Auditory perception

Question 1

Physical aspects of sound

Answer 1

Air molecules move back ad forth
Sound is a pressure wave
Molecules vibrating

Question 2

Pure tone

Answer 2

Air pressure changes overtime described in a sine wave
The higher the frequency the higher the pitch
The greater the amplitude the louder of sound and is measured in

Question 3

Complex tone

Answer 3

Addition of 2 or more pur tones
200 hz known as the fundamental frequency and first harmonic
400 second harmonic, 600 = 3rd harmonic and 800= fourth harmonic
Wave repeated every 5 hz

Question 4

Loudness

Answer 4

Loudness also depends on frequency
Perceptual loudness is measured in phons
Phon are units of loudness of pure tones
Sensitivity to frequency causes the need for a smaller amplitude to hear the same

Question 5

Pitch

Answer 5

• For a pure tone, pitch is determined by the frequency
• For a complex tone pitch is usually determined by the fundamental frequency
• All notes corresponding to the same latter are multiples of the same frequency pitch increase
• Cyclic aspect
• Octave are notes with the same letter and sound similar - said to have the same chroma
  -Tone height increase moving from left ot right
• PITCH CAN BE TONE HEIGHT OR CHROMA
• Chroma is cyclic in that neighbouring letters of the same type sound similar
  -Tone height increase form left to right on the piano keyboard in a continuous manner

Question 6

Missing fundamental

Answer 6

Complex tones can be decomposed into their constituent frequency components
For many sounds their frequency components are multiples of a particular frequency (fundamental frequency)
For example if a tone comprises four frequencies, 200, 400, 600 and 800 the fundamental frequency are multiple of 200
Thus the tone will repeat at 200
When fundamental frequency is absent, fundamental frequency will continue to repeat as all other components if the tone are multiples of the fundamental frequency
Missing fundamental will determine the pitch of the complex tone

Question 7

timbre

Answer 7

No change in pitch just tone when harmonics were removed
Each instruments play many harmonics of the fundamental frequency
Amplitude of harmonics are different for different instruments which causes a different waveform
Instruments are siad to have different timbre

Question 8

Periodic vs apreiodic

Answer 8

Periodic : this means each wave form repeats at a regular interval
Aperiodic : non-repeating waveforms

Question 9

Auditory localisation

Answer 9

refers to determining the location of a sound source
Based on binaural and monaural cues

Question 10

Binaural cues

Answer 10

1. Interaural time difference
   - depending on where the sound is coming from there will be a small different from when the sound is heard
2. interaural level difference
   For high frequency sounds, there can be a large interaural level difference between the two ears due to sound shadow caused by the head
   For low frequency sounds the interaural level difference is much less

Question 11

cone of confusion

Answer 11

Any two points connected by a circumference line on the surface of this cone have the same interaural time difference and interaural level difference
So binaural cues cannot be use to distinguish between the two points

Question 12

Why dont we hear echoes all the time?

Answer 12

Precedence effect
Hearing the smae sound twice with a temporal separation of 5-20ms will not hear the second sound therefore no echo
This is why you typically hear only direct sound
Temporal separation between 2 sound is more than a 10th of a second you will hear two sounds as separate , causing an echo

Question 13

Architectural acoustics

Answer 13

Indirect sound affects the perceived quality of the sound
The architectural acoustics of a concert hall affect the quality of the sound in the concert hall
Have four factors that determine the quality of the architectural acoustic: reverberation time, intimacy time, bass ratio and spaciousness factor

Question 14

Reverberation time

Answer 14

Time taken for sound to decrease by 60 dB
Sound to decrease quicker - make sound more intelligible

Question 15

Intimacy time

Answer 15

Temporal difference between the direct sound arrives and the first indirect sound arrives

Question 16

Base ratio

Answer 16

Measured for the indirect sound
Ratio of low frequeincies to middle frequencies fr the indirect sound
You want a high base ratio ideally

Question 17

Spaciousness factor

Answer 17

Ratio of indirect sounf to total sound
The greater the proportion of indirect sound, the greater the spaciousness factor
You want a high one ideally

Question 18

Seperating sound sources and the 5 cues used

Answer 18

1. Location: make use of interaural time differences and level differences, strong cue but not necessary
2. Onset time: sound starting at different times will originate from different sources
3. Timbre and pitch: allow for segregation
4. Auditory continuity : Tone disrupted by silence= distinct, noise=continuous through noise
   5.Experience:Knowing what the 2 melodies played simultaneously are increases chances of segregation