Juneau Flightseeing Noise Informational Work Session November 6, 2000

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Juneau Flightseeing NoiseInformational Work
Session November 6, 2000
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How is Noise Measured?

• Single Event Metrics
• Maximum Noise Level (Lmax)
• Sound Exposure Level (SEL)
• Spectral Content of the Noise
• Cumulative Noise Metrics
• Hourly LEQ Noise Level
• Time Above Noise Level
• DNL Noise Level
• Modified DNL Noise Level (8 am to 9 pm)

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Single Event Noise Metrics
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LEQ Noise Level
Bonnie Brae
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Time Above Noise Level
Douglas 2th
TA75
TA65
TA55
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DNL Noise Level
Douglas 5th
Modified DNL
DNL
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Frequency Character of the NoiseWhy is some
noise more annoying?
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How does Noise Effect People?

• Hearing Loss
• Speech Interference
• Sleep Interference
• Classroom Learning
• Physiological Response
• Annoyance

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Speech Interference
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Sleep Interference
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How does Noise Effect People?

• Hearing Loss
• Speech Interference
• Sleep Interference
• Classroom Learning
• Physiological Response
• Annoyance

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Annoyance (FAA Research)
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Annoyance (NPS Research)
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Factors that Affect Individual Annoyance to Noise
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Factors that Affect Noise Source Levels

• Engine technology
• Aircraft technology
• Rotor or propeller design
• Power Level
• Prop Pitch
• Speed

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Factors that Affect Noise Propagation

• Distance from Noise Source
• 6 dB per doubling of the distance
• Meteorology
• Temperature and Humidity
• Cloud Cover
• Wind Speed Direction
• Ground Absorption
• Soft or hard surfaces
• Terrain and shielding
• Home Construction

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Temperature and Humidity
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AVI 2
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Helicopter Noise?

• Loudness of Helicopters
• 65 to 80 dBA
• Viabilities
• Meteorology
• Alters path and noise propagation
• Speed
• Higher speed shortens the duration
• Point of Flight Path
• Loudness about the same in all modes but duration
  may change
• Altitude
• Change in 5 dBA per doubling of the distance
• Terrain and Ground Surface
• Hard vs. Soft surfaces
• Number of Helicopters
• Duration increases

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Helicopter Events
Brotherhood Park
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Long Duration Helicopter Events
Bonnie Brae
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Character of Noise
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Float Plane Noise?

• Loudness of Float Planes
• 65 to 80 dBA
• Viabilities
• Meteorology
• Less important than with helicopters
• Propeller Pitch
• Changes the noise characteristics
• Point of Flight Path
• Takeoff usually louder than approach
• Flight path important
• Altitude
• Lower level flights
• Type of Aircraft
• New generation technology is quieter
• Number of Float Planes
• Increases the duration

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Float Plane Events
Douglas 5th
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Character of Noise
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Overall Noise

• Ambient metric shows background levels in low 40
  dBA
• Single Event
• Typical single event peak aircraft levels 65 to
  80 dBA
• Highest levels of 85 dBA
• Typical durations of helicopter events ranged
  from 1 to 3 minutes
• Time Above during Daytime hours
• Aircraft noise is above clearly audible levels
  15 to 25 of the time
• During Peak aircraft can be above clearly audible
  over 90 of the time
• Aircraft noise is above typical speech
  interference levels 2 to 5 of the time
• Aircraft noise is above higher interruption
  levels about 1 of the time
• DNL
• Aircraft DNL noise levels ranged from 50 to 57
• Peak DNL days were 3 to 5 DNL higher
• Modified DNL (summer daytime hours) about 1 to 3
  dB higher
• Spectral Content
• Unique low frequency content of helicopter noise
• Pure tones from variable pitch prop aircraft

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1994 vs. 2000 Noise

• Changes between 1994 and 2000
• Increased Operations
• Improved Flight Paths
• Quieter Technology

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Unique Issues at Juneau

• Meteorology
• Closed terrain with limited flight paths
• Water area
• Limited Research on this type of aircraft noise
• Relatively low level noise with long duration
  exposure
• Lower frequency noise sources

