Objectives1. Understand that a sound wave is acompressional wave2. Label compression, rarefaction, wavelength,and amplitude3. Recognize how sound moves and therelated terms, loudness, pitch, frequency,and acoustics
The Nature of Waves What is a wave? A wave is a repeating disturbance ormovement that transfers energythrough matter or space
Waves transfer energy not matter.Waves below are carrying energy but are not moving.Can only exist as they have energy to carry.
What are mechanical waves? Mechanical waves are waves which require amedium. A medium is a form of matter through whichthe wave travels (such as water, air, glass,etc.) Waves such as light, x-rays, and other formsof radiation do not require a medium.
• Compressional WavesIn a longitudinal wave the matter in the wave movesback and forth parallel to the direction of the wave
Sound Waves are compressional waves. Sound travels as vibrations moving throughthe air as a compressional wave. Sound travels through air, but travels throughother materials as well. Whale communicate through long distancesby producing sounds under water.
What are Seismic Waves? An energy wave which vibrates through theearth’s crust as the crust bends or breaks. Seismic waves are exist as both transverseand compressional waves. Some travel through the earth and sometravel across the earth’s surface.
Anatomy of a Seismic Wave
CompressionalLongitudinal wavearea squeezed together iscalled the compression.The areas spread out arecalled the rarefaction.The wavelength is thedistance from the center ofone compression to thecenter of the nextcompression.
What is sound?Sound is a compressional wave which travels throughthe air through a series of compressions andrarefactions.
Sound travels through different media. We hear sound which usuallytravels through air. Sound travels through othermedia Sound travels different speedsin different media. Sound travels faster in a solid thata liquid faster in a liquid than a gas.
The denser the medium, the faster sound willtravel. The higher the temperature, the faster theparticles of the medium will move and thefaster the particles will carry the sound.
What is sound intensity? Sound intensity - energy that the sound wavepossesses. greater the intensity of sound the farther thesound will travel louder the sound will appear. Loudness is very closely related to intensity.Loudness is the human perception of the soundintensity. decibels.
Loudness in Decibels
How is frequency related to pitch? The pitch of a sound wave is directly relatedto frequency. A high-pitched sound has a high frequency (ascreaming girl). A low-pitched sound has a low frequency (afog-horn).
A healthy human ear can hear frequencies in therange of 20 Hz to 20,000 Hz. Humans cannot hear below 20 Hz. Soundsbelow this frequency are termed infrasonic. Sounds above 20,000 Hz are termedultrasonic. Some animals, such as dogs, can hearfrequencies in this range in which humans cannothear.
Using SoundWhat is Acoustics?Acoustics is the study of sound and ways to optimizethe hearing of sound inside various structures.