Auditory perception Flashcards
Physical aspects of sound
Air molecules move back ad forth
Sound is a pressure wave
Molecules vibrating
Pure tone
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
Complex tone
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
Loudness
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
Pitch
- 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
Missing fundamental
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
timbre
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
Periodic vs apreiodic
Periodic : this means each wave form repeats at a regular interval
Aperiodic : non-repeating waveforms
Auditory localisation
refers to determining the location of a sound source
Based on binaural and monaural cues
Binaural cues
- Interaural time difference
- depending on where the sound is coming from there will be a small different from when the sound is heard - 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
cone of confusion
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
Why dont we hear echoes all the time?
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
Architectural acoustics
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
Reverberation time
Time taken for sound to decrease by 60 dB
Sound to decrease quicker - make sound more intelligible
Intimacy time
Temporal difference between the direct sound arrives and the first indirect sound arrives
