Lecture 6 Flashcards
What are some properties of sound?
Sound requires a medium full of molecules to propagate
• When these molecules are forced together they have more collisions
• This results in a net movement of concentrated molecules out of the area of concentration until the average distance of the medium is restored
Sound is generated by producing what?
a local concentration of molecules in a medium.
This concentration moves as a sphere of increasing diameter.
Only the disturbance is propagated frm layer to layer
Some disturbance energy is lost as heat when the molecules collide.
Give an example of a transverse wave?
guitar string
Describe longitudinal waves?
sound in gases and liquids is based on longitudinal waves
What are the 3 basic components of sound?
frequency, intensity and time
Describe frequency
Measured in cycles per second or Hz
The more cycles per second the higher the pitch sounds
High frequency waves…
Sound waves have properties in _________ and _________.
time and frequency
What kind of studies allow you to quantify changes?
playback studies
When can distortions happen?
either in time domain or frequency domain
What distortions can be analyzed in a cross correlational design?
time distortions
- No distortion results in a correlation of 1
- Any correlation less than 1 indicates a time distortion
The results of playback studies indicates a difference spectrum. What is a difference spectrum?
it highlights the effects of the environment on the signal that is being produced.
When do high frequency waves occur?
occur in short range communciation
When do low frequency waves occur?
occur in long range communication
Sound production involves…?
production and modulation of acoustical energy
coupling of vibrations to the medium
Transmission through medium involves…?
impedence matching
sources of distortion
sound reception involves…?
Coupling of vibrations to sound receptors
mechanical to neural transduction
What factors affect acoustic transmission?
Absorption Attenuation diffraction geometric spreading interference reflection refraction reverberation scattering
Define absorption
object takes in sound energy when sound waves are encountered, as opposed to reflecting the energy. Part of the absorbed energy is transformed into heat and part is transmitted through the absorbing body.
define attenuation
measure of the energy loss of sound propagation in media
Define diffraction
how waves bend, or change direction, as they travel around the edges of obstacles
define geometric spreading
As the sound moves away from the source, the area that the sound energy covers becomes larger and thus sound intensity decreases
define interference
signals reflected from the substrate later interact with the originally transmitted signal
define reflection
When sound travels in a given medium, it strikes the surface of another medium and bounces back in some other direction
Define refraction
is the bending of waves when they enter a medium where their speed is different.
define reverberation
multiple scattering events produce time delay in the arrival of the signal – Echo
define scattering
the real part of a plane wave travelling upwards
Define intensity
perceived as loudness, measured in decibels, higher the intensity of a sound, the louder it sounds
How are frequency distortions calculated
by subtracting the fourier transforms of each signal’s waveform
ability to perceive a sound depends on 2 main points?
biological ability to detect and register signal
Attentional preparedness to receive signal
what is the basis of signal detection theory?
the relationship between physical ability and attention
How do you quantify a receiver’s optimum strategy for detecting a stimulus especially in marginal conditions?
- probability distribution of a signal being present given level of noise
- costs associated with the failure to detect signal that is present versus reacting to one that is not there
Define just noticeable difference
The smallest change in signal that a perceptual system can register under ideal conditions
Define just meaningful difference
The amount of change the perceptual system CHOOSES to recognize as a biologically significant difference
Define habituation
occurs at brain level of perception
–Signals are still being relayed from sense organs to the brain, but subcortical areas of the brain are altering level of response
Define sensory adaptation
- -occurs at sensory detection level
- -sensory detectors are picking up the signal, but are no longer relaying info to brain.
