Characteristics of Sound

1
Characteristics of Sound
PHYSICAL
PSYCHOLOGICAL

• Amplitude (dB)
• Intensity
• Pressure
• Frequency (Hz or cps)
• Phase (degrees or rads)
• Duration (sec)

• Loudness (sone)
• Pitch (mel)

2
Simple vs. Complex Sound

• Simple vibration
• Single frequency (pure tone)
• Sounds tonal (identifiable pitch)
• Complex vibration
• Multiple frequencies at same time
• May have tonality or not

3
Simple Harmonic Motion
a.k.a. simple vibration, sinusoidal motion,
uniform circular motion
PHYSICAL
compression

atmospheric pressure
amplitude
0

• Amplitude
• pressure
• displacement
• decibels (dB)
• volts

-
rarefaction
time (sec)
4
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL
1

• Peak amplitude (Ap)

• Amplitude (dB)

Ap
amplitude
0
-1
time
5
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL
1

• Amplitude (dB)
• Peak amplitude (Ap)

Ap-p
amplitude
0

• Peak-to-peak amplitude (Ap-p)

-1
time
6
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL
1

• Amplitude (dB)
• Peak amplitude (Ap)
• Peak-to-peak amplitude (Ap-p)

amplitude
0

• rms amplitude (Arms)
• root-mean-square
• average amplitude

-1
time
7
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL
Ap
Ap-p

• Amplitude (dB)
• Peak amplitude (Ap)
• Peak-to-peak amplitude (Ap-p)

Ap

• rms amplitude (Arms)
• root-mean-square
• average amplitude

Ap-p
8
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL
1
0.5

• Amplitude (dB)
• Peak amplitude (Ap)
• Peak-to-peak amplitude (Ap-p)

amplitude
0

• rms amplitude (Arms)
• root-mean-square
• average amplitude

-1
time
Square
Square root
Take mean
9
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL

• Amplitude (dB)

• Frequency (Hz or cps)

amplitude
1 sec
10
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL

• Amplitude (dB)

• Frequency (Hz or cps)

amplitude
1 msec
11
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL

• Amplitude (dB)

• Frequency (Hz or cps)

amplitude
40 msec
12
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL
7500 Hz

• Amplitude (dB)

• Frequency (Hz or cps)

amplitude
1.5 cycles
200 msec
13
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL
160 Hz

• Amplitude (dB)

• Frequency (Hz or cps)

amplitude
0.025 sec
25 msec
14
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL
90o

• Amplitude (dB)
• Frequency (Hz or cps)

360o
amplitude
0o
180o

• Phase (degrees)

270o
phase
15
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL
p/2

• Amplitude (dB)
• Frequency (Hz or cps)

2p
amplitude
p
0

• Phase (radians)

3p/2
phase
16
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL

• Amplitude (dB)
• Frequency (Hz or cps)

amplitude

• Starting Phase

0o
or
0 radians
phase
17
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL

• Amplitude (dB)
• Frequency (Hz or cps)

amplitude

• Starting Phase

90o
or
p/2
phase
18
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL

• Amplitude (dB)
• Frequency (Hz or cps)

amplitude

• Starting Phase

270o
or
3p/2
phase
19
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL

• Amplitude (dB)
• Frequency (Hz or cps)

amplitude

• Starting Phase

180o
or
p
phase
20
Simple Harmonic Motion
a.k.a. sinusoidal motion, uniform circular
motion, simple vibration
PHYSICAL

• Amplitude (dB)
• Frequency (Hz or cps)
• Phase (degrees/rads)

amplitude

• Duration (secs)

time/phase
21
Simple Harmonic Motion
90o
1
0
.707
.5
1
360o
amplitude
0
0
0o
180o
-1
45o
-1
0
270o
time/phase
22
Uniform Circular Motion
Simple Harmonic Motion linear projection of
uniform circular motion
90o
One time around the circle in one second 1 cps
or Hz
radius 1
180o
0o
/360o
270o
23
Uniform Circular Motion
Simple Harmonic Motion linear projection of
uniform circular motion
1 sec
1 Hz
90o
0.25
0.5
0.75
1
1
0.25 s
radius 1
180o
0o
amplitude
0
0.5 s
0/1 s
0.75 s
-1
270o
time
24
Uniform Circular Motion
1 sec
1 Hz
90o
0.25
0.5
0.75
1
1
0.25 s
h1
45o
180o
0o
amplitude
0
0.5 s
radius 1
0/1 s
0.75 s
-1
270o
time
25
Uniform Circular Motion
1 sec
1 Hz
90o
0.25
0.5
0.75
1
1
0.25 s
A f q
67.5o
180o
0o
amplitude
0
0.5 s
radius 1
0/1 s
0.75 s
-1
270o
time
26
Uniform Circular Motion
A
radius
Amplitude
27
Uniform Circular Motion
f
Frequency
28
Uniform Circular Motion
q
Starting phase 0o
Starting Phase
29
Instantaneous Amplitude
Amplitude of simple vibration at time (t)
Ap f q rove t
30
Instantaneous Amplitude
Radians
Degrees
31
Instantaneous Amplitude
EXAMPLE

• A 5 V
• f 10 Hz
• q p
• at t 134ms

32
Instantaneous Amplitude

• EXERCISE 3
• A 5 V
• f 2 Hz
• q p/2 (90 degrees)
• t every 31.25ms

in msecs
0
5.0
31.25
4.6
62.5
3.5
93.75
125
33
Instantaneous Amplitude
0
5.0
31.25
4.6
62.5
3.5
93.75
125