302)
Figure 5.14 Measurements in vicinity of schools (Photo #1292)
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.
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.
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.
Figure 5.16 Wet roadways preclude valid noise measurements. Snow cover normally precludes valid measurements, except if a typical condition (Photo #1299)
To the extent possible, measurement locations and time periods selected for the evaluation of noise generated by construction operations should be the same as those used to determine background or pre-construction noise levels. Such measurements are conducted in conformance with established measurement protocols, as previously discussed. Separate noise measurement protocols exist for measurement of individual pieces of construction equipment, and are discussed later in this section.
Most measurements of noise from construction activities are conducted in exterior locations. Depending upon how a particular controlling ordinance, regulation, or procedure is written, such measurements may be taken at different locations, including:
Figure 5.17 Measurement near a residence (Photo #1286)
Figure 5.18 Measurement on a raised deck (Photo #1285)
Many local ordinances specifically require consideration of noise to be addressed at the property line location, while some regulations are less definitive in terms of precise locations. Measurements taken at or near the actual residence are more easily converted to interior levels through application of building reduction factors.
Figure 5.19 Property line noise measurement (Photo #1290)
Figure 5.20 Noise measurement inside church sanctuary (Photo #1284)
On occasion, it may be necessary to take interior noise measurements to establish interior levels. Building noise reduction factors can be obtained by simultaneous exterior and interior measurements.
Figure 5.21 Noise measurement in courtyard outside church sanctuary (Photo #1130)
When it has been determined that an analysis of construction noise is required, consideration of particular events or activities associated with the project's construction is appropriate. Each project is typically evaluated individually considering the relationship of both stationary and mobile construction activities to sensitive adjacent receptors and considering the timing of construction activities in relation to activities occurring within the community. Several options that exist in terms of the measurement of construction operations are discussed below.
Ideally, the most accurate representation of a project's construction noise level at any given location would be obtained by extensive and/or continuous monitoring of noise levels from all construction operations at that location. For the limited complex projects where such monitoring has been performed, complex noise monitoring systems and/or programs have been employedref009, ref082, and ref103. Except for complex projects and projects where construction is of short duration and occurring within a limited project area, such monitoring is probably not practical based on timing, manpower, and equipment constraints.
Measuring an entire operation suggests that all activities associated with a particular construction operation are occurring in a relatively short timeframe. An example may be a paving operation that occurs in the vicinity of a particular home or neighborhood over a one-day period. In such a case, the collective noise generated from all components of the operation could be measured and compared to background levels and/or absolute noise level criteria. Evaluation and screening of the project's schedule of individual construction operations can be used to determine, in advance, which construction operations are likely to produce the greatest noise levels at a particular location. Emphasis can then be placed on monitoring the operations with the potential to create the highest noise levels at that location.
Figure 5.22 High concentration of activity, a good candidate for measuring an entire operation (Photo #462)
Since construction of a highway typically involves many different phases and operations, it is appropriate to consider the following operations and the sensitive receptors that could be potentially impacted by each operation:
The evaluation and screening process used to determine the activities with the highest potential for construction noise impacts may identify specific portions of an operation that could warrant noise monitoring. For instance, a bridge construction project, blasting for foundation construction, pile driving activities, or rock excavation operations may be identified as having significantly greater potential for noise impacts than other activities such as forming, concrete pours, rod setting, etc. Obviously, each activity may have its own established noise level limit that may need to be considered in this process.
Figure 5.23 Blasting operation (Photo #1309)
Figure 5.24 Pile driving operation (Photo #856)
Figure 5.25 Rock excavation operation (Photo #981)
Construction projects often create activities that extend beyond the project limits. It is essential to consider the potential for noise effects of such activities on adjacent sensitive receptors, particularly those located in communities particularly sensitive to noise. Examples of such activities include:
Figure 5.26 Steel beam transported adjacent to residences (Photo #1208)
Figure 5.27 Dump truck on local roadway (Photo #1179)
Figure 5.28 Concrete batch plant operation; shown here with temporary noise barrier for community to the right (Photo #322)
Figure 5.29 Stock pile operation in vicinity of residence (Photo #1258)
Figure 5.30 Communities can be affected by traffic diverted by construction activities (Photo #1046)
Compared to noise generated by construction operations, equipment noise levels can be measured under more controlled conditions. Standard measurement practices and techniques and acceptable limits (for certain projects) have been established for the measurement of noise from many specific types of construction equipment. Practices and techniques for the measurement of construction equipment noise levels on highway-related projects are described in Chapter 7 of Reference 006. Noise measurement procedures used in determining equipment noise levels that were ultimately incorporated into the RCNM program are described in Section 3.01 of Reference 023. In many cases, these protocols and limits account for the typical operational characteristics of the piece of equipment, such as stationary equipment (generators, pile drivers, jackhammers, compressors, etc.), mobile equipment (on-road trucks), and cyclical operating equipment (pans, graders, front end loaders, on-site truck operations, etc.).
Figure 5.31 Stationary construction operation (Photo #123)
Figure 5.32 On-road construction vehicle (Photo #1243)
Figure 5.33 Construction vehicle involved in cyclical operation (Photo #1005)
A wide variety of noise measurement equipment is currently available for use in the measurement of construction noise levels. Some examples of the range of such equipment include:
Figure 5.34 Type I sound level meters (Photo #1296)
Figure 5.35 Type II sound level meter (Photo #1297)
Figure 5.36 Permanent automated wireless noise monitoring system; note solar cell, antenna, transmitter, and microphone (Photo #48)
The need obviously exists to tailor the type of equipment utilized to the complexity of the project and its construction noise monitoring requirements.
In performing valid construction noise measurements, the following factors should generally be considered:
References to documents containing specific information related to the following topics include:
In addition to the factors discussed above, other factors to consider in setting up a construction noise-monitoring program include: