There are several clues you could use: 1.arrival time 2.phase lag (waves are out of sync) 3.sound shadow (intensity difference)- sound is louder at ear closer to sound source Localization What are some limitations if these are the only cues?

These cues only provide azimuth (left/right) angle, not altitude (up/down) and not distance Localization Left Ear Right Ear Azimuth

Localization Additional cues:

Localization Additional cues: Head Related Transfer Function: Pinnae modify the frequency components differently depending on sound location

Localization Additional cues: Room Echoes: For each sound, there are 6 “copies” (in a simple rectanguluar room!). Different arrival times of these copies provide cues to location of sound relative to the acoustic space

Localization What would be the “worst case” scenario for localizing a sound?

Pitch and Music

Pitch Pitch is the subjective perception of frequency time -> Air Pressure Period - amount of time for one cycle Frequency - number of cycles per second (1/Period)

Pitch Pure Tones - are sounds with only one frequency f = 400 hz f = 800 hz

Tone Height Tone Height is our impression of how high or low a sound is but there’s something more to our impression of how something sounds than just its tone height…

Chroma Tone Chroma is the subjective impression of what a tone sounds like Notes that have the same Chroma sound similar 400 hz 500 Hz 800 Hz

Chroma Tones that have the same Chroma are octaves apart

Chroma chroma is best represented as a helix chroma repeats every octave tones with the same chroma are above or below each other on a helix

Chroma Tones that are octaves apart have the same chroma one octave is a doubling in frequency

Chroma frequency is determined (in part) by location of stimulation on the basilar membrane

Chroma frequency is determined (in part) by location of stimulation on the basilar membrane but that relationship is not linear (it’s logarithmic)

Chroma doublings of frequency map to equal spacing on the basilar membrane

Pure Tones are Very Rare in Nature! What are real sounds composed of?

Pure Tones are Very Rare in Nature! What are real sounds composed of? Virtually all sounds are composed of several (or many) frequencies all going at once

Pure Tones are Very Rare in Nature! What are real sounds composed of? Virtually all sounds are composed of several (or many) frequencies all going at once “Extra” frequencies are called harmonics

What are harmonics? position up down imagine a guitar string:

What are harmonics? position up down imagine a guitar string:

What are harmonics? time -> position up down But more than one frequency can “fit” between the end points

What are harmonics? time -> position up down f0f0 f1f1 f2f2 In fact many frequencies can be superposed.