Introduction to Sound and Hearing

Question 1

What is sound?

Answer 1

• Sound consists of propagated waves of disturbance in air pressure due to vibration
• Spectral envelope/frequency envelope: sum of multiple sinusoids of different frequencies and amplitudes

Question 2

Which dimensions can sound exist?

Answer 2

• Perceptual dimension: loudness, timbre, pitch
• Physical dimension: intensity, frequency, spectral and amplitude envelope

Question 3

What is timbre?

Answer 3

What distinguishes two sounds of same pitch and loudness (same note being played on diff instruments)

Question 4

What are the 3 classes of sound in the world around us?

Answer 4

Transients - may be periodic or aperiodic

Periodic sounds - musical notes, voiced part of speech

Aperiodic sounds

Question 5

What are simple sounds?

Answer 5

Pure tones, sinusoidal waves and sounds not found in nature

Question 6

What is fourier analysis?

Answer 6

• essential technique for spectral analysis
• advanced maths but basic concept understandable
  ◦ any complex periodic sound can be made by summing together sinusoids of the appropriate frequencies and amplitudes (and phases)
• aperiodic sounds do not have discrete harmonics but can think of them being composed of multiple individual frequencies but not in neat pattern

Question 7

What is Fundamental Frequency and Harmonics in Periodic Sounds

Answer 7

• harmonics will occur at integer multiples (f1, f2, f3, … fn) of the fundamental frequency (f0)
• the relative power of diff harmonics will influence the timbre
• harmonics will occur at integer multiples (f1, f2, f3, …fn) of the fundamental frequency, f0
• a spectogram is a 3D plot to show variation in both time and frequency domains