Sound intended to be heard as if it were emanating from one position
"Monophonic" redirects here. For musical term, see
monophony
.
Monaural
or
monophonic sound reproduction
(often shortened to
mono
) is sound intended to be heard as if it were emanating from one position.
[1]
This contrasts with stereophonic sound or
stereo
, which uses two separate audio channels to reproduce sound from two microphones on the right and left side, which is reproduced with two separate
loudspeakers
to give a sense of the direction of sound sources. In mono, only one
loudspeaker
is necessary, but, when played through multiple loudspeakers or headphones, identical
signals
are fed to each speaker, resulting in the perception of one-channel sound "imaging" in one sonic space between the speakers (provided that the speakers are set up in a proper symmetrical critical-listening placement). Monaural recordings, like stereo ones, typically use multiple microphones fed into multiple channels on a recording console, but each channel is "
panned
" to the center. In the final stage, the various center-panned signal paths are usually
mixed down
to two identical tracks, which, because they are identical, are perceived upon playback as representing a single unified signal at a single place in the soundstage. In some cases, multitrack sources are mixed to a one-track tape, thus becoming one signal. In the
mastering
stage, particularly in the days of mono
records
, the one- or two-track mono master tape was then transferred to a one-track
lathe
used to produce a master disc intended to be used in the pressing of a monophonic record. Today, however, monaural recordings are usually mastered to be played on stereo and multi-track formats, yet retain their center-panned mono soundstage characteristics.
Monaural sound has largely been replaced by
stereo
sound in most entertainment applications, but remains the standard for
radiotelephone
communications,
telephone
networks, and
audio induction loops
for use with
hearing aids
.
[2]
FM radio
stations broadcast in stereo, while most
AM radio
stations broadcast in mono. (Although an
AM stereo
broadcast standard exists, few AM stations are equipped to use it.) A few FM stations?notably
talk-radio
stations?choose to broadcast in monaural because of the slight advantage in
signal strength
and
bandwidth
the standard affords over a stereophonic signal of the same power.
History
[
edit
]
While some experiments were made with stereophonic recording and reproduction from the early days of the
phonograph
in the late-19th century, monaural was the rule for almost all
audio recording
until the second half of the 20th century.
Monaural sound is normal on:
Incompatible standards exist for:
- Later vinyl records (although monophonic records?which had almost disappeared in the United States by the end of 1967?could be played with a stereo
cartridge
)
- Reel-to-reel audio tape recording
(depending on track alignment)
Compatible monaural and stereophonic standards exist for:
No native monaural standards exist for:
In those formats, the mono-source material is presented as two identical channels, thus being technically stereo.
At various times artists have preferred to work in mono, either in recognition of the technical limitations of the equipment of the era or because of simple preference (this can be seen as analogous to filmmakers working in
black and white
). An example is
John Mellencamp
's 2010 album
No Better Than This
, recorded in mono to emulate mid-20th century blues and folk records. Some early recordings such as
The Beatles
' first four albums (
Please Please Me
,
With the Beatles
,
A Hard Day's Night
,
Beatles for Sale
) were re-released in the
CD
era as monophonic in recognition of the fact that the source tapes for the earliest recordings were two-track, with vocals on one track and instruments on the other (even though this was only true on the first two albums, while the latter two had been recorded on four-track). This was actually intended to provide flexibility in producing a final mono mix, not to provide a stereo recording, although because of demand this was done anyway, and the early material was available on vinyl in both mono and stereo formats. In the 1960s and 1970s, it was common in the pop world for stereophonic versions of mono tracks to be generated electronically using filtering techniques to attempt to pick out various instruments and vocals; but these were often considered unsatisfactory, owing to the artifacts of the conversion process.
[
citation needed
]
Directors
Stanley Kubrick
and
Woody Allen
, among others, preferred to record their films'
sound tracks
in mono.
Monaural LP records were eventually phased out and no longer manufactured after the early 1970s, with a few exceptions. For example, Decca UK had a few double issues until the end of 1970 ? the last one being Tom Jones's "I Who Have Nothing"; in
Brazil
records were released in both mono and stereo as late as 1972.
[
citation needed
]
During the 1960s it was common for albums to be released as both mono and stereo LPs, occasionally with slight differences between the two (again, detailed information of The Beatles' recordings provides a good example of the differences). This was because many people owned mono record players that were incapable of playing stereo records, as well as the prevalence of AM radio. Because of the limited quantities pressed and alternative mixes of several tracks, the monaural versions of these albums are often valued more highly than their stereo LP counterparts in record-collecting circles today.
