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Construction Noise and Vibration Impact on Sensitive Premises

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Construction Noise and Vibration Impact on Sensitive Premises Proceedings of ACOUSTICS 2009 23-25 November 2009, Adelaide, Australia Construction noise and vibration impact on sensitive premises Cedric Roberts Engineering and Technology Division, Department of Transport and Main Roads, Brisbane, Queensland, Australia ABSTRACT Construction noise and vibration must be considered an essential part of the development of any transportation facility. Road and tunnel construction is often conducted in close proximity to residential and commercial premises and should be pre- dicted, controlled and monitored in order to avoid excessive noise and vibration impacts. Construction noise and vibration can threaten a project's schedule if not adequately analysed and if the concerns of the community are not addressed and in- corporated. AIRBORNE NOISE transportation facility. Road and tunnel construction is often conducted in close proximity to residential and commercial Construction over the length of a project can take place 24 premises and associated noise and vibration should be pre- hours a day and for major projects, in excess of 2 to 3 years. dicted, controlled and monitored in order to avoid excessive Construction equipment can operate in very close proximity noise and vibration impacts. Construction noise and vibration to residential and commercial (and even industrial) premises. can threaten a project's schedule if not adequately analysed Many items of equipment can be found operating at any time and if the concerns of the community are not addressed and throughout a project. Equipment types range from mobile incorporated. cranes, pile drivers, jackhammers, dump trucks, concrete pumps and trucks, backhoes, loaders, dozers, rock-breakers, In general a project's schedule can be maintained by balanc- rock drills, pile boring machines, excavators, concrete and ing the type, time of day and duration of construction activi- chain saws, and gas and pneumatically powered hand tools. ties: adhering to local or state noise control requirements and being proactive to community concerns. An additional factor of great importance is the presence of low frequency noise (< 200 Hz) in the source sound spectra Airborne noise of many items of equipment for which the 'true' annoyance capability at sensitive receptors is not reflected either in the Construction over the length of the project can take place 24 measurement or prediction using the overall A-weighted hours a day. Construction equipment can operate in very sound pressure level, or dB(A). close proximity to residential and commercial premises. Many items of equipment can be found operating at any time GROUND VIBRATION throughout the project. The full gambit of equipment types are used such as mobile cranes, pile drivers, jackhammers, The total attenuation of vibration from an item of construc- dump trucks, concrete pumps and trucks, backhoes, loaders, tion equipment to a receptor is estimated from the spreading dozers, rock-breakers, rock drills, pile boring machines, ex- loss, a value dependent on whether the source of vibration is cavators, concrete and chain saws, and gas and pneumatically considered a point, line or planar source, attenuation due to powered hand tools. internal losses in the soil and rock, being a function of loss factor η, velocity of propagation c, frequency of the vibration Typical construction equipment is shown in Figure 1. and distance to the receptor and attenuation due to changes in soil or rock along the propagation path, being a function of mechanical impedances of individual differing rock compo- nents. Mechanical impedance is derived from the density of the various media and longitudinal wave speeds for each media.Wave propagation is usually surface or Rayleigh (or R-wave) type. Here again the perception of ground-borne vibration outside and especially inside premises is of a low frequency character. This paper describes methods adopted to estimate the overall noise level and airborne spectra at the boundary of sensitive premises and within these premises using various software modelling packages applied to a typical road making con- Figure 1. Typical construction equipment struction project. The indoor receptor levels are then com- pared to acceptable criteria. Ground-borne vibration at the Source: (FHWA 2006) boundary of premises is compared to established vibration perception evaluation criteria. Noise control specifications can contain both relative noise INTRODUCTION criteria limits at identified noise sensitive receptor locations, as well as absolute noise emission limits for all equipment Construction noise and vibration issues must be considered used on site. The noise specification boundary line criterion an essential part of the assessment of the development of any is primarily a relative criterion in which construction-induced Australian Acoustical Society 1 Proceedings of ACOUSTICS 2009 23-25 November 2009, Adelaide, Australia LAeq noise levels in general cannot exceed