Chapter 15.2 Nature of Sounds

Chapter 15.2Nature of SoundsPhysics of SoundsSound WavesReflectionInterferenceRefractionDiffractionSpeed of SoundSounds PressureSound IntensityGasLiquidSolidTransverse WavesLongitudinal WavesexhibitAre characterized byinNature of SoundsSound is a pressure disturbance that moves through a medium in the form of mechanical waves. When a force is exerted on an atom, it moves from its rest or equilibrium position and exerts a force on the adjacent particles. These adjacent particles are moved from their rest position and this continues throughout the medium.This transfer of energy from one particle to the next is how sound travels through a medium.Nature of SoundsSound or pressure waves are made up of compressions and rarefactions.Compressionhappens when particles are forced, or pressed, together.Rarefactionis just the opposite, it occurs when particles are given extra space and allowed to expand.The alternating compressions and rarefactions produce a wave. One compression and one rarefaction is called awavelength. Different sounds have different wavelengths.

Nature of SoundsTap the video to play.Propagation of SoundSound is one kind of longitudinal wave, in which the particles oscillate to and fro in the same direction of wave propagation. Sound waves cannot be transmitted through vacuum. The transmission of sound requires at least a medium, which can be solid, liquid, or gas.

Transverse WavesLongitudinalCrestsTroughsCompressionRarefaction

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Propagation of SoundSpeed of SoundIs affected by several factorsElasticityDensityTemperatureElastic PropertiesThe speed of sound is also different for different types of solids, liquids, and gases. One of the reasons for this is that the elastic properties are different for different materials. Elastic properties relate to the tendency of a material to maintain its shape and not deform when a force is applied to it. A material such as steel will experience a smaller deformation than rubber when a force is applied to the materials. Steel is a rigid material while rubber deforms easily and is a more flexible material.Speed of SoundDensityThe density of a medium is the second factor that affects the speed of sound.Densitydescribes the mass of a substance per volume. A substance that is more dense per volume has more mass per volume. Usually, larger molecules have more mass. If a material is more dense because its molecules are larger, it will transmit sound slower. Sound waves are made up of kinetic energy. It takes more energy to make large molecules vibrate than it does to make smaller molecules vibrate. Thus, sound will travel at a slower rate in the more dense object if they have the same elastic properties.Speed of SoundTemperatureTemperature is also a condition that affects the speed of sound. Heat, like sound, is a form of kinetic energy. Molecules at higher temperatures have more energy, thus they can vibrate faster. Since the molecules vibrate faster, sound waves can travel more quickly. The speed of sound in room temperature air is 346 meters per second. This is faster than 331 meters per second, which is the speed of sound in air at freezing temperatures.

Speed of SoundThe formula to find the speed of sound in air is as follows:v = 331m/s + 0.6m/s/C * Tv is the speed of sound and T is the temperature of the air. One thing to keep in mind is that this formula finds the average speed of sound for any given temperature. The speed of sound is also affected by other factors such as humidity and air pressure.

Speed of SoundReceiving Sound Waves

Tap the video to play.Receiving Sound Waves

The fleshy part of ear, thepinna,collects the sound. The sound wave then travels through the auditory canal which funnels the sound to the ear drum causing it to vibrate. The ear drum then amplifies the sound by vibration of bones. It is in the middle ear where sound energy is converted into mechanical energy. The cochlea in the inner ear converts the vibrations into electrical impulses before sending signals to the brain. The brain then interprets the impulses as sound.

Receiving Sound WavesThank you!SAY AHH!!Prepared by : Darlene M. Roxas