Exam 1

Question 1

What is needed to produce & transmit a sound?

Answer 1

A source (oscillations) such as a tuning fork and a material medium to conduct the oscillations such as air.

Question 2

Frequency

Answer 2

of cycles*/second. Unit is Hz

_{(1 cycle = 1 compression + 1 rarefaction)}

Question 3

What range of frequencies can humans hear?

Answer 3

20 - 20,000 Hz

Question 4

Equation for frequency & period

Answer 4

“Indirect” relationship

Question 5

Absolute vs. relative units for sound intensity, pressure & power

Answer 5

Question 6

Why is the relative decibel scale used instead of absolute scales?

Answer 6

• Absolute units deal with too large/small numbers
• The dB scale is a log scale, so big numbers are squeezed into smaller units
  
  • Log 10 = 1; Log 100 = 2, Log 1000 = 3, Log 10000 = 4

Question 7

Equation for dB (SPL)

Answer 7

• P_ref = 0.0002 dynes/sq.cms (Lowest absolute sound pressure normal hearing subjects can hear at 1000 Hz)
• P = absolute sound pressure

Question 8

Equation for dB (IL)

Answer 8

• I_ref=10^-12 watts/Sq.mts (Lowest absolute sound intensity normal hearing subjects can hear at 1000 Hz
• I= absolute sound intensity

Question 9

Equation for wavelength

Answer 9

v = 340 m/s at 20º C

Question 10

What is wavelength?

Answer 10

• Refers to the distance a sound wave occupies during one cycle of oscillation
• “Indirectly” related to frequency

Question 11

In-phase vs. out-of-phase sounds & effect on amplitude

Answer 11

Question 12

Pitch

Answer 12

• Psychological attribute corresponding with frequency (Hz)
• “Directly” related to frequency; higher freq. = higher pitch
• Unit is mels

Question 13

Loudness

Answer 13

• Psychological attribute corresponding with sound intensity & pressure levels
• “Directly” related to sound intensity & pressure levels; higher dB = higher loudness
• Units are Sone & Phon

Question 14

Pitch vs. Frequency Graph

Answer 14

We’re not that good at resolving frequency changes beyond 1500 Hz. Completely normal.

Question 15

Equal loudness contour graph

Answer 15

• Hearing system is not very sensitive to hearing the very lows & very highs (dB SPL levels).
• For a sound at 100 Hz, you need a minimum of 40 dB SPL to hear it. At 30 Hz, you need almost 70 dB SPL to hear it. AT 1000 Hz, you only need 0 dB SPL.

Question 16

Minimum Audibility Curve (MAC)

Answer 16

• Dark line on graph
• Shows that there’s more energy (dB SPL) needed to hear very low & high frequencies, and less needed for middle frequencies.

Question 17

Threshold of feeling (on ELCG)

Answer 17

Top line: threshold of feeling/discomfort/pain. At this level, it doesn’t matter if it’s a very low/high frequency. We can still hear it.

Question 18

Best volume for listening to music

Answer 18

If you really want to appreciate changes in frequency, you should listen at 50-70 dB. Here, you can isolate different frequencies & pick up pitch & loudness variations.

Question 19

Best frequencies for hearing

Answer 19

• Relatively less energy (less dB SPL) is required to for frequencies between 1000 to 4000 Hz (these are most sensitive frequencies for hearing)
• More energy (more dB SPL) is required to hear very low frequencies below 500 Hz and above 4000 Hz

Question 20

Simple sounds

Answer 20

• Have a single frequency of oscillation (ex: sounds from a tuning fork, pure tones from an audiometer)
• Have Simple Harmonic motion (SHM)

Question 21

Complex sounds

Answer 21

Have multiple frequencies of oscillation (ex: human voice)

Question 22

Complex periodic sounds

Answer 22

Have fundamental frequency (lowest pitch, maximum amplitude) and all additional frequencies are harmonically related to F_O

(music, voiced speech sounds)

Question 23

Complex aperiodic sounds

Answer 23

• No F_O
• All additional freq. are not harmonically related to the F_O
• Cannot assign a pitch
• Ex: voiceless speech sounds, white noise

Question 24

Transient vs. continuous complex aperiodic sounds

Answer 24

• Transient: finger snap
• Continuous: waterfall

Question 25

What does an audiometer do?

