Psychoacoustics and Perception of Sound
Psychoacoustics bridges the physics of sound waves and the biology of the human receiver. A pressure wave with measurable amplitude and frequency becomes a subjective percept of loudness and pitch that no single physical variable fully captures.
This quiz tests your ability to:
- Separate objective acoustic quantities from their perceptual counterparts.
- Apply logarithmic scales such as the decibel correctly.
- Reason about pitch, loudness, masking, and binaural localization.
Recall that sound pressure level uses a reference pressure of ##20\ \mu\text{Pa}##, and that the factor of 10 in the intensity formula becomes 20 in the pressure formula. Keep the Weber–Fechner logarithmic law and the equal-loudness contours of Fletcher and Munson in mind as you work through the questions.
Q1. Psychoacoustics is best described as the study of:
Psychoacoustics shifts the analytical frame from the physical medium to the biological receiver, studying how pressure waves become subjective percepts of loudness and pitch.
Q2. The reference sound pressure used in the definition of sound pressure level is approximately:
Sound pressure level is defined relative to ##p_0 = 20\ \mu\text{Pa}##, approximately the threshold of hearing at 1 kHz.
Q3. The sound pressure level in decibels is correctly written as:
Because intensity scales with the square of pressure, the factor of 10 in the intensity formula becomes 20 in the pressure formula.
Q4. Doubling the sound pressure raises the sound pressure level by approximately:
Doubling the pressure adds about 6 dB, whereas doubling the intensity adds about 3 dB.
Q5. A tenfold increase in sound pressure corresponds to an increase in level of:
A tenfold pressure increase adds 20 dB, since ##20\log_{10}(10) = 20##.
Q6. The decibel is fundamentally:
The decibel is a ratio, not an absolute unit, and this distinction is the source of most examination errors.
Q7. Two tones have equal sound pressure level but appear unequally loud. This is explained by:
The equal-loudness contours of Fletcher and Munson capture how perceived loudness depends on frequency at a given sound pressure level.
Q8. The Weber–Fechner law is used in psychoacoustics to describe:
The Weber–Fechner logarithmic law converts perceptual phenomena into quantitative relationships, compressing a wide physical range into a manageable perceptual range.
Q9. The human auditory system maps a frequency range of about 20 Hz to 20 kHz onto a pitch continuum that is:
Pitch is not linear in hertz; the auditory system reports compressed, non-linear transformations of physical quantities.
Q10. The basilar membrane is important in hearing because it:
Lesson 28 asks how the basilar membrane decomposes complex signals, forming the basis of frequency selectivity in the cochlea.
Q11. Binaural hearing refers to:
Binaural localization cues arise from neural processing that compares signals at the two ears, enabling sound localization.
Q12. Auditory masking refers to:
Masking is one of the four interlocking themes of the lesson: the presence of one sound reduces the audibility of another, linked to frequency selectivity and critical bands.
Q13. In problems involving multiple identical incoherent sources, the correct procedure is to:
For incoherent sources, intensities add; coherent addition of pressures does not apply. This subtlety recurs in JEE numericals.
Q14. The cocktail party effect is best classified under which theme of the lesson?
The cocktail party effect concerns the ability to attend to one source among many, which depends on binaural hearing and sound localization.
Q15. Which pair correctly matches perceptual scales with their physical anchors as treated in the lesson?
The lesson treats pitch with the mel scale and loudness with the phon and sone scales, each anchored in quantitative relationships.