The Basics of Noise and Noise Mitigation

Transcription

1 The Basics of Noise and Noise Mitigation Mn/DOT FHWA Presenters: Peter Wasko, Mn/DOT Metro District Mel Roseen, Mn/DOT Environmental Services 1

2 What is Noise? Noise is any unwanted sound that a person hears 2

3 What is sound then? Sound is vibrations transmitted through an elastic solid or a liquid or gas, with frequencies in the approximate range of 20 to 20,000 hertz, capable of being heard by the average human ear. Sound pressure levels are used to measure the intensity of sounds and are described in terms of decibels. 3

4 Common noise sources 4

5 Source-Path-Receiver Concept Source Path Receiver 5

6 Sound Pressure Levels and Decibels 0 ) 2 Relative Pressure Relative Energy Decibel, db (P1/P0) (P1/P0) 2 10 Log (P 1 /P 10 0 = = = = = = = = 1, = = 10, = = 100, = 1, = 1,000, = 3, = 10,000, = 10, = 100,000, = 31, = 1,000,000, = 100, = 10,000,000,

7 What are A-weighted decibels (dba)? The sensitivity of the human ear to sound depends on the frequency or pitch of the sound. People hear some frequencies better than others. If a person hears two sounds of the same sound pressure but different frequencies, one sound may appear louder than the other. This occurs because people hear high frequency noise much better than low frequency noise. A-weighting serves two important purposes: 1. gives a single number measure of noise level by integrating sound levels at all frequencies 2. gives a scale for noise level as experienced or perceived by the human ear 7

8 A, B, & C Weighting Network Filters 8

9 Changes in noise levels in an outdoor environment 3 dba (increase or decrease) is barely perceptible 5 dba (increase or decrease) is clearly noticeable 10 dba (increase or decrease) is perceived as twice as loud (or half as loud) 9

10 Regulatory Agencies Noise regulations are either source standards or receiver-based standards. Department of Natural Resources (DNR) The Minnesota DNR has source standards for snowmobiles, motorboats, personal watercraft and off-highway vehicles. Federal Aviation Administration (FAA) The FAA has source regulations for commercial jet engines. All commercial jet engines must meet noise emission criteria prior to being certified for flight. Federal Highway Administration (FHWA) The FHWA does not have actual noise standards, but has guidelines of an L10 of 70 dba which are used to trip a federal funding mechanism for noise abatement on highway projects. Federal Railroad Administration (FRA) Regulation of railroad related noise is the responsibility of the FRA 10

11 Regulatory Agencies Housing and Urban Development (HUD) HUD has noise regulations that establish acceptable noise zones HUD housing projects must fall into. Occupational Safety and Health Administration (OSHA) OSHA has regulations to protect against hearing loss in the workplace. These are dose standards that restrict the amount of noise an employee receives over a period of time, such as eight hours. Local Agency A local governing agency, such as a city, may or may not have an ordinance regulating noise levels. Minnesota Pollution Control Agency (MPCA) The MPCA has a receiver-based standard intended to limit noise levels and protect the health and welfare of the general public. 11

12 Is there a traffic noise impact? Do noise levels approach or exceed the FHWA criteria? (Mn/DOT has defined approaching as 1 dba less than N.A.C.*) Is there a substantial increase in noise? (Mn/DOT has defined substantial change as a 5 dba change.) Do noise levels exceed Minnesota noise standards (if applicable)? *N.A.C is Noise Abatement Criteria 12

13 23 C.F.R C.F.R. 772 Mn/DOT Noise Policy for Type I and Type II Federal-aid Projects as per 23 CFR 772 Purpose: The document sets forth procedures for noise studies and noise abatement measures to help protect the public health and welfare, to supply noise abatement criteria, and to establish requirements for information to be given to local officials for use in the planning and design of Federal-aid highways approved pursuant to Title 23, United States Code (U.S.C.). Authority: 23 U.S.C. 109(h), 109(I): 42 U.S.C. 4331, 4332; and 49 CFR 1.48(b). 13

14 Federal Noise Abatement Residential: Criteria L 10 of 70 dba both day and night Commercial: L 10 of 75 dba both day and night L 10 is the sound level that would be exceeded 10% of the time ie: 6 minutes of a 1 hour monitoring period 14

15 Type I Project A proposed project for the construction of a highway at a new location. A physical alteration of an existing highway that significantly changes either the horizontal or vertical alignment or increases the number of through lanes." 15

16 Minnesota Noise Rules Minnesota Rules Chapter 7030, defines the allowable receiver-based noise limits and source-based motor vehicle noise limits for trucks, motorcycles, and automobiles. Minnesota Statute , empowers the MPCA to enforce the limits defined in the state rule. 16

17 Minnesota Noise Rules Noise Area Classifications (NAC) NAC-1 Residential NAC-2 Business NAC-3 Industrial 17

18 Minnesota Noise Rules Receiver Based Noise Limits (dba) Daytime Nighttime NAC L50 L10 L50 L Minnesota s noise pollution rules are based on statistical calculations that quantify noise levels according to duration over a one-hour monitoring period. The L10 calculation is the noise level that is exceeded for 10%, or 6 minutes, of the hour, and the L50 calculation is the noise level exceeded for 50%, or 30 minutes, of the hour. 18

19 How does Mn/DOT determine if a noise wall is feasible and reasonable? 19

20 Mn/DOT Reasonability Criteria Cost effectiveness: Will the wall meet a cost effectiveness value $3250 per residence per dba of reduction? (usually based on a $15/sq ft cost ($18/sq ft on bridges)) Acoustical effectiveness: Will the wall provide a substantial (at least a 5 dba) reduction in noise? 20

21 Construction Noise 21

22 Needs to be addressed during the Environmental Phase of the projects and during construction. What can you commit to? What can t you commit to? Time frame for project (length of construction phase) Types of equipment (limits on use or time period) Roadway Construction Noise Model Communication with residents is the key! 22

23 Other Resources wwwcf.fhwa.dot.gov/environment/noise/ wwwcf.fhwa.dot.gov/environment/noise/table.htm 23

24 Contact Information Mel Roseen Peter Wasko Anne Claflin

25 Questions? 25