Physics Chapter 11: Sound

Sound

• Sound is a form of energy that is transferred from one point to another as a longitudinal wave.
• Sound is produced by vibrating sources placed in a medium.
• The vibrating source displaces the molecules of the medium around it, which in turn displaces their neighboring molecules.

How Sound Waves Propagate

• Sound waves propagate as a series of compressions (C) and rarefactions (R).
• Compressions are regions where the medium's density is higher than the surrounding density.
• Rarefactions are regions where the medium's density is lower than the surrounding density.

Transmission of Sound

• Sound needs a medium to travel from one point to another.
• The speed of sound differs in solids, liquids, and gases.
• The speed of sound in air is approximately 300 m/s.
• The speed of sound in water is approximately 1500 m/s.
• The speed of sound in iron is approximately 5000 m/s.
• The speed of sound in granite is approximately 5400 m/s.

Reflection of Sound

• Sound cannot travel through a vacuum.
• An echo is formed when a sound is reflected off a hard, flat surface.
• The angle of incidence is equal to the angle of reflection.
• Echoes can be used to measure large distances, such as the depth of the sea.
• Echoes can also be used to detect the location of objects, such as in echolocation.

Ultrasound

• Ultrasound is sound with frequencies above the upper limit of the human range of audibility (20,000 Hz).
• Ultrasound can be used in quality control to check for cracks and cavities in concrete slabs and metal pipes.
• Ultrasound can be used in prenatal scanning to obtain images of structures in the body.

Pitch and Loudness

• Pitch is related to the frequency of a sound wave.
• The higher the frequency, the higher the pitch.
• Loudness is related to the amplitude of a sound wave.
• The larger the amplitude, the louder the sound.