Bill Schmidt

1
The Analysis and Protection of the Natural
Soundscape in National Parks
Bill Schmidt NRSS WASO
2
The Basic Ideas

• The soundscape is the totality of sounds
• The natural soundscape (the soundscape)
  (human noise)
• The natural soundscape is a protected natural
  resource of the National Park Service.
• It is neither necessary nor practical to return
  NPS soundscapes to their pre-1492 conditions.
• Monitoring the soundscape is neither as difficult
  as you might fear nor as easy as you might hope. 
• There is no time like the present to start.

3
Fundamentals of Sound (pressure)
4
Fundamentals of Sound (frequency)
5
Fundamentals of Sound (loudness)
6
Frequency Weighting
7
Soundscape Metrics
 Decibel The dB 20 Log10 ((sound pressure in
Pascals)/20 x 10-6 Pascals))  SEL (Sound Exposure
Level) This metric is the unit used to describe
the total amount of sound for an event compressed
into 1 second.   Lmax and Lmin The highest and
lowest instantaneous sound levels within a
certain time period  Leq (Equivalent sound level)
The average sound level in a period of time.
8
Soundscape Metrics
TA (Time above) The amount of time in a given
period that the sound level exceeds a specified
threshold.  Ln (Exceedance levels) These are
statistical values for a series of readings.  For
example, L90 43 dBA means 43 dBA was exceeded
90 percent of the time. DNL Day night level (also
called Ldn) This is a 24-hour average hourly
noise level with a 10 dB penalty for nighttime
noise events between 10 PM and 7 AM.
9
Some useful facts and rules of thumb.

• Low frequency sounds, e.g., mechanical noise,
  can be heard at greater distances than high
  frequency sounds.
• The decrease in sound pressure levels from a
  point source, i.e., one whose lateral dimension
  is small, is about 6 dB per doubling of distance
  about 5 dB over water. For example, a boom box
  whose SPL at 50 feet is 80 dB, would have a SPL
  of about 74 dB at 100 feet, 68 dB at 200 feet,
  etc.
• The decrease in SPL for a line source, e.g., a
  highway, is about 3 dB for each doubling of
  distance.

10
Why worry about the soundscapes?

• Because it is part of our job
• Because the critters are depending on you
• Because it is important to visitor enjoyment

11
Why worry about the soundscapes?- Job Related

• The natural soundscape is a natural resource and
  the Organic Act says Thou shall protect natural
  resources.
• Directors Order 47
• Develop soundscape plans (or components of GMPs,
  RMPs, WMPs, etc.) (Sections C.3, 6, and 7)
• Inventory and monitor the soundscape (Section
  C.5)

12
DO 47 also

• Directs the parks to use the natural soundscape
  as the affected environment for NEPA matters
  related to the impacts of sound. (Section C.7 )
•  
• Unless there is better information, parks are to
  use the L90 exceedance levels as the level of the
  natural ambient,i.e., the value for the natural
  soundscape in C.7. (Section D.4)

13
Tactical use of the L90/Natural values

• In a defense of the parks soundscapes, get the
  discussion revolving around your concepts and
  issues rather than those of the proponents of an
  action.
• Avoid allowing use of assumed ambient values.
• Dont let the proponents choose the appropriate
  metrics its your park.
•  

14
Why worry about the soundscapes?- Critters

• Most studies of effect of noise on wildlife are
  ad hoc a species or two and short term.
• Most acoustic studies of wildlife are for
  trophies.
• There is a growing interest in studies of the
  biophony the biota in the context of the
  ecosystem.

15
Why worry about the soundscapes?- Visitors

• The NPS is the keeper of some of the quietest
  places in the US.
• The natural soundscape is a major reason visitors
  come to the parks.
• approximately 93 of surveyed visitors reported
  that the reason for their visit was to view the
  natural scenery.
• 91 per cent reported that their reason for the
  park visit was to enjoy the natural quiet.

16
Monitor a park?How?

• A few thoughts
• This park-wide area acoustics is new the NPS is
  helping write the book.
• A parks soundscape is dynamic, varying with time
  and place. You will never have all the answers.
• If you wait to get the data until a crisis hits,
  it is generally too late to be able to use them.

17
Monitor a park?How as an IM effort?

• Use consultants
• Expensive 11.5K/day expenses
• Come with expertise (and equipment)
• Use rotating teams
• Collateral duty
• Assemble a lot of data in a few years
• Use equipment from pool
• Funding being sought
• Park funded people and equipment
• Can meet more urgent or specialized needs

18
Monitor a park?How?

• Define your goals.
• Plan your study before you get to the field.
• Do a reconnaissance study first.
• Build on the reconnaissance.
• Keep things simple.

19
Monitor a park?What type of instrumentation?

• What are you trying to do?
• Measure park-caused noise? A 50 Radio Shack
  33-2055 will probably work just fine.
• Do reconnaissance or have an observer document
  levels? An 850 CEL 254 may be just the ticket.
• Longer term logged monitoring? One of the logging
  meters from Larson Davis, BK, or Norsonics --
  3,000-10,000.

20
Monitor a park?What is measured?

• The meters take instantaneous pressure level data
  and assemble it as you specify generally 1
  second Leq values.
• A-weighting is the lingua franca of the industry.
• 1/3 OB. narrow band, and analyses like d-prime or
  FFT (and more) may serve specialized needs.

21
Monitor a park?Where to measure?

• Unless obvious noise sources are of interest,
  e.g., a proposed highway expansion, stay out of
  their area of influence when monitoring.
• Try for representative conditions and seasons
  (reconnaissance).
• Absent a better hypothesis, try for balanced
  geographic coverage.

22
Some Current Issues

• Microphone Height
• Bird spikes etc.
• Acoustic Zoning
• To .WAV or not to .WAV
• Noise floor of mics
• Duration of monitoring
• Wind-mic interaction
• Form of the record

23
Some other available tools

• NPS Acoustic database
• Data viewers
• NMSIM, NPS version.
• ISIS

24
Data viewers

• The common database allows common data structure
  and useful tools like this viewer.

25
NMSIM

• Prospective actions generally require noise
  modeling. The NPS is about to acquire its own.