Lecture 17 - Sound and Perception

Question 1

sound is….

Answer 1

…transmission of the relative pressure in a repeated oscillation from the source to a detector

Question 2

frequency

Answer 2

basically the rate of repetition of compressions and rarefactions: how the amplitude is repeating over time

– Number of cycles within a given time period

– Measured in Hertz (Hz): 1 Hz is one cycle per second

– Perception of pitch: the tone height: faster something is oscillating the higher the pitch

– Tone height is the perceptual experience of increasing pitch that happens when frequency is increased.

Question 3

tone height has nothing to do with

Answer 3

amplitude

Question 4

lowest rate that we perceive oscillations

lowest human audibility

Answer 4

20Hz: 20 cycles per second

Question 5

limit of human hearing

highest rate that we can perceive oscillations

Answer 5

16,000 - 20,000 Hz

Question 6

we don’t hear all rates of presentation as the same

Answer 6

percieved loudness

Question 7

pure tones are rare in the environment, most tones we experience are…

Answer 7

COMPLEX

Question 8

To build a complex tone, you begin with…

Answer 8

…a periodic (repeating) pure tone. This first tone establishes the fundamental frequency of the complex tone.

This fundamental frequency is also the first harmonic. When you build the complex tone, you add more harmonics that are multiples of the first harmonic’s frequency.

– The building of a complex tone in this way is called additive synthesis.

Question 9

fundamental frequency is also

Answer 9

the first harmonic

Question 10

Fourier analysis

Answer 10

mathmatical way of decomposing the waveform signal into its simplest pure forms

used to decompose forms to find out the harmonics

Any complex wave can be decomposed into a series of sine
waves

Question 11

additive synthesis

Answer 11

the building of complex tone

Question 12

most sound is really….

Answer 12

MESSY

Question 13

Complex tones can be constructed from multiple pure tones
using additive synthesis. If you begin with a fundamental
frequency that is 300 Hz, what would the 3rd harmonic be?

Answer 13

900 Hz

Question 14

amplitude

Answer 14

Sound pressure level that produces perceived loudness (for a given frequency).

Question 15

frequency

Answer 15

Number of cycles per second in which the sound pressure repeats corresponds to perceived pitch.

The fundamental frequency usually determines perceived pitch.

Question 16

complexity

Answer 16

Complexity is perceived as timbre, and is associated with all other perceptual aspects of a sound besides loudness, pitch, and duration.

– It is closely related to the harmonics (relative amplitude of the harmonics), attack and decay of a tone.

Question 17

musical instruments may play the same tone (note) and share a fundamental frequency, but the _____ of the tones will differ

why?

Answer 17

timbre (quality)

even if they’re playing the same note, they sound very different because they have different harmonics at different amplitudes and some harmonics are absent (don’t resonate - they fade very quickly)

Question 18

Timbre is also affected by

Answer 18

the time course of a tone’s attack and decay

Question 19

attack

Answer 19

is the intensity of the sound before the tone is actually present

is the build-up of sound intensity before onset of the tone.

Question 20

decay

Answer 20

how that tone fades over time

is the decrease as the tone fades.

Question 21

The loss of a harmonic, even the fundamental frequency,

maintains

Answer 21

the same perceived pitch.

Question 22

the effect of the missing fundamental.

Answer 22

The loss of a harmonic, even the fundamental frequency,
maintains the same perceived pitch.

Note that the fundamental frequency also remains the
same.

• The spacing of the harmonics and the repetition rate of the waveform carry the pitch information related to the
fundamental frequency.

it’s still repeating at the same rate: the frequency info is still present even though you’ve taken out a tone: because they’re all just multiples of each other

the timbre will change cause the complexity has changed

Question 23

The physical property most related to the perceptual quality of tone height is _____________.

Answer 23

frequency

Question 24

human hearing range

Answer 24

20 to 20,000 Hz

Question 25

audibility curve

Answer 25

shows the threshold of hearing in relation to
frequency of the stimulus

– Changes on this curve show that humans are most
sensitive to 2,000 to 4,000 Hz.

think threshold: can i hear the tone being presented

Question 26

Auditory response area:

Answer 26

falls between the audibility curve (green) and the threshold for feeling (pain blue)

– It shows the range of response for human audition.

perceiving the stimuli as having some tone (that doesn’t hurt)

Question 27

equal loudness curces

Answer 27

basically trying to see how sensitive we are to diff frequencies so at diff frequencies they’re perceived as the same level of loudness

determined by using a standard 1,000 Hz tone:

– Two initial dB levels are used for comparison: 40 and 80

– Participants match the perceived loudness of all other tones (frequencies) to a 1,000 Hz standard. [First at 40 dB, then at 80dB]

• Example: A 100 Hz tone would need to be played at 60 dB to be perceived as the same ‘loudness’ as a 1000 Hz tone played at 40 dB.
• Many frequencies perceived as equal ‘loudness’ at 80 dB.
• At high (12 kHz) and low (20 Hz) frequencies, amplitude must be higher to be perceived as the same ‘loudness’.

Question 28

by pumping up the volume….

Answer 28

you become equally sensitive to the frequencies present

you can hear more !

Question 29

Tone height

Answer 29

is the perceptual experience of increasing pitch that happens when frequency is increased.