Sound Notes

Chatfield Senior High

Department of Physics

Sound is a Wave

It is a longitudinal

(1-D) wave

Properties of Sound

Transmission-sound goes through a material

Reflection- waves bounce off at the same angle it was received

Absorption- waves are blocked by a substance (opposite of transmission)

Transmission in space?

Sound requires a medium to travel

Speed of Sound

It is variable based upon temperature and density of the material

Approximate values of speed of sound Air (00-) 330 m/s Air (25o) 343 m/s Water-1440 m/s Glass-4550 m/s Iron and Steel- 5000m/s

Lab 1- Verifying frequency of a tuning fork

Determine period of wave by averaging 10 wavefronts as below and then use f=1/T to

verify frequency

FFT Curve

Lab 2-Sound through echo

Find distance of the tube and double it (why?) Use v=d/t to determine the speed of sound in

air.

Lab 3-Finding Resonance of Tube Find frequency where sound rings out The sound is reflecting off the water and

therefore creates a closed ended tube The is basically a quarter of a wavelength

(why?)

Resonance in Sound

Wavelengths that have the same amplitude and frequency that result in an increase of amplitude

Closed Ended Tube (Pipe organ)

Open-Ended Tubes and Strings(Organ / Guitar String) (1/2

The decibel

A logarithmic scale that shows the loudness of soundL=10 A A= log L

Table of valuesThreshold of hearing- 0 dBWhisper-20 dBLibrary-40 dBRefrigerator-45 dBRestaurant- 50 dBOrdinary Conversation-65 dBBusy Traffic- 70 dBScreaming Child- 90 dBiPod at Maximum Volume-108 dBCSH Fire Alarm-115 dBThreshold of Pain-120 dBJet Airplane-140 dB

Frequencies of Sound

The human ear hears sound from the range from 20-20000 Hz

We hear sounds the best from 1000-5000 Hz

Frequencies of Music

Range of Audibility of the Human Ear

Ultrasound (Frequencies above human hearing)

Beats

Two waves constructively interfering whose frequencies are above or below each other

The Ear

Function of the Ear’s parts

Outer ear-pinna-collects sound Middle ear-transmits vibrations to the

inner ear Inner ear-fluid transmitted to hair cells

that have nerve endings (also used for balance)

Doppler Effect

When an object is moving toward the observer the pitch is higher

When an object is moving away from the observer the pitch is lower

Sonic Boom

Sound and Music

Most pure…the Blue Man Group