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Questions and Answers
What fraction of the Final Exam questions will focus on Units 2 and 3?
Which type of question will NOT be included in the Final Exam?
From which resources will Unit 1 questions be derived?
What key concepts should you know for Units 2 and 3?
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For how long will students have to complete the Final Exam?
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What type of graphs must students know how to read for the Final Exam?
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If a student lives more than 100 KM from campus, what should they do?
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Which of the following terms is NOT defined in the study guide?
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What do decibels represent in terms of sound?
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What is the fundamental frequency when multiple frequencies are present?
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What is the primary characteristic of aperiodic sound?
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How is audibility level measured in audiometric terms?
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What effect does increasing the decibel level have on Sound Pressure Level (SPL)?
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What does the term 'localization' refer to in terms of hearing?
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What does 0 dB HL represent in terms of hearing?
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Which type of energy is primarily used by the cochlea?
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What happens to the decibel count when two sound waves of the same frequency and intensity combine?
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How is loudness different from intensity?
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What does audiometric zero represent in hearing measurements?
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What does a negative Signal to Noise Ratio indicate?
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Which part of the ear is responsible for converting sound waves into mechanical vibrations?
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What is tonotopic organization?
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Which components are part of the conductive system in the ear?
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How does the sound transition from the eardrum to the oval window?
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Study Notes
Final Exam Overview
- The final exam will cover units 2 and 3, with ¾ of the questions coming from these units.
- Unit 1 will account for ¼ of the exam questions.
- There will be one short essay question titled "How We Hear."
- The exam will consist of multiple choice, fill in the blank, and true/false questions.
- You will need to label anatomical structures of the outer, middle, and inner ear.
Units 2 & 3: Sound, Physics, Acoustics & Psychoacoustics
- You will need to know how to interpret X-Y graphs and sine wave graphs.
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Key terms to know:
- Volume
- Time
- Amplitude
- Hertz
- Period
- Velocity
- Cycle
- Oscillation
- Frequency
- Wavelength
- Compression
- Rarefaction
- Resonance
- Stiffness
- Power
- Mass
- Sound
- Impedance
- Distance
- Pressure
- Length
Complex Sounds
- Periodic Sounds: Repetitive patterns, predictable, examples include music and pure tones.
- Aperiodic Sounds: Irregular patterns, unpredictable, examples include noise and speech.
- Noise: Inconsistent, random sound waves, examples include traffic or rain.
- Speech: A complex periodic sound with varying frequencies, created by vocal folds and the vocal tract.
- Fundamental Frequency: The lowest frequency in a complex sound, often the most noticeable frequency.
Cavity/Tube Resonance
- Description: When the natural frequency of a cavity matches a sound wave's frequency, the cavity amplifies the sound.
- Example: 2700 Hz resonating in the ear canal.
- Relevance to Hearing: Ear canal resonance affects frequency perception.
Audiometric Zero
- Description: The reference point for measuring hearing loss, set at 0 dB HL.
- Connection to HL: Measures the threshold of hearing at various frequencies.
- Connection to SPL: Converts dB HL to dB SPL for specific frequencies.
Fourier Analysis
- Description: Breaks down complex sounds into individual frequencies and amplitudes.
- Application: Used to analyze speech, music, and other sounds.
Decibels
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Definition: A logarithmic unit measuring sound intensity.
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Representation: Represent the ratio of sound pressure levels relative to a reference point.
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Connection to Hearing: Human hearing is logarithmic, meaning that a small change in dB can be perceived as a large change in loudness.
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Logarithmic Relationship: The increase/decrease in decibels is not directly proportional to the change in sound pressure level.
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Effect of Combining Sound Waves:
- Same intensity, phase, and frequency: The overall sound intensity increases by 6 dB.
- Same intensity, different phase, and frequency: Interference patterns occur, leading to unpredictable changes in intensity.
- Different intensities, phase, and frequency: The overall sound intensity is the sum of the individual intensities, potentially exceeding the intensity of the individual sound sources.
Hearing Level Scales
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dB HL (Hearing Level): Measured in relation to average normal hearing across various frequencies.
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dB SL (Sensation Level): Measured relative to an individual's hearing threshold at a specific frequency.
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dB SPL (Sound Pressure Level): Measures the absolute sound pressure in the environment.
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Audiometric Zero: Represents the reference point for dB HL, not directly related to dB SL.
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Audiogram: A graph depicting hearing thresholds at various frequencies.
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HL and SL on Audiogram: Connected by the individual's hearing threshold.
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HL and SPL on Audiogram: Convertible through a specific conversion table.
