Sound

Outcomes 1. Describe the sonic spectrum and the range of human hearing. 2. Describe the motion of air molecules as sound waves travel past them. 3. Relate the pitch of sound to frequency. 4. Describe the characteristics of a sound wave that determine loudness and quality. 5. Compare the transmission of sound through air, solids, liquids, and a vacuum. 6. Describe factors that affect the speed of sound. 7. Give examples of forced vibrations. 8. Describe the conditions necessary for resonance to occur. 9. Describe the conditions necessary for beats to occur. 10. Describe the decibel scale of relative intensities. 11. Match structures of the human ear with their function.

Characteristics of Sound Lab Demo with keyboard Program

If a tree falls in the woods and there is no one there to hear it, does it make a sound?

The Origin of Sound All sounds are produced by the vibrations of material objects. Vibrating material sends a disturbance through a medium (usually air) in the form of a longitudinal wave. Under normal conditions, the frequency of the source = the frequency of the waves produced. Pitch—our subjective impression of the frequency of a sound. People with normal hearing can perceive pitches with frequencies from 20 Hz to 20,000 Hz. Infrasonic—sound waves with frequencies below 20 Hz. Ultrasonic—sound waves with frequencies above 20,000 Hz.

Sound in Air and Media that Transmit Sound Compression—a pulse of compressed air. Rarefaction—a region (pulse) of low pressure air. Remember: It is the pulse that travels; not the medium. In general, sound is transmitted faster in liquids than gases, and still faster in solids. Sound cannot travel in a vacuum.

The Sonic Spectrum – all mechanical, longitudinal waves.

Boy bands

Sound Ranges Infrasonic – less than 20 Hz Ultrasonic – more than 20,000 Hz Range of Human Hearing 20 – 20,000 Hz 0 – 120 dB

Typical Loudspeaker Driver Ranges Driver Type Minimum Frequency Maximum Frequency Subwoofer < 20Hz 100Hz Woofer 40Hz 300-3kHz Mid Woofer 3kHz Midrange 300Hz Tweeter 1.5kHz > 20kHz Super Tweeter 10kHz 30kHz

Approximate Range (Hz) Species Approximate Range (Hz)  human 64-23,000 dog 67-45,000  cat 45-64,000  cow 23-35,000  horse 55-33,500  sheep 100-30,000  rabbit 360-42,000  rat 200-76,000  mouse 1,000-91,000  opossum 500-64,000  guinea pig 54-50,000  hedgehog 250-45,000  raccoon 100-40,000 ferret 16-44,000  chinchilla 90-22,800  bat 2,000-110,000  beluga whale 1,000-123,000 elephant 16-12,000  porpoise 75-150,000 goldfish 20-3,000  catfish  50-4,000  tuna  50-1,100  bullfrog  100-3,000  tree frog canary  250-8,000  parakeet  200-8,500  cockatiel owl  200-12,000  chicken  125-2,000 

What do these sound like? We hear from 20-20000 Hz. Will 2000 Hz sound “high”, “medium” or “low” pitched? Predict

Speed of Sound Distance and time Wavelength and frequency Characteristics of the material the sound is traveling in

Speed of Sound In air, sound travels about 330 meters per second. Water vapor in the air increases this speed slightly. Increased temperature also increases this speed. Each degree increase above 0o C increases the speed of sound by 0.60 m/s. Sound travels 4 times faster in water than in air and 15 times faster in steel than in air. Sound travels faster through elastic materials than inelastic materials. Elasticity—the ability of a material to change shape in response to a force and then regain its initial shape. Example: Steel Example of an inelastic material: putty

Speed of Sound in Air Sound Travels Faster in Hotter Air

At 25°C

At -25°C

Ear Diagram Test questions require that you match important structures with their function. You will not have to label or identify structures on a diagram.

What are the functions of… Outer ear Middle ear Inner ear

What do these do? middle ear bones- amplify the sound cochlear hair cells- stimulate nerve cells when moved auricle/pinna- collects sound from outside auditory nerve tympanic membrane- can be scarred by loud sounds auditory canal Cochlea- transmits sound through a fluid round window

Auditory nerve 8

Size of the ossicles

Size of the cochlea

“tubes”