audio system is an electroacoustic transducer

1. FEDERAL TECHNICAL AND
VOCATIONAL EDUCATION AND
TRAINING INSTITUTE
Faculty of Electrical-Electronics and
ICT Department of Electronics and
communication Technology
Course Title: Consumer Electronics ECTe 4037
Instructor: Samson Negera (MSc.)

2. Chapter #1: Audio System
Introduction of audio video system:
nAudio systems convert sound (acoustic) signals
into electrical signals, process these electrical
signals, and convert them back into sound.
nSound is a variation in air pressure created by
mechanical vibration which will last for a duration
of
some defined time which we call it a sound wave.
uComponents of a sound are: Frquency, Intensity
and Tembre quality (pitch).

3. • Sound's intensity corresponds to the decibel (dB)
value used for measuring the sound's energy in a
way that is relevant to how humans perceive
loudness.
• The decibel is given as:
dB = 10log10 (I/I₀)
#where I = the measured intensity (W/m²)
I₀ = 10¯¹² W/m², which represents the
lowest sound intensity detectable by the
human ear

4. Typical sound ranges, audiometer

5. Microphones
• A microphone is an electroacoustic transducer. Its
output is an electrical signal that reproduces the
sound pressure variations that it senses.
• A microphone whose output depends on the
velocity of the response, operating near the
resonant frequency.
• Microphones work under three interconnected
elements:
ü acoustic input,
üsound waves
üa diaphragm

6. Inside a microphone

7. How microphones work?
üWhen you speak, sound waves created by your
voice carry energy toward the microphone, moves
back and forth when the sound waves hit it.
üThe coil, attached to the diaphragm, moves back
and forth as well.
üThe permanent magnet produces a magnetic field
that cuts through the coil. the coil moves back
and forth through the magnetic field, an electric
current flows through it.
üFinally the electric current flows out from the
microphone to an amplifier or sound recording
device.

8. • The operation of a microphone is very greatly
affected by the motion of the diaphragm,
sometimes influenced by air volumes and
passages behind it.
• Types of microphones:
a. Dynamic microphone and
b. Condenser microphones
Note: Reading assignment.
üTypes of microphones, working principles,
advantages and disadvantages.

9. Microphone Characteristics
1.Electrical Impedance / Low-Z & High-Z Mics: any
resistance that voltage encounters in the circuit.
üLow-impedance (low-Z): 600 ohms or less.High-
impedance (high-Z): 10,000 ohms or higher.
üProfessionals prefer low-impedance mics. Much
less susceptible to hum and electric noise, such as
static from motors and fluorescent lights.
2. Directionality: Pickup Pattern
üOmnidirectional: Equal output or sensitivityoy at
all angles
üBidirectional: Used for picking up two opposing

10. üUnidirectional: Picks up sound directly from
the rear: the rear lobe.
3. Frequency Response: output level or
sensitivity of the microphone over its operating
range from lowest to highest frequency.
üA microphone whose output is equal at all
frequencies has a flat frequency response

11. Loud Speaker
• Loud speakers convert back the original signal
in to acoustic signal which is the original signal
and the required signal after amplification and
signal processing.
• Loud speaker is a transducer which converts
electrical signals of audio frequency into
sound waves of the same frequency .

12. Characteristics of loud speaker
• The performance of a loud speaker is
determind by: