Chapter 21 sections 3 & 4Vocabulary

andQuestions

EchoEcho-

A reflected sound wave.

The strength of a reflected sound wave depends on the reflecting surface.

Sound waves reflect best off smooth, hard surfaces.

Echolocation Echolocation-

The use of reflected sound waves to find objects

Whales, Dolphins, bats, and even certain types of birds use echolocation to find food and their way.

SONAR

Sonar is a type of electronic echolocation

• SONAR which stands for • Sound • Navigation and • Ranging

• Used in the military for war ,commercial fishing industry, and help ships navigate.

Ultrasonography

Ultrasonography –

is a medical procedure that uses echoes to “see” inside a patient’s body without doing surgery.

InterferenceInterference -happens

when two or more waves overlap.

Sonic Boom sonic boom is the explosive sound heard when a shock wave reaches your ears.

At their outer edges, the sound waves combine by constructive interference to form a shock wave.

Standing wave• A standing wave is a pattern of vibration

that looks like a wave that is standing still. Waves and reflected waves of the same frequency are going through the string.

• Where you see maximum amplitude, waves are interfering constructively. Where the string seems to be standing still, waves are interfering destructively.

What causes a Standing Wave

• The frequencies at which standing waves are made are called resonant frequencies.

ResonanceResonance happens

when an object vibrating at or near a resonant frequency of a second object causes the second object to vibrate.

Resonant Frequency in a wind instrument

• In a clarinet, vibrations are caused by blowing air into the mouthpiece.

• The vibrations make a sound, which is amplified when it forms a standing wave inside the instrument.

Sound QualitySound Quality

The result of several pitches mixing together through interference.

The notes sound different because a single note on an instrument actually comes from several different pitches: the fundamental and several overtones.

Music InstrumentsThree main types

1. string instruments

2. wind instruments

3. percussion instruments.

To be heard all instruments must vibrate.

So

All instruments produce sound by vibrating.

Noise

Noise Any sound,

especially a nonmusical sound, that is a random mix of frequencies (or pitches).