Sound

1
Sound

• 4.03 Compare and contrast the frequency and
  wavelength of sound produced by a fixed source of
  sound, the Doppler Effect.

2
Sound

• Sound is a form of energy that causes molecules
  of a medium to vibrate back and forth.
• Sound travels as a longitudinal wave.
• The speed of sound in air is 340 m/sec.
• Three factors affect the speed of sound
• 1. Temperature,
• 2. Elasticity of the medium,
• 3. Density.

3
Sound

• Intensity is the amount of energy in a wave
  therefore intensity of a sound is determined by
  the amplitude of the wave.
• Intensity determines the loudness of a sound.
• Measured in units called decibels greater than
  120 decibels causes pain in humans.
• Pitch is how high or low the sound is, this is
  not loud and soft.
• Pitch depends on the frequency of the wave
• High frequency produces high pitch low frequency
  produces low pitch.
• Humans can hear sounds that range from 20 Hz to
  20,000 Hz.
• Sounds with frequencies higher than 20,000 Hz are
  called ultrasonic.

4
Doppler Effect

• The Doppler effect is a change in the frequency
  and pitch of a sound due to the motion of either
  the sound source or the observer.
• Example the sound of a race car engine changes
  from high to low as the car approaches you and
  then moves past you.

5
Sound Quality

• Sound quality is the blending of pitches to
  produce sound, also called timbre (TAM-ber).
• Sound quality is why different instruments sound
  different even though they are playing the same
  note.
• Fundamental note is a note produced at the
  lowest frequency at which a standing wave occurs.

6
Sound Quality

• Overtones are tones produced at frequencies
  higher than the fundamental at which a standing
  wave occurs.
• Sounds normally have a fundamental tone and one
  or more overtones.
• The blending of the fundamental tone and the
  overtones produces the characteristic quality, or
  timbre, of a particular sound.

7
Music or Noise?

• A sound is music if it has a pleasing quality, a
  definite identifiable pitch, and a repeated
  timing called rhythm.
• Noise has no pleasing quality, no identifiable
  pitch, and no definite relationship between the
  fundamental tone and the overtones.
• Noise pollution is when noise reaches a level
  that causes pain or stress.
• Has a serious health effect such as causing high
  blood pressure and ulcers, and damages hearing.

8
Sonar

• Sonar sound navigation ranging, a technique of
  using sound waves to measure distance.
• Distance speed x time, divide the total
  distance by ½, ½ going down and ½ coming back.
• Used to locate schools of fish to find oil and
  minerals on the ocean floor.
• Sends ultrasonic waves toward an object to be
  bounced back.

9
Ultrasonic Waves

• Ultrasonic cleansing is used to clean delicate
  objects.
• The object is placed in a mild liquid.
• Sound waves are sent through the liquid causing
  vibrations at great intensity knocking dirt off
  the object.
• Ultrasound works like sonar an ultrasonic wave
  is directed into the body, reflection from
  barriers, such as organs, is then detected.
• Ultrasonic waves are used to destroy unwanted
  material in the body and in physical therapy to
  provide heat to injured muscles.

10
Sound in Humans

• In humans sound is detected by the ear.
• Sound waves enter the outer ear, move through the
  ear canal and strike the eardrum.
• Vibrating air particles cause the eardrum to
  vibrate much like a musical drum.
• The vibrations then enter the middle ear, the
  hammer picks up the vibrations and passes them to
  the anvil which transmits the vibrations to the
  stirrup which sets another membrane vibrating
  transmitting the vibrations to the liquid filled
  inner ear.
• The vibrations are then channeled to the cochlea
  (contains a liquid and hundreds of cells attached
  to nerve fibers).
• The nerve fibers join together to form one nerve
  that goes to the brain.
• The cells detect the vibrations and convert them
  to electrical impulses and transmit those
  impulses to the brain where they are interpreted
  as sound.

11
Other Sound Facts to Know

• Amplifier is an electronic device that increases
  the strength of either an electric or sound
  signal.
• To examine kidney tissue in a patient without
  doing surgery, a doctor uses sound eaves to
  produce a sonogram.
• Bell Jar sound cannot travel in a vacuum.