baseline (pre- An absolute noise criterion is applied to generic classes of construction) LAeq noise levels by more than 5 dB at identified heavy equipment to limit their noise emission levels. Equip- noise sensitive receptor locations. While an increase of 5 dB ment specific A-weighted LAmax noise limits in dB(A) ex- may be noticeable, it should not present an unacceptable pressed at a reference distance of 15m are defined in the noise hardship condition. Noise Code similar to those given in Table 2. Baseline LAeq noise levels must be established prior to con- struction operations in accordance with the draft Construction Noise and Vibration Code (CNVC 2009) which requires col- Equipment Sound L Acoustic lection of at least two non-consecutive weekday 24 hour Amax noise readings as well as one Sunday noise reading at speci- Description Power Level noise limit Usage fied noise receptor locations throughout the construction area. at 15m, Factor These baseline LAeq noise readings are then reduced into day- time, evening, and night-time average levels and used to es- dB(A) re. 1 dB(A) tablish boundary line noise criteria limits by adding 5 dB, or picowatt % by defaulting to the higher LAeq option (where existing back- ground ambient noise level exceeds the standard noise limits) during the relevant time period specified in the Noise Code. Blasting 125 94* 1 Standard noise limits for general construction during re- stricted hours at residential receptors are given in Table 1. Crane (mobile 116 85 16 or stationary) Time Period General construction activities 38t Bulldozer 118 87 40 LAeq,15min dB(A) Impact Pile 126 95* 20 Driver (diesel Duration of Activity or drop) Short Medium Long Rock drill 116 85 20 term term term Dump truck 115 84 40 Daytime, restricted 65 60 55 hours 35t Excavator 114 83 40 Evening period, 60 55 50 Rock-breaker 120 89 20 6.00pm to 10.00pm, on any day Front end 111 80 40 loader Late night/early 45 45 45 morning period, Grader 116 85 40 10.00pm to 7.00am on any day. Table 2. Typical construction equipment noise emission criteria limits Table 1. Standard noise limits for restricted hours *Indicates impactive device Restricted hours means the period between 6.00pm and These emission limits are achievable but are conservatively 7.00am Monday to Friday and 1.00pm to 12.00 midnight set as low as possible in order to require equipment to be well Saturday and at any time on a Sunday or a Public Holiday. maintained, and often requires some form of source noise Standard working hours allow noise limits 10 dB(A) greater control. Each and every item of equipment should be pre- than those presented in Table 1 for medium to long term ac- certified by the contractor's acoustical engineer to pass their tivities. respective 15m noise emission limit before the equipment is allowed to work on site. Short term construction and maintenance activities are those which would affect any one noise or vibration sensitive site The 'Acoustic Usage Factor' represents the percentage of time for up to 14 days, medium term for more than 14 days and up that a particular item of equipment is assumed to be running to 20 weeks while long term activities exceed 20 weeks but at full power while working on site. The influence of idling less than18 months. noise may be disregarded when the difference between the 2 Australian Acoustical Society Proceedings of ACOUSTICS 2009 23-25 November 2009, Adelaide, Australia operating equipment noise and the idling noise is more than 10 dB(A). Drive-by Caterpillar 85 40 83 Thus, a contract specification can include two types of noise on haul- 657B criteria limits, relative boundary line limits and absolute road scraper equipment emissions limits, both of which should be com- plied with by the contractors at all times. Consequently, if measured or anticipated construction noise limits exceed the Earthworks Front end 80 40 78 allowable noise criteria limits, then noise mitigation measures are warranted and must be implemented prior to and main- loader tained during associated work activities. An added concern is that of the impact of low frequency Earthworks Dump 84 40 82 noise (<200 Hz) especially inside residential properties. The truck traditional methods of using LAeq and LAmax are not appropri- ate for such situations. This paper applies the draft Ecoaccess Guideline ‘Assessment of Low Frequency Noise’ (LFN 2008) Earthworks Bulldozer 87 40 85 to assess the impact of low frequency noise from earthmov- ing equipment and the criteria set out in this document. Earthworks Excavator 83 40 81 PREDICTION METHODS Broadband noise Total 89 Noise levels at receptor locations can be calculated by using LAeq,1h accepted point-source strength propagation algorithms such as that below, summed over all operating equipment: Table 3. Prediction of noise level at apartment from earth- moving operations LAeq,15min = LAmax,15m - 20 log10 (d/15) + 10 log10 (U.F.%/100) –ILbar – 10G log10 (d/15), dB(A) (1) Low frequency noise where LAmax,15m is the A-weighted noise emission limit for The internal overall dB(A) and low frequency (LF) noise the equipment at 15m (see Table 2).
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