M2 Lecture 14: Feb 28 Flashcards
Sound comes from what
pressure fluctuations in the air
Speed of sound through air:
340m/s
Speed of sound through water:
1500m/s
how to calculate decibels
dB = 20 log(p/p0)
what is p in dB = 20 log(p/p0)
Pressure of the sound
what is p0 in dB = 20 log(p/p0)
Smallest pressure perceivable
dB shows perceived or actual?
dB are more reflective of subjectively perceived sound than actual sound pressure.
one dB ~= ___ JND
one
If sound pressure ratio increases by x10 (e.g. from 100 to 1000, or from 1000 to 10000), dB increases by what
20 (40 to 60 or 60 to 80).
what is Loudness:
The psychological aspect of sound related to perceived intensity or amplitude.
Air pressure is related to the what
amplitude of the sound wave
Take the minimal audible sound as a reference point This makes 0dB correspond to what
hearing threshold
what is Intensity
is the the square of pressure
Sound waves propagate in 3D. Intensity corresponds to what
the energy of the sound wave when it hits a 2D surface, like the eardrum.
what is Pitch:
The psychological aspect of sound related mainly to the fundamental frequency.
The frequency (Hz) is what
the number of cycles per second.
Ex.: if there are 2 cycles in a second, the frequency is 2Hz
Sounds that only have one frequency are called what
pure tones
what does a Equal-loudness curve show
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.
Complex sounds can be understood as a combination of what
several frequencies
Complex sounds can be described by what
their spectrum.
what is Harmonic spectrum:
The spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency
Harmonic spectrum typically caused by what
Typically caused by a simple vibrating source (e.g., string of a guitar, or reed of a saxophone)
what is Fundamental frequency:
The lowest-frequency component of a complex periodic sound.
what is Timbre:
The psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar
Timbre quality is conveyed by what
the profile of the harmonics
what is Missing-fundamental effect:
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.
see folder for ear diagrams
in folder
what is Characteristic frequency (CF):
Auditory nerve (AN) fibers are relatively selective for a given frequency
what is Temporal coding:
Auditory nerve (AN) firing is also «phase-locked», i.e. neurons systematically fire at a given time point of the cycle.
what is the refractory period for Temporal coding
, above 4000 Hz – 5000 Hz the refractory period of AN fibers doesn’t allow neurons to fire fast enough
what is Volley principle:
Even if individual AN fibers can’t keep the pace, the whole population of neurons can still temporally encode the frequency
