General Wave Properties II: Sound

• Definition: Sound is energy from vibrating sources in a medium.

• Type of Wave: Longitudinal waves where particles move parallel to wave direction.

Characteristics of Sound Waves

• Basic Components:

  • Compression: Higher pressure region.

  • Rarefaction: Lower pressure region.

Graphical Representation

• Pressure-Distance Graph: Relationship between pressure and distance.

• Displacement-Distance Graph: Shows particle movement from equilibrium position.

  • Amplitude: Greater amplitude results in louder sound.

Transmission of Sound

• Medium Requirement: Requires a physical medium (solid, liquid, gas); cannot travel in a vacuum.

• Speed of Sound:

  • Air: 330 m/s

  • Water: 1500 m/s

  • Steel: 6000 m/s

Audible Frequencies

• Human range: 20 Hz to 20 kHz.

• Infrasound: Below 20 Hz.

• Ultrasound: Above 20 kHz.

Reflection of Sound

• Reflects off hard surfaces, producing echoes.

• Laws of Reflection: Angle of incidence = angle of reflection.

• Reverberation: Prolonged sound effects from multiple reflections.

Uses of Sound

• Echo Applications:

  • Measuring sea depth.

  • Locating fish.

  • Detecting land mines.

  • Locating submarines.

• Ultrasound Applications:

  • Medical imaging.

  • Breaking kidney stones.

Characteristics Affecting Loudness and Pitch

• Loudness: Depends on amplitude; larger amplitudes = louder sounds.

• Pitch: Depends on frequency; higher frequency = higher pitch.

Summary of Effects on Sound

• Velocity and Changes in Medium:

  • Faster in solids than gases; frequency remains constant, wavelength changes.

Measurement of Sound Speed

• Methods:

  • Pistol Method: Stopwatch measures time from a known distance.

  • Echo Method: Measure time for an echo to return.

Conclusion

• Sound is vital in music, communication, medicine, and environmental studies.