Sound Basics Overview

What is soundSpeedFrequency Range

Students will…

Know what causes soundPredict how the speed of sound

changes through various materialsDefine different frequency ranges

and how the human ear detects them

Hearing

Stereoscopic

The Ear

The outer ear consists of the ear canal that terminates at the eardrum

Just behind the eardrum is the middle ear The bones in the middle ear transmit sounds to the inner ear

The ear detects very small pressure fluctuations As a result, the ear is very susceptible to hearing damage

Producing a Sound Wave

Something has to vibrateSound waves are longitudinal waves traveling

through a mediumA tuning fork can be used as an example of

producing a sound wave

Tuning Fork The vibrating tuning fork creates a succession of compressions and rarefactions

Compressions Rarefactions

A sinusoidal curve can be used to represent the longitudinal waveCrests correspond to compressions Troughs correspond to rarefactions

Speed of Sound in Air

Main point: The higher the temperature the faster the sound wave moves!

331273

m Tv

s K

Speed of Sound, General

The speed of sound is faster in solids than in gasesslower in liquids than in solids

propertyinertial

propertyelasticv

Predict: in which is sound faster?

1. Air at the north pole or equator

2. Air during the summer or winter

3. Water or air

4. Steel or water

5. Big gummies or smaller gummies

Categories of Sound Waves Audible waves

Lay within the normal range of hearing of the human ear

Normally between 20 Hz to 20,000 Hz Infrasonic waves

Frequencies are below the audible rangeEarthquakes are an example

Ultrasonic wavesFrequencies are above the audible rangeDog whistles are an example

Hearing Test!

The Threshold of hearing is strongly dependent on frequency

Which is the easiest frequency to hear?

~ 3300 Hz

When the sound is loud (top curve, threshold of pain) all frequencies can be heard equally well.

Frequency Response Curves

Applications of Ultrasound

Can be used to produce images of small objects Widely used as a diagnostic and treatment tool

in medicine Ultrasonic flow meter to measure blood flow Ultrasounds to observe babies in the womb Cavitron Ultrasonic Surgical Aspirator (CUSA) used to surgically remove

brain tumors

Ultrasonic ranging unit for cameras

Applications of Ultrasound