3 Sound waves Compressional waves All sounds are caused by vibrations formed when a vibrating object collides with air molecules, transferring energy to themCompressional waveshave two regions, called compressions and rarefactions, which push air molecules together and then spread them apart
4 Mediumthe type of matter, whether liquid, solid, or gas; that sound waves travel throughA sound wave’s speed depends on the substance of the medium and whether the medium is solid, liquid, or gas.Sound travels more quickly through solids and liquids because the individual molecules are closer together than the molecules in gas.As a medium’s temperature increases, its molecules move faster and it conducts sound waves faster.
6 Properties of Sound Amplitude Intensity Loudness Decibel The amount of energy a wave carries corresponds to its amplitudewhich is related to the density of the particles in the compressions and rarefactions.Intensitythe amount of energy that flows through a certain area in a specific amount of timeLoudnesshuman perception of sound intensityDecibelEach unit on a scale that measures sound intensity
7 Infrasonic or subsonic waves Pitchhow low or high a sound seems to beFrequencyis the number of compressions or rarefactions of a sound wave that pass per secondhuman ears can hear frequencies from ~20 to ~20,000 HzUltrasonic wavessound frequencies over 20,000 Hz that have medical and scientific uses.Infrasonic or subsonic wavesfrequencies below 20 Hz usually can’t be heard but may feel like a rumble.Doppler effectchange in pitch or wave frequency due to a moving wave sourceeither the source of the wave or the observer can be moving
9 Fundamental frequency Overtone Musicsounds that are deliberately used in a regular patternNatural frequencyfrequency at which the a material vibratesResonancethe ability of a medium to vibrate by absorbing energy at its own natural frequencySound qualitydifferences among sounds of the same pitch and loudnessFundamental frequencythe main tone played and heardOvertonevibration with a frequency that is a multiple of the fundamental frequency
10 Percussion instruments Beats Musical instrumentsdevices used to make musical soundsStringsinstruments in which sound is produced by plucking, striking, or drawing a bow across tightly stretched stringsBrass and woodwindsair vibration in a resonator with the pitch determined by the length of the vibrating tube of airResonatorHollow chamber that amplifies soundPercussion instrumentsproduce sound by being struck, shaken, rubbed, or brushed.Beatspulsing vibration in loudness
12 Uses of sound Acoustics Echolocation Sonar Ultrasound waves entertainment, warning signals, informationAcousticsstudy of sound, which can prevent excessive reverberation and create good listening environmentsEcholocationprocess of locating objects by sending out sounds and interpreting the waves reflected backSonaruses reflection of underwater sound waves to locate objectsUltrasound wavesused to diagnose, monitor & treat many medical conditionsCan produce images of internal structures for detection of medical problemsCan treat medical problems such as kidney or gallstones