M2 Lecture 14: Feb 28

Question 1

Sound comes from what

Answer 1

pressure fluctuations in the air

Question 2

Speed of sound through air:

Answer 2

340m/s

Question 3

Speed of sound through water:

Answer 3

1500m/s

Question 4

how to calculate decibels

Answer 4

dB = 20 log(p/p0)

Question 5

what is p in dB = 20 log(p/p0)

Answer 5

Pressure of the sound

Question 6

what is p0 in dB = 20 log(p/p0)

Answer 6

Smallest pressure perceivable

Question 7

dB shows perceived or actual?

Answer 7

dB are more reflective of subjectively perceived sound than actual sound pressure.

Question 8

one dB ~= ___ JND

Answer 8

one

Question 9

If sound pressure ratio increases by x10 (e.g. from 100 to 1000, or from 1000 to 10000), dB increases by what

Answer 9

20 (40 to 60 or 60 to 80).

Question 10

what is Loudness:

Answer 10

The psychological aspect of sound related to perceived intensity or amplitude.

Question 11

Air pressure is related to the what

Answer 11

amplitude of the sound wave

Question 12

Take the minimal audible sound as a reference point This makes 0dB correspond to what

Answer 12

hearing threshold

Question 13

what is Intensity

Answer 13

is the the square of pressure

Question 14

Sound waves propagate in 3D. Intensity corresponds to what

Answer 14

the energy of the sound wave when it hits a 2D surface, like the eardrum.

Question 15

what is Pitch:

Answer 15

The psychological aspect of sound related mainly to the fundamental frequency.

Question 16

The frequency (Hz) is what

Answer 16

the number of cycles per second.

Ex.: if there are 2 cycles in a second, the frequency is 2Hz

Question 17

Sounds that only have one frequency are called what

Answer 17

pure tones

Question 18

what does a Equal-loudness curve show

Answer 18

A graph plotting sound pressure level (dB SPL) against the frequency for which a listener perceives constant loudness.

note: the unit used is the «phon», which corresponds to the dB value of the curve at 1k Hz.

Question 19

Complex sounds can be understood as a combination of what

Answer 19

several frequencies

Question 20

Complex sounds can be described by what

Answer 20

their spectrum.

Question 21

what is Harmonic spectrum:

Answer 21

The spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency

Question 22

Harmonic spectrum typically caused by what

Answer 22

Typically caused by a simple vibrating source (e.g., string of a guitar, or reed of a saxophone)

Question 23

what is Fundamental frequency:

Answer 23

The lowest-frequency component of a complex periodic sound.

Question 24

what is Timbre:

Answer 24

The psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar

Question 25

Timbre quality is conveyed by what

Answer 25

the profile of the harmonics

Question 26

what is Missing-fundamental effect:

Answer 26

The pitch listeners hear corresponds to the fundamental frequency, even if it is missing.

This is because the superposition of the different harmonics will recreate a peak that has the frequency of the missing fundamental.

For instance, harmonics at 500 Hz, 750 Hz, and 1000 Hz will create a peak every 4 ms, corresponding to a frequency of 250 Hz.

Question 27

see folder for ear diagrams

Answer 27

in folder

Question 28

what is Characteristic frequency (CF):

Answer 28

Auditory nerve (AN) fibers are relatively selective for a given frequency

Question 29

what is Temporal coding:

Answer 29

Auditory nerve (AN) firing is also «phase-locked», i.e. neurons systematically fire at a given time point of the cycle.

Question 30

what is the refractory period for Temporal coding

Answer 30

, above 4000 Hz – 5000 Hz the refractory period of AN fibers doesn’t allow neurons to fire fast enough

Question 31

what is Volley principle:

Answer 31

Even if individual AN fibers can’t keep the pace, the whole population of neurons can still temporally encode the frequency