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Sound Transmission and Song Divergence

A Comparison of Urban and Forest Acoustics

Andrew Barbeau

on 21 May 2013

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Transcript of Sound Transmission and Song Divergence

Hans Slabbekoorn, Pamela Yeh, and Kimberly Hunt Sound Transmission and Song Divergence:
A Comparison of Urban and Forest Acoustics Sound Perception Sound Degradation Previous Studies Why is this Significant? What are we dealing with? Hypothesis? Dark-eyed Juncos Outline
Discussion Methods
Transmission Experiment
Song Recordings
Statistical Analysis Location Controls Statistical Analysis
Kolmogorov-Smirnoff Test
Levene's Test
Kruskal-Wallis Test
Mann-Whitney U-Test
2-way ANOVA
3-way ANOVA Song Variation Urban vs. Forest Transmission Results
Effect of Microphone Type
Tail Amplitude and Variability
Urban vs. Forest Transmission
Song Variation Among Populations Effect of microphone type Tail Amplitude and Variability Terminology Discussion
Sound Transmission
Urban Song Divergence
Perception of Urban Degraded Song Sound Transmission Evolution in Bird Song Andrew Barbeau Birds must now communicate around buildings and over concrete. Urban Habitats are evolutionarily new. General Factors:
atmospheric spread
air turbulance
reflections off the ground
penetration ATTENUATION is the gradual loss of intensity of sound through a medium. (en.wikipedia.org/wiki/attenuation) IRREGULAR AMPLITUDE FLUCTUATIONS alter the signal amplitude envelope. REVERBERATIONS are echoes of the original signal that are reflected multiple times against surfaces in the environment. Urban Environment -> An urban habitat is distinct from any natural habitat. Sound has only been studied in the context of propagation of traffic noise. -> Urban habitat is typically characterized by relatively little vegetation and mainly concrete walls. -> Buildings are placed at various angles and distances from each other, with streets sparsely alternated with grass as ground cover. a common species in mountainous pine forest habitat Junco hyemalis http://buildyourownbirdhouseplans.com/images/DarkEyedJunco.jpg they produce a small repertoire of stereotypic trilled songs http://img.tfd.com/wn/58/65EBA-eighth-note.gif Laguna Mountain Recreational Area Campus of University California-San Diego Transmission Experiments Song Recordings The effect of an urban landscape on sound transmission and song divergence. Mission:
Species- Dark-Eyed Junco
Location- San Diego, CA
Objective- Listen & Record Sound Transmission
Song Divergence http://www.sandiegoconcierge.com/images/San-Diego-photo2.jpg http://www.mbr-pwrc.usgs.gov/Infocenter/Song/h5670so.mp3 Facts people don't realize about cities: 3 Important Facts Benefits of Vocalizing
Selection Pressure
Fitness Consequences
Natural Selection
Evolution http://www.salford.ac.uk/news/images/upload/large/1233921138undated_charles_darwin.jpg Genetics vs. Environment "Dr. Hess Lecture in Animal Behavior" 3 Main Contributors Transmission
-Discovery based but with
a focus on reverberations. Divergence
-Hypothesized that birds in urban areas should sing shorter
songs at higher frequencies, and have a slower trill rate
compared to birds in natural habitats. References Discussion Questions http://www.wisegeek.com/what-are-omnidirectional-microphones.htm Fremont, Santa Barbara County, CA
Mill Valley, Mendocino County, CA Tranmission Pathways Laguna Mtns. UCSD Conducted sound transmission experiments in urban and forest habitat and analyzed the impact of reverberations on artificial tones after transmission. Played artificial sounds from a speaker at 3m height and recorded the sound also at 3m height after transmission over 25m. near field recording, 1m away, as a reference or test signal
weather conditions were quiet and dry during all recordings
no traffic conditions Long Interval Sequence: 2 40ms tones at 2.5kHz with 100ms interval reflecing a slow junco song trill rate of about 7 syllables per second.

Short Interval Sequence: 2 40ms tones at 2.5kHz with 20ms interval reflecting a fast junco song trill rate of about 17 syllables per sceond. Details 2 Sequences Fast & Slow
Recorded 4x
*2x with an Omni
*2x with a Uni
Tone 2.5kHz
21 Total pathways
*7 Forest
* 7 Grass
* 7 Concrete 3m Sender Receiver 3m 25m "Google Maps" Details Only unidirectional microphone
*UCSD, Laguna Mtns., Fremont, Mill Valley
Spontaneous vs. Triggered
Avg. 10 songs of 1 song type per individual Measurements Max Frequency
Min Frequency
Trill Rate Sample Size 580 songs for 58 birds
*UCSD 20
*Laguna Mtns 9 and 12
*Fremont 8
*Mill Valley 9 Controls No variation in spontaneous or triggered recordings
Song type diversity was high and similar between populations
Weather conditions were quiet and dry during recordings
No traffic noise whats a trill? http://www.artadox.com/wp-content/uploads/2008/05/a-studio-recording-session.jpg Unidirectional Omnidirectional Signal to Noise Tail to Signal Concrete Grass Forest Concrete Grass Forest Tail to Signal Signal to Noise Concrete Concrete Grass Forest Grass Forest 50.5 43.6 47.4 150.0 106.5 206.0 0.12 0.08 0.06 0.21 0.18 0.22 Omnidirectional vs Unidirectional
Short vs. Long Interval
Spontaneous vs. Triggered
Reference Location
True Duplicates
Tail-to-Signal Rufous-collared Sparrow for which strong habitat correlations have been found for trill rate dialects. Birds in Indianapolis The American Robin: Turdus migratorius Learning reverberations lead to an extension of the echo threshold resulting in the supression of echoes with longer delay times afer a few exposures. http://www.zuropak.com/photogallery/2008-favourites/American-Robin-149.jpg Timing
* Silent Intervals
* Duration
Phantom Sources
* Direction
* Distance
Signal Recognition Reverberations effect songs with:
Longer Duration
Faster Trill Rate
Lower Frequencies 35ms http://filebox.vt.edu/users/jcastner/rufs%20closeup.jpg Tail-to-Signal Ratios
Trill Rates
Habitat Gradual Tails vs. Echoes
Delay Max Frequency
Min Frequency
Trill Rate
Song Varieties Reverberations Delay Times Tail to Signal Fill Silent Intervals Song Perception Signal Meaning Lost Fitness Consequences Song Divergence Expected Why Occured Questions in General?

Problems with this study?

What studies can be done in the future?

Should we be concerned?

If we are can we adjust the environment?

What extent are birds city followers?

Cities as a mode of Natural Selection?

Other animals depend on sound, as well as other forms of signaling what would be other similar examples?

Is overall sound pollution affecting the environment?

Are there any cases in which we would want to prevent animals form communicating? Perception of Urban Degraded Song There are clearly some differences in sound transmission, but in this particular population of Juncos there is limited habitat dependent divergence. Tails and Echoes Mask Subsequent Sound Slow Trills
Higher Frequencies
Shorter Songs Only in the urban habitat were short songs recorded, and the minimum frequency was higher. No significant difference in frequency, trill rate, duration, or types of songs. No firm conclusions could be made. Still unclear of perception Loss of spatial Information hgfhjgfhf
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