Sound

SoundOverviewThe Facts of SoundThe Ear and SoundSound VocabularyMusical Instruments and SoundThe FactsSound

1. Is a form of energy produced & transmitted by vibrating matter2. Travels in waves3. Travels more quickly through solids than liquids or gases

The EarSound is carried to our ears through vibrating air molecules.Our ears take in sound waves & turn them into signals that go to our brains.Sound waves move through 3 parts of the ear; outer ear, middle ear, & inner ear.

Middle EarVibrationBack and forth movement of molecules of matterFor example,

CompressionWhere molecules are being pressed together as the sound waves move through matterFor example,a wave travels through the springs just like sound waves travel through the airthe places where the springs are close together are like compressions in the air.

Sound WavesAlternating areas of high & low pressure in the airALL sound is carried through matter as sound wavesSound waves move out in ALL directions from a vibrating object

Sound SpeedThe speed of sound depends on the type of medium through which it travels.Fastest in solidsSlowest in gasesSpeed of sound (at 20C, dry air) = 342 m/s

Sound & FrequencyThe frequency of a sound wave depends on how fast the source of the sound is vibrating.Faster vibrating = higher sound

Pitch

A measure of how high or low a sound isPitch depends on the frequency of a sound waveFor example,

Low pitch Low frequency Longer wavelength

High pitch High frequency Shorter wavelength

Sound and InstrumentsInstruments can be played at different pitches by changing lengths of different parts.For example, Another way to make different pitches is to change the thickness of the material that vibrates.For example,

A trombones mute absorbs some of the sound waves produced, thus producing a softer note when played.

Intensity Vs LoudnessIntensity rate at which a waves energy flows through a given area.Sound intensity depends on the waves amplitude and the distance from the source.

Intensity Vs LoudnessMeasured in decibels (dB).Loudness is how loud or soft a sound is perceived to be (subjective).

Ultrasound and Sonar

Ultrasound sound waves with frequencies above the normal human range of hearing. Sounds in the range from 20-100kHz

Ultrasound and Sonar

Infrasound sounds with frequencies below the normal human range of hearing.Sounds in the 20-200 Hz rangeUltrasound and SonarSonar -An instrument that uses reflected sound waves to find underwater objectsFor example,

Animals use sonar or echo location to find their prey; these sounds have such a high pitch or frequency that the human ear cannot hearHumans use sonar to locate or map objects

Doppler EffectDoppler Effect is the change in sound frequency of a sound caused by the motion of either the listener or the source of the sound. As a source of sound approaches, an observer hears higher frequency.When sound moves away, the observer hears a lower frequency.

Thats all folks!