The Nature of Sound

New VocabularyVibrations- back and forth

movements of matter

Sound- form of energy that you can hear and travels through matter as waves

Compression- region where the particles have been pushed closer together

New VocabularyRarefaction- region where there

are fewer particles than normal

Overtones- softer, higher tones that are mixed with the basic tones

Timbre- special sound produced by a musical instrument

The Nature of SoundVibrations, or the back and forth

movement of matter, are what causes us to hear our favorite songs.

As you saw in the rubber band experiment, as the band vibrated you hear the noise along with it.

Air carries the vibrations to your eardrums and causes them to vibrate.

The Nature of SoundThe vibrations in your ears

produce nerve impulses that are carried to your brain.

These impulses are interpreted as sounds.

Sound WavesSound is a form of energy that

you can hear and travels through matter as waves.

Anything that is in motion has energy, and sound is certainly in motion.

Objects that vibrate create a back and forth motion

Sound WavesIt is this back and forth motion that

pushes against air particles around them and creates sound waves.

The sound waves travel outward in all directions from the source.

The areas that have been pushed closer together are called compression.

Sound WavesAir pressure is greater than usual in

this compression region

The region where there are fewer particles than normal is called a rarefaction. Air pressure is lower than usual here.

A sound wave is a series of compressions and rarefaction moving outward from the source of a vibration.

Sound WavesA sound wave can be

represented as seen below. The crests represent the compressions and the troughs represent the rarefactions

Sound WavesWhen a sound wave travels from its

source to your ear, the particles that carry the wave do not travel along with the wave. Think of it like surfing. Where would find the majority of surfers… on the wave bro!!!

Measuring Sound WavesThe distance from one compression

to the next is wavelength.

Wavelength depends on the frequency of vibration of the source of the sound.◦High sounds have high frequency◦Low sounds have low frequency

Amplitude is the distance from the rest to the crest. It is the measure of the amount of energy in the sound

Measuring Sound WavesLarge Amplitude = loud soundSmall Amplitude = soft sound

Quality of Sound- TimbreTones are a form of sound that has

a single frequency and a single wave pattern.

Most sounds we hear however have a combination of different waves.

Instruments have complex sounds as well. The sound of a musical instrument is made up of a basic tone and overtones.

Quality of Sound- TimbreOvertones are softer, higher

tones that are mixed with the basic tone. This mixing of basic tones and overtones is what gives instruments their unique sounds.

The special sound created by an instrument is called its timbre.

NoiseNot all sound is pleasant. Many

sounds like jackhammers and broken dishes are unpleasant.

Unpleasant sounds have irregular sound waves. Compare below….