Waves and Sound

Mechanical Waves Waves are created by an energy source making a vibration that moves through a medium. Mechanical waves are disturbances in matter that can carry energy from one place to another. The matter it goes through is called a medium, which it can be solids, liquids or gases.

Transverse Waves Transverse Waves are a form of mechanical waves. Transverse Waves are waves that makes mediums vibrate at a right angle in the direction that the wave travels. They have a trough and crest, or the low and high points of a wave. The wave itself will move in an up and down motion.

Longitudinal Waves Longitudinal Waves are the second type of mechanical waves. Longitudinal Waves is where the vibration of the medium is parallel with the direction that it travels. It carries energy left and right through it. A compression is when they are close together while a rarefraction is when they are spread further apart. This is a type of a earthquake wave

Surface Wave A Surface Wave is the third and final type of mechanical wave. A Surface Wave travels on the surface separating two medias. Ocean waves are a type of surface wave, separating the air and water. They are like longitudinal waves and transverse waves combined. It can move objects up in down with the crest and trough, and it can move it along like in a longitudinal wave.

Periodic Motion A periodic motion is the interval between wave crests, while a period is the time required for one cycle. These are important because it helps you know when another is coming.

Frequency Every periodic motion has a frequency. This is the number of complete cycles in a given time, it is measured in cycles per second, or hertz.

Wavelength Wavelength is the distance between a point on one wave and the same point on the next wave cycle. In transverse waves it is measured between the adjacent crest or troughs. In longitudinal waves it is measured in the distance between adjacent compressions or rarefactions.

Wave Speed The wave speed, or how fast a wave is moving, can be calculated by multiplying wavelength by frequency. S = W x F

Amplitude The amplitude is defined by the space between the rest to the crest. The more energy the wave has, the greater the amplitude.

Reflection Reflection occurs when a wave bounces off a surface that it cannot pass through. Reflections do not change the speed or frequencies of a wave, but the wave can be flipped upside down.

Refraction Refractions is the bending of a wave as it enters a new medium at an angle. Refraction occurs because one side of the wave moves slower than the other side.

Diffraction Diffraction is the bending of a wave as it moves around an obstacle or passes through a narrow opening. A wave diffracts more if its wavelength is large compared to the size of another obstacle.

Interference Interference occurs when two or more waves overlap and combine together. Two types of interference are constructive interference and destructive interference.

Constructive Interference Constructive Inference occurs when two or more waves combine to produce a wave with a larger displacement.

Standing Waves Standing Waves are waves that appear to stay in one place, and do not seem to move through a medium. A node is a point on standing wave that has no displacement from the rest position. An antinode is a point where the crest or trough occurs midway between two nodes.

Properties of Sound Waves ● Sound waves are longitudinal waves. Many behaviors of sound waves can be explained using a few properties, speed, intensity, loudness, frequency, and pitches.

Intensity of Sound Waves ● Intensity is the rate at which a waves energy flows through a given area. the decibal is a unit that compares the intensity of different sounds.

loudness of Sound Waves Loudness is a physical response to the intinsity of sound, modified by physical factors. the loudness you hear depends on sound intinsity. as intinsity increases, loudness increases.

Frequency of Sound Waves The frequency of a sound wave depends on how fast the source of the sound is vibrating. You should be able to see the vibration become faster as you hear the sound frequency become highe r.

Pitch of Sound Waves Pitch is the frequency of a sound as you perceive it. Pitch depends upon a waves frequency. High frequency sounds have a high pitch, and low frequency sounds have a low pitch. Pitch also depends on loudness.

Ultrasound An ultrasound is used in a variety of applications, including sonar and ultrasound imaging. Infer sound at frequencies lower than most people can hear and an ultrasound is sound frequencies higher than most people can hear.

The Doppler Effect The Doppler Effect is a change in sound frequency caused by motion of the sound source, motion of the listener, or both. As a source of sound approaches, a listener hears a higher frequency. When the sound source moves away, the listener hears a lower frequency.

Hearing and The Ear The outer ear gathers and focuses sound into the middle ear, which receives and amplifies the vibrations. The inner ear uses nerve endings to sense vibrations and send signals to the brain.

How Sound is Reproduced Sound is reproduced in many ways, from old fashioned records to modern technologies. Sound is recorded by converting sound waves into electronic signals that can be processed and stored. Sound is reproduced by converting electronic signals back into sound waves.

Music Musical instruments produce a wide variety of sounds. Most musical instruments vary pitch by changing frequency and standing waves. Musical instruments often use resonance to amplify sound. Resonance is the response of one standing wave to another wave of the same frequency. Resonance can produce dramatic increases in amplitude.