Sound Waves

CHAPTER 11: SOUND WAVE

• 11.1 INTENSITY AND BEATS
• 11.2 AMPLIFICATION STATIONARY WAVES
• 11.3 DOPPLER EFFECT

11.1. INTENSITY AND BEATS

Formula: Unit: Definition : periodic
Wm¯² variation in amplitude
Factors
influence Definition: superposition two
the value of the rate of sound wave having
intensity
sound slightly different
Amplitude energy flow frequency
of sound: across unit
Intensity I BEATS
I α A² area
Unit: Hz / Formula:
Quantity : s¯¹
scalar ƒb=|ƒ2 ─ ƒ1|

Distance from

the source of

sound:

Iα 1
r²

FUNDAMENTAL OVERTONE HARMONICS
FREQUENCYOR
FUNDAMENTAL TONE • Upper tone than the • Frequency which are
fundamental tone multiple of fundamental
• Lowest frequency frequency Real number
or harmonics number

All harmonics Odd harmonics

harmonic overtone frequency harmonic overtone frequency =

1ˢᵗ Fundamental ƒ=ƒₒ 1ˢᵗ Fundamental ƒ=ƒₒ V = wave speed of string
(n=1) (n=1) Unit: ms¯¹
tone 3ᴿᵈ tone
2ᵑᵈ (n=3)
(n=2) ​ First ƒ=2ƒₒ First ƒ=3ƒₒ
overtone 5ᵀᴴ overtone
3ᴿᵈ (n=5)
(n=3) Second ƒ=3ƒₒ Second ƒ=5ƒₒ
overtone overtone

APPLICATIO CLOSE PIPE OPEN PIPE
N (air column with (air column with

STRETCHED one closed) both closed)
STRING

n ALL nv OOD nv ALL
HARMONIC
HARMONICS HARMONIC

11.3 DOPPLER EFFECT ƒ˳= V ± Vo (ƒs) INFO!!

DEFINATION Change in V Vs ƒo- frequency observe
the apparent (observe) ƒs-frequency source
frequency of wave relative V-speed of sound
motion between source Vo-velocity observe
Vs-velocity source
and observe
±

Moving source and Moving observe and
stationary observer stationary source

V V ƒ˳= V + Vo (ƒs) ƒ˳= V–Vo (ƒs)
ƒ˳= V–Vs (ƒs) ƒ˳= V+Vs (ƒs) V V

THE VARIATION OF APPARENT FREQUENCY AND SOUND INTENSITY WHEN A
SOURCE MOVES TOWARD PASSES THROUGH AND MOVES AWAY FROM THE
STATIONARY OBSERVE

ƒ(Hz)

toward

away

r(m)

~THE END~

Lost in the soundwaves of the soul
that's lost in the heatwaves and out of control.

THANK YOU FOR WATCHING
AND

GOOD LUCK!!