[
citation needed
]
On 9 September 2009, The Beatles re-released a remastered box set of their mono output spanning the
Please Please Me
album to
The Beatles
(commonly called "The White Album"). The set, simply called
The Beatles in Mono
, also includes a two-disc summary of the mono singles, B-sides and EP tracks released throughout their career. Also included were five tracks originally mixed for an unissued mono
Yellow Submarine
EP
.
Bob Dylan
followed suit on 19 October 2010 with
The Original Mono Recordings
, a box set featuring the mono releases from
Bob Dylan
(1962) to
John Wesley Harding
(1967). On 21 November 2011,
The Kinks
' mono recordings were issued as
The Kinks in Mono
box set, featuring the releases of the band's albums from
Kinks
(1964) to
Arthur
(1969), with three additional CDs of non-album tracks that appeared as singles or EP tracks. When the initial run of the box set sold out, no more were pressed, unlike the Beatles and Dylan sets.
Compatibility between mono and stereo sound
[
edit
]
Sometimes
mono sound
or
monaural
can simply refer to a merged pair of stereo channels - also known as "collapsed stereo" or "folded-down stereo". Over time some devices have used mono sound amplification circuitry with two or more speakers since it can cut the cost of the hardware. Some consumer electronics with stereo RCA outputs have a microswitch in the red RCA output (i.e., the right stereo channel) that disables merging of stereo sound into the white (left stereo channel) RCA output. Common devices with this are
VCRs
,
DVD
/
Blu-ray players
, information appliances,
set-top boxes
, and the like.
Video game consoles
sometimes have male RCA ends of cables with a proprietary multi-A/V plug on the other end, which prevents automatic stereo merging unless adapters are used.
Disadvantages of merged stereo involve phase cancellations that may have the effect of muffling the final sound output. If channels are merged after being sent through a power amplifier but before being connected to a loudspeaker, it places more stress on the
loudspeaker
. It has usually been the practice in recording studios to make separate mixes for mono recordings (rather than folded-down stereo-to-mono), so that the final mono master will avoid the pitfalls of collapsed stereo. In video games, merging stereo to mono sound prevents player from discerning what direction distant SFX are coming from, and reverse stereo has a similar setback too. Having an array of loudspeakers connected to their own amplifier outputs can mitigate issues with the electrical load for a single loudspeaker coil and allow the listener to perceive an "image" of sound in the free space between the speakers.
Mirrored mono
[
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]
Mirrored mono sound is the opposite of merged stereo, since it can be a case where media with mono sound that stereo playback devices automatically mirror it with are played on both channels of the receiver. It can also mean having a mono input mixed down to stereo amplification circuitry, or a mono system with a headphone output compatible with stereo
headphones
. An example of an application where both merged stereo and mirror mono apply is when a
compact audio cassette
respectively plays back "summed" stereo channels on a mono reading head, and when a compact cassette recorded with mono sound is played back with a stereo tape head.
Other instances of "mirrored mono" also include using the right stereo channel in lieu of a "left" one (or vice versa) where both channels are wired to mirror only one.
Both
[
edit
]
Instances of both "merged stereo" and "mirrored mono" can occur when the stereo channels are merged to a mono system with stereo headphone compatibility or when a mono system has "twin speakers" (or "pseudo-stereo").
Other applications that involve mirrored mono with merged stereo occur when MONO is available as an internal feature of a device that can toggle between STEREO and MONO, for instance many
FM radios
are capable of toggling between MONO and STEREO in a way where stereo can both MERGE into mono, and then MIRROR between both stereo speakers. This tactic can also be used on other devices, of which computer software and some
video games
will have a feature that will allow STEREO or MONO for the soundtrack, in which sometimes this can facilitate MERGING stereo internally to spare one from using a Y adapter with LEFT and RIGHT RCA plugs when using mono equipment, such as
guitar amplifiers
.
Native stereo equipment with mono-only features
[
edit
]
Some
TV/VCR combo
decks on the market had stereo TV functionality with "twin speakers", whereas the VCR feature was only mono, which is typical of "consumer-grade VCRs" from decades ago. Some of these devices even had front RCA inputs for composite video (yellow), and mono audio (white) in which many of these devices didn't even have a right-channel RCA plug (red) even if it was just for "merging" stereo into mono for mono soundtracks to be recorded onto videotapes. This is odd since one would think that a "right channel" would be included for A/V in on a TV which had MTS stereo TV sound on its tuner.
Some stereo receivers will also include mono microphone inputs.
See also
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References
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