Sound

18A Sound Waves

• Acoustic Energy

  • Sound Energy: a type of mechanical wave energy that can be detected by the human ear

• Characteristics of Sound Waves

  • Acoustic Spectrum: the continuum of all possible sound waves

  • Pitch: how high or low an audible tone sounds to the human ear; related to the concept of wave frequency

  • Loudness: human perception of the intensity of a sound value

  • Intensity: a measure of the power contained in a wave; often refers to sound or electromagnetic waves

  • Decibel: the unit for measuring relative sound intensity

  • Timbre: the distinctive sound of an instrument; also called quality

18B Hearing and Music

• Producing Sound

1. Larynx: the box-like structure located at the top of the trachea that supports the vocal cords

2. Vocal Cords: folds of tissue in the throat that when vibrated produce the sound waves that humans use to communicate

3. throat and sinus passages

4. tongue, teeth, and lips

5. diaphragm

The Human Ear

• Outer ear

1. auditory canal

2. Tympanic Mmembrane: the thin, flexible membrane that separates the outer ear from the middle ear and converts acoustic energy to kinetic energy

Middle ear

1. Hammer: one of the three bones, along with the anvil and stirrup, of the middle ear that transmit energy from the outer ear to the inner ear

2. Anvil: one of the three bones, along with the hammer and stirrup, of the middle ear that transmit energy from the outer ear to the inner ear

3. Stirrup: one of the three bones, along with the anvil and hammer, of the middle ear that transmit energy from the outer ear to the inner ear

4. Eustachian Tube: the canal that connects the middle-ear cavity with the throat to allow the equalization of pressure on both sides of the ear drum

• Inner ear

1. Cochlea: the inner-ear organ that converts kinetic energy to electrical impulses

2. auditory nerve

3. semicircular canals

• Tones

Fundamental Tone: the longest ( lowest frequency) standing wave produced by a vibration of a structure

Overtone: a shorter, faster vibration (higher pitch) in addition to the fundamental tone produced by a vibrating structure

Harmonics: the fundamental tone and its overtones

18C Using Sound Waves

• Sound Technologies

  • Acoustic Amplification: the process of making a sound louder

  • Echolocation: the process that uses the time interval and direction of an echo to determine the position of an object

  • Passive Sonar: a system of underwater microphones that can only receive, not produce, underwater sounds in order to detect a submerged object

    Active Sonar: an underwater device that produces short pulses of sound that echo back to the sending object; used to find the bearing and range of submerged objects

• Infrasonic and Ultrasonic

  • Infrasonic Sound: sound having frequencies below the range of human hearing

  • Ultrasonic Sound: sound having frequencies above the range of human hearing

  • Sonography: technology that uses ultrasound to create images of objects found inside other objects

• Putting Ultrasound to Work

  • Sonograms

  • Nondestructive testing

  • Veterinary medicine