Upload
kellie-boyd
View
216
Download
0
Tags:
Embed Size (px)
Citation preview
References
Young, D (1989) Nerve cells and animal behaviour CUP [1st edition, chapter 7]
Also, chapters in: Carew Behavioral neurobiology Zupanc Behavioral neurobiology
papers are on the webhttp://biolpc22.york.ac.uk/632/movelectures/sound/
insect.htm
Main points of lecture Sound transmission is inefficient Insects use sound in a major way Overcoming physical obstacles Modifying
wings for sound production the environment for sound production cuticle to hear
Private communication
About sound
sound is a wave of particle compression and rarefaction
energy (or power) is transferred from sender to hearer
sound gets quieter further away sound has to be discriminated according
to species, context and from random noise
Speed of sound
speed c determined by the Pressure P, the density and a fudge factor (close to 1)
for water 1430 m/s
for air 330 m/s
Pc
Sound properties
speed c (m s-1) wavelength (m) frequency f (Hz, cycles/s)
for 330Hz, wavelength 1m for 3.3kHz, wavelength 0.1m for 33kHz, wavelength 0.01m =
10mm
fc
Acoustic impedance
impedance Z determined by speed c and density
for water 1.5 * 106 kg m-2 s-1
for air 330kg m-2 s-1
PcZ
Power transfer - i
First problem for an insect - Power transferred from one medium to
another (plane wave)
for air/water interface about 0.02%
)()( zZzZ
zZ
Power transfer - ii
Usually other insect far away -
With distance, power decreases
more bad news for insects!
2
1
d
Power transfer - iii
Usually insects small - sound emitted is dependent
on ratio of insect size / wavelength of sound
Insects use sound in a major way Mantids* Grasshoppers/crickets* bugs* beetles* diptera (true flies)* lacewings moths
Resonance
Mass and a spring; resonant frequency
s is stiffness, m mass below fo in phase; at fo 90o; above fo out
of phase
m
sfo
2
1
Tympanum structure
Muller’s organ has sensory endings in it
Tympanum (ear drum) taut membrane
side view
top view
Movement
peaks at 3 & 6kHz indicate resonance resonance also shown by phase plot folded body not in phase with membrane
even when at 4kHz amplitude is same relative movement needed to stretch
axons of Muller’s organ
Summary so far
Modified wings for sound production Modifying the environment for sound
production Modified cuticle to hear