PROPERTIES OF SOUND WAVES

CATEGORIES OF SOUND WAVES

| Audible sound wave y sound wave in the range of human hearing y frequency of 20 Hz to 20 kHz

| Infrasonic wave y sound wave with a frequency below 20 Hz y earthquake waves

| Ultrasonic wave y sound wave with a frequency above 20 kHz y ultrasound machines

THE SPEED OF SOUND

| Speed of sound through air depends on the temperature and density of the air

| Value increases by 0.606 m/s for every increase of 10 C

| where T is the temperature in degrees Celsius

0331.4 / (0.606 / / / )v m s m s C T �

PG. 393 PRACTICE #1 - 2 Sig digs

Givens Izzi' 3

Sig digs

Required r

Analysis : V = 331.4 Ysto@6mlsk)si

v. .

350.8 m/s✓ = 350M$

PG. 393 PRACTICE #2

Givers : ✓=333mk

Retief: T= ?

Analysis f- 331.4ms .to#6o6m1sldT

Steps V . 331 .4m/s=¢606mls/°DT

T = 333 mls -

331.4M¥ionF- 333.331.4

°C

← 6

T= 2.64°C

MACH NUMBER

| Mach number (M) y the ratio of the airspeed of an object to the local speed

of sound

| Remember ratios have no units !!!! | Sonic booms

airspeedMspeedofsound

PG. 394 PRACTICE #1

Givens Vs344nAVE 910km/h Mls

ao€xioooExx¥oI¥a

910k¥ 252.8 Ys

M = 252.8 Mls-

344 mAM= 0.73

PG. 394 PRACTICE #3

850kngxloooenxbhg.net#sVa=236.ln1svs=236.lnd

0.81=236.tn/=VVs=291m1sVs=1049knk

SPEED OF SOUND IN VARIOUS MEDIA

| Speed of sound depends not only on the temperature of the medium but also on the mediums properties

SOUND INTENSITY

| Loudness depends on sound intensity | Sound intensity

y the amount of sound energy being transferred per unit area

y units are watts per square metre ( W / m2 )

| Decibel (dB) y unit of sound level y used to describe sound intensity

SOUND SAFETY

| Exposure to high sound levels can cause hearing damage

| Damage is not reversible | Ministry of Labour | Musicians | Personal listening devices

WORK

| Pg. 397 #2,3,9,10