Hearing part 1 Flashcards
Is perception and recognition influenced by knowledge?
Yes
What is sound?
a physical phenomenon
Pressure changes in air or another medium (waves)
What causes sound?
Vibrating/moving objects such as vocal cords, speaker diaphragm, car engine, fan
What does vibrating objects cause? (2)
Condensation and rarefaction
What is condensation
air molecules are pushed together - increase in pressure
What is rarefaction?
air molecules are spread out - decrease in pressure
What is the distal stimulus in hearing?
The thing generating the sound
What is the proximal stimulus in hearing?
sound waves at ear
What is the speed of sound in air?
343.2 m/s o4 1236 km/h
How long does it take for sound to travel 1 km?
2.9 seconds
How does sound compare to light for speed?
light travels a million times faster in air
sound is decently slow
What does a speaker cone do?
physically pushes against air
What generates pure tones?
tuning fork or computer
What are the three characteristics of pure tones?
Sine wave
Frequency
Amplitude
What is a sine wave?
a sinusoidal change in air pressure
What is frequency?
Number of cycles (of condensation and rarefaction) per second
What is amplitude?
The size of the air pressure change
How forceful condensation and rarefaction is
What is sound frequency measured in?
Hertz = cycles per second
What is the perception of frequency (physical)?
pitch
How do we describe frequency?
High or low
What is amplitude measured in?
decibels = dB
What is the equation for decibels?
dB = 20 x log (air pressure in micropascals/20 uPa)
Is amplitude usually measured relative to reference?
Yes
How do we describe amplitude? What is the perception of amplitude?
Loud or soft
Can decibels be negative?
Yes
Decibels increase on a log scale. How would an air pressure of 20 be represented in decibels compared to an air pressure of 2000?
it is 100x as loud but the decibels would only go from 0 to 40
What is the barely audible threshold for decibels?
0
What is the pain threshold for decibels?
140
How can complex tones we made?
summing pure tones
Can any sound be described as a sum of pure tones? Fourier analysis
Yes
How can you represent tones instead of time?
frequency
What are periodic tones?
complex tone waveform repeating regularly
What is the repetition rate of of periodic tones?
fundamental frequency
What are harmonics?
pure tone components of of complex tones
What is the 1st harmonic?
the fundamental frequency
What is the second harmonic?
2x the fundamental frequency
What is the third harmonic?
3x the fundamental frequency
What happens if you remove the tone at the 1st harmonic?
still repeats at fundamental frequency
What does a spectrogram show?
How frequencies in sound change over time
What does this spectrogram represent?
Sounds like frequency is increasing
What is this called?
Square wave
What is white noise?
a random mix of frequencies
What is a square wave?
energy at a bunch of harmonics that sounds harsh
If frequency is ramping down that does the time diagram look like?
Waves getting further apart
If frequency is ramping up what does the time diagram look like?
Closer together
What does the time diagram look like for a square wave?
rectangles
What does the time diagram look like for white noise?
bunch of different frequencies together
What does the waveform of speech look like? What about the spectrogram?
Very complex sound with different parts
What is loudness?
Perceptual quality most closely related to level or amplitude of an auditory stimulus
Does Loudness = amplitude?
no - not a direct linear relationship
What does an audibility curve show?
Loudness varies with frequency
What is the threshold of feeling?
where you start physically feeling the sound
What are equal loudness curves? What thing that we hear are found along these curves?
all points along each line sounds about the same
conversational speech
What is the audibility curve?
threshold of hearing that varies with frequency - lowest amplitude we can hear
What frequencies are we most sensitive to?
5000 Hz
According to the audibility curve, when do you need higher decibels to detect sound?
at low frequencies
What frequency and decibels can humans hear?
20 Hz to 20000 Hz and 8dB to 150 dB
What does the audibility curve show overall?
Quietest detectable sound varies greatly with frequency
For 40 dB reference, loudness varies more with frequency
For 80 dB reference loudness is similar across frequencies
What is pitch?
Perceptual quality we describe as high and low
Is pitch the same thing as frequency?
No
What is pitch related to?
fundamental frequency - rate at which pattern repeats
What is tone height?
perceptual experience of the relative highness or lowness of a sound goes up as frequency increases
Generally goes up with fundamental frequency
What is tone chroma? Give an example
notes whose fundamentals are multiples of two have the same chroma
Different A notes have the same chroma: A1= 55.0 frequency, A2 = 110.0 frequency, A3 = 220 frequency
What tones have different chroma?
all the letter notes on a piano have different chroma
A lower and higher C have the same chroma because the Hz is twice as much - 261.6 and 523.2
What is the chroma and the height for all A notes on a piano?
Have the same chroma but different height
What is the effect of the missing fundamental?
removing the fundamental frequency or another harmonic does not change the pitch
What would it sound like if you played all Cs on a piano vs all Cs except the lowest C vs all Cs except the highest C?
Hard to tell they are different
What is Timbre?
Difference between two tones that have the same loudness and pitch but still sound different
What is timbre related to?
number and strength of harmonics - mix of harmonics in the sound
If you played middle C on the horn, sax, violin at the same loudness and pitch what would differ?
the timbre
What are the two auditory illusions we looked at?
A Shepard-Risset glissando
Constant spectrum melody
What does the Shepard-Risset glissando illusion sound like?
sounds like the pitch goes down forever but higher frequencies are being added back in
What is the constant spectrum melody illusion?
Sound at different frequencies that stays the same
The frequency spectrum does not change over time but our perception changes
How does the constant spectrum melody illusion work?
energy at a cluster of nearby frequencies - goes in and out of phase and cancels each other out
What does the constant spectrum illusion tell us?
There is more to our perception of sound than just frequency because these frequencies stay the same over time but sound different
