Sound recordings from the 2007 emergence of Brood XIII cicada

1pAB4: Sound recordings of the 2007

Brood XIII cicada emergence

Ralph T. Muehleisen

Civil, Architectural, and Environmental Engineering

Director of the Miller Acoustics Lab

Illinois Institute of Technology

[email protected]

Periodical Cicada

• Periodical Cicada are flying, plant-sucking insects of the species Magicicada and have 13 or 17 year synchronized life cycles where adults mature within a few weeks of each other.

• The 17 year cicada consist of three species that are usually identified by the calls they make

1pAB4 RT Muehleisen, [email protected], Brood XIII 2007 Cicada Recordings

(photos and recordings from U. of Michigan Museum of Zoology cicada page)

http://insects.ummz.lsa.umich.edu/fauna/michigan_cicadas/Periodical/Index.html

M. cassini M. septendecim M. septendecula

Cicada Sound Mechanisms

• Sound is primarily radiated by

the tymbal, a plate that is

located under the wings

• Spectrum is dominated by resonance peaks

related to the size of the internal body

cavities

– cassini : Primary Peak at 6 kHz with Q5

– septendecim: Primary Peak at 1.3 kHz with Q25

– septendecula: Many broadband peaks from 2

kHz to 10 kHz.


Brood XIII Cicada

• Brood XIII last emerged in late May 2007, with

peak populations in early June

• Brood XIII are located primarily in Northern Illinois

and Southern Wisconsin, but the population

extends as far west as Iowa, and east to Indiana

and Michigan

• Very high densities found

in Chicago suburbs


Photos of Brood XIII Emergence at Peak


http://www.cicadamania.com/cicadas/page/6/

http://www.flickr.com/photos/juliamdr/516312969/in/photostream/

Recording Location

• Level calibrated recordings of cicada were made at the Thatchter Woods Nature Preserve in River Forest, IL from 12:00 pm – 12:30 pm on June 17, 2007


Recording Conditions and Equipment

• Environmental Monitor: Fluke 975 Airmeter

– 30 C, 50% RH at start, 30 C, 60% RH at end

– No measureable wind

• Microphones: BSWA MP 206 on SMA 4000P

– Mounted at 1 m and 2.4 m, with 25 mm windscreens

• Digital Recorder: Zoom H4 Digital Recorder

– Recorded at 24 bit, 96 kHz

– Software gain at 100%, Hardware gain at low setting

• Calibrator: CEL 282, 114 dB @1kHz

– Calibrator applied and recorded on each channel for 30 seconds

before and after recording


Preliminary filtering and calibration

• An initial analysis made using Cooledit Pro 2.1 showed little energy above 10 kHz – Data were resampled at 32 kHz using the highest quality

settings in Cooledit Pro

• Calibration tones were filtered with an 18th order Chebyshev Type 1 filter from 975 Hz to 1025 Hz – Middle 10 seconds was analyzed to determine calibration

constant for each channel

• 1 m mic channel calibration was 27.20 mV/Pa

• 2.4 m mic channel calibration was 23.66 mV/Pa

• A 2 min segment was found that was free of audible extraneous sounds such as airplanes, automobiles, or other people for further analysis


Further Matlab Analysis

• Additional analysis was made using MATLAB 7.2 with the

signal processing toolbox for the 2 min segment

• A sonogram was created for the 1 m mic

– 8192 pt. Hanning window with 50% overlap, 1024 pt. FFT

• The sound pressure level for both microphones was

computed for the entire 2 min segment

– Overall sound pressure level re 20 Pa using 125 ms integration

time (to mimic the fast setting on a SLM)

– Overall Leq for each mic was also computed

• An overall power spectrum was generated for the 1 m mic – Welsh modified periodogram with a 8192 pt Hanning window with 50%

overlap and 1024 pt. FFT as used in the sonogram



Leq,1m=77.7 dB

Leq,2.4m=76 dB

M. cassini

M. septendecium

Sonogram and Lp Analysis

• Sonogram shows a 6 kHz peak with a 10 sec

periodicity that comes from start-stop time

synchronized cassini singing.

– Synchronization is not in frequency and phase

• Sonogram also shows a 1.3 kHz narrow peak

that is fairly continuous that comes from the

septendecim singing

• Lp plot shows the 1 m mic has an Leq=77.7 dB

and the 2.4 m mic has an Leq = 76 dB

– There is a 3-5 dB variation with 10 sec period

• This is indicative of chorus singing of cassini



f0=5.95 kHz, 0dB, Q6

From cassini

f0=4.5 kHz, -11dB, Q4.5

From septendecula?????

f0=1.35 kHz, -5.7dB, Q13.5

From septendecim

Overall Power Spectrum

• Power spectrum shows two distinct peaks

– Highest peak at 5.95 kHz with Q6 from cassini

– Second highest peak at 1.35 kHZ with Q13.5 from septendecim.

• Single decim usually generate powers 20 dB less than

cassini so this high level suggests a large percentage of

decim in the population

• A third peak, mostly masked by the 5.95 kHz cassini

peak, can be seen at 4.5 khz with a Q=4.

– This might be septendecula, but it could also be a

population of smaller cassini


Summary

• Level calibrated recordings of Brood XIII periodic cidada

were taken on June 17, 2007 near Chicago

• Spectral analysis shows the presence of M. cassini, M.

septendecim, and possibly M. septendecula

– The high level of the septendecim peak relative to the cassini

peak indicates a high population of septendecim

• The 1.7 dB difference between the 1 m and 2.4 m mic can

be further analyzed to determine the effective sound

power of the ground plane

– This can be used to estimate individual cicada sound power if the

population is known or the population if the individual cicada

sound power is known assuming incoherent sources


Special Thanks

A special thanks to my

assistant, Alexandra, who

had to walk through way

more crunchy cicada

exuvia than she really

wanted to in order to help

me set up the

microphones.


Sound recordings from the 2007 emergence of Brood XIII cicada

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