In this essay I am going to write about different sound systems, for instance: Monophonic
system, Stereophonic system, Surround sound and THX. I would like to focus on the special
features of each one and to describe in detail how does it work. My aims by doing so are:
 To expand horizons about the field of Physics of sound.
 To provide a comprehensive analysis concerning prominent functions of each sound system.
Accompanied with highly schematic fashion illustrations, the most crucial similarities as well as
differences between those sound systems are emphasized and well-explained.
For clarification, a channel is an individual discrete audio track. When referring to more
than two channels it is called multichannel. Monophonic Sound System
Monophonic, or monaural, sound reproduction (often shortened to mono) is a single-
channel of audio for sound output . In this sound system, the original sound is picked up by one
(or more) microphone(s). Regardless of the number of microphones, however the significant fact
is that only one signal is recorded and only one signal is involved in the playback stage. In other
words, the signal sent to the sound system encodes one signal stream of sound and it usually uses
just one speaker. The monophonic system is illustrated in the following figure : 2 Sound systems for home use can take many forms. The program sources available are record
albums, tapes, and AM/FM signals. These program sources which are audio sources require a
turntable, a tape deck, and a tuner for their implementation. A preamplifier (control unit) and a
power amplifier prepare the signal for delivery to the loudspeaker. A monophonic sound
reproduction system is shown in the block diagram below : 2
The boxes represent the components and the lines represent the interconnections between
components. Since there is only one signal involved in a monophonic system, a single cable-two
conducting paths- between each component is sufficient. The main components are shortly
explained in the following passage:
Audio source – The recorded audio information, which is recorded from a digital
or analog recording, is being read by the audio source. Then the information is
sent in an electrical signal via audio cable .
Turntable (or phonograph) – is a device which is used in order to record and
reproduce sound recordings . Tape deck (or tape recorder) - is an audio storage device that his main feature is to
record and play back sounds by using magnetic tape for storage .
Tuner – a subsystem that receives radio frequency transmissions and converts the
selected carrier frequency and its associated bandwidth (the difference between
the upper and lower frequencies in a continuous set of frequencies )into a fixed
frequency that is suitable for further processing usually because a lower frequency
is used on the output .
Preamplifier - serves as control unit in 4 steps: reading the signal, breaking it
down into appropriate channels, increasing the voltage of the signal slightly from
a source and finally sending it to the amplifier .
Amplifier – The signal sent from preamplifier is too weak to effectively drive the
speakers and vibrate the coil so that one can hear sound. Thus, the amplifier is
needed in order to add significant power to that signal .3
Speakers - a conventional speaker uses several drivers, each od them contains (1)a
stationary magnet, (2) an electromagnetic coil and (3) a cone. The electric signal
sent from the amplifier is an AC or alternating current signal -this means that the
current switches directions on a regular basis. Running through a wire coil, the
alternating current creates a magnetic field that is persistently reversing polarity.
The reversion of the polarity of coil causes a constant shift between attraction and
repulsion with the stationary magnet. The electric voice coil is continually
oscillating because of this magnetic force and in turn vibrates the cone. This vibration cause to a motion of air molecules, which become the vessel by which
sound is delivered to the ears .
The tuner, preamplifier, and power amplifier cab be separate components or they can be
combined into a signal chassis called a receiver.
Monaural sound, commonly called non-stereo sound, has been replaced by stereo sound
in most entertainment applications. Nonetheless, it remains the standard for radiotelephone
communications, telephone networks, and audio induction loops for use with hearing aids.
Thanks to the fact that a monaural signal has a slight advantage in signal strength over a
stereophonic signal of the same power, few FM radio stations choose to broadcast in monaural. Stereophonic Sound System
Stereophonic sound is a method of sound reproduction that creates an illusion of sound
heard from various directions, as in natural hearing, which is usually achieved by using two or
more independent audio channels through a configuration of two or more . 8
A stereophonic sound system employs two or more microphones to pick up the original sound.
The spacing between these microphones is large enough so that the acoustic signals reaching them are distinctly different. Two different signals are recorded and the individual integrity of
these signals is maintained in the playback stage .
As the monophonic sound system, a stereo system must contain an audio source which
requires a turntable, a tape deck and a tuner for its implementation. The next component in the
stereo is a preamplifier which reads and decodes audio information sent from the source to the
amplifier. The amplifier increases the power of the signal to properly drive the speakers. Finally,
the speakers convert the electrical audio signal to sound. The interconnections are not simply
wires; rather, they are shielded audio cables designed to reduce unwanted harm and noise. A
diagram of a stereophonic sound system is given below :
Although the layouts of the stereo and mono systems are very similar, the fundamental
differences are obvious. A stereo system is equipped to handle two independent signals. There
are in essence two preamplifiers, two power amplifiers, and there are two loudspeakers.
Stereo sound is now common in entertainment systems such as: broadcast radio, recorded
music, TV and the cinema . Surround Sound
Surround Sound is a system in which the sound output appears to surround the listener by
360 degrees — in other words, this technology gives the impression that sounds are coming from
all possible directions.
The surround sound works because multiple audio channels are received
through speakers that are positioned at various locations in the room. This is programmed into
the source and the sound tracks are decoded when the source is played.
Moreover, it is important to remember that sound systems started out with monophonic
sound, a single channel system. Advancements led to stereophonic sound (stereo) where the
sound was split between two channel