Sound Duration
- Effect on Hearing: The duration of a sound influences its perception of loudness and clarity.
Lateralization
- Definition: The ability to perceive the location of a sound source.
- Effect on Hearing: Influenced by interaural time differences and intensity differences.
Head Shadow Effect
- Definition: The shadowing effect created by the head, blocking high-frequency sounds from reaching the ear furthest from the sound source.
- Effect on Hearing: Makes sound localization more difficult for high frequencies.
Loudness Summation
- Definition: The perceived loudness of combined sounds is greater than the sum of the individual loudnesses.
- Effect on Hearing: We perceive sounds as louder even when individual intensities may be similar.
Masking
- Definition: The ability of one sound to mask the perception of another.
- Effect on Hearing: Can interfere with understanding speech or distinguishing between different sounds.
Range of Human Hearing
- Total Range: 20 Hz to 20,000 Hz.
- Speech Frequencies: Primarily between 500 Hz and 4000 Hz.
Localization
- Definition: The process of determining a sound's source in three-dimensional space (azimuth, elevation, and distance).
- Factors: Interaural time differences (ITDs), interaural level differences (ILDs), and head movements.
Pitch vs. Frequency
- Pitch: The subjective perception of how high or low a sound is.
- Frequency: The physical measurement of sound waves in cycles per second (Hz).
- Connection: Pitch is closely related to frequency but influenced by factors like timbre and loudness.
Intensity vs. Loudness
- Intensity: The physical measure of sound energy per unit area.
- Loudness: The subjective perception of the strength of a sound.
- Connection: Loudness is perception based on intensity, influenced by frequency and other factors.
“Normal” Hearing
- Establishment: Based on average hearing thresholds across a population.
- 0 dB HL: The reference point indicating the threshold of average normal hearing.
- Air Conduction vs. Bone Conduction: Air conduction is the usual pathway for sound transmission through the outer and middle ear, while bone conduction bypasses the outer and middle ear, transmitting sound directly to the inner ear.
Signal to Noise Ratio (SNR)
- Meaning: The difference in decibels between a target signal (e.g. speech) and background noise.
- Negative SNR: Noise is louder than the signal, making it difficult to understand the signal.
- Positive SNR: The signal is louder than the noise, making it easier to understand.
Unit 1: Anatomy and Physiology
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Anatomy:
- Pinna: The visible part of the ear that captures and channels sound.
- Tympanic membrane: The eardrum, which vibrates in response to sound waves.
- Middle ear: A small air-filled cavity containing three ossicles: Malleus, incus, and stapes.
- Cochlea: The snail-shaped inner ear structure filled with fluid, containing the organ of Corti, responsible for converting sound into electrical signals.
- Organ of Corti: The sensory receptor organ within the cochlea that houses hair cells.
- Auditory cortex: The area of the brain in the temporal lobe responsible for processing sound information.
- Temporal lobe: The part of the brain that houses the auditory cortex.
- Cerebellum: The part of the brain that coordinates movement, balance, and posture.
- Cerebrum: The largest part of the brain responsible for higher cognitive functions.
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Energy Transduction:
- Acoustic Energy: Sound waves in the air.
- Mechanical Energy: Vibrations of the tympanic membrane and ossicles.
- Hydrodynamic Energy: Fluid movement within the cochlea.
- Electric/Neurologic Energy: Action potentials generated by hair cells in the cochlea.
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Conductive System:
- Parts: Outer ear (pinna and ear canal) and middle ear.
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Function: To transmit sound energy from the external environment to the inner ear.
- Air-to-Ear Drum: Sound waves travel through the ear canal and cause the tympanic membrane to vibrate.
- Ear Drum-to-Oval Window: The ossicles amplify and transmit vibrations from the tympanic membrane to the oval window.
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Sensory System:
- Parts: Inner ear (cochlea and auditory nerve).
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Function: Convert mechanical energy into electrical signals in the inner ear.
- Oval Window-to-Auditory Cortex: Vibrations at the oval window create fluid waves in the cochlea, causing hair cells to bend and generate electrical signals that travel up the auditory nerve to the auditory cortex in the brain.
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Tonotopic Organization: Different frequencies are processed at different locations along the basilar membrane within the cochlea (low frequencies at the apex, high frequencies at the base).
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Description
Prepare for your final exam covering units 2 and 3 on sound physics and psychoacoustics. This quiz includes key terms and concepts like volume, amplitude, frequency, and more. Additionally, review the anatomy of the ear and the essay question on 'How We Hear' to solidify your understanding.
