By Moira Whitehouse PhD

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SOUND IS A FORM OF ENERGY CAUSED BY

SOMETHING VIBRATING.

SOUND IS A FORM OF ENERGY THAT YOU CAN HEAR

CAUSED BY SOMETHING VIBRATING

A FORM OF WHAT??

ENERGY

CAUSED BY WHAT??

VIBRATIONS

WATCH THE SALT BOUNCE AROUND AS THE SOUND WAVES FROM THE RADIO

CAUSE THE STRETCHED RUBBER TO VIBRATE.

YOU SAW THE STRETCHED RUBBER BOUNCED ABOUT

BY THE SOUND VIBRATIONS.

WE CALL THESE VIBRATIONS SOUND

WAVES.

WE HEAR THE SOUND, WE SEE THE THUMB NAIL PIANO TINES BEING PLUCKED BUT THE

VIBRATIONS ARE SO FAST THAT WE CAN NOT SEE

THEM.

NOW WE WILL SEE THAT THE SOUND COMING

FROM A TUNING FORK IS ACTUALLY CAUSED BY

VIBRATIONS.

SOUND VIBRATIONS, REMEMBER, ARE

ALSO CALLED SOUND WAVES

NEXT WE OBSERVE SOME CHIMES CHIMING BUT WE SEE NOTHING

VIBRATING.

WHAT IS VIBRATING INSIDE THOSE TUBES THAT MAKES THE “BELL- LIKE” SOUND?

THE ONLY THING IN THE TUBES WAS

AIR

IT MUST HAVE BEEN THE AIR VIBRATING

HERE WE STRIKE BOTTLES WITH

DIFFERENT AMOUNTS OF

WATER AND NOTE THE SOUND.

WAS THE AIR VIBRATING TO MAKE THIS SOUND, OR

WAS IT THE WATER?

IT WAS THE WATER. WE KNOW, BEAUSE THE JARS WITH LESS WATER MADE

THE HIGHER PITCHED SOUND.

AH, PITCHWHAT IS IT?

HIGH PITCH, LOW PITCH AND HOW LOUD A SOUND BECOMES, IS

DETERMINED BY SOUND WAVES

SOUND WAVELENGTH IS DETERMINED BY HOW FAST THE

SOURCE OF THE SOUND WAS VIBRATING.

THE MORE SOUND WAVES THAT PASS BY YOUR EAR

IN ONE SECOND THE HIGHER THE PITCH.

THE DISTANCE FROM ONE SOUND WAVE PEAK TO THE

NEXT IS THE WAVELENGTH OF A SOUND WAVE.

FAST VIBRATIONS GIVE SHORT WAVELENGTHS

MAKES HIGHER PITCH

SLOWER VIBRATIONS GIVE LONGER WAVELENGTHS

MAKES LOWER PITCH

HOW LOUD SOUND BECOMES IS

DETERMINED BY HOW MUCH ENERGY IS IN THE SOUND WAVE.

THE DISTANCE FROM CREST TO A CREST

OR FROM A CREST TO A TROUGH

SHOWS THE ENERGY IN A SOUND WAVE

THE LESS ENERGY

THE SOFTER OR QUIETER THE

SOUND

THE MORE ENERGY

THE LOUDER THE SOUND

MANY THINGS AFFECT PITCH.

ON A GUITAR FOR EXAMPLE, PITCH IS AFFECTED BY THE THICKNESS OF THE VIBRATING STRING.

STRING LENGTH ALSO

AFFECTS PITCH

AND HOW TIGHT THE STRING IS

AFFECTS PITCH.

IN THE NEXT LESSON WE WILL FIND OUT HOW

SOUND TRAVELS.