Speech Science

lec 4 pgs 23-29; COMPLEX TONES/INTERFERENCE/POWER SPECTRUM

frequency + period have a ___ relationship

inverse relationship

the more cycles/frequencies the less the period/duration each cycle will have

the longer the duration/period the less cycles/frequencies will happen

periodicity and frequencies algebraic relationship

f=1/T

f= frequency

1= 1 second

T= duration or the period

if f=1/t then T is T=1/F (bcs of their inverse relationship)

what is the period (T) of this waveform?

0.01 secs 10ms

what is the frequency of this waveform? (how many cycles occur per second)

100Hz

if the frequency of sound is 200Hz then what is the period?

5ms

3 types of interference

constructive interference

destructive interference

complex interference

interference means

multiple waves in a medium at once, simultaneous sounds set up multiple wave patterns, complex sounds transmit multiple frequencies simultaneously, waves bouncing off objects set up reflected waves

what might happen during interference patterns

a sound may be louder in some places and softer in others

in phase

2 waves that align either peak + peak or valey + valey equal 1 wave with larger amplitude making it louder; waves crest and trough at the same time

90 degrees out phase

slight minor change, waves crest and trough at different times

little effect on speech sounds the human ear wont notice

180 degrees out of phase

misaligned waves crest and through at different times resulting in slience

phase described how patters relate to each other

• in phase: higher amp or higher loudness (constructive interference)

• out of phase: mostly cancels each other out (destructive interference)

phase essentially describes

where the sinewave begins; a measure of the position along the sinusoidal vibration important for sound localization

constructive interference

compression meets compression

rarefaction meets rarefaction

leads to reinforcement (wave has greater intensity) of comp and rarefactions

destructive interference

comp meets rarefactions

leads to cancellation of compressions and rarefactions

waves have weaker intensity or slience

complex interference

most common, not completely constructive or destructive

boundaries

sound meets an obstruction as it travels, interference between 2 mediums

3 boundary behaviors

• reflection: bouncing off

• diffraction: bending around

• transmission: going through

reflection

• incident wave: og wave

• reflected wave: part of that og wave goes back (reflected waves) in vocal tract

the amount of energy reflected back depends on the similarity between 2 mediums

complex tones

• have a periodic wave

• 2 or more pure tones of different frequency are added

superposition principle

combine amplitude when 2 or more waves meet at a point resultant displacement equals the vector sum of all individual displacements at that point and time

Y= y1+y2

what does our ear do when hearing complex tones?

our ear decomposes complex tone into a set of pure tones (sine waves)

fourier’s theorem

any complex waveform can be decomposed into a set of sine waves