SOUND WAVES, HEARING AND INTERACTIONS

UNIT 2 – LESSONS 1 & 2

BE ABLE TO DEFINE THE FOLLOWING:•SOUNDWAVE•LONGITUDINAL WAVE•PITCH•LOUDNESS

•DECIBEL•DOPPLER EFFECT•ECHO• INTERFERENCE•RESONANCE

A sound wave is a longitudinal, mechanical wave that is caused by vibrations and travels through a medium.

• SOLID - fastest• LIQUID – slower than solid• GAS – slowest*Sound travels faster at higher temperatures

LONGITUDINAL WAVES ARE ALSO CALLED COMPRESSION WAVES.------------------- - - - - - - - - ----------------- COMPRESSION RAREFACTION COMPRESSION

SOUND WAVES NEED A MEDIUM……

•A MEDIUM REFERS TO THE MATERIAL, MADE UP OF MOLECULES TO TRAVEL THROUGH…..NO MEDIUM, NO SOUND. THERE IS NO SOUND IN SPACE.

OUR EARS CONVERT MECHANICAL SOUND WAVE VIBRATIONS TO ELECTRICAL SIGNALS. THESE ELECTRICAL SIGNALS ARE SENT TO THE BRAIN TO ALLOW US TO INTERPRET SOUNDS.

VIBRATIONS ARE GATHERED AND SENT TO THE AUDITORY NERVE, A STRUCTURE THAT CHANGES THE VIBRATIONS TO ELECTRICAL SIGNALS AND SENDS THEM TO THE BRAIN.THIS IS HOW WE HEAR SOUND.

PITCH!LOW PITCH = LOW FREQUENCYHIGH PITCH = HIGH FREQUENCY

FREQUENCY IS EXPRESSED IN HERTZ (Hz).1 HERTZ = 1 WAVE LENGTH.

THE HIGHER THE FREQUENCY – THE SHORTER THE WAVE LENGTH – THE HIGHER THE PITCH!

THE LOWER THE FREQUENCY – THE LONGER THE WAVE LENGTH – THE LOWER THE PITCH!

A SOUND’S LOUDNESS IS ITS WAVE HEIGHT OR AMPLITUDE. AMPLITUDE IS MEASURED IN UNITS CALLED DECIBELS (Db).

THE DOPPLER EFFECT IS A CHANGE IN THE OBSERVED FREQUENCY (PITCH) OF A SOUND WAVE WHEN THE SOURCE, THE OBSERVER, OR BOTH ARE MOVING. MOVING TRAIN & CAR HORN SOUNDS ARE BEST.

BEFORE THE SOURCE = HIGH PITCH.AFTER THE SOURCE = LOW PITCH.

ECHO!-------------------------ECHOOO!

A REFLECTED SOUND IS AN ECHO. THE MORE REFLECTED THE BETTER THE ECHO.

BATS, DOLPHINS & WHALES USE ECHOLOCATION TO FIND FOOD AND EACH OTHER.

SONAR IS A TYPE OF ECHOLOCATION ORIGINALLY USED BY THE NAVY – NOW WE USE TO FIND FISH.

INTERFERENCE HAPPENS WHEN TWO OR MORE SOUND WAVES OVERLAP OR COMBINE TO FORM LARGER OR SMALLER WAVES.

WHEN INTERFERENCE FORMS A LARGER WAVE = CONSTRUCTIVE INTERFERENCE

WHEN INTERFERENCE CAUSES A SMALLER WAVE = DESTRUCTIVE INTERFERENCE.

A SONIC BOOM HAPPENS WHEN WE TRAVEL FASTER THAN THE SPEED OF SOUND. WE BREAK THE SOUND BARRIER. SUPERSONIC SPEEDS CREATE A SONIC BOOM!!!