Physics of Sound Exam 2

Inverse Square Law

every time you double your distance from the source, the sound pressure level (L_p) drops by 6 dB

at what frequency are phons equal to dB?

1000 Hz

How find combined loudness of n coherent sounds

L_tot = L_single + 20 log (n)

how to find combined loudness of n incoherent sounds

L_tot = L_single + 10 log (n)

What does the outer ear contain?

pinna, meatus, and tympanic membrane (eardrum)

What does the pinna do?

collects sound waves and helps determine location

What does the meatus do?

pipe resonator that boosts hearing sensitivity

What does the tympanic membrane (eardrum) do?

vibrates when sound pressure waves strike it

What does the middle ear contain?

Ossicles and oval window

What do the ossicles in the middle ear do?

Amplify sound by converting pressure on eardrum into physical force that pushes on the oval window to create fluid pressure in the inner ear

What does the inner ear contain?

cochlea and basilar membrane

What is the cochlea?

a spiral apparatus that houses the mechanism that converts pressure variations to neural impulses

Where do high frequencies excite the basilar membrane?

at base

Where do low frequencies excite the basilar membrane?

at the apex

What are critical bands?

frequency resolution regions on the basilar membrane

How does distance in frequency effect masking?

tones closer in frequency mask each other more

How does frequency effect masking?

Lower tones mask higher tones

How does volume effect masking?

the louder the sound, the more frequencies it can mask

What is masking like with broadband noise?

masks tones of all frequencies

What is forward masking?

when a preceding sound masks the following sound

What is backward masking?

when the following sound masks a preceding sound

What is central masking?

when a sound in one ear masks a sound in the other ear

How do you find a harmonic series when given only the fundamental?

use the harmonic series formula

How do you find virtual pitch when given a harmonic series?

find the greatest common factor

What parts of speech involve oscillations of the vocal folds?

all vowels and some but not all consonants

How are vowels differentiated?

by the frequencies of the vocal formants

How are consonants classified?

by manner and place of articulation

What is a spectrogram?

a 2D display of frequency vs time, but discards phase information

What does timbre arise from?

relative intensity of elements of the harmonic series

What is pressure measured in?

Pa

What does milli mean?

divide by 1000

What is on the y axis of a frequency spectrum?

amplitude

What is on the x axis of a frequency spectrum?

frequency

What happens to the frequency spectrum when a carrier tone is modulated with a signal tone?

3 distinct lines, carrier tone - signal tone on left, carrier tone in center (tallest), and signal tone + carrier tone on right

what is the ratio of semitones?

2^n/12

how to find the ratio of just temperament and equal temperament

ratio_et/ratio_jt

what is the loudest noise you can make for the least energy expended?

Blowing a high frequency emergency whistle because it turns air from your lungs into sound vibrations without much physical energy and nearly all of its’ acoustical output is between 3-4 kHz, where human hearing is most sensitive