Auditory Theory: Acoustics

Lecture 009 Hearing III

Reading Assignment for Lecture 010

Before next lecture please read Sections

• 3.2.n Hearing pitch

pages 119 to 136 of Acoustics and Psychoacoustics. We may have a brief quiz on these sections at the beginning of the next class.

Brain Bullets

• Musical notes
  • In this book the system which uses A4 to represent the A above middle C has been adopted.
• Fundamental frequency
  • The period is measured from any point in one cycle to the point in the next (or last) cycle where it repeats, for example, a positive peak, a negative peak or a point where it crosses the zero amplitude line.
• Musical Notes and their Harmonics
  • Every instrument therefore has an underlying set of partials in its spectrum from which we are able to recognise it from other instruments. These can be thought of as the frequency component 'recipe' underlying the particular sound of that instrument.
  • If the pattern of vibration on the basilar membrane varies when comparing different sounds, for example, a violin and a clarinet, then the sounds are perceived as having a different 'timbre' whether or not they have the same pitch.
  • Harmonics can be calculated by multiplying the fundamental by the harmonic number
• Musical intervals between harmonics
  • Follows an open voiced chord
  • Uses whole number ratios
    • octave (2:1)
    • perfect fifth (3:2)
    • perfect fourth (4:3)
    • major third (5:4)
    • minor third (6:5)
    • flat minor third (7:6)
    • sharp major second (8:7)
    • major whole tone (9:8)
    • minor whole tone (10:9)
• Repetition Pitch
  • Non pitched sounds can be made to be pitched by repeating them fast enough