Measuring Audible Wind Turbine Noise Measuring Audible Wind Turbine - - PowerPoint PPT Presentation

Measuring Audible Wind Turbine Noise Measuring Audible Wind Turbine Noise

Consultation Session June 22, 2010

Introduction

Our Mandate

To develop an objective measurement protocol to determine the noise impact from wind turbines in the determine the noise impact from wind turbines in the audible frequency range.

Session Goal

To obtain comments/suggestions/concerns from participants for consideration in the development of participants for consideration in the development of the Measurement Protocol.

Agenda

Presentation of framework Presentation of data analysis techniques Open Forum discussion of 1st half of framework p Break Open Forum discussion of 2nd half of framework Summary & Closing y g

Acoustic Audit vs. Complaint

Measurement protocol and methodology to remain the same for audit p gy and compliant Initiation of process is different Audit may require a certain sampling of turbines for a given plant Complaint investigation may also require additional measurements

Process Flow Process Flow

Complaint

Duty Officer to determine if measurement is warranted No Report Filed Y e s M t

Audit

Measurement conducted

Framework Framework

Measurement Intervals (Section 4.2) ( )

• LAeq will be the primary descriptor used. Additional statistical indices may be used to

complement the LAeq.

• Interval time will be 1-2minutes (for both sound and wind)
• 1/3

b d i l

• 1/3 octave band measurements are essential
• Audio recordings for intervals to be used primarily for reference during post processing.

Audio recordings may also be used for tonality assessment.

• Total duration of measurement to be sufficient to provide at least 1 hour of data per

p p integer wind speed (Section 4.4.)

Framework Framework

Instrumentation Requirements (Section 4.3) q ( )

• Requirements of appropriate standards and guidelines shall be satisfied (IEC, NPC)
• Shall incorporate methods to reduce wind induced noise
• Anemometer to have an accuracy of +/- 0.2m/s and resolution of 0.1m/s
• Anemometer to be calibrated and traceable to a test facility
• Anemometer shall record in same interval as sound is captured

Measurement Location (Section 4.5 & 4.6)

• At receptor, located at least 5m from facade
• Height to be either 4.5m or 1.5m depending on receptor
• Anemometer to be located at receptor, at 10m height

Framework Framework

Ambient Noise (Section 4.7) ( )

• Measurements to be conducted only during nighttime hours
• Ambient measurements are not required if it can be shown that sound level limits are

satisfied with background noise and turbines operational

• A

bi i l l b d h i d d

• Ambient noise levels to be measured over the same wind speed range
• Ambient noise levels are to also be measured at receptors with turbines in vicinity of

receptor shut down

Tonality (Section 4.8)

• Tonality should be assessed objectively, using the Joint Nordic Method, IEC 61400-11 or

ISO 1996-2 ISO 1996-2.

• Tonal adjustment should be applied using a sliding scale as outlined in the standards.

Framework Framework

Data Analysis (Section 4.9) y ( )

• Only data from 19:01 until 04:59 will be used for the analysis.
• Remove any intervals where rainfall occurred from one hour before and one hour after
• 1-minute intervals where the max/min wind speed differs by more than 2m/s from the

i d d id d “ ” d h ld b i l d d i d average wind speed are considered “gusty events” and should not be included in data set.

• Intervals with noise from insects shall be adjusted by filtering the 1/3octave bands

which may be affected

• Up to 3rd order polynomial regression line to be fit through the remaining data for both

“ON” and “OFF” periods

• The ambient curve can be logarithmically subtracted from the total sound level curve to
• btain the noise contribution from the wind plant at the receptor for integer wind speeds
• btain the noise contribution from the wind plant at the receptor for integer wind speeds.
• Standard deviation of data sets at integer wind speeds to be reported

Example Example

Measurements with turbines operating p g

Example Example

Measurements with turbines parked p

Example Example

Results

Wind Speed [m/s] 4 5 6 7 8 Total Sound Level [dB] 39.9 43.3 46.3 48.9 51.0 Standard Deviation [dB] 3.5 3.2 2.1 1.6 1.3 Ambient Sound level [dB] 37.4 42.0 45.5 48.1 NA Turbine Sound Level [dB] 36 38 38 41 NA

a e r c o u s t i c s . c o m