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