SOUND

• SOUND IS A FORM OF ENERGY• SOUND IS A WAVE• SOUND WAVES REQUIRE A MEDIUM• SOUND HAS PROPERTIES:

– AMPLITUDE– FREQUENCY

• SOUND VOLUME IS MEASURED IN DECIBELS

• THE EAR

SOUND IS A FORM OF ENERGY

SOUND IS A WAVE

Sound waves are longitudinal waves. Sound waves move from a vibrating tuning fork in the form of air compressions followed by areas of less dense air.

SOUND REQUIRES A MEDIUM

• Sound is different from light in that it requires a medium.

• Sound travels as molecules knock against each other,passing on their kinetic energy.

AIR IS A MEDIUM THROUGH WHICH A VIBRATION CAN TRAVEL

SOUND TRAVELS THROUGH WATER

Sound waves travel more swiftly and efficiently in water than in dry air, allowing animals such as whales to communicate with one another over great distances. Whales and porpoises also use sound waves to help them navigate in dark water, directing and receiving sound waves in much the same way as the sonar on a ship

or submarine.

SOUND IS A VIBRATION

Each instrument produces a characteristic vibration.The vibrations travel through the air in sound waves that reach our ears, allowing us to identify the instrument being played even when we cannot see it.The four sound waves shown here demonstrate signature wave forms of some common instruments..

SOUND AMPLITUDE IS VOLUME or LOUDNESS

• The height of a wave is called “amplitude”

• This amplitude controls the volume of sound, how “loud” it is heard.

• Loudness is measured in Decibels

AMPLITUDE

• Amplitude is the characteristic of sound waves that we perceive as volume. The maximum distance a wave travels from the normal, or zero, position is the amplitude; this distance corresponds to the degree of motion in the air molecules of a wave.

• As the degree of motion in the molecules is increased, they strike the ear drum with progressively greater force. This causes the ear to perceive a louder sound.

• A comparison of samples at low, medium, and high amplitudes demonstrates the change in sound caused by altering amplitude. These three waves have the same frequency, and so should sound the same except for a perceptible volume difference.

FREQUENCY OF SOUND GIVES PITCH

440 Hz 880 HZ

•Pitch is about the note we hear, high note or low note.•Pitch is related to the frequency, how fast the sound wave is wiggling

SOUND VOLUME OR AMPLITUDE IS MEASURED IN DECIBELS

Sound intensities are measured in decibels (dB). For example, the intensity at the threshold of hearing is 0 dB, the intensity of whispering is typically about 10 dB, and the intensity of rustling leaves reaches almost 20 dB. Sound intensities are arranged on logarithmic scale, which means that an increase of 10 dB corresponds to an increase in intensity by a factor of 10. Thus, rustling leaves are about 10 times louder than whispering.

FREQUENCY and PITCH

• We perceive frequency as "higher" or "lower" sounds. The frequency of a sound is the number of cycles, or oscillations, a sound wave completes in a given time.

• Frequency is measured in hertz, or cycles per second. Because the amplitude (height) of the waves above remains constant, we are able to hear the same note at different frequencies, from 110.00 Hz to 880.00 Hz.

• Waves propagate at both higher and lower frequencies, but humans are unable to hear them outside of a relatively narrow range.

THE EAR

• Designated as outer ear structures are the visible part of the ear, called the auricle, and the waxy, dirt-trapping auditory canal.

• The eardrum, or tympanic membrane, begins the middle ear, which also comprises the eustachian tube and the three vibrating bones of the ear: malleus, incus, and stapes.

• The cochlea and semicircular canal make up the inner ear. Information passes from the inner ear to the brain via the auditory nerve.