Acoustic Monitoring in National Parks

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Acoustic Monitoring in National Parks

• Damon Joyce --- National Park Service

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The importance of acoustical environments

• 95 of Americans regard opportunities to
  experience natural peace and the sounds of nature
  as an important reason for preserving national
  parks 72 thought it was very important (Haas
  and Wakefield 1998).
• Escaping noise ranks fourth in importance (behind
  enjoying nature, physical fitness, and reducing
  tension) among sixteen preference domains by
  users of wilderness and nonwilderness
  recreational areas (Driver, Nash, and Haas 1987).
• 91 of park visitors consider enjoyment of
  natural quiet and the sounds of nature as
  compelling reasons for visiting National Parks
  (McDonald, Baumgartner, and Ichan 1995).

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Sound Levels What do decibels mean?
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Listening Area Reduction
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Listening Area Reduction

• No Change
• 3dB
• 6dB
• 10dB

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Outline

• Data Collection
• Methods
• Large Systems
• Small Systems
• Onsite Listening
• Data Analysis
• 24h Spectrograms
• SPLat
• Offsite Listening
• Noise Free Intervals

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Data Collection
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Methods Site Selection

• Requirements
• At least 1km from motor traffic corridors
• Avoid high wind speeds
• Considerations
• Vegetation
• Topography
• Usage type (climbing, hiking, etc.)

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Equipment

• Type-1 Systems
• Larson Davis 824 or 831
• Edirol R-09 Field Recorder
• Weather station
• Solar panels or Lithium-Ion battery packs
• 35 lbs for a one month monitoring station
• Consumer Grade Systems
• Inexpensive horn loaded microphones
• Solid state MP3 field recorder
• 10 lbs for a one week deployment

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Haleakala National Park
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Data Criteria

• Type-1 Calibrated data
• 1 sec. LEq values (dBA)
• 1 sec. 1/3 octave data (12.5Hz 20,000Hz)
• Wind speed measurements
• Continuous audio (MP3, 64kbps, mono)
• At least 25 days of data
• Non Type-1 data
• Continuous audio (MP3, 64kbps, mono)
• Metadata (site, GPS location, time, etc.)

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On-Site Listening

• PalmOS based application
• Method of logging sound events in a given
  interval
• Several events can be logged concurrently
• Great education tool

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Data Analysis
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Visualizing the acoustic environment
Frequency pitch 20,000 Hertz . . . 33
one-third octave bands (3 of them span a doubling
in frequency) . . 12.5 Hertz
Time 24 Hours of the Day Midnight 1 am 2 am 3
am 4 am 5 am 6 am 7 am 8 am 9 am 10 am 11
am Noon 1 pm 2 pm 3 pm 4 pm 5 pm 6 pm 7 pm 8
pm 9 pm 10 pm 11 pm
Amplitude in dB 80 dB 70 dB 60 dB 50 dB 40 dB 30
dB 20 dB 10 dB 0 dB -10 dB
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SPLat

• Plots SPL data one hour at a time
• Allows user to annotate SPL data
• Linked to audio recorded from site
• Outputs number of events and percent time audible

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Off-Site Listening

• Useful for sites with complex soundscapes
• Split 24 hours of MP3 data into 10sec samples
  2min apart
• Using Excel spreadsheet, mark sound sources
  present for audio sample
• Percent time audible statistics can be calculated
  from the spreadsheet

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Sounds of Nature