Class Notes (837,698)
Psychology (5,220)
PSYCH 3A03 (56)
Paul Faure (56)
Lecture

# Week4 outline

3 Pages
63 Views

School
Department
Psychology
Course
PSYCH 3A03
Professor
Paul Faure
Semester
Fall

Description
This outline summarizes major points covered in lecture. It is not intended to replace your own lecture notes. Filters  Cut-off frequency (f ) is frequency where signal energy = ½ input signal energy (i.e. the -3 dB frequency) c  Low pass – allows frequencies below cutoff frequency to pass through unattenuated  High pass – allows frequencies above cutoff frequency to pass through unattenuated  Band pass – allows frequencies between lowpass cutoff and highpass cutoff to pass unattenuated  Band reject – attenuates frequencies between lowpass cutoff and highpass cutoffs  A linear filter does not affect frequency component of signal, only amplitude and/or phase  Band pass and band reject filters have both a low-pass and a high-pass cutoff frequency  Roll-off rate: amount of attenuation (in dB) per doubling of frequency (octave)  Roll-off rate is measured starting from the cut-off frequency (c )  Filter bandwidth: difference in Hz between high pass and low pas cut off frequencies (only applies for band pass and band reject filters)  Filter bandwidth determines the pass band range of frequencies (i.e. the frequencies that pass through the filter with little or no attenuation) Concept of Linearity  A device is linear when it fulfills the relationships of: 1. Superposition 2. Homogeneity  Superposition. A system (e.g. device) is linear when the output of a device in response to a number of independent inputs presented simultaneously is equal to the sum of the outputs that would have been obtained if each input had been presented alone  Homogeneity. If the input to a device is changed in magnitude by a factor of k, then the output should also change in magnitude by a factor of k, but otherwise be unaltered  The output of a linear device never contains components that were not present in the original signal How sound is heard: EAR  Mechanical energy reaches the eardrum, moves to the middle ear, and then to the inner ear  Energy changes from mechanical to electrochemical at nerve impulse stage in inner ear Outer and Middle ear  Transform energy from mechanical air pressure to motion of fluids in inner ear that leads to the generation of action potentials  Most important function: overcome impedance mismatch between air and bone and inner ear fluids  Sound travels through ear starting at pinnae  ear canal (external auditory canal)  ear drum (tympanic membrane) Outer ear  Air pressure collected by pinna (plural = pinnae)  Major outer ear function is sound amplification  The outer ear also has protective functions (e.g., wax captures invading foreign bodies)  The outer ear is composed of epidermal tissue  Going from external to ear to internal: at the centre of pinna is concha, then external auditory meatus, then ear canal (see diagrams)  External auditory canal ~2-3 cm long  Only mammals have pinnae, and only high frequency hearing mammals have mobile pinnae  Resonance of concha and external auditory canal produce 5-20 dB SPL gain from 500 Hz – 9 kHz. Sound alterations by body  Head, ear, body act as a filter that influences received signal amplitude and phase  Impinging sound is altered in amplitude and time by head and torso  Head Related Transfer Function (HRTF) describes how these effects vary with source location as a function of frequency (i.e. how amplitude and phase are modified by impinging on listener) Psych 3A03 28 September 2012 Week 4 Dr. Paul A. Faure Rayleigh head model  Rayleigh head model describes properties of HRTF  Transfer Function describes the relationship between the input and output of a system (can also think of it as the transfer characteristics of a system  Pinna and head have a large influence on received sound, depending on angle and frequency  Amplitude changes through pressure gain (dB) depends on angle of incidence and signal frequency  Measured SPL at ear usually increases in amplitude between 0 - 90 degrees Function of outer ear  Sound frequencies vary in received sound pressure and time of arrival depending on source location  Interaural Level Difference (ILD) – difference in signal amplitude between two ears  Interaural Time Difference (ITD) – difference in time of arrival between the two ears  ITD is mostly constant as a function of frequency (b/c speed of sound is also constant)  Most amplification occurs between 1-6 kHz, and this coincides with speech spectrum  HRTF is a nice summary of how ITD and ILD cues vary at listener’s ear with position of source Function of the Outer ear (cont’d)  Interaural time difference (ITD) & Interaural level difference ILD – main cues to sound localization  ILD (or IID) = interaural level difference (ILD) or interaural intensity difference (IID) — level/intensity is difference in
More Less

Related notes for PSYCH 3A03
Me

OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Join to view

OR

By registering, I agree to the Terms and Privacy Policies
Just a few more details

So we can recommend you notes for your school.