Animal Communication

Pregunta	Respuesta
Signal	A stimulus provided by the sender and monitored by the receiver to the net benefit of both parties.
Cue	Assessable properties that are correlated with a condition of interest
Cues v. Signals	Cues - generated inadvertently or for purposes other than communication Signals - function specifically to provide information to another animal
Manipulation and Deceit	Dishonest or deceptive signals that benefit the sender but not the receiver.
True communication benefits whom?	Sender and receiver
Cues, or Eavesdropping benefits whom?	The sender does not benefit but the receiver does.
Manipulation or Deceit benefits whom?	The sender but not the receiver.
Ignoring and Spite benefits whom?	Does not benefit the sender nor the receiver.
Sound	The propagation of a local perturbation in the density molecules of a medium.
Sound in Cicada's	1. Air molecules hit the tymbal 2. Muscles distort the original position, creating sound 3. Rigid membrane pops back to its original position.
Sound production	Sound pressure produces a series of concentrations and rarefactions in the molecules of the transmission medium.
Types of Waves	1. Longitudinal - moves in a parallel direction 2. Transverse - molecules move perpendicular to the direction that the disturbance is propagating.
Temporal Properties of Waves	Period - time for one complete cycle Frequency - cycles/sec = 1/period Amplitude - peak of the frequency
Spatial Properties of Waves	Wavelength - Distance between successive repeats of a propagating sound.
Key Relationships	1. Lambda = c/f frequency and wavelength are inversely related 2. High frequency sounds have shorter wavelengths than low frequency sounds
How does the medium affect wavelength?	0.33 m in air 1.5 m in water 5-6 m in a solid
Doppler Shift	Stationary sound source, approaching sounds are higher in frequency, receding sounds are lower in frequency.
Acoustic impedance	the resistance a medium exerts against a force trying to move some of it. Z=pc
Sound Attenuation	Sounds lose energy as they move away from the original sound source.
Sources of Sound Attenuation	1. Inverse Square Law - spreading loss doubling the loudness = 6 dB increase in amplitude, and sound falls off at 6 dB per doubling distance from the source 2. Medium absorption - Collisions covert sound energy into heat in the medium. 3. Boundary Effects - Reflection or Refraction 4. Interference - similar frequencies and amplitudes. 5. Scattering - objects with a different acoustic impedance from the propagating medium will reflect the sound energy (less sound reaches)
Tasks for Sound Production (3)	1. Produce a Vibration 2. Modify to match function 3. Couple to propagation medium
4 General Ways to Produce Vibrations	1. Movement to create surface waves 2. Movement of a body part against another solid 3. Movement of a body part to create waves in a fluid. 4. Movement of a fluid medium against a body part
Percussion (Body part against a Solid)	animal strikes two solid objects together in a rapid motion.
Stridulation (Body Part Against a Solid)	a set of teeth or ridges on one body part and a scraper on the other. (anthropods use this)
Buckling (Body Part Against A Solid)	bending of an elastic cuticle by muscles until the plate buckles and snaps into a different configuration causing vibrations. (Cicada)
Tremulation (Body part against a solis)	rocking entire body and transmitting the vibrations into a solid substrate through legs. (Chameleons)
Pulsation (movement of a body part in a fluid)	Contract and expand the surface of a closed but flexible object. (swim bladder in fish)
Fanning (movement of a body part in a fluid)	moving a flat solid object perpendicular to its surface to produce movement in a fluid (insect wings moving very fast produce fanning)
Streaming (move a body part in a fluid)	animal moves rapidly through a fluid medium so that flow over appendages causes vibrations (Birds produce whistling while in flight)
Basic Mechanisms of sound in vertebrates	Respiratory system is used. Mammals frogs and toads use the larynx, which are then modified in the resonator. Birds use the syrinx, which is lower than the larynx. They can vibrate the two sides independently, allowing for two concurrent sources of sound.
Modifications of Vibrations (2)	1. Modification of the vocal cords 2. Modification of the surrounding structures or medium
Positive Interference (resonators)	frequencies that match the natural modes of the modifier creates reflected waves in phase with the next set of waves.
Negative interference (resonators)	frequencies that dont match the modifier will cause reflected waves that are out of phase, and are filtered out.
Resonators	filters out some frequencies, and amplifies others. (Howler monkey)
Trumpet Flares	Instead of a simple tube opening, a "trumpet" shape is attached. This provides a gentler gradation between impedances, with less loss through reflection at the boundary. (bats)
Air Sacs	Used in frogs and birds to ease the impedance mismatch.
Oil Sacs in Aquatic Animals	Porpoises and other toothed whales use a melon as an impedance device.
Visualizing Sounds	1. In the time domain 2. In the frequency domain
Why is Propagation Important	1. Our Measurements: affects what we record from a study animal. 2. Evolutionary theory: important constraint on the evolution of communication by sound. 3. ConBio: how human sounds interfere with animal communication.
Sound Degradation (4)	1. Overall Attenuation 2. Distortion of frequency composition 3. Distortion of temporal pattern 4. Masking by noise
Overall Attenuation (2)	1. Spreading loss - intensity falls off with the square distance from the source. 6 dB per doubling of distance. 2. Refraction - Large bodies of water and air often have gradients which the speed of sound varies with temperature, pressure or density.
Refraction Process (high low)	Second medium higher speed of sound - sound refracted towards boundary and away from 2nd medium. Second medium has lower speed of sound - bends away from boundary surface and toward 2nd medium.
Refraction (open air, warm day)	Sounds are refracted into the cooler air, not reaching the receiver, because air near ground is warmer than above the ground. The opposite would occur on a cold day.
Refraction (forest air warm day)	sun heats top of canopy, sound emitted under canopy is refracted down allowing it to be heard from farther away
Refraction (shallow water warm day)	sound refracted away from the surface layer.
Refraction (moderate depth, cold day)	The sound is bent backward toward surface as it reaches the warm water.
Refraction (deep ocean)	No effect here, creates a sound channel. This is called the SOFAR channel. Used in baleen whales.
Distortion of Frequency Composition (3)	1. Heat loss 2. Scattering 3. Boundary Reflections
Heat losses	varies by medium and sound frequency. much greater in air than in water. Medium absorption also increases with the frequency of sound.
Scattering	depends on the size of objects, size of wavelengths, acoustic impedances of mediums, and shape and conformation of objects.
Boundary Reflections (Two types of waves)	1. Substrate or ground wave - horizontal propagation through 2nd medium and re-radiation back to the 1st medium. 2. Surface Wave - bounces on the surfaces in and out of mediums.
The Notch	combined effects of reflected and ground waves produce a (notch) of poor propagation at moderate frequencies.
Reverberations	Echoes, sounds between 1 and 3 kHz experience the least reverberations. (birds and frogs)
Temporal Pattern Distortion (3)	1. Reverberations 2. Added Modulation 3. Dispersion
Dispersion	Different frequencies propagate at different speeds, resulting in temporal and spatial dispersion.
Noise	any concurrent sound that obscures the reception of a sound signal by a receiver.
Basic Hearing Process (3)	Capture - transfer of the sound energy in the medium to ear of receiver. Modification - involves selective filtering and impedance matching Transduction - conversion of sound energy into nerve impulses in the receiver.
Near Field v. Far Field	Near - near the sound source, individual medium molecules move back and forth more than expected. Far Field - regular molecule movement.
The Ideal Ear (7)	1. Near and far field sensitivity 2. Wide frequency range 3. Wide Dynamic range (amplitude) 4. Ability to localize sound source (direction and distance) 5. Fine frequency resolution 6. Fine temporal resolution 7. Good pattern recognition
Types of Ears (3)	1. Particle Detectors - Hairs that move when pushed by moving molecules in the near field. (directional) Need many hairs to detect sounds coming from all directions 2. Pressure Detectors - Thin membrane stretched over a closed cavity. Sensitive to both near and far field, common in large mammals 3. Pressure Differential Detectors - tube with a membrane across the cavity (frogs, insects)
Binaural Comparison (4)	1. Time delays - distance between 2 ears 2. Amplitude Differences - Wavelengths smaller than the head blocks the ear from receiving some energy and the sound is therefore fainter in that ear. 3. Phase Differences - Rotate the head until the amplitude difference is nullified. 4. Adding a pinna - folds reflect sounds into ear canal

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	Creado por Corey Denomme hace alrededor de 8 años