Bioaccoustics Flashcards
What is bioacoustics ?
The scientific study of biological sounds.
What is bioacoustics concerned with ?
The production and propagation of sound in water and air
The reception of sound
Echolocation
The affect of manmade sound on organisms.
Why is sound a useful signal ?
Works in darkness Works when organisms out of sight Omnidirectional (don't have to be facing one another) Enables localisation Sound can be adapted
Describe how sound signals can be adapted.
Can be switched off
Can carry different meanings
Can cover a desired distance
Can be signal for partner selection
Sound does not require a medium
True or False ?
False,
Sound must have air, water or other substrate
How do sound waves oscillate ?
They oscillate (medium particles) relative to their resting position
Give the key features of the Longitudinal sound wave.
Sounds in air and water
Propagation direction >
Oscillation direction
Give the key features of the Transverse wave
Sounds in solids
Propagation direction >
Oscillation direction (up/down)
What two separate speeds does sound involve ?
The propagation speed of the waves
The speed of the oscillating particle
What is another name for the propagation speed of the wave ?
The speed of sound
What is another name for the oscillation speed of the particle ?
The Particle velocity.
What is the speed of sound in air ?
340 m/s (770mph)
What is the speed of sound in water ?
1500 m/s
What is the Particle velocity dependent on ?
Amplitude
What is the Particle velocity at the threshold of pain ?
Only 0.16 m/s
Who invented the Dezibel dB scale ?
Professor Graham Bell
How is sound used in the mating selection of crocodiles ?
Males that emit roars at the lowest pitch have the largest bodies
Will be sexually selected by females
How is sound pressure measured ?
As a change in the local pressure in Pascal’s
What Is ambient pressure ?
101325 Pascal’s
Pressure exerted by the weight of the earth in most circumstances.
What does sound pressure oscillate between ?
20 to 63 uPa
The louder sound we perceive….
The higher the pressure oscillation amplitude, A
How did Bell create the dezibel dB scale ?
Created a sound pressure level
Set human hearing 20uPa as 0
Added a logarithmic scale
Give the Dezibel formula.
20* log10 (Pm/Pr)
In dB SPL
What does Pm (dezibel formula) stand for ?
Measured sound pressure
What does Pr (dezibel formula) stand for ?
Threshold sound pressure,
20 uPa
Give the human hearing threshold on the Decibel scale.
0 dB SPL
What is the smallest change (in sound) we can perceive as being different ?
1 dB
What is the numerical change in pressure level that occurs when a sound gets half as loud when its pressure halves ?
- 6 dB
What is the numerical change in pressure level that occurs when a sound gets twice as loud when its pressure doubles ?
+ 6 dB