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Measurement Sites

• Longer-term Sites
• 16 sites
• Continuous measurement of all noise
• Computer DNL, LEQ Single Event and Time Above
• Short-term and Background Sites
• 15 sites
• Continuous measurement of all noise for
  short-term periods
• Computer LEQ, Single Event and Time Above
• Indoor Sites
• 4 sites
• Outdoor to indoor noise reduction

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Noise Monitoring Locations
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Noise Monitoring Locations (south)
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AVI 1
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Noise Monitoring Locations (north)
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Continuous Measurement of Noise
Fritz Cove Rd
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Sequence of Noise Measurement
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Measurement Results

• Ambient or Background Noise Levels
• Single Event Noise Levels
• Time Above Noise levels
• DNL and Modified DNL noise levels
• Frequency Characteristics

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Single Event NoiseHow loud are the single event
noise levels?
Douglas 2nd
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Airport Jet Events
Fritz Cove Rd
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Single Event Measurement Results

• Typical Lmax events are 65 to 80 dBA
• Occasional Lmax events up to 85 dBA
• Similar levels in most areas
• Helicopter time durations are 1 to 3 minutes

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Time Above Noise LevelsHow often is noise above
different thresholds?
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Time Above Measurement Results

• Time Above 55 dBA
• Represents when aircraft maybe clearly audible
• Daytime hours noise above 55 dBA 15 to 25 of
  the time
• During Peak hours noise above 55 dBA over 90 of
  the time
• Events occur 100 to 200 times per daytime hours
• Time Above 65 dBA
• Represents when speech disturbance starts to
  occur
• Daytime hours noise above 65 dBA 2 to 5 of the
  time
• During Peak hours noise above 65 dBA up to 30 of
  the time
• Events occur 50 to 120 times per daytime hours
• Time Above 75 dBA
• Represents when noise is hard to speak above
• Daytime hours noise above 75 dBA 1 of the time
• During Peak hours noise above 75 dBA up to 3 of
  the time
• Events occur 5 to 20 times per daytime hours

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DNL and Modified DNL Noise LevelsHow high are
the cumulative noise levels?
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DNL Measurement Results

• Average Aircraft DNL noise levels ranged from 50
  to 57
• Peak day levels 3 to 5 dB higher
• Modified DNL (8 am to 9 pm) noise levels 1 to 3
  dBA higher

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Summary of Measurement

• Ambient metric shows background levels in low 40
  dBA
• Single Event
• Typical single event peak aircraft levels 65 to
  80 dBA
• Highest levels of 85 dBA
• Typical durations of helicopter events ranged
  from 1 to 3 minutes
• Time Above during Daytime hours
• Aircraft noise is above clearly audible levels
  15 to 25 of the time
• During Peak aircraft can be above clearly audible
  over 90 of the time
• Aircraft noise is above typical speech
  interference levels 2 to 5 of the time
• Aircraft noise is above higher interruption
  levels about 1 of the time
• DNL
• Aircraft DNL noise levels ranged from 50 to 57
• Peak DNL days were 3 to 5 DNL higher
• Modified DNL (summer daytime hours) about 1 to 3
  dB higher
• Spectral Content
• Unique low frequency content of helicopter noise
• Pure tones from variable pitch prop aircraft

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What to do with the data?

• Conduct dose-response survey
• Explore mitigation options
• Model alternative proposal relative to how they
  may change these noise levels
• Use in Mediation process

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Mitigation Options

• Promote Federal level research
• Develop local regulations
• Alternative flight paths and procedures
• New technology
• Fly quiet programs
• Mediation process

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Daily Noise Events
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Single Event Noise by Aircraft
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Outdoor to Indoor Noise Levels
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Example Noise Metrics

• Number of SEL events per day
• Daytime Time duration that aircraft are audible
• Daytime LEQ above the ambient
• Daily DNL noise level

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Ambient NoiseHow quiet is it when aircraft are
not present?
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Ambient Noise Levels (by Site)
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Ambient Noise Levels (by Day)
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Ambient Noise Levels (by Hour)
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Non-Aircraft Noise Events