Juneau Flightseein

g 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 LevelDouglas 5th

Modified DNL

DNL

Frequency Character of the NoiseWhy is some noise more annoying?

31.5Hz

63Hz

125Hz

250Hz

500Hz

1kHz

2kHz

4kHz

8kHz

16kHz

S1

S12

S23

S34

S45

S56

S67

S78

S89

S100

S111

S122

0

10

20

30

40

50

60

70

80

90

How does Noise Effect People?

Hearing Loss Speech Interference Sleep Interference Classroom Learning Physiological Response Annoyance

Speech Interference

0 5 10 15 20 25 30 40

50

60

70

80

90

100

110

120

TA L K E R T O L IS T E N E R D IS TA N C E IN F E E T

L O W

BA

CK

GR

OU

ND

NO

ISE

(dB

A)

H IG H

C O M M U N IC AT IO N IM P O S S IB L E

M A X IM U M V O C A L E F F O RT

A R E A O F N E A R LY N O R M A L S P E E C H C O M M U N IC AT IO N

E L E VAT E D V O IC E L E V E L

C O M M U N IC AT IO N P O S S IB L E

S H O U T

C O M M U N IC AT IO N D IF F IC U LT

SO U R C E: E nv ironm en tal Im pact A na lysis H andbook John G . R au and D av id C . Wooten , 1980

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

Primary Acoustic Factors Sound Level Frequency Duration Secondary Acoustic Factors Spectral Complexity Fluctuations in Sound Level Fluctuations in Frequency Rise-time of the Noise Localization of Noise Source Non-acoustic Factors Physiology Adaptation and Past Experience Listener's Activity Affects Annoyance Predictability of When a Noise will Occur Is the Noise Necessary? Individual Differences and Personality

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

Source: “Noise and Vibration Control”, by Leo

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 EventsBrotherhood Park

Long Duration Helicopter EventsBonnie Brae

Character of NoiseCharacter of Noise

AS350 AVERAGE DEPARTURE SPECTRA

0

10

20

30

40

50

60

70

80

20Hz

25Hz

31.5Hz

40Hz

50Hz

63Hz

80Hz

100Hz

125Hz

160Hz

200Hz

250Hz

315Hz

400Hz

500Hz

630Hz

800Hz

1kHz

1.25kHz

1.6kHz

2kHz

2.5kHz

3.15kHz

4kHz

5kHz

6.3kHz

8kHz

10kHz

12.5kHz

16kHz

20kHz

Frequency (Hz)

Le

ve

l (d

B)

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 EventsDouglas 5th

Character of NoiseCharacter of Noise

OTTER AVERAGE DEPARTURE SPECTRA

0

10

20

30

40

50

60

70

80

20Hz

25Hz

31.5Hz

40Hz

50Hz

63Hz

80Hz

100Hz

125Hz

160Hz

200Hz

250Hz

315Hz

400Hz

500Hz

630Hz

800Hz

1kHz

1.25kHz

1.6kHz

2kHz

2.5kHz

3.15kHz

4kHz

5kHz

6.3kHz

8kHz

10kHz

12.5kHz

16kHz

20kHz

Frequency (Hz)

Le

ve

l (d

B)

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. 2000 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