Intensity Determines Loudness

Sect. 16-3

How is Amplitude Related to Loudness? Pg 533 How did the loudness of the sounds

compare? How is amplitude related to loudness? Challenge: Using what you learned

from experimenting with the rubber band, explain why swinging a drumstick harder on a drum would make a louder sound than swinging a drumstick lightly.

Intensity determines loudness.

SECTIONOUTLINESECTIONOUTLINE

intensity

decibel

amplification

acoustics

A sound wave with a lower amplitude and energy is perceived as a softer sound.

16.316.3

CHAPTERRESOURCESCHAPTERRESOURCES

Intensity determines loudness.

SECTIONOUTLINESECTIONOUTLINE

intensity

decibel

amplification

acoustics

A sound wave with a higher amplitude and energy is perceived as a louder sound.

16.316.3

CHAPTERRESOURCESCHAPTERRESOURCES

Intensity determines loudness.

SECTIONOUTLINESECTIONOUTLINE

intensity

decibel

amplification

acoustics

A sound wave with a higher amplitude and energy is perceived as a louder sound.

16.316.3

VISUALIZATION

Discover how particles move as sound waves move through the air.

CHAPTERRESOURCESCHAPTERRESOURCES

The more energy a sound wave carries, the more intense it is and the louder it will sound.

The intensity of a sound is the amount of energy its sound wave has.

A unit called the decibel(dB) is used to measure sound intensity

Amplitude is also a measure of wave energy; The greater the amplitude, the more intensity a sound wave has and the louder the sound will be.

Approximate Sound Intensities pg. 534 At more than 100 decibels sounds

become very loud. What is the source of the most

intense sound in the picture? What is the source of the least

intense sound in the picture?

Why is it harder to hear a person talking far away from you than someone who is closer to you?Sound waves spread out from their source in all directions.

As they spread out, their energy spreads out, so the

loudness decreases.

Controlling the Intensity of Sound As the amplitude of a sound

decreases, the frequency stays the same.

Change intensity without changing its quality by taking energy away from or adding energy to a sound wave.

Sound intensity can be controlled in many ways. Ex) muffler

Amplification Increases the strength of an

electrical signal. Often used to increase the

intensity of a sound wave. Experienced when you listen to a

t.v., radio, or stereo.

Amplification When the frequency of an applied

force matches the natural frequency of a system, large amplitude vibrations results in what’s called resonance.

Resonance explains why a glass shatters at a pitch that matches its natural frequency.

Amplification in a Stereo Sound input comes from a microphone

in the form of weak electrical signals Transistors turn these signals into

stronger ones, which are converted into vibrations in a coil in the speakers.

The coil is attached to a cone, which vibrates and sends out sound waves.

Acoustics Involves how sound is produced Involves how sound is received and

heard Refers to the way sound waves

behave inside a space.

Compare and Contrast p.535 Imagine sound waves reflecting off

the surfaces in the two photographs.

How do the reflections differ? How would the addition of sound

absorbing materials affect sound?

Intense sound can damage hearing Damage and destroy the hair cells

inside the ear Ear damage can be lessened by

wearing ear protection, such as ear plugs, or by covering the ears.

If the damage is slight, injured cells might be repaired, but such delicate cells could be permanently damaged.

Sound has many uses.

SECTIONOUTLINESECTIONOUTLINE

sonar

echolocation

16-4: Human uses of sound:

sonar

ultrasound

music

telephone

recording

16.416.4

CHAPTERRESOURCESCHAPTERRESOURCES

Sound has many uses.

SECTIONOUTLINESECTIONOUTLINE

sonar

echolocation

Bats use sound to locate objects.

16.416.4

CHAPTERRESOURCESCHAPTERRESOURCES

Objects that can be detected by ultrasound

Food sources Objects underwater Inside of the body

Echolocation Sending out of ultrasound waves

and interpreting the returning echo.

Bats use sound to locate objects

Explore Echoes: How did sound change when you

added the book? How can an echo be used to detect

an object?

Explore Echoes: How did sound change when you

added the book? The sound was louder with the book than without the book.

How can an echo be used to detect an object? An echo can be used to detect an object by reflecting off the object. If there is no object to reflect off, there would be no echo.

Sonar Instruments that

use echolocation to locate objects

Stands for sound navigation and ranging

Can detect sounds from submarine propellers

Can locate underwater objects

Can find schools of fish

Can be used to map the ocean floor

Can be used to find sunken ships

Ultrasound can be safely used on humans

Ultrasound waves cannot be heard by humans, so they can be used on humans at very high intensities without damaging hearing.

Medical Uses of Ultrasound Examine internal organs Check the health of a fetus during

pregnancy. Can break up kidney stones

Sound waves can produce music – Characteristic sounds of instruments

All of the pitches of the instrument, along with the resonance of the instrument itself, produce the characteristic sound of the instrument.

Changing the pitch of a drum Loosen or

tighten the drum skin

While playing a particularly long and loud song on your guitar, it may become out of tune.

What has happened is that the strings have loosened and the pitch has changed.

Two inventions in the late 1800s that changed the world of sound

Telephone phonograph

How telephones transmit your voice to another telephone As you speak into the mouthpiece, your

sound waves cause a thin disk inside to vibrate.

A microphone turns these vibrations into electrical signals.

These signals are sent over wire to a switching station.

Computers connect the wire to the other telephone.

How Edison’s Phonograph machine worked Edison’s phonograph had a needle

connected to a diaphragm that could pick up sound waves.

The vibrations of the sound waves were sent to the needle, which cut into a piece of foil.

To play back the sound, Edison used another needle to track along the grooves made in the foil.