notes-2.1-sound properties-3u

Sound Properties

• Production of Sound

  • Sound requires a medium to travel through.

  • Speed of sound varies by medium:

    • Solid: Fastest

    • Liquid: Slower

    • Gas: Slowest

  • Sound travels due to the collision of particles within the medium.

Nature of Sound Waves

• Type of Wave: Sound is a longitudinal wave.

• Wave Behavior: Sound exhibits behaviors similar to other waves, including:

  • Diffraction: Bending of waves around obstacles.

  • Interference: Interaction between sound waves can create constructive or destructive interference.

Characteristics of Sound

• Pitch: Determined by the frequency of the sound wave (higher frequency = higher pitch).

• Loudness: Related to the amplitude of the sound wave (larger amplitude = louder sound).

• Types of Sounds:

  • Music: Regular pattern of frequencies.

  • Noise: Irregular mixture of frequencies.

Hearing Sound

• Human Audible Range: 20 Hz to 20 kHz.

• Types of Frequencies:

  • Infrasonic: Frequencies below 20 Hz.

  • Ultrasonic: Frequencies above 20 kHz.

Intensity of Sound

• Loudness vs Intensity:

  • Loudness is subjective (perception), while intensity is objective (measurable).

• SI Unit for Intensity: picowatts per square meter (pW/m²).

• Decibel Scale:

  • Measured in decibels (dB), with 1 bel (B) equating to 10 dB.

  • Sample Calculation: 1.0 x 10^9 pW/m² = 9B = 90 dB.

Structure and Function of the Human Ear

• Homework assignments:

  • p.270: Questions 1, 2, 3, 5.

  • p.276: Questions 1, 3, 4, 5, 6, 7, 8.

• Read next section: Speed of Sound.