SGS Environmental Services Environmental Noise INTRODUCTION - PowerPoint PPT Presentation

SGS Environmental Services Environmental Noise

INTRODUCTION INTRODUCTION  What is noise?   Defined as "unwanted sound“ Defined as unwanted sound  Expressed in decibels (dB) on a logarithmic scale, where 0 dB is nominally the "threshold of hearing" and 120 dB is nominally the "threshold of pain"   Sound levels expressed using “A-weighting” to account for the non-linearity of the Sound levels expressed using A-weighting to account for the non-linearity of the sensitivity of the human ear in response to different frequencies  Denoted db(A)   If you have to shout the background noise If you have to shout the background noise level is typically 75-80 dBA. A busy office would typically have a noise level of about 60 dB(A) while busy road traffic would 60 dB(A) while busy road traffic would generate about 70-80 dB(A) (measured on the pavement) 2

NOISE IMPACTS NOISE IMPACTS  Effects  Effects  According to WHO, exposure to increased noise levels can result in: – Pain and hearing fatigue – Hearing impairment H i i i t – Annoyance – Interference with speech communication – Sleep disturbance – Cardiovascular effects – Affect performance at work and school – Decreased productivity 3

NOISE REGULATION NOISE REGULATION  Noise regulation differs from country to country but are generally g y y g y performed for :  Baseline surveys – New industrial sites airports etc New industrial sites, airports, etc.  Compliance auditing according to regulations and legislation – Industrial site fenceline and sensitive receptor monitoring  Complaint handling C l i t h dli – Nightclubs, fairgrounds, etc. 4

NOISE NOISE  The most important factors affecting noise propagation are:  Type of source – Point – Line  Distance from source  Weather conditions  Obstacles such as barriers and buildings  Obstacles such as barriers and buildings  Ground absorption  Reflections  To arrive at a representative result for measurement these factors must be taken into account  Regulations will often specify conditions for each factor 5

NOISE MEASUREMENT NOISE MEASUREMENT  Noise emissions are measured using sound-level meters  Type 1 Sound Level  1/1 Octave, 1/3 Octave  Percentile levels (LN01 → LN99)  Weighting filters: A & C filters  Annual calibration certificate  Response checked in the field before and after any measurements with an acoustic calibrator similarly calibrated  R li bl  Reliable brands: b d  Larson Davis  Bruël & Kjær  Norsonic  Quest etc. 6

OCCUPATIONAL NOISE: NOISE DOSIMETERS OCCUPATIONAL NOISE: NOISE DOSIMETERS  Noise dosimeter (noise badge)  Worn carried at ear height  Measurements performed over a set time (8 hour shift)  Data downloaded  Analysis on PC y 7

NOISE MEASUREMENTS NOISE MEASUREMENTS  Typical environmental noise measurement parameters are:  L Aeq : Average noise level during the measurement period L : Average noise level during the measurement period  L A90 : The noise level exceeded for 90% of the time – Mepresentative of the steady background noise at a location, excluding short events such as cars passing, dogs barking etc. t h i d b ki t  L A10 : The noise level exceeded for 10% of the time – Measure of higher noise levels present in the ambient noise – Commonly used to describe traffic noise  L Amax : The maximum sound level measured during the sample period  L Amin : The minimum sound pressure measured during the sample period p g p p Amin  Fast, is generally the preferred time-weighting, especially for statistical data and for variable noise levels  Tonal or impulsive elements (sound audible at a level near or above the general ambient noise eg. fan, compressor) requires the use of a third octave or narrow band frequency analyser 8

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EXECUTING MEASUREMENTS: UNMANNED EXECUTING MEASUREMENTS: UNMANNED  Class I sound level meter coupled with a weather station weather station  Longer duration measurement  Usually for measurement of background noise (traffic baseline measurement noise (traffic, baseline measurement,.....) )  Time History, percentile levels, periodical averages (hourly, daily,.....)  Measurements are only usefull under certain weather conditions → check your local legislation (wind speed, precipitation)  According to ISO 1996 (environmental noise) or local regulation  If possible, it’s usefull to record the measured noise (peaks, windturbine noise,....) 10

EXECUTING MEASUREMENTS: MANNED EXECUTING MEASUREMENTS: MANNED  Class I sound level meter   SLM mounted on a tripod SLM mounted on a tripod  Care should be taken not to make noises whilst observing the meter in this method and ensuring the least amount of reflective surface from your body is exposed to the meter  To avoid the reflection, set up tripod more than 3.5m away from a reflective surface  Shorter duration 15 to 30 minutes per point (stable level)  According to ISO 1996 or local regulation  Noise reading taken at the height of the receptor (1.2–1.5 m above ground level g g p ( g  Time history, percentile levels, periodical averages (hourly, daily,.....), spectra in 1/3 octaves ( → tonality), peak values, minimum values  Used for measurement of background noise g  More information can be distilled from these measurements  Shorter period of time (measurement untill stable level)   Measuring periods Measuring periods  Day: 7am to 6 pm  Evening: 6pm to 10pm  Night: 10pm to 7am.  If possible, make notes during measurements 11

REPORT REPORT  Reporting   The manufacturer model type and serial number of the sound level meter The manufacturer, model type and serial number of the sound level meter, calibrator and microphone used  The type of windshield  The date the equipment was last calibrated to a traceable standard  On-site calibration details and after the measurements  The frequency weighting networks and meter responses used  A description of the measurement site and of the range of sound sources including the type of sound (continuous intermittent impulsive tones) the type of sound (continuous, intermittent, impulsive, tones)  Methodologies followed throughout the survey  A map of the measurement site showing the locations of the measurement positions (GPS) p ( )  Details of the intervening ground between sources and measurement positions and the presence of barriers etc.  The time and date of the measurement  A description of the meteorological conditions  The background noise level (where practicable)  The names of the person/s that undertook the survey and drafted the survey report 12