Answer 25

Generates pure tones

Question 26

Spectral Analyzer

Answer 26

* Electronic device that performs a fourier analysis. * Gives you a graph with amplitude on the Y axis and frequency on the X axis.

Question 27

How do we generate periodic & aperiodic speech sounds?

Answer 27

* Air from lungs is source. * If vocal folds are engaged, we produce a complex periodic signal. * Vocal tract: VFs to lips (pharyngeal cavity, tongue, oral cavity, lips). * All voiceless consonants we produce are aperiodic. Vowels & voiced consonants are periodic.

Question 28

How are speech sounds modified beyond the vocal folds?

Answer 28

* A: Spectral analysis of the glottal pulse coming from the vocal folds. There is an Fo (right around 100 Hz, which would be avg. for male adult speaker). * B: When sound passes through the vocal tract, it changes what comes out of it. Length of straightened vocal tract in avg. adult is 17cm. Resonating frequencies R 1-3 (peaks): frequency point w/ maximal amplitude. * C: Output: interaction of glottal pulse + resonating frequencies of vocal tract. A + B = C. Energy levels close to resonating frequencies are enhanced & vice versa. Peaks are **formant frequencies**. All of the vowels that we produce sound different because the formant frequencies significantly change when the position of the tongue/lips changes.

Question 29

Central suditory system structures

Answer 29

* Brainstem Auditory Nuclei * Auditory Cortex of the Temporal Lobe

Question 30

Peripheral auditory system structures

Answer 30

* Outer, Middle and Inner Ear * Auditory Nerve

Question 31

Peripheral auditory system functions

Answer 31

* Outer & middle ear collect & conduct sound energy * Cochlea in inner ear analyzes frequency & intensity (Fourier analysis) * Auditory nerve transmits electrical energy/spikes to the brain

Question 32

Central auditory system functions

Answer 32

* Receive & Transmit Electrical Signals * Responsible for: * Localization * Middle Ear Muscle Reflex Function * Improved Speech Discrimination in Noise * Auditory Memory

Question 33

Temporal bone: petrous portion

Answer 33

* at base of skull * houses essential organs of: * hearing (cochlea & cochlear branch of 8th nerve) * equilibrium (semicircular canals, vestibule, & vestibular branch of 8th nerve) * houses internal auditory meatus, where 8th nerve exits

Question 34

Temporal bone: mastoid portion

Answer 34

Posterior portion. You can feel the mastoid process. Contains mastoid air cells.

Question 35

Temporal bone: squamous portion

Answer 35

Forms part of cranium. Contains EAM.

Question 36

Temporal bone: tympanic portion

Answer 36

Forms base of ear canal.

Question 37

Pinna/Auricle

Answer 37

* Works as an antennae * Collects and transmits sounds to the External Auditory Meatus * Helix: outermost rim * Antihelix: innermost rim * Tiny space at the top: triangular fossa * Concha: deep cavity * Tragus: little bump * Lobule: lobe; no functional benefit in terms of amplification

Question 38

Concha Effect

Answer 38

* Open concha area improves hearing for high frequency sounds (3-6000 Hz) * 5000 Hz sound improved by 12 dB SPL on average * Referred to as the resonance frequency related to the concha effect

Question 39

External Auditory Meatus/Canal Structures

Answer 39

* Length = 24 mm/2.4 cms (Adults) * Anterior 1/3= Cartilaginous (Wax producing glands and Hair follicles located in this region) * Posterior 2/3 = Bony

Question 40

External Auditory Meatus/Canal Functions

Answer 40

* Protective (Wax and shape of the EAM) * Conductive (Transmit to the Middle Ear) * EAM acts like tube open at one end and closed at the other end * Provides Improved Hearing at 3 kHz (Referred to as the Resonance Frequency of the EAM). About **15 dB SPL at 3 kHz**