Juneau Flightseeing Noise Informational Work Session November 6, 2000

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)

Single Event Noise Metrics

LEQ Noise Level Bonnie Brae

Time Above Noise Level Douglas 2th TA75 TA65 TA55

DNL Noise Level Douglas 5th Modified DNL DNL

Frequency Character of the Noise Why is some noise more annoying?

How does Noise Effect People?  Hearing Loss  Speech Interference  Sleep Interference  Classroom Learning  Physiological Response  Annoyance

Speech Interference

Sleep Interference

How does Noise Effect People?  Hearing Loss  Speech Interference  Sleep Interference  Classroom Learning  Physiological Response  Annoyance

Annoyance (FAA Research)

Annoyance (NPS Research)

Factors that Affect Individual Annoyance to Noise

Factors that Affect Noise Source Levels  Engine technology  Aircraft technology  Rotor or propeller design  Power Level  Prop Pitch  Speed

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

Temperature and Humidity

AVI 2

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

Helicopter Events Brotherhood Park

Long Duration Helicopter Events Bonnie Brae

Character of Noise

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

Float Plane Events Douglas 5th

Character of Noise

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

1994 vs Noise  Changes between 1994 and 2000  Increased Operations  Improved Flight Paths  Quieter Technology

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

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

Noise Monitoring Locations

Noise Monitoring Locations (south)

AVI 1

Noise Monitoring Locations (north)

Continuous Measurement of Noise Fritz Cove Rd

Sequence of Noise Measurement

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

Single Event Noise How loud are the single event noise levels? Douglas 2nd

Airport Jet Events Fritz Cove Rd

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

Time Above Noise Levels How often is noise above different thresholds?

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

DNL and Modified DNL Noise Levels How high are the cumulative noise levels?

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

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

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

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

Daily Noise Events

Single Event Noise by Aircraft

Outdoor to Indoor Noise Levels

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

Ambient Noise How quiet is it when aircraft are not present?

Ambient Noise Levels (by Site)

Ambient Noise Levels (by Day)

Ambient Noise Levels (by Hour)

Non-Aircraft Noise Events