(1) GCSE Physics - Sound Waves and Hearing #73

Sound Waves

• Sound waves are vibrations that travel through the molecules of a medium.

• They are classified as longitudinal waves.

• Travel in the form of compressions and rarefactions:

  • Compressions: Areas where vibrating particles are closest together, causing a bunched up effect.

  • Rarefactions: Areas where particles are furthest apart, creating a spread out effect.

Transmission of Sound

• In solids, sound waves cause particles to vibrate, leading to a chain reaction where particles collide and pass on the vibrations.

• Sound travels fastest in solids, slower in liquids, and slowest in gases due to particle density.

• Sound cannot travel in a vacuum as there are no particles to transmit the vibrations.

Relationship Between Speed, Frequency, and Wavelength

• Sound waves can change speed when moving between mediums but maintain their frequency.

• Relevant equation: Speed = Frequency × Wavelength

  • If speed increases and frequency remains constant, the wavelength increases.

  • In higher density mediums (solids), wavelengths get longer; in lower density materials (gases), wavelengths get shorter.

Refraction, Reflection, and Absorption

• Sound can be refracted (similar to light) when it moves between different mediums.

• Sound can also be reflected (echoes) and absorbed:

  • Hard, flat surfaces reflect most sound waves.

Anatomy of Hearing

• Important parts of the human ear:

  • Ear Canal: Path sound waves travel through.

  • Eardrum: Vibrates in response to sound waves.

  • Ossicles: Three small bones that transmit vibrations from the eardrum.

  • Semicircular Canals: Help with balance.

  • Cochlea: Converts vibrations into electrical signals.

  • Auditory Nerve: Sends signals to the brain for interpretation.

Process of Hearing

• Sound waves hit the eardrum, causing it to vibrate.

• Vibrations transmit through ossicles to semicircular canals, leading to the cochlea.

• Cochlea converts vibrations into electrical signals, which travel through the auditory nerve to the brain.

• Brain interprets these signals:

  • Higher frequencies correlate with higher pitches (like screams).

  • More intense signals are perceived as louder.

Frequency Range of Human Hearing

• Human hearing ranges from approximately 20 Hz to 20,000 Hz.

• Variation in hearing range exists among individuals; generally decreases with age due to cochlea and auditory nerve wear and tear.