Sound

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 Sonic Spectrum – all mechanical, longitudinal waves.

RAP

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

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

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” or “low” pitched?

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 Faster in Hotter Air

At 25°C

At -25°C

Ear Diagram Use the diagram that I pass out to you record the function for important parts of the ear. Test questions require that you match important structures with their function. You will not have to label or identify structures on a diagram.

Size of the ossicles

Size of the cochlea

“tubes”

Decibels – a measure of the relative intensity of sounds.

Normal Conversation – 60 dB

85 decibels - prolonged exposure can cause gradual hearing loss 85 decibels - prolonged exposure can cause gradual hearing loss. 100 decibels - no more than 15 minutes prolonged exposure recommended 110 decibels - regular exposure of more than one minute risks permanent hearing loss without hearing protection.  

Loudest Sounds Ever! dragster 155-160 400,000 Watt speakers 135-145 decibel fireworks 145-150 dragster 155-160 Space shuttle 165-170 blue whale 188 The Tunguska event 315 June 30, 1908

Important Decibel Ideas This is a “relative” (comparing) scale. Humans can distinguish about 1 dB. 10dB higher “sounds” 2x louder. Logarithmic, not linear. 10x more energy = 10dB higher 100x more energy = 20dB higher 1000x more energy = 30dB higher 10,000,000x more energy = 70dB higher

Bettendorf – measured 4 ft above the ground at property line Residential (7am-10pm) 60dB (10pm-7am) 50dB No lawn mower, trimmer chain saws Commercial (all times) 65dB Industrial (all times) 75 dB

Beats

Two similar sounds played together

Sonometer

Sound Frequency = Average Beat Frequency = Difference