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A headset is a headphone combined with a microphone.
Used in call centers and by people in telephone-intensive jobs,
headsets provide the equivalent functionality of a telephone handset
with hands-free operation. Many people use headsets at the computer so
they can converse and type comfortably. Headsets typically have only
one speaker like a telephone, but also come with speakers for both ears. 
History
The first-ever headset was invented in 1910, by a Stanford University student named Nathaniel Baldwin.
However, Baldwin's design was ahead of his time, as he wasn't able to
interest anyone in mass producing this innovative communication tool.
Not until during the World War I
did the US Army purchase 100 headsets for their pilots. Hence the early
usage and markets for headsets were mainly for aviation purposes. In
fact, Plantronics< was started by two pilots, and their main goals were to develop headsets which are lightweight and comfortable for pilots and subsequently general users.
Understanding headsets
Monaural, binaural, and stereo headsets
Headphones usually come in double earpiece design, whereas headsets
can come in single-earpiece and double earpiece designs. Single
earpiece Headsets are known as monaural stereo type or binaural
type. Stereo refers to two channels of audio signal, one for each
earpiece, and binaural headsets offer the same audio channel for both
ear-pieces. Headphones are designed mainly for music listening, so most
often they come in stereo version. headsets. However, double earpiece headsets comes in both
Professional users may choose to wear monaural headsets because they
free up the users' other ear, so they can be more conscious of their
work surroundings. Telephone headsets only come in Binaural type for
double earpiece designs because telephone only offers single-channel
input and output, so all double earpiece telephone headsets are
Binaural.
However, for computer or other audio applications, where the sources
offer two-channel output, stereo headsets are the norm. Telephone
Headsets generally use 150 Ohm loudspeakers frequency range, so sound outside the voice band
is less audible to reduce background noise. Stereo computer headsets,
on the other hand, use 32 ¦¸ loudspeakers which have a much broader
frequency range, and is more suitable of music listening. with a narrower
External microphone vs. microtube
The microphone arm of headsets come in external microphone type and
transparent voicetube type. External microphone designs have the
microphone housed in the front end of the microphone arm, inside a
microphone capsule. Transparent voicetube designs are also called
Internal Microphone design, meaning the microphone is housed near the
arm-rotation mechanism. The sound from the user travels through the
sealed transparent tube to the hidden microphone. Voicetube designs
look better, and are considered professional based on pre-set norms;
however when compared with an external microphone design, an external
microphone headset usually has a much better performance. Voicetube
headsets usually only come in the form of telephone headset or mobile
headset, there are not any computer headsets using voicetube designs
and there is no particular technical reason for this, it is probably
purely the industry norm.
Noise-canceling microphone vs. omni-directional microphone
External microphone design also comes in two major types:
omni-directional and noise-canceling. Noise-canceling microphone
headsets use bi-directional microphone as elements. receptive field
is, as its name suggests, two angles only. In fact, its receptive field
is limited to only the front and the direct opposite back of the
microphone. This will create an "8" shape field,
and this design is the best method for only picking up sound from a
close proximity of the user, meanwhile not picking up most surrounding
noises. Bi-directional microphone works better than uni-directional
microphone (single angle reception field) because uni-directional
microphone also picks up some of the sound 90-degrees (both sides) to
the desired angle. Omni-directional microphone picks up the complete
360-degree field, hence it is also the best receptive microphone but it
also picks up most of the surrounding noises. In some instances, when a
higher sensitivity is required for the microphone, or when the sound
source is further away from the microphone, omni-direction microphone
is the preferred choice. In fact, almost all voicetube designs employ
an omni-directional microphone (since the sound source needs to travel
through the voicetube before it reaches the microphone). A bi-directional microphone's
Different styles of headsets
Standard headsets with the headband wearing over the head are known
as over-the-head headsets. Headsets with headband going over the back
of the user's neck are known as backwear-headset or behind-the-neck
headsets. Headsets that are worn over the ear with a soft ear-hook are
known as over-the-ear or earloop headset; these headsets do not have a
headband. There are also headsets in the market which are designed so
that users can change the wearing method by assembling and
dis-assembling various parts, known as convertible headsets.
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