How Well Does Sound Travel
Through Dierent Mediums?
An “inventor card” exploration activity inspired by
U.S. Patent No. 3,118,022 (James West & Gerhard
Sessler co-inventors)
es is a scienis, an engineer, and
an inenor. His or ih elecre oil
microphones and echniques reoluionied
he elephone and recording indusries. Oer
90o he more han  billion microphones
produced oda are based on echnolog he
helped deelop.
James
West
To learn more about inventors, patents and trademarks, visit uspto.gov/kids
or contact the Oce of Education and Outreach at [email protected]v
From Idea to Invention!
ll inenions sar ih ideas, bu ha ou do ih
hose ideas can mae all he dierence in he orld.
ha ideas do ou hin spared he inenion o
he elecre oil microphone?
In order o deelop he idea or he elecre oil
microphone ino an acual inenion he inenors
had o undersand he concep o “sound” and ho
i raels.
Hands-on Activity:
How Well Does Sound
Travel Through Dierent
Mediums?
Maerials:
* Plastic sandwich bag
* Water
* Wooden block
* Pencil/Pen
Insrucions
* Blow into the sandwich bag and quickly seal it
to create a pued bag of air. Cover one ear with
your hand and the other ear with the bag of air.
Have an assistant tap the bag with a pencil. How
does it sound?
* Now fill the bag with water and seal it. Hold the
water-filled bag against one ear while covering
the other ear with your hand. Have an assistant
tap this bag with a pencil. How does it sound?
* Finally hold a wooden block over one ear while
covering the other ear with your hand. Have an
assistant tap the block with the pencil. How does
it sound? Compare and discuss observations.
What is sound?
Sound is a pe o energ made b ibraions.
hese ibraions creae sound aes hich moe
hrough mediums such as air, aer and ood.
hen an objec ibraes, i causes moemen in he
paricles o he medium. his moemen is called
sound aes, and i eeps going unil he paricles
run ou o energ. I our ear is ihin range o he
ibraions, ou hear he sound. Our ears ibrae in a
similar manner o he original source o he ibraion,
alloing us o hear man dieren sounds.
To learn more about inventors, patents and trademarks, visit uspto.gov/kids
or contact the Oce of Education and Outreach at [email protected]v
Electroacoustic transducers
Microphone — n acousic-o-elecric ransducer or
sensor ha coners sound ino an elecrical signal.
Electret Microphone —  pe o condenser
microphone, hich uses a permanenl charged
maerial called elecre. n elecre is a sable dielecric
maerial ih a permanenl em-bedded saic elecric
charge. he name comes rom elecro-saic and
magne. oil elecre pe as inened using a hin meallied eon oil. Due o heir good perormance and
ease o manuacure, hence lo cos, he as majori o microphones made oda are elecre microphones.
Mos cell-phones and headse microphones are elecre pe. lecre mi-crophones are also used in hearing
aids and aling os.
Design and improvements to electro acoustic devices
Ne ‘Ou o his orld’ Space Sehoscope aluable Here on
arh, oo - “ eam o sudens a he Johns Hopins Uniersi’s
hiing School o ngineering has designed a ne sehoscope
ha he beliee ill delier accurae hear- and bod-sounds o
medics ho are ring o assess asronaus’ healh on long missions
in “nois spacecra.” “he sudens ored under he guidance o
James es, a Johns Hopins research proessor in elecrical and
compuer engineering and co-inenor o he elecre microphone
used in elephones and in almos 90 percen o he more han o
billion microphones produced oda.” 01, Ma 0.
Test Your Sound IQ
Sound Waves
* o-requenc Sound ae:
o pich
* High-requenc Sound ae:
High pich
* o olume Sound ae:
oer ampliude
* High olume Sound ae:
arger ampliude
1. Can sound travel under water?
2. Does sound travel faster through water or through
the air?
3. Does sound travel faster through wood or through
the air?
4. Is there sound on the moon?
5. What is the speed of sound?
Answers
1. Yes, sound can travel under the water.
2. It moves four times faster through water than through air.
3. It moves about thirteen times faster in wood than air.
4. No, there is no sound in space. Sound needs something to travel
through; matter, air, liquid, solid wood.
5. Sound travels through air at 1,120 feet (340 meters